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Dr Brad Murray


Brad has research and teaching interests in ecology, botany, evolution and biodiversity conservation. His research focuses on three overlapping themes: the flammability of native and exotic plants, interactions between exotic plants and native flora and fauna, and vegetation responses to environmental gradients.

Image of Brad Murray
Senior Lecturer, School of Life Sciences
BSc (Hons) (Syd), PhD (Macquarie)
+61 2 9514 4075

Research Interests

Further information can be found at the Murray Ecology Lab web page.

Can supervise: Yes

91154 Ecology – Subject Coordinator & Lecturer

91309 Biodiversity Conservation – Subject Coordinator & Lecturer

60701 Undergraduate Project – Principal Supervisor

91107 The Biosphere – Lecturer


Godfree, R.C. & Murray, B.R. 2014, 'Invasive species: Plants' in Van Alfen, N.K. (ed), Encyclopedia of Agriculture and Food Systems, Vol. 4, Elsevier, San Diego, pp. 66-77.
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Stohlgren, T., Pysek, P., Kartesz, J., Nishino, M., Pauchard, A., Winter, M., Pino, J., Richardson, D.M., Wilson, J., Murray, B., Phillips, M., Celesti-Grapow, L. & Graham, J. 2013, 'Globalization Effects on Common Plant Species' in Simon Levin (ed), Encyclopedia of Biodiversity, Elsevier Inc., Waltham, MA, USA, pp. 700-706.
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The trade of goods by humans has bridged the continents, in effect restoring the old supercontinent of Pangaea. In the past century, humans have been responsible for an exponential increase in plant migrations, moving plant species around the globe for food, fuel, forage, horticulture, landscaping, and medicines. Trade within and among continents is breaking geographic barriers and providing long-range dispersal for seeds and propagules at unprecedented rates (Richardson et al., 2000; Wilson et al., 2009). Here, the authors provide a brief review of the globalization effects on common plant species and ââhomogenizationââ of the worldâs plant communities.
Booth, D.J. & Murray, B. 2008, 'Coexistence' in Jørgensen, S.E. & Fath, B.D. (eds), Encyclopedia of Ecology, Five-Volume Set, Elsevier, Amsterdam, pp. 664-668.
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Murray, B., Dickman, C.R., Robson, T.C., Haythornthwaite, A., Cantlay, A.J., Dowsett, N.S. & Hills, N. 2007, 'Effects of exotic plants in native vegetation on species richness and abundance of birds.' in Lunney, D. (ed), Pest or guest : the zoology of overabundance, Royal Zoological Society of New South Wales, Mosman, N.S.W, pp. 216-221.
We reviewed published, quantitative studies examining the effects of exotic plants in native vegetation on the species richness and abundance of birds and mammals. We asked whether the incursion of exotic plants into native vegetation has led to consistent declines, increases or no changes in bird and mammal species richness and abundance. Bird species richness and abundance tended not to be lower in sites with exotic plants (exotic sites) compared with sites without exotic plants (native sites). However, there are some reported cases of declines in richness, and declines and increases in abundance of birds in exotic sites. While there is not enough evidence to generate broad patterns in relation to species richness of mammals in exotic sites, abundances of individual mammal species demonstrated idiosyncratic responses (either increases, decreases, or no changes) to the incursion of exotic plants. Any differences observed in species richness and abundance of birds and mammals between exotic and native sites are probably due to habitat modifications by exotic plants resulting in changes to vegetation that is important for foraging, protection, and reproduction of the vertebrates. Importantly, our review found no published, quantitative evidence that the incursion of exotic plants into native vegetation leads to the over-abundance of any bird or mammal species. Nevertheless, the results of our review must be viewed as preliminary findings: there is still much to be done to untangle the complex ecological effects of exotic plants on birds and mammals in native vegetation.
Dickman, C.R. & Murray, B. 2006, 'Species interactions: complex effects' in Attiwell, P. & Wilson, B. (eds), Ecology: An Australian Perspective, Oxford University Press, South Melbourne, Australia, pp. 317-334.
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Interactions within ecological communities usually involve many species and pose intriguing challenges for ecologists who wish to map and disentangle them. To simplify this task we often assume that the interactions do not change in strength or direction and that the identities of the key species remain the same. Species can be 'pigeon-holed' into convenient categories such as 'pollinator', 'competitor', 'pest' or even 'redundant' using these assumptions. This makes programs of conservation or pest management easier to implement, but is also ignores an emerging body of evidence that interactions between species vary between situations, places and times. In this chapter we will explore the complexity of effects that arise from changes in tereactions between species. We also consider how such effects may be modelled and predicted,a nd illustrate how ecological insight can be used to guide management decisions.
Thrall, P.H., Burdon, J.J. & Murray, B. 2000, 'The metapopulation paradigm: a fragmented view of conservation biology' in Young, A.G. & Clarke, G.M. (eds), Genetics, Demography and Viaability of Fragmented Populations, Cambridge University Press, Cambridge,United Kingdom, pp. 75-95.
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In the past, single-population approaches have dominated ecology and evolutionary biology. However, populations are not isolated either in time or space, but are connected by among-population processes such as migration and gene flow.While this concept is not new, until recently, there have beenrelatively few studies that have explicitly investigated the effects od spatial structure on demographic and genetic processes in the context of conservation. The metapopulation framework explicitly recognises and provides a conceptual tool for dealing with the interactions of within - (e.g. birth, death, competition) and among-population processes (e.g. dispersal, gene flow, colonisation and extinction). The ever-growing diversity of empirical and theoretical studies that demonstrate the importance of spatial structure in determining ecological and evolutionary trajectories also indicates that long-term conservation programmes need to focus on regional rather than local within-population persistence. In this regard, it is important to realise that ultimately all populations are ephemeral, and therefore colonisation processes must also be preserved. Clearly, not all species whose populations have undergone fragmentation fit the definition of a metapopulation. Nevertheless, a metapopulation approach to conservation biology is likely to provide a useful tool for developing management strategies as it addresses genetic, species and community effects of fragmentation in a single framework, therby making explicit questions regarding extinction, population connectedness, species behavioural patterns and the survival of coevolved systems. In essence, a metapopulation perspective ensures a process oriented, scale-appropriate approach to conservation that focuses attention on among-population processes critical for persistence of many natural systems.

Journal articles

Gribben, P.E., I'Ons, S., Phillips, N.E., Geange, S.W., Wright, J.T. & Murray, B.R. 2013, 'Biogeographic comparisons of the traits and abundance of an invasive crab throughout its native and invasive ranges', Biological Invasions, vol. 15, no. 8, pp. 1877-1885.
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High abundances of non-native species in the invaded range may be linked to changes in fitness related traits. However, few studies have compared differences in both life-history traits and abundances of introduced species between their native and invaded ranges. We determined differences in 12 morphological traits, an important fitness related trait (body size), and the abundance of the porcelain crab, Petrolisthes elongatus, in its native (New Zealand) and invasive (Tasmania, Australia) ranges. P. elongatus was more abundant in the introduced range; however, changes in abundance depended on tidal height, with higher abundances only at mid and low tidal zones. The biomass of male crabs was higher in the invaded range compared to the native range, but there was no difference in female biomass between ranges. Despite increases in male biomass, sex ratios between native and invasive populations did not differ. In addition, principal components analysis showed no differences in overall morphology between Tasmania and New Zealand. Our study indicates that increased abundance in the invaded range of P. elongatus may be linked to high values of an important trait (greater biomass) in the invaded range. Importantly, changes in biomass and abundance may be due to P. elongatus being able to utilise mid/low zones more in the invaded range. Furthermore, our findings indicate that understanding how sex specific changes in biomass interact with the recipient environment (biotic and abiotic) in the introduced range will be important for determining the mechanisms underpinning the establishment and spread of P. elongatus. © 2013 Springer Science+Business Media Dordrecht.
Martin, L.J. & Murray, B.R. 2013, 'A preliminary assessment of the response of a native reptile assemblage to spot-spraying invasive Bitou Bush with glyphosate herbicide', Ecological Management and Restoration, vol. 14, no. 1, pp. 59-62.
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During recent work examining the effects of Bitou Bush (Chrysanthemoides monilifera ssp. rotundata) invasion on native reptile assemblages in coastal heathland vegetation in Eastern Australia, unplanned spot-spraying of glyphosate occurred at some of our experimental sites invaded by Bitou Bush. We used this unexpected herbicide application as an opportunity to provide a preliminary assessment of the short-term impacts on reptiles of glyphosate spot-spraying of Bitou Bush. Using an M-BARCI design, we compared reptile assemblages among uninvaded (reference) sites, invaded (control) sites and invaded and sprayed (impact) sites before and after spraying. We found no significant short-term (7 - 10 months) differences in reptile abundance, species richness or assemblage composition among invaded, uninvaded and sprayed sites before and after glyphosate application. We cautiously interpret our results to generate a preliminary finding that spot-spraying of Bitou Bush with glyphosate appears not to have a deleterious effect on reptile assemblages at seven and ten months following herbicide application. While we would not recommend basing management decisions on the outcomes of our study alone, we suggest that our findings can be used to assist in the development of strategic analyses of glyphosate impacts on native flora and fauna. © 2012 Ecological Society of Australia.
Murray, B.R., Hardstaff, L.K. & Phillips, M.L. 2013, 'Differences in leaf flammability, leaf traits and flammability-trait relationships between native and exotic plant species of dry sclerophyll forest', PLoS ONE, vol. 8, no. 11.
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The flammability of plant leaves influences the spread of fire through vegetation. Exotic plants invading native vegetation may increase the spread of bushfires if their leaves are more flammable than native leaves. We compared fresh-leaf and dry-leaf flammability (time to ignition) between 52 native and 27 exotic plant species inhabiting dry sclerophyll forest. We found that mean time to ignition was significantly faster in dry exotic leaves than in dry native leaves. There was no significant native-exotic difference in mean time to ignition for fresh leaves. The significantly higher fresh-leaf water content that was found in exotics, lost in the conversion from a fresh to dry state, suggests that leaf water provides an important buffering effect that leads to equivalent mean time to ignition in fresh exotic and native leaves. Exotic leaves were also significantly wider, longer and broader in area with significantly higher specific leaf area-but not thicker-than native leaves. We examined scaling relationships between leaf flammability and leaf size (leaf width, length, area, specific leaf area and thickness). While exotics occupied the comparatively larger and more flammable end of the leaf size-flammability spectrum in general, leaf flammability was significantly correlated with all measures of leaf size except leaf thickness in both native and exotic species such that larger leaves were faster to ignite. Our findings for increased flammability linked with larger leaf size in exotics demonstrate that exotic plant species have the potential to increase the spread of bushfires in dry sclerophyll forest. © 2013 Murray et al.
Phillips, M.L. & Murray, B.R. 2012, 'Invasiveness in exotic plant species is linked to high seed survival in the soil', Evolutionary Ecology Research, vol. 14, no. 1, pp. 83-94.
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Background: Exotic species often do no harm for many generations and then become invasive. The science of invasion ecology seeks to determine the nature or causes of this change. Among the possibilities is that soil-borne fungi play a significant role in reducing the potential for invasiveness in the introduced range. Predictions: The seed survival of invasive species in the soil exceeds that of non-invasives. Seed survival, both in invasives and non-invasives, is higher in the presence of fungicide, but fungicide improves the seed survival of non-invasives more than that of invasives. Methods: A common garden experiment under field conditions to compare seed survival in the soil between invasive and non-invasive exotic plant species. We contrasted seven congeneric pairs of invasive and non-invasive species. The species in each pair originated from the same donor continent, shared similar growth form, habitat occurrence, and residence times in Australia. The addition of fungicide was used as an experimental treatment. Results: Seed survival was significantly higher in invasive species. The addition of fungicide improved seed survival. However, there was also a significant interaction: the fungicide treatment had a significantly stronger effect on the seed survival of non-invasive species. Seed mass differences between congeners did not provide a consistent, significant explanation of seed survival differences. Conclusion: The seeds of invasive species are better equipped to survive in the soil than those of non-invasive species. Moreover, soil-borne fungi play a key role in the lower seed survival of non-invasive species. © 2012 Megan L. Phillips.
Murray, B. & Phillips, M. 2012, 'Temporal introduction patterns of invasive alien plant species to Australia', NeoBiota, vol. 13, pp. 1-14.
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Baker, A.C. & Murray, B.R. 2012, 'Seasonal intrusion of litterfall from non-native pine plantations into surrounding native woodland: Implications for management of an invasive plantation species', Forest Ecology and Management, vol. 277, pp. 25-37.
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Radiata pine (. Pinus radiata) is commonly grown throughout the world as a major plantation species. Non-native radiata pine plantations are often established as monocultures amongst large tracts of remnant native vegetation. While the direct impacts on native biodiversity of such vegetation replacement have been well documented, much less is known about how plant litterfall from such plantations influences ecosystem dynamics beyond the confines of the plantation limits. In this study, we assessed the inputs of plant litterfall from radiata pine plantations into surrounding native woodland vegetation over a two-year period in south-eastern Australia. We found that pine litter was a significant and even dominant component of litterfall at certain times of the year, typically autumn and winter, when quantities of pine needles falling were up to three times the fall of native leaves. Pine litter was found to be lower in quality than native litter, containing less carbon (C) and nitrogen (N) and having a higher C:N ratio than native litter. Although the comparatively larger inputs of pine litter resulted in C and N inputs that were 2-3 times those of native litter during some seasons, the influx of low-quality pine litter is likely to decompose slowly and immobilise N, thereby limiting the availability of N for plant growth in the long term. The intrusion of large quantities of pine litter into native eucalypt woodland may have a suite of further short and long term impacts on native biodiversity through a number of mechanisms including alteration of leaf-litter invertebrate communities, increased fire intensity and changes in microclimate. These impacts may be alleviated by preventing pine litter entering woodland communities through the use of modified buffer zones and by employing appropriate plantation design. We discuss the merits and shortfalls of various options available to land mangers to minimise pine-litter intrusion into adjacent native woodlands. © 2012 ...
Lloyd, H.B., Murray, B.R. & Gribben, P.E. 2012, 'Trait and abundance patterns in two marine molluscs: The influence of abiotic conditions operating across multiple spatial scales', Marine Ecology Progress Series, vol. 463, pp. 205-214.
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Theoretical mechanisms describing species abundance distributions should also underpin geographic variation in life-history traits. However, recent studies suggest that abundance and trait patterns may not co-vary and may respond differently to abiotic conditions acting at different spatial scales. We examined patterns in abundance and body size of 2 estuarine molluscs, the arkshell Anadara trapezia and the mudsnail Batillaria australis, across their wide distributions in eastern Australia. We related abundance and body size patterns to abiotic variables including water temperature, pH, salinity, sediment redox and dissolved oxygen content at multiple spatial scales. Two hypotheses were tested: (1) geographic patterns in abundance and body size do not co-vary, and (2) patterns in abundance are more strongly influenced by abiotic conditions occurring at a large spatial scale (e.g. across latitudinal gradients) whereas body size is more strongly influenced by variation in abiotic conditions occurring at smaller scales. The influence of spatial scale and associated abiotic variables on abundance and body size distributions was determined using multiple linear regression, ANOVA and variance component analyses. Geographic variation in abundance and body size were independent of each other in both species. Abiotic variation across latitudinal gradients was the strongest predictor of abundance, but factors that varied substantially at local scales (e.g. dissolved oxygen and sediment redox) were the strongest predictors of body size. Our data indicate that geographic patterns in body size and abundance can be disconnected from each other, most likely due to differential responses to abiotic variation acting at different spatial scales. © Inter-Research 2012 www.int-res.com.
Konarzewski, T.K., Murray, B.R. & Godfree, R.C. 2012, 'Rapid Development of Adaptive, Climate-Driven Clinal Variation in Seed Mass in the Invasive Annual Forb Echium plantagineum L.', PLoS ONE, vol. 7, no. 12.
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We examined adaptive clinal variation in seed mass among populations of an invasive annual species, Echium plantagineum, in response to climatic selection. We collected seeds from 34 field populations from a 1,000 km long temperature and rainfall gradient across the species' introduced range in south-eastern Australia. Seeds were germinated, grown to reproductive age under common glasshouse conditions, and progeny seeds were harvested and weighed. Analyses showed that seed mass was significantly related to climatic factors, with populations sourced from hotter, more arid sites producing heavier seeds than populations from cooler and wetter sites. Seed mass was not related to edaphic factors. We also found that seed mass was significantly related to both longitude and latitude with each degree of longitude west and latitude north increasing seed mass by around 2.5% and 4% on average. There was little evidence that within-population or between-population variation in seed mass varied in a systematic manner across the study region. Our findings provide compelling evidence for development of a strong cline in seed mass across the geographic range of a widespread and highly successful invasive annual forb. Since large seed mass is known to provide reproductive assurance for plants in arid environments, our results support the hypothesis that the fitness and range potential of invasive species can increase as a result of genetic divergence of populations along broad climatic gradients. In E. plantagineum population-level differentiation has occurred in 150 years or less, indicating that the adaptation process can be rapid. © 2012 Konarzewski et al.
Konarzewski, T.K., Murray, B.R. & Godfree, R.C. 2012, 'Rapid development of adaptive, climate-driven clinal variation in seed mass in the invasive annual Forb Echium plantagineum L.', PLoS One, vol. 7, no. 12, p. e49000.
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We examined adaptive clinal variation in seed mass among populations of an invasive annual species, Echium plantagineum, in response to climatic selection. We collected seeds from 34 field populations from a 1,000 km long temperature and rainfall gradient across the species' introduced range in south-eastern Australia. Seeds were germinated, grown to reproductive age under common glasshouse conditions, and progeny seeds were harvested and weighed. Analyses showed that seed mass was significantly related to climatic factors, with populations sourced from hotter, more arid sites producing heavier seeds than populations from cooler and wetter sites. Seed mass was not related to edaphic factors. We also found that seed mass was significantly related to both longitude and latitude with each degree of longitude west and latitude north increasing seed mass by around 2.5% and 4% on average. There was little evidence that within-population or between-population variation in seed mass varied in a systematic manner across the study region. Our findings provide compelling evidence for development of a strong cline in seed mass across the geographic range of a widespread and highly successful invasive annual forb. Since large seed mass is known to provide reproductive assurance for plants in arid environments, our results support the hypothesis that the fitness and range potential of invasive species can increase as a result of genetic divergence of populations along broad climatic gradients. In E. plantagineum population-level differentiation has occurred in 150 years or less, indicating that the adaptation process can be rapid.
Murray, B.R. 2012, 'Book review: Fifty Years of Invasion Ecology: The Legacy of Charles Elton', Austral Ecology: a journal of ecology in the Southern Hemisphere, vol. 37, p. e43.
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Simberloff, D., Alexander, J., Allendorf, F., Aronson, J., Antunes, P.M., Bacher, S., Bardgett, R., Bertolino, S., Bishop, M., Blackburn, T.M., Blakeslee, A., Blumenthal, D., Bortolus, A., Buckley, R., Buckley, Y., Byers, J., Callaway, R.M., Campbell, F., Campbell, K., Campbell, M., Carlton, J.T., Cassey, P., Catford, J., Celesti-Grapow, L., Chapman, J., Clark, P., Clewell, A., Clode, J.C., Chang, A., Chytry, M., Clout, M., Cohen, A., Cowan, P., Cowie, R.H., Crall, A.W., Crooks, J., Deveney, M., Dixon, K., Dobbs, F.C., Duffy, D.C., Duncan, R., Ehrlich, P.R., Eldredge, L., Evenhuis, N., Fausch, K.D., Feldhaar, H., Firn, J., Fowler, A., Galil, B., Garcia-Berthou, E., Geller, J., Genovesi, P., Gerber, E., Gherardi, F., Gollasch, S., Gordon, D., Graham, J., Gribben, P., Griffen, B., Grosholz, E.D., Hewitt, C., Hierro, J.L., Hulme, P., Hutchings, P., Jarosik, V., Jeschke, J.M., Johnson, C., Johnson, L., Johnston, E.L., Jones, C.G., Keller, R., King, C.M., Knols, B.G.J., Kollmann, J., Kompas, T., Kotanen, P.M., Kowarik, I., Kuehn, I., Kumschick, S., Leung, B., Liebhold, A., MacIsaac, H., Mack, R., McCullough, D.G., McDonald, R., Merritt, D.M., Meyerson, L., Minchin, D., Mooney, H.A., Morisette, J.T., Moyle, P., Heinz, M.-.S., Murray, B.R., Nehring, S., Nelson, W., Nentwig, W., Novak, S.J., Occhipinti, A., Ojaveer, H., Osborne, B., Ostfeld, R.S., Parker, J., Pederson, J., Pergl, J., Phillips, M.L., Pysek, P., Rejmanek, M., Ricciardi, A., Ricotta, C., Richardson, D., Rilov, G., Ritchie, E., Robertson, P.A., Roman, J., Ruiz, G., Schaefer, H., Schaffelke, B., Schierenbeck, K.A., Schmitz, D.C., Schwindt, E., Seeb, J., Smith, L.D., Smith, G.F., Stohlgren, T., Strayer, D.L., Strong, D., Sutherland, W.J., Therriault, T., Thuiller, W., Torchin, M., van der Putten, W.H., Vila, M., Von Holle, B., Wallentinus, I., Wardle, D., Williamson, M., Wilson, J., Winter, M., Wolfe, L.M., Wright, J., Wonham, M. & Zabin, C. 2011, 'Non-natives: 141 scientists object', NATURE, vol. 475, no. 7354, pp. 36-36.
Stohlgren, T.J., Pyšek, P., Pyšek, P., Kartesz, J., Nishino, M., Pauchard, A., Winter, M., Pino, J., Richardson, D.M., Wilson, J.R.U., Wilson, J.R.U., Murray, B.R., Phillips, M.L., Ming-yang, L., Celesti-Grapow, L. & Font, X. 2011, 'Widespread plant species: Natives versus aliens in our changing world', Biological Invasions, vol. 13, no. 9, pp. 1931-1944.
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Estimates of the level of invasion for a region are traditionally based on relative numbers of native and alien species. However, alien species differ dramatically in the size of their invasive ranges. Here we present the first study to quantify the level of invasion for several regions of the world in terms of the most widely distributed plant species (natives vs. aliens). Aliens accounted for 51.3% of the 120 most widely distributed plant species in North America, 43.3% in New South Wales (Australia), 34.2% in Chile, 29.7% in Argentina, and 22.5% in the Republic of South Africa. However, Europe had only 1% of alien species among the most widespread species of the flora. Across regions, alien species relative to native species were either as well-distributed (10 comparisons) or more widely distributed (5 comparisons). These striking patterns highlight the profound contribution that widespread invasive alien plants make to floristic dominance patterns across different regions. Many of the most widespread species are alien plants, and, in particular, Europe and Asia appear as major contributors to the homogenization of the floras in the Americas. We recommend that spatial extent of invasion should be explicitly incorporated in assessments of invasibility, globalization, and risk assessments. © 2011 Springer Science+Business Media B.V.
Kühn, I., Kowarik, I., Kollmann, J., Starfinger, U., Bacher, S., Blackburn, T., Bustamante, R., Celesti-Grapow, L., Chytrý, M., Colautti, R., Essl, F., Foxcroft, L., Gollasch, S., García-Berthou, E., Hierro, J., Hufbauer, R., Hulme, P., Jarošik, V., Jeschke, J., Karrer, G., Mack, R., Molofsky, J., Murray, B., Nentwig, W., Osborne, B., Pyšek, P., Rabitsch, W., Rejmanek, M., Roques, A., Shaw, R., Sol, D., van Kleunen, M., Vilà, M., von der Lippe, M., Wolfe, L. & Penev, L. 2011, 'Open minded and open access: introducing NeoBiota, a new peer-reviewed journal of biological invasions', NeoBiota, vol. 9, pp. 1-12.
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Martin, L.J. & Murray, B.R. 2011, 'A predictive framework and review of the ecological impacts of exotic plant invasions on reptiles and amphibians', Biological Reviews, vol. 86, no. 2, pp. 407-419.
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The invasive spread of exotic plants in native vegetation can pose serious threats to native faunal assemblages. This is of particular concern for reptiles and amphibians because they form a significant component of the world's vertebrate fauna, play a pivotal role in ecosystem functioning and are often neglected in biodiversity research. A framework to predict how exotic plant invasion will affect reptile and amphibian assemblages is imperative for conservation, management and the identification of research priorities. Here, we present a new predictive framework that integrates three mechanistic models. These models are based on exotic plant invasion altering: (1) habitat structure; (2) herbivory and predator-prey interactions; (3) the reproductive success of reptile and amphibian species and assemblages. We present a series of testable predictions from these models that arise from the interplay over time among three exotic plant traits (growth form, area of coverage, taxonomic distinctiveness) and six traits of reptiles and amphibians (body size, lifespan, home range size, habitat specialisation, diet, reproductive strategy). A literature review provided robust empirical evidence of exotic plant impacts on reptiles and amphibians from each of the three model mechanisms. Evidence relating to the role of body size and diet was less clear-cut, indicating the need for further research. The literature provided limited empirical support for many of the other model predictions. This was not, however, because findings contradicted our model predictions but because research in this area is sparse. In particular, the small number of studies specifically examining the effects of exotic plants on amphibians highlights the pressing need for quantitative research in this area. There is enormous scope for detailed empirical investigation of interactions between exotic plants and reptile and amphibian species and assemblages. The framework presented here and further testing of...
Martin, L.J. & Murray, B.R. 2011, 'A comparison of short-term marking methods for small frogs using a model species, the striped marsh frog (Limnodynastes peronii)', Herpetological Journal, vol. 21, no. 4, pp. 271-273.
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We compared three methods of marking individual small frogs for identification in short-term studies (several days) using a model species, Limnodynastes peronii (the striped marsh frog). We performed a manipulative experiment under laboratory conditions to compare retention times of gentian violet, mercurochrome and powdered fluorescent pigment. Gentian violet produced the most durable marks with retention times between two and four days. Mercurochrome was retained for at least one day by all treated frogs. Fluorescent pigment was either not retained at all or for one day at most, which suggests that this marking method may not be reliable for short-term studies where identification is required. No adverse reactions to any of the marking methods were detected in our study. Our findings indicate that gentian violet represents a promising alternative as a minimally invasive marking technique for studies of small frogs requiring only shortterm retention of identification marks.
Murray, B.R. & Phillips, M.L. 2010, 'Investment in seed dispersal structures is linked to invasiveness in exotic plant species of south-eastern Australia', Biological Invasions, vol. 12, no. 7, pp. 2265-2275.
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Naturalized plant species disperse their populations over considerable distances to become invasive. We tested the hypothesis that this shift from naturalization to invasion is facilitated by increased investment of resources in seed dispersal appendages, using an assemblage of naturalized plants of south-eastern Australia. Compared with non-invasive species, we found in both cross-species and independent-contrasts analyses that invasive species invested more heavily in seed dispersal appendages, regardless of the structure present on the seed associated with the mode of dispersal (e. g., wings versus fleshy fruits). Invasive species such as Lonicera japonica, Hedera Helix and Acetosa sagittata were found to invest as much as 60-70% of total diaspore mass in dispersal appendages. The positive relationship between dispersal investment and invasion success was still prevalent after controlling for the effects of plant growth form, seed mass and capacity for vegetative growth. Our findings demonstrate that a plant's investment in dispersal appendages helps to overcome the dispersal barrier in the shift from naturalization to invasion. © 2009 Springer Science+Business Media B.V.
Manoharan, V., Yunusa, I.A.M., Loganathan, P., Lawrie, R., Skilbeck, C.G., Burchett, M.D., Murray, B.R. & Eamus, D. 2010, 'Assessments of Class F fly ashes for amelioration of soil acidity and their influence on growth and uptake of Mo and Se by canola', Fuel, vol. 89, no. 11, pp. 3498-3504.
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Coal fly ash can be used to ameliorate productivity constraints in agricultural soils, but their efficacy still remains highly variable. To ascertain the capacity of Class F fly ashes to modify pH of acidic soils, and their effects on the yield and uptake of molybdenum (Mo) and selenium (Se) by canola (Brassica napus L.), we applied two acidic and two alkaline Class F ashes at rates equivalent to 0, 12, 36, and 108 Mg/ha to the top layer (0-10 cm) of 100 cm long intact cores of acidic sandy clay and clay loam soils. Only the alkaline ash which had the highest calcium carbonate equivalent (2.43%) increased the pH of the top 10 cm of the sandy clay soil. However, this ash was also highly saline and when applied at ?36 Mg/ha it increased the electrical conductivity in the top soil layer. Increases in soil pH as a result of alkaline ash addition also elevated concentrations of Se in the plant shoot. The ashes with high concentrations of Mo and Se generally increased uptake of these elements in the plant shoot and/or seed. When these ashes were applied at 108 Mg/ha they increased the concentrations of these elements in the treated topsoil. © 2010 Elsevier Ltd. All rights reserved.
Manoharan, V., Yunusa, I.A.M., Loganathan, P., Lawrie, R., Murray, B.R., Skilbeck, C.G. & Eamus, D. 2010, 'Boron contents and solubility in Australian fly ashes and its uptake by canola (Brassica napus L.) from the ash-amended soils', Australian Journal of Soil Research, vol. 48, no. 5, pp. 480-487.
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Phytotoxicity due to excessive boron (B) uptake by plants impedes routine agronomic utilisation of coal fly ash. We assessed 11 fly ashes (pH 3.1410.77) having total B content (Bt) of 12136mg/kg, of which 2030% was hot water soluble (Bs) in the acidic ashes (pH 5) and 510% in the alkaline ashes, for their potential to supply B to plants and their risk associated with phytotoxicity. We found the Bs/Bt to be negatively correlated (R2?0.63, N?11) with ash pH. We conducted two pot trials in which canola was grown in soils amended with fly ash. In the first trial, an alkaline fly ash (Bt 66mg/kg) was incorporated at 5 rates of up to 625Mg/ha into the top 50mm of 2 acidic soils in 0.30-m-long intact cores, and sown with canola. Boron concentration in leaves at flowering reached the phytotoxic threshold, and both plant growth and seed yield were reduced, only at 625Mg/ha. In the second trial, 4 fly ashes (pH 3.2910.77, Bt 12127mg/kg) were incorporated at 4 rates of up to 108Mg/ha into the top 0.10m of 2 acidic soils in 1.0-m-long intact cores and then sown with canola. Ashes with highest Bt, when applied at 108Mg/ha, increased B concentration in the topsoil only. Of the 2 ashes with the highest B t, only that which produced low soil pH and applied at 108Mg/ha increased B concentration in the shoot, but was still below phytotoxic threshold. The results suggest that B derived from these ashes may not cause phytotoxicity and excessive soil B accumulation if the ashes are applied at modest rates (36Mg/ha) to the topsoil layers. © 2010 CSIRO.
Phillips, M.L., Murray, B.R., Leishman, M.R. & Ingram, R. 2010, 'The naturalization to invasion transition: Are there introduction-history correlates of invasiveness in exotic plants of Australia?', Austral Ecology, vol. 35, no. 6, pp. 695-703.
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Of the large number of exotic plant species that become naturalized in new geographic regions, only a subset make the transition to become invasive. Identifying the factors that underpin the transition from naturalization to invasion is important for our understanding of biological invasions. To determine introduction-history correlates of invasiveness among naturalized plant species of Australia, we compared geographic origin, reason for introduction, minimum residence time and growth form between naturalized non-invasive species and naturalized invasive plant species. We found that more invasive species than expected originated from South America and North America, while fewer invasive species than expected originated from Europe and Australasia. There was no significant difference between invasive and non-invasive species with respect to reason for introduction to Australia. However, invasive species were significantly more likely to have been resident in Australia for a longer period of time than non-invasive species. Residence times of invasive species were consistently and significantly higher than residence times of non-invasive species even when each continent of origin was considered separately. Furthermore, residence times for both invasive and non-invasive species varied significantly as a function of continent of origin, with species from South America having been introduced to Australia more recently on average than species from Europe, Australasia and North America. We also found that fewer invasive species than expected were herbs and more invasive species than expected were primarily climbers. Considered together, our results indicate a high propensity for invasiveness in Australia among exotic plant species from South America, given that they appear in general capable of more rapid shifts to invasiveness than aliens from other regions. Furthermore, our findings support an emerging global generality that introduction-history traits must be statist...
Baker, A.C. & Murray, B.R. 2010, 'Relationships between leaf-litter traits and the emergence and early growth of invasive Pinus radiata seedlings', Weed Research, vol. 50, no. 6, pp. 586-596.
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Summary: Pinus radiata is an invasive weed in Australia that spreads from plantations and establishes in surrounding native eucalypt woodlands. To determine factors linked to the invasiveness of P. radiata, we compared emergence and growth traits of P. radiata seedlings at five different depths of leaf litter under pine needles, native eucalypt leaves and an equal mix of the two. Seedling emergence, height, survival and establishment were significantly reduced as leaf-litter depth increased. Seedlings had lower root:shoot ratios and higher specific leaf area (SLA) under deeper litter treatments, shifts linked to the provision of more surface area for light capture and greater light access by seedlings. Total seedling dry weight was highest in treatments with 1 cm of litter cover due to greater moisture retention provided by a small amount of leaf litter outweighing the costs of seedling penetration through leaf litter. Importantly, we found that at any given depth of leaf litter, there were no significant differences in emergence and growth traits between pine, eucalypt or mixed leaf-litter treatments. The ability of P. radiata seedlings to succeed equally well under a range of different leaf-litter types is undoubtedly an important trait linked to its invasiveness. Given ethical concerns of introducing highly invasive species, such as P. radiata into remnant native woodland in field-based studies, glasshouse research is highly desirable and invaluable in elucidating important factors underpinning the invasiveness of weed species such as P. radiata. © 2010 The Authors. Weed Research © 2010 European Weed Research Society.
Nevill, T.C., Hancock, P.J., Murray, B.R., Ponder, W.F., Humphreys, W.F., Phillips, M.L. & Groom, P.K. 2010, 'Groundwater-dependent ecosystems and the dangers of groundwater overdraft: A review and an Australian perspective', Pacific Conservation Biology, vol. 16, no. 3, pp. 187-208.
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In many parts of the world, access to groundwater is needed for domestic, agricultural and industrial uses, and global groundwater exploitation continues to increase. The significance of groundwater in maintaining the health of rivers, streams, wetlands and associated vegetation is often underestimated or ignored, resulting in a lack of scrutiny of groundwater policy and management. It is essential that management of groundwater resources considers the needs of natural ecosystems, including subterranean. We review the limited Australian literature on the ecological impacts of groundwater overdraft and place Australian information within an international context, focusing on lentic, lotie, stygobitic and hyporheic communities as well as riparian and phreatophytic vegetation, and some coastal marine ecosystems. Groundwater overdraft, defined as abstracting groundwater at a rate which prejudices ecosystem or anthropocentric values, can substantially impact natural communities which depend, exclusively or seasonally, on groundwater. Overdraft damage is often underestimated, is sometimes irreversible, and may occur over time scales at variance to those used by water management agencies in modelling, planning and regulation. Given the dangers of groundwater overdraft, we discuss policy implications in the light of the precautionary principle, and make recommendations aimed at promoting the conservation of groundwater-dependent ecosystems within a sustainable use context.
Phillips, M.L., Murray, B.R., Pyšek, P., Pyšek, P., Pergl, J., Pergl, J., Jarošík, V., Jarošík, V., Chytrý, M. & Kühn, I. 2010, 'Plant species of the Central European flora as aliens in Australia', Preslia, vol. 82, no. 4, pp. 465-482.
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The Central European flora is an important source pool of plant species introduced to many regions throughout the world.In this study, we identifieda total of 759 plant species of the Central European flora that are currently recognized as alien species in Australia. We explored temporal patterns of introduction of these species to Australia in relation to method of introduction, growth form, naturalization status and taxonomy. Across all species, substantially larger numbers of species were introduced between 1840 and 1880 as well as between 1980 and the present, with a small peak of introductions within the 1930s. These patterns reflect early immigration patterns to Australia, recent improvements in fast and efficient transportation around the globe, and emigration away from difficult conditions brought about by the lead up to the Second World War respectively. We found that the majority of species had deliberate (69%) rather than accidental (31%) introductions and most species have not naturalized (66% casual species, 34% naturalized species). A total of 86 plant families comprising 31 tree species, 91 shrub species, 533 herbaceous species and 61 grass species present in Central Europe have been introduced to Australia. Differential patterns of temporal introduction of species were found as a function of both plant family and growth form and these patterns appear linked to variation in human migration numbers to Australia.
Wang, Y., Li, Y., Wu, Z. & Murray, B.R. 2009, 'Insular shifts and trade-offs in life-history traits in pond frogs in the Zhoushan Archipelago, China', Journal of Zoology, vol. 278, no. 1, pp. 65-73.
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Island and mainland populations of animal species often differ strikingly in life-history traits such as clutch size, egg size, total reproductive effort and body size. However, despite widespread recognition of insular shifts in these life-history traits in birds, mammals and reptiles, there have been no reports of such life-history shifts in amphibians. Furthermore, most studies have focused on one specific life-history trait without explicit consideration of coordinated evolution among these intimately linked life-history traits, and thus the relationships among these traits are poorly studied. Here we provide the first evidence of insular shifts and trade-offs in a coordinated suite of life-history traits for an amphibian species, the pond frog Rana nigromaculata. Life-history data were collected from eight islands in the Zhoushan Archipelago and neighboring mainland China. We found consistent, significant shifts in all life-history traits between mainland and island populations. Island populations had smaller clutch sizes, larger egg sizes, larger female body size and invested less in total reproductive effort than mainland populations. Significant negative relationships were found between egg size and clutch size and between egg size and total reproductive effort among frog populations after controlling for the effects of body size. Therefore, decreased reproductive effort and clutch size, larger egg size and body size in pond frogs on islands were selected through trade-offs as an overall life-history strategy. Our findings contribute to the formation of a broad, repeatable ecological generality for insular shifts in life-history traits across a range of terrestrial vertebrate taxa. © 2009 The Zoological Society of London.
Cadotte, M.W., Hamilton, M.A. & Murray, B.R. 2009, 'Phylogenetic relatedness and plant invader success across two spatial scales', Diversity and Distributions, vol. 15, no. 3, pp. 481-488.
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Aim Successful invaders often possess similar ecological traits that contribute to success in new regions, and thus under niche conservatism, invader success should be phylogenetically clustered. We asked if the degree to which non-native plant species are phylogenetically related is a predictor of invasion success at two spatial scales. Location Australia - the whole continent and Royal National Park (south-eastern Australia). Methods We used non-native plant species occupancy in Royal National Park, as well as estimated continental occupancy of these species from herbarium records. We then estimated phylogenetic relationships using molecular data from three gene sequences available on GenBank (matK, rbcL and ITS1). We tested for phylogenetic signals in occupancy using Blomberg's K. Results Whereas most non-native plants were relatively scarce, there was a strong phylogenetic signal for continental occupancy, driven by the clustering of successful species in Asteraceae, Caryophyllaceae, Poaceae and Solanaceae. However, we failed to detect a phylogenetic signal at the park scale. Main Conclusions Our results reveal that at a large spatial scale, invader success is phylogenetically clustered where ecological traits promoting success appear to be shared among close relatives, indicating that phylogenetic relationships can be useful predictors of invasion success at large spatial scales. At a smaller, landscape scale, there was no evidence of phylogenetic clustering of invasion success, and thus, relatedness plays a much reduced role in determining the relative success of invaders. © 2009 Blackwell Publishing Ltd.
Wallach, A.D., Murray, B.R. & O'Neill, A.J. 2009, 'Can threatened species survive where the top predator is absent?', Biological Conservation, vol. 142, no. 1, pp. 43-52.
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Top predators have been described as highly interactive keystone species. Their decline has been linked to secondary extinctions and their increase has been linked to ecological restoration. Several authors have recently argued that the dingo Canis lupus dingo is another example of a top predator that maintains mesopredators and generalist herbivores at low and stable numbers, thereby increasing biodiversity and productivity. Due to the sensitivity of many Australian species to introduced mesopredators and herbivores, the top predator hypothesis predicts that threatened species will not survive where dingoes are rare or absent. However, several threatened species have survived inside the Dingo Barrier Fence (DBF). We present a new view on the survival of the yellow-footed rock-wallaby Petrogale xanthopus xanthopus and the malleefowl Leipoa ocellata inside the DBF where the dingo is considered very rare, or in areas where the dingo is believed to have been eradicated several decades ago. We found that dingoes co-occurred with both threatened species. Dingoes were present at all wallaby colonies surveyed and occurred throughout their range. The most common predator detected in areas inhabited by the wallabies was in fact the dingo, and we found no significant difference between dingo abundance inside compared to outside the DBF. Malleefowl nests were found to be scent marked by dingoes at the three sites that we surveyed, despite these sites being close to human settlement and sheep farms, and in small and fragmented patches of wilderness. These findings provide further evidence for an association between the presence of dingoes and the survival of threatened species, which is in agreement with the top predator hypothesis. The results of this study challenges the current assumption that the presence and ecological consequence of dingoes in sheep country are negligible and we suggest that wildlife managers verify whether dingoes are present before predator control i...
Robson, T.C., Baker, A.C. & Murray, B.R. 2009, 'Differences in leaf-litter invertebrate assemblages between radiata pine plantations and neighbouring native eucalypt woodland', Austral Ecology, vol. 34, no. 4, pp. 368-376.
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We investigated the structure, composition and environmental correlates of leaf-litter invertebrate assemblages in Pinus radiata plantations and in neighbouring native eucalypt woodland in the Jenolan Caves Karst Conservation Reserve, south-east Australia. Invertebrate assemblages of plantations were compared with remnant eucalypt woodland located well away from the influence of plantations to determine the direct effects of plantations as a result of habitat-replacement with a non-native plantation species. We also included in our comparisons edge habitat of eucalypt woodland located immediately adjacent to plantations. This unique edge habitat is exposed to the intrusion of large volumes of pine leaf-litter from plantations, which has the potential to affect indirectly invertebrate assemblages of surrounding woodland. We found that species richness of invertebrates was significantly lower in pine plantations compared with remnant eucalypt woodland. There was a complete absence of species from 12 invertebrate orders that were found in surrounding eucalypt woodland. A rich and abundant native plant understorey that provides increased habitat heterogeneity is the most likely explanation for the richer invertebrate assemblage found in remnant eucalypt woodland. The total abundance of all invertebrate taxa in pine plantations in winter was significantly higher than in remnant eucalypt woodland, pine-litter edges and pine-free edges. Plantations were characterized by particularly high abundances of species in two orders, Acari and Collembola. High abundances of acarine and collembolan species in plantations were associated with a decompositional environment represented by comparatively higher moisture contents and higher C : N ratios of both leaf-litter and soil, higher soil conductivity and lower soil pH. We suggest that implementation of The Plantation Biodiversity Benefits Score will be a fruitful way forward to assess the environmental benefits that can be gained...
Moles, A.T., Wright, I.J., Pitman, A.J., Murray, B.R. & Westoby, M. 2009, 'Is there a latitudinal gradient in seed production?', Ecography, vol. 32, no. 1, pp. 78-82.
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We compiled data from seed rain studies at 33 sites from around the world to determine whether the greater mean seed mass of tropical plants is associated with production of fewer seeds per square meter of ground. We found no significant linear relationship between latitude and annual seed rain density, but found some evidence for a mid-latitude peak in seed rain density (quadratic relationship, p=0.018; R2=0.23). Combining seed rain data with seed mass data suggests that vegetation at the equator produces between 19 and 128 times more total mass of seed per year than does vegetation at 60°. This gradient in seed production would far outweigh the doubling in net primary productivity (NPP) over the same range of latitudes. Thus, our (admittedly small) dataset suggests that tropical vegetation allocates a much greater proportion of NPP to reproduction. This raises two important questions for the future: 1) why might tropical vegetation commit more energy to seed production than vegetation further from the equator? 2) What aspect of plant growth might receive proportionally less energy in tropical ecosystems? © 2009 Ecography.
Zhang, F., Li, Y., Guo, Z. & Murray, B.R. 2009, 'Climate warming and reproduction in Chinese alligators', Animal Conservation, vol. 12, no. 2, pp. 128-137.
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The Chinese alligator Alligator sinensis is a critically endangered species endemic to China, and one of the most endangered crocodilian species in the world. Like many other reptiles, important aspects of alligator biology such as foraging, timing of hibernation, breeding and the sex ratio of offspring are all affected by temperature variation. We examined the effects of long-term temperature change on oviposition dates and clutch sizes of the Chinese alligator in a semi-natural facility in southern China. Our study focused on two captive generations including an old breeding generation captured from the wild and a generation composed of their F1 offspring. Median oviposition date shifted to earlier in the year and mean clutch size was larger for both generations as the monthly mean air temperature in April increased over the 19 years of data collection. We observed a mean advance in oviposition date of 10days for the old breeding generation from 1987 to 2005 and 8 days for both generations from 1991 to 2005. Correspondingly, clutch sizes for the two generations also increased during this period. There were no differences in median oviposition dates and clutch sizes between the two generations from 1991 to 2005. Our results suggest that Chinese alligators have responded to increasing global temperatures. Our findings also suggest that recent increasing global temperatures have the potential to have a substantial effect on Chinese alligator populations in the wild, thus prompting an urgent need for field monitoring of the effects of global warming on this endangered alligator species. © Journal compilation © 2009 The Zoological Society of London.
Murray, B., Baker, A.C. & Robson, T.C. 2009, 'Impacts of the replacement of native woodland with exotic pine plantations on leaf-litter invertebrate assemblages: a test of a novel framework', International Journal of Ecology, vol. 2009, no. 49035, pp. 1-6.
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We present an empirical comparison of invertebrate community sturcture between aereras of undisturbed native eucalypt woodland and areas that have been cleared and replaced with plantations of exotic radiata pine (Pinus radiata). Implementation of a novel conceptual framework revealed that both insect (in autumn) and arachnid (in winter) assemblages demonstrated inhibition in response to the pine plantations.
Hills, N., Hose, G.C., Cantlay, A.J. & Murray, B.R. 2008, 'Cave invertebrate assemblages differ between native and exotic leaf litter', Austral Ecology, vol. 33, no. 3, pp. 271-277.
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Allochtonous leaf litter is an important source of energy and nutrients for invertebrates in cave ecosystems. A change to the quality or quantity of litter entering caves has the potential to disrupt the structure and function of cave communities. In this study, we adopted an experimental approach to examine rates of leaf litter decomposition and the invertebrate assemblages colonizing native and exotic leaf litter in limestone caves in the Jenolan Caves Karst Conservation Reserve, New South Wales, Australia. We deployed traps containing leaf litter from exotic sycamore (Acer pseudoplatanus) and radiata pine (Pinus radiata) trees and native eucalypts (Eucalyptus spp.) in twilight zones (near the cave entrance) and areas deep within the caves for 3 months. Thirty-two invertebrate morphospecies were recorded from the litter traps, with greater richness and abundance evident in the samples from the twilight zone compared with areas deep within the cave. Sycamore litter had significantly greater richness and abundance of invertebrates compared with eucalypt and pine litter in samples from the twilight zone, but there was no difference in richness or abundance among litter samples placed deep within the cave. Relative rates of decay of the three litters were sycamore > eucalypt > pine. We discuss the potential for the higher decomposition rates and specific leaf area in sycamores to explain their higher invertebrate diversity and abundance. Our findings have important implications for the management of exotic plants and the contribution of their leaf litter to subterranean ecosystems. © 2008 The Authors.
Yunusa, I.A.M., Manoharan, V., DeSilva, D.L., Eamus, D., Murray, B.R. & Nissanka, S.P. 2008, 'Growth and elemental accumulation by canola on soil amended with coal fly ash', Journal of Environmental Quality, vol. 37, no. 3, pp. 1263-1270.
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To explore the agronomic potential of an Australian coal fly ash, we conducted two glasshouse experiments in which we measured chlorophyll fluorescence, CO2 assimilation (A), transpiration, stomacal conductance, biomass accumulation, seed yield, and elemental uptake for canola (Brassica napus) grown on soil amended with an alkaline fly ash. In Experiment 1, application of up to 25 Mg/ha of fly ash increased A and plant weight early in the season before flowering and seed yield by up to 21%. However, at larger rates of ash application A, plant growth, chlorophyll concentration, and yield were all reduced. Increases in early vigor and seed yield were associated with enhanced uptake of phosphorus (P) by the plants treated with fly ash. Fly ash application did not influence accumulation of B, Cu, Mo, or Zn in the stems at any stage of plant growth or in the seed at harvest, except Mo concentration, which was elevated in the seed. Accumulation of these elements was mostly in the leaves, where concentrations of Cu and Mo increased with any amount of ash applied while that of B occurred only with ash applied at 625 Mg/ha. In Experiment 2, fly ash applied at 500 Mg/ha and mixed into die whole 30 cm soil core was detrimental to growth and yield of canola, compared with restricting mixing to 5 or 15 cm depth. In contrast, application of ash at 250 Mg/ha with increasing depth of mixing increased A and seed yield. We concluded that fly ash applied at not more than 25 Mg/ha and mixed into the top 10 to 15 cm of soil is sufficient to obtain yield benefits. Copyright © 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.
Harris, C.J., Murray, B.R., Hose, G.C. & Hamilton, M.A. 2007, 'Introduction history and invasion success in exotic vines introduced to Australia', Diversity and Distributions, vol. 13, no. 4, pp. 467-475.
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The ecological damage caused by invasive vines poses a considerable threat to many natural ecosystems. However, very little data are available for this potentially environmentally destructive functional group in Australia. In order to address this paucity of information, we assembled the first inventory of exotic vines that have become established in natural ecosystems across Australia. The influence that introduction history attributes, variables that relate to the introduction of a species to a new area, may have on the occurrence and distribution of exotic vines was also determined. We asked whether the continent of origin, reason for introduction, and residence time related to the prevalence and distribution of exotic vines across Australia. A total of 179 exotic climbing plant species from 40 different families were found to have become established across continental Australia. However, five families accounted for over 50% of these species. Most exotic vines originated from South America, and were introduced for ornamental purposes. The length of time in which an exotic vine had been present in its new range was significantly related to its distribution, with a positive relationship found between residence time and area of occupancy across the continent. No other introduction history attribute was significantly related to the area of occupancy, or distribution, of a species. This suggests that while the trends found among introduction history attributes are important in explaining the prevalence of exotic vines in Australia, only residence time is currently a useful predictor of their future success. © 2007 The Authors.
Baker, A.C., Murray, B.R. & Hose, G.C. 2007, 'Relating pine-litter intrusion to plant-community structure in native eucalypt woodland adjacent to Pinus radiata (Pinaceae) plantations', Australian Journal of Botany, vol. 55, no. 5, pp. 521-532.
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Radiata pine (Pinus radiata D.Don) plantations are often found in close proximity to vegetation set aside for biodiversity conservation. We examined the intrusive effects of radiata pine beyond the confines of plantations by quantifying the penetration of pine litter (needles, cones, twigs and seeds) and wildings from plantations into adjacent eucalypt woodland in the Jenolan Caves Karst Conservation Reserve (south-eastern Australia). We then investigated the relationship between pine-litter intrusion and plant-community structure in adjacent woodland vegetation. We found significantly higher quantities of pine litter and wildings at all sites adjacent to plantations than at reference woodland sites that were not adjacent to plantations. At adjacent sites, pine litter decreased significantly with increasing distance from plantations. Alarmingly, native plant species richness declined and exotic plant species richness increased with increasing quantities of pine litter. Thus, there were fewer native plant species and more exotics in areas bordering pine plantations. Our findings suggest a potentially important link between the intrusion of pine litter and a loss of native biodiversity and facilitation of exotic-species invasion. We suggest the provision of a buffer zone around plantations in order to minimise intrusive impacts of plantations on native biodiversity. © CSIRO 2007.
Yunusa, I.A.M., Eamus, D., DeSilva, D.L., Murray, B.R., Burchett, M.D., Skilbeck, G.C. & Heidrich, C. 2006, 'Fly-ash: An exploitable resource for management of Australian agricultural soils', Fuel, vol. 85, no. 16 SPEC. ISS., pp. 2337-2344.
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Agricultural soils in Australia have inherent limitations of structural and nutritional nature that pose major constraints to crop productivity. These soils are still productive due to intensive management that involves routine treatments with lime and gypsum at significant costs both to the farmer and the environment. Production costs associated with these inputs average about 30% of the total cost of soil treatment. Furthermore, reserves of gypsum are under pressure. There is therefore an opportunity for the more than 13 million tonnes of coal combustion products (CCPs) produced annually by coal-fired power stations to be utilised in the management of agricultural soils. At present, about 70% of the ash is emplaced within landfills. In this paper we briefly describe the main constraints of major agricultural soils that could be ameliorated with fly-ash. We used a model to estimate that application of fine (<20 ?m) fly-ash to the top 0.15 m coarse textured (sandy) soil would reduce hydraulic conductivity by 25% and so improve water-holding capacity. The same treatment of fine textured clayey soil with coarse (>20 ?m) fly-ash would increase conductivity by up to 20%. We cite examples of studies that have shown beneficial use of coal-ash for crop production, including our ongoing glasshouse study in which fly-ash was found to increase early growth vigour and seed yield by 20% for canola (Brassica napus). There are several issues, including costs and regulation, and knowledge-gaps that need to be addressed before adoption of CCP for routine soil management. &copy; 2006 Elsevier Ltd. All rights reserved.
Wu, Z., Li, Y. & Murray, B.R. 2006, 'Insular shifts in body size of rice frogs in the Zhoushan Archipelago, China', Journal of Animal Ecology, vol. 75, no. 5, pp. 1071-1080.
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1. Differences in body size between mainland and island populations have been reported for reptiles, birds and mammals. Despite widespread recognition of insular shifts in body size in these taxa, there have been no reports of such body size shifts in amphibians. 2. We provide the first evidence of an insular shift in body size for an amphibian species, the rice frog Rana limnocharis. We found significant increases in body size of rice frogs on most sampled islands in the Zhoushan archipelago when compared with neighbouring mainland China. 3. Large body size in rice frogs on islands was significantly related to increased population density, in both breeding and non-breeding seasons. Increases in rice frog density were significantly related to higher resource availability on islands. Increased resource availability on islands has led to higher carrying capacities, which has subsequently facilitated higher densities and individual growth rates, resulting in larger body size in rice frogs. We also suggest that large body size has evolved on islands, as larger individuals are competitively superior under conditions of harsh intraspecific competition at high densities. 4. Increases in body size in rice frogs were not related to several factors that have been implicated previously in insular shifts in body size in other taxa. We found no significant relationships between body size of rice frogs and prey size, number of larger or smaller frog species, island area or distance of islands from the mainland. 5. Our findings contribute to the formation of a broad, repeatable ecological generality for insular shifts in body size across a range of terrestrial vertebrate taxa, and provide support for recent theoretical work concerning the importance of resource availability for insular shifts in body size. &copy; 2006 The Authors.
Murray, B.R., Hose, G.C., Eamus, D. & Licari, D. 2006, 'Valuation of groundwater-dependent ecosystems: A functional methodology incorporating ecosystem services', Australian Journal of Botany, vol. 54, no. 2, pp. 221-229.
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Groundwater-dependent ecosystems (GDEs) are ecosystems that must have access to groundwater to maintain their ecological structure and function. Rapidly expanding numbers of humans are placing increased demands on groundwater for consumption, industry and agriculture. These demands alter groundwater regimes of GDEs that have evolved over millennia, resulting in the degradation of ecosystem health. As a consequence, the goods and services (ecosystem services) that GDEs provide for humans, which include food production and water purification, are at serious risk of being lost. Effective management of GDEs and their ecosystem services requires prioritisation of the most valuable ecosystems, given that increasing human demands and limited time and money preclude complete protection of all GDEs. Here, we provide an eight-step method for the valuation and initial prioritisation of GDEs. The proposed methodology improves on previous, primarily subjective methods for the valuation of GDEs by employing both economic valuation of the ecosystem services provided by GDEs, and ecological valuation of significant environmental attributes of GDEs. We apply the eight-step method to a hypothetical case study in order to demonstrate its applicability to a catchment containing a range of GDEs of different sizes, each possessing its own suite of threatened taxa. The major benefit of the valuation methodology presented here is that it can be used at three levels of complexity: (1) a full-desktop study, (2) a semi-desktop study requiring stakeholder consultation, and (3) a full field-based study, according to the time and money available for initial prioritisation efforts. &copy; CSIRO 2006.
Cadotte, M.W., Murray, B.R. & Lovett-Doust, J. 2006, 'Ecological patterns and biological invasions: Using regional species inventories in macroecology', Biological Invasions, vol. 8, no. 4, pp. 809-821.
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Macroecology depends heavily on a comparative methodology in order to identify large-scale patterns and to test alternative hypotheses that might generate such patterns. With the advent and accessibility of large electronic databases of species and their life history and ecological attributes, ecologists have begun seeking generalities, and examining large-scale ecological hypotheses involving core themes of range, abundance and diversity. For example, combinations of ecological, life history and phylogenetic data have been analysed using large species sets to test hypotheses in invasion biology. Analysis of regional species inventories can contribute cogently to our understanding of invasions. Here we examine several ways in which database analysis is effective. We review 19 studies of comparative invasions biology, each using >100 species of plants in their analyses, and show that invader success is linked to seven correlates: short life cycle, abiotic (mostly wind) dispersal, large native range size, non-random taxonomic patterns (emphasizing certain families or orders), presence of clonal organs, occupying disturbed habitats, and earlier time of introduction. These phylogenetically influenced, comparative analyses using regional species inventories are only just beginning and have much potential. &copy; Springer 2006.
Hose, G.C., Murray, B.R., Park, M.L., Kelaher, B.P. & Figueira, W.F. 2006, 'A meta-analysis comparing the toxicity of sediments in the laboratory and in situ', Environmental Toxicology and Chemistry, vol. 25, no. 4, pp. 1148-1152.
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Sediment toxicity tests in the laboratory are an important part of ecological risk assessments, yet how they relate to sediment toxicity in situ has rarely been explored. Using meta-analysis, we examined differences in the toxicity of sediment tested in the laboratory and in situ. Data from four published studies were subjected to rigorous statistical analyses. Overall, the toxicity of sediments in laboratory tests was substantially less than their toxicity in situ. Differences between laboratory and in situ toxicity, expressed using the log odds ratio effect size, varied significantly among published studies. Effect size increased significantly with increasing sediment toxicity, showing that the more toxic the sediment, the greater the disparity between laboratory and field toxicities. Our findings may not apply to all laboratory/field comparisons; however, we consider that the overlying water in field situations is a significant contributor to this relationship through additional contamination and toxicity. Our findings also have important implications for the use of laboratory tests to assess improvements in sediment quality and remediation, because changes in laboratory toxicity may not reflect the true improvements to sediment quality in situ. &copy; 2006 SETAC.
Eamus, D., Froend, R., Loomes, R., Hose, G. & Murray, B. 2006, 'A functional methodology for determining the groundwater regime needed to maintain the health of groundwater-dependent vegetation', Australian Journal of Botany, vol. 54, no. 2, pp. 97-114.
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In the past, the phrase 'environmental allocations of water' has most often been taken to mean allocation of water to rivers. However, it is now accepted that groundwater-dependent ecosystems are an important feature of Australian landscapes and require an allocation of water to maintain their persistence in the landscape. However, moving from this theoretical realisation to the provision and implementation of a field-based management regime is extremely difficult. The following four fundamental questions are identified as being central to the effective management of groundwater-dependent ecosystems (GDEs): (1) How do we identify GDEs in the field; put another way, which species or species assemblages or habitats are reliant on a supply of groundwater for their persistence in the landscape; (2) what groundwater regime is required to ensure the persistence of a GDE; (3) how can managers of natural resources (principally water and habitats), with limited time, money and other resources, successfully manage GDEs; and (4) what measures of ecosystem function can be monitored to ensure that management is effective? This paper explicitly addresses these questions and provides a step-by-step theoretical and practical framework for providing answers. In particular, this paper provides an introduction to some of the relevant literature and from this, presents a synthesis, presented in the form of a functional methodology for managing groundwater dependent ecosystems. &copy; CSIRO 2006.
Baker, A.C., Hose, G.C. & Murray, B.R. 2006, 'Vegetation responses to Pinus radiata (D. Don) invasion: A multivariate analysis using principal response curves', Proceedings of the Linnean Society of New South Wales, vol. 127, no. 1, pp. 191-197.
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Radiata pine (Pinus radiata D. Don) has been introduced to many new regions outside its native range as a plantation species. Plantations are frequently located adjacent to native vegetation. This proximity allows not only pine wildings, but also large amounts of non-native leaf litter, to enter the surrounding natural vegetation. Our aim in the present study was to assess the composition of plant communities in vegetation surrounding plantations in relation to proximity to pine plantations. Using multivariate Principal Response Curves (PRC) analysis, we show significant differences in the composition of native vegetation between transects adjacent to and not adjacent to pine plantations. Species-level analysis identified a suite of native species that were frequently found in transects adjacent to pine plantations, and a second suite of native species that were reduced in abundance in transects next to pine plantations. This second group of species should be the focus of future conservation work, since they appear to be sensitive to disturbance wrought by pine plantations. We show that the ability of PRC analysis to reveal both community-level and species-level responses to disturbance brought about by exotic species can lead to the generation of testable hypotheses bridging species and community ecology.
Cadotte, M.W., Cadotte, M.W., Murray, B.R. & Lovett-Doust, J. 2006, 'Evolutionary and ecological influences of plant invader success in the flora of Ontario', Ecoscience, vol. 13, no. 3, pp. 388-395.
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It is not clear why some species are able to naturalize and spread in a new region while so many other species are not.Several general properties have been reported for successful non-indigenous plant species (NIPS). These include presence of a lag time and population expansion following invasion, arrival from a similar climate, ability to self-fertilize, a short lifespan, clonal growth (if perennial), and production of small fruits. We examined these patterns in comparisons of all recorded abundant and rare NIPS in Ontario (n = 1153). We used cross-species and phylogenetic regressions to examine ecological patterns across present-day species and to determine whether evolutionary divergences in NIPS success have been correlated consistently with divergences in any of the life-history traits. We found a significant time lag in invader spread, with species arriving after 1952 being more likely to be rare. Successful invaders (i.e., abundant NIPS) were significantly over-represented among species originating in Europe and Eurasia. Successful invaders were significantly more likely to demonstrate clonal growth, to grow on variable soil moistures, and to have comparatively long flowering periods. While analyses such as this do not reveal causal mechanisms for the observed patterns, our correlative findings suggest important mechanisms for NIPS success that we discuss in light of the theoretical expectations of the attributes of successful plant invaders.
Murray, B.R. & Hose, G.C. 2005, 'The interspecific range size-body size relationship in Australian frogs', Global Ecology and Biogeography, vol. 14, no. 4, pp. 339-345.
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Aim: There is substantial residual scatter about the positive range size-body size relationship in Australian frogs. We test whether species' life history and abundance can account for this residual scatter. Location. Australia. Methods: Multiple regressions were performed using both cross-species and independent contrasts analyses to determine whether clutch size, egg size and species abundance account for variation in range size over and above the effects of body size. Results: In both cross-species and independents contrasts models with body size, clutch size and egg size as predictors, partial r2 values revealed that only egg size was significantly and uniquely related to range size. Contrary to expectation, neither body size nor clutch size could account for significant variation in range size. Incorporating species abundance as a predictor in further multiple regression analysis demonstrated that while abundance accounted for a significant proportion of range size variation, the contribution of egg size was reduced but still significant. Notably, non-significant relationships persisted between range size and both body size and clutch size. Conclusions: The weak positive correlation between body size and range size in Australian frogs disappears after accounting for species abundance and egg size. Our findings demonstrate that species with both high local abundance and small eggs occupy comparatively wider geographical ranges than species with low abundance and large eggs. &copy; 2005 Blackwell Publishing Ltd.
Murray, B.R. & Hose, G.C. 2005, 'Life-history and ecological correlates of decline and extinction in the endemic Australian frog fauna', Austral Ecology, vol. 30, no. 5, pp. 564-571.
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Frog populations are rapidly disappearing throughout the world. An important issue for ecologists to resolve is why some frog species are more susceptible to decline than others. Here, we performed a comparative study of the endemic Australian frog fauna to determine whether the life history and ecology of declining species have predisposed them to extinction. Decline was consistently found to be correlated with geographical range size across contemporary species and in analyses based on phylogenetically independent contrasts (PICs). Species with narrow geographical ranges have been disproportionately more susceptible to decline. Across species, decline was also correlated with large body size and a high proportion of the geographical range overlapping with the distribution of cane toads and landscape stress (e.g. land clearing). We show that with the exception of range size, however, correlates of decline across species are underpinned by a small number of evolutionary events. Hence, the suite of traits that correlate with decline in the cross-species analysis is only relevant to a small number of clades. We also found that clutch size, testes mass, ova size and distributional overlap with feral pigs were not significantly related to decline. In the ongoing search for life-history and ecological correlates of decline and extinction, our results highlight the importance of performing analyses across contemporary species and using PICs.
Murray, B.R., Kelaher, B.P., Hose, G.C., Figueira, W.F. & Leishman, M.R. 2005, 'A meta-analysis of the interspecific relationship between seed size and plant abundance within local communities', Oikos, vol. 110, no. 1, pp. 191-194.
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Hose, G.C., Gordon, G., McCullough, F.E., Pulver, N. & Murray, B.R. 2005, 'Spatial and rainfall related patterns of bacterial contamination in Sydney Harbour estuary', Journal of Water and Health, vol. 3, no. 4, pp. 349-358.
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Water quality in recreational areas in Sydney Harbour, Australia, was analysed first to identify spatial patterns in faecal coliform and enterococci densities, and then to determine the relationship between bacterial densities and catchment rainfall. Non-metric multidimensional scaling separated sites closest to the mouth of the harbour from those further up the harbour's west and north-west arms. Sites closest to the harbour mouth generally had lower frequencies of high bacterial densities that exceeded median water quality guideline values. We attribute this to greater tidal flushing at sites closer to the harbour mouth. Eight site groups were identified within the harbour. Within each group, multiple regression analyses indicated rainfall accounted for between 15 and 66% of the variability in the bacterial densities. Variation in bacterial densities explained by rainfall was lower for sites closer to the harbour mouth where tidal flushing is greatest. Thus, our findings indicate that simple rainfall-based regression models are appropriate for predicting bacterial concentrations when flushing at a site is limited. More complex models incorporating a suite of environmental variables may improve the ability to predict bacterial concentrations at well-flushed sites, but even then, their predictive ability may be low. &copy; IWA Publishing 2005.
Eamus, D., Macinnis-Ng, C.M.O., Hose, G.C., Zeppel, M.J.B., Taylor, D.T. & Murray, B.R. 2005, 'Ecosystem services: An ecophysiological examination', Australian Journal of Botany, vol. 53, no. 1, pp. 1-19.
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This review aims to discuss ecosystem services, provide illustrative case studies at catchment and local scales and present future research needs. This review discusses the following: (1) Ecosystem services (ES) are those goods and services that are provided by or are attributes of ecosystems that benefit humans. Examples of ES include the timber derived from a forest, the prevention of soil and coastal erosion by vegetation and the amelioration of dryland salinity through prevention of rises in the water table by trees. The provision of ES globally is in decline because of a lack of awareness of the total economic value of ES in the public, policy and political fora. (2) Providing a scientific understanding of the relationships among ecosystem structure, function and provision of ES, plus determining actual economic value of ES, are the central challenges to environmental scientists (including triple-bottom-line economists). (3) Some ES are widely dispersed throughout many different ecosystems. Carbon accumulation in trees and the contribution of biodiversity to ES provision are two examples of highly dispersed attributes common to many ecosystems. In contrast, other ES are best considered within the context of a single defined ecosystem (although they may occur in other ecosystems too). Mangroves as 'nursery' sites for juvenile fish is one example. (4) Examples of catchment-scale and local-scale provision of ES are discussed, along with future research issues for the nexus between ES and environmental sciences. &copy; CSIRO 2005.
Hamilton, M.A., Murray, B.R., Cadotte, M.W., Hose, G.C., Baker, A.C., Harris, C.J. & Licari, D. 2005, 'Life-history correlates of plant invasiveness at regional and continental scales', Ecology Letters, vol. 8, no. 10, pp. 1066-1074.
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We implemented cross-species and independent-contrasts multiple regression models to compare life-history correlates of invasion success between regional and continental spatial scales among non-native plants of eastern Australia. We focussed on three life-history traits that represent major axes of variation in plant life history: specific leaf area (SLA), plant height and seed mass. After controlling for residence time and cross-correlation with other life-history traits, small seed mass was significantly and uniquely correlated with invasion success at continental and regional scales. High SLA was significantly and uniquely correlated with invasion success at the continental scale only. Plant height could not explain unique variation in invasion success at either spatial scale. Variation among spatial scales in the significance and strength of life-history relationships with invasion success suggests that the search for predictive tools of invasion need not be fruitless, as long as predictive investigations are targeted at appropriate spatial scales. &copy;2005 Blackwell Publishing Ltd/CNRS.
Pohlman, C.L., Pohlman, C.L., Nicotra, A.B. & Murray, B.R. 2005, 'Geographic range size, seedling ecophysiology and phenotypic plasticity in Australian Acacia species', Journal of Biogeography, vol. 32, no. 2, pp. 341-351.
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Aim: The degree to which eco-physiological traits critical to seedling establishment are related to differences in geographic range size among species is not well understood. Here, we first tested the idea that seedling ecophysiological attributes associated with establishment differ between narrowly distributed and geographically widespread plant species. Secondly, we tested the notion that species occupying wide geographic ranges have greater phenotypic plasticity in response to the environment than contrasted species with more restricted distributions. Location: Eastern Australia. Methods: We compared five pairs of geographically restricted and widespread Acacia species grown under glasshouse conditions for differences in seedling relative growth rate and associated allocational, morphological and physiological traits. We then examined whether widespread species displayed greater phenotypic plasticity in these traits than narrowly distributed species in response to changes in soil water availability. Results: Neither relative growth rate nor any measure of biomass accumulation or allocation differed significantly between seedlings of narrowly distributed and widespread species. In addition, the plasticity of biomass allocation was not greater in widespread species. However, the leaflets of widespread species had higher photosynthetic capacity and greater plasticity of water use efficiency than the leaflets of narrowly distributed species. Main conclusions: We demonstrated fundamental differences in the physiology and plasticity of leaflets of widespread and narrowly distributed species. The greater plasticity of these seedling leaflet traits may allow widespread Acacia species to utilize a wider range of environmental conditions in relation to soil moisture than restricted Acacia species. However, we did not find corresponding differences in mean or plasticity of seedling growth and allocational traits. In general, we suggest that relationships between rarity ...
Murray, B.R. & Lepschi, B.J. 2004, 'Are locally rare species abundant elsewhere in their geographical range?', Austral Ecology, vol. 29, no. 3, pp. 287-293.
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Ecologists have long sought to understand why some species are rare and others common. For the most part, inconsistent relationships between local rarity and underlying mechanisms have emerged. One possibility for this inconsistency is that locally rare species may not always be rare. However, it is largely unknown whether most locally rare species in a community possess the capacity to become abundant elsewhere in their geographical range. Here, we identified 57 locally rare plant species of open forest in south-eastern Australia. We found that most of these species (91%) occurred in higher abundance at other sites within their geographical range (somewhere-abundant species), while the remaining small percentage of locally rare species were consistently rare (everywhere-sparse species). Somewhere-abundant species had significantly smaller seeds on average than everywhere-sparse species in cross-species regression analysis. This pattern was not maintained when the influence of other life-history attributes was controlled for, or when phylogenetic relatedness among species was considered explicitly in phylogenetic regression analysis. In both cross-species and phylogenetic regressions, somewhere-abundant and everywhere-sparse species did not differ significantly with respect to growth form, height, regeneration-after-fire strategy, or dispersal. Our findings provide further evidence for the notion that theories to account for local rarity which are couched in terms of within-community interactions alone are incomplete for the majority of species, because they need to account for different outcomes in different places.
McPherson, S., Eamus, D. & Murray, B.R. 2004, 'Seasonal impacts on leaf attributes of several tree species growing in three diverse ecosystems of south-eastern Australia', Australian Journal of Botany, vol. 52, no. 3, pp. 293-301.
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Patterns of leaf attributes were examined for six woody species growing in a eucalypt woodland, a mangrove, or a heathland in coastal New South Wales, Australia, during winter and summer. It was found that the rate of assimilation per unit leaf dry mass (Amass) of the mangrove species was largest, woodland species exhibiting an intermediate rate and heathland species the smallest values of Amass. Mean habitat Amass did not change from winter to summer in the woodland or mangrove species but increased significantly in the heathland species. Average specific leaf area (SLA) was largest for the mangrove species and smallest for the heathland species, with woodland species showing intermediate values. SLA of all species within a habitat did not change from winter to summer. Mean foliar nitrogen content (Nmass) of the mangrove species was highest, intermediate for woodland species and lowest for heathland species. Nmass was significantly related to Amass in both summer and winter and the individual slopes for this relationship in the summer and winter differed. In contrast, a common slope was fitted to the relationship between SLA and A mass for the two seasons. A common slope between seasons was also shown for the relationship between SLA and Nmass. There was no significant difference in slope elevation between summer and winter for the SLA v. Nmass relationship. Trends within relationships among leaf attributes were the same as those found for a wide range of plant species worldwide, but the absolute values were lower than those found elsewhere. Therefore, the 'global relationships' in terms of trends (positive or negative) that have been determined overseas apply in Australia but the elevation of the slope and the magnitude of the slope are reduced (Amass v. N mass) or increased (Amass v. SLA and Nmass v. SLA) compared with global trends.
Hose, G.C., Murray, B.R. & Eamus, D. 2004, 'Water quality guidelines to protect groundwater-dependent ecosystems', Ecological Management and Restoration, vol. 5, no. 1, pp. 78-80.
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Zeppel, M.J.B., Murray, B.R., Barton, C. & Eamus, D. 2004, 'Seasonal responses of xylem sap velocity to VPD and solar radiation during drought in a stand of native trees in temperate Australia', Functional Plant Biology, vol. 31, no. 5, pp. 461-470.
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Xylem sap velocity of two dominant tree species, Eucalyptus crebra F. Muell. and Callitris glaucophylla J. Thompson & L.A.S. Johnson, in a native remnant forest of eastern Australia was measured in winter and summer during a prolonged (> 12 months) and extensive drought. The influence of vapour pressure deficit (VPD) and solar radiation levels on the velocity of sap was determined. Pronounced hysteresis in sap velocity was observed in both species as a function of VPD and solar radiation. However, the rotation of the hysteresis curve was clockwise for the response of sap velocity to VPD but anti-clockwise in the response of sap velocity to radiation levels. A possible reason for this difference is discussed. The degree of hysteresis (area bounded by the curve) was larger for the VPD response than the response to solar radiation and also varied with season. A simple linear model was able to predict sap velocity from knowledge of VPD and solar radiation in winter and summer. The consistent presence of hysteresis in the response to sap velocity to VPD and solar radiation suggests that large temporal and spatial models of vegetation water use may require some provision for the different responses of sap velocity, and hence water use, to VPD and solar radiation, between morning and afternoon and between seasons.
Murray, B.R., Brown, A.H.D., Dickman, C.R. & Crowther, M.S. 2004, 'Geographical gradients in seed mass in relation to climate', Journal of Biogeography, vol. 31, no. 3, pp. 379-388.
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Aim: To determine whether latitudinal and longitudinal gradients in seed mass are related to variation in climatic features including temperature, solar radiation and rainfall. Location: Australia. Methods: Seed mass was estimated from over 1600 provenances covering the latitudinal and longitudinal extents of 34 perennial Glycine taxa in Australia. Climatic data were obtained from ANUCLIM 5.1 for collection locations based on long-term meteorological records across Australia. These climatic data were subject to principal components analysis to extract three components as climatic indices. Generalized linear models were used in three separate sets of analyses to evaluate whether seed mass-latitude and seed mass-longitude relationships persisted after taking climatic variation into account. First, relationships were examined across species in analyses that did not explicitly consider phylogenetic relationships. Secondly, phylogenetic regressions were performed to examine patterns of correlated evolutionary change throughout the Glycine phylogeny. Within-species analysis was also performed to examine consistency across different taxonomic levels. Results: Geographical variation in seed mass among species was related primarily to temperature and solar radiation, while rainfall was much less influential upon seed mass. Partialing out the influence of temperature and solar radiation in models resulted in the disappearance of significant seed mass-latitude and seed mass-longitude relationships. Patterns within species were generally consistent with patterns among species. However, in several species, factors additional to these climatic variables may contribute to the origin and maintenance of geographical gradients in seed mass, as significant seed mass-latitude and seed mass-longitude relationships remained after controlling for the influence of climatic variables. Main conclusions: Our empirical results support the hypotheses that (1) seed mass is larger at low latit...
Hose, G.C., Murray, B. & Eamus, D. 2004, 'Water quality guidelines to protect groundwater-dependent ecosystems', Ecological Management & Restoration, vol. 5, pp. 78-80.
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Murray, B. 2003, 'Reproductive characteristics of Road-verge and Reserve-interior populations of Exocarpos cupressiformis Labill (Santalaceae)', The Victorian Naturalist, vol. 120, no. 1, pp. 10-14.
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Murray, B.R., Zeppel, M.J.B., Hose, G.C. & Eamus, D. 2003, 'Groundwater-dependent ecosystems in Australia: It's more than just water for rivers', Ecological Management and Restoration, vol. 4, no. 2, pp. 110-113.
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Murray, B.R. & Leishman, M.R. 2003, 'On the relationship between seed mass and species abundance in plant communities', Oikos, vol. 101, no. 3, pp. 643-645.
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Zeppel, M.J.B., Murray, B.R. & Eamus, D. 2003, 'The potential impact of dryland salinity on the threatened flora and fauna of New South Wales', Ecological Management and Restoration, vol. 4, no. SUPPL..
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We used digital map overlays in a geographical information system (GIS) to quantify the potential impact of dryland salinity on the threatened flora and fauna of New South Wales (NSW). Geographical areas of conservation priority were identified based on richness of threatened species with distribution records overlapping dryland salinity. Two alternative schemes - Interim Biogeographical Regionalization for Australia (regions) and catchment boundaries (catchments) - were used to subdivide NSW. Sydney Basin, North Coast and South-western Slopes regions - and Hunter, Sydney, Macquarie, Murrumbidgee and Lachlan catchments - were identified as priority areas with more than 10 salinity-overlap species present. Five threatened plant species were identified as priority species due to more than half of their known distributions overlapping areas of dryland salinity. Threatened animal species of most concern had 10-50% of their records overlapping areas of dryland salinity. Our findings demonstrate that landscape exposure to dryland salinity should be used in conjunction with total richness of threatened species for prioritizing conservation of geographical areas with respect to the potential impact of dryland salinity on threatened species.
Murray, B.R., Brown, A.H.D. & Grace, J.P. 2003, 'Geographic gradients in seed size among and within perennial Australian Glycine species', Australian Journal of Botany, vol. 51, no. 1, pp. 47-56.
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In the Northern Hemisphere, a latitudinal gradient of increasing seed size towards the equator has been well documented. Because of a paucity of studies from the Southern Hemisphere, however, the global generality of this latitudinal gradient in seed size is unknown. This study investigated variation in seed size in relation to latitude among and within perennial Glycine species across Australia. Seed size was estimated from over 1500 provenances covering the latitudinal, longitudinal and altitudinal extents of 37 taxa within the subgenus. In order to ensure that any observed latitudinal gradient in seed size existed independently of two other major geographic variables, longitude and altitude, we controlled for their influence via the use of general linear models. Among species, a significant negative relationship emerged between seed size and latitude when latitude was considered on its own and after accounting for the influence of longitude and altitude in models. For Australian populations of the subgenus Glycine, mean species seed size increased by 4.23% with each shift of one degree of latitude towards the equator and increased significantly along an east-west cline across the continent, by 2.25% with each degree of longitude. This latter relationship was obtained both when longitude was considered on its own and after controlling for the influence of latitude and altitude in models. Patterns of seed size variation with latitude and longitude within species mirrored patterns among species, although there were some notable exceptions. Altitude was significantly related to seed size among species only after removing the linear effects of latitude and longitude, when the trend was for lowland species to have smaller seeds. In contrast to the interspecific pattern, some intraspecific negative trends were found within G. canescens and G. cyrtoloba, which accords with Baker's hypothesis for an inverse relation between seed size and altitude. We discuss the relati...
Murray, B.R., Thrall, P.H. & Lepschi, B.J. 2002, 'Relating species rarity to life history in plants of eastern Australia', Evolutionary Ecology Research, vol. 4, no. 7, pp. 937-950.
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We examined species rarity in relation to life history in plants of eastern Australia. Correlated-divergence analysis (using phylogenetically independent contrasts) and cross-species analysis (exploring patterns across present-day species) were employed in a complementary fashion to test the hypothesis that rare and common species differed with respect to life history. Two measures of rarity, threat of extinction and geographical range size, were investigated for relationships with growth form, longevity, pollination mode, mating system, dispersal and seed mass. Species threatened with extinction had, on average, significantly smaller seed mass than non-threatened species. This emerged in both correlated-divergence and cross-species analyses, independently of the effects of the other life-history traits. In cross-species analysis, but not as phylogenetic contrasts, a significant number of species with short life spans were less likely to be threatened with extinction. This arose because most short-lived species not threatened with extinction diverged from long-lived species threatened with extinction at a major node deep in the phylogenetic tree (where monocotyledons diverged from dicotyledons). Mating system was significantly related to geographical range size in correlated-divergence analysis, but not across present-day species. There was evidence that evolutionary divergences for dioecy have been significantly correlated with the occupation of a wide geographical range, although this relationship has not been maintained across present-day species. Growth form, pollination mode and dispersal could not account significantly for variation in either threat of extinction or range size. Because relationships for plants of eastern Australia were found to differ considerably from those emerging for other species assemblages on other continents, support is provided for the notion that associations between species rarity and life history are highly dependent on geograph...
Murray, B.R., Thrall, P.H., Gill, A.M. & Nicotra, A.B. 2002, 'How plant life-history and ecological traits relate to species rarity and commonness at varying spatial scales', Austral Ecology, vol. 27, no. 3, pp. 291-310.
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Comparative studies investigating relationships between plant traits and species rarity and commonness were surveyed to establish whether global patterns have emerged that would be of practical use in management strategies aimed at the long-term conservation of species. Across 54 studies, 94 traits have been examined in relation to abundance, distribution and threatened status at local, regional and geographical spatial scales. Most traits (63) have yet to be the focus of more than one study. Half of the studies involved less than 10 species, and one-quarter did not replicate rare-common contrasts. Although these features of the literature make it difficult to demonstrate robust generalizations regarding trait relationships with species rarity, some important findings surfaced in relation to traits that have been examined in two or more studies. Species with narrow geographical distributions were found to produce significantly fewer seeds (per unit measurement) than common species (in four of six studies), but did not differ with respect to breeding system (five of five studies). The majority of traits (including seed size, competitive ability, growth form and dispersal mode) were related to rarity in different ways from one study to the next. The highly context-dependent nature of most trait relationships with rarity implies that application of knowledge concerning rare-common differences and similarities to management plans will vary substantially for different vegetation types and on different continents. A comparative analysis of distribution patterns in relation to several life-history and ecological traits among 700 Australian eucalypt species was then performed. A significantly disproportionate number of tall species and species with long flowering durations had wide geographical ranges. Trait relationships with distribution were explored further through the development of a methodology incorporating multiple spatial scales. Eight theoretical categories we...
Murray, B. 2002, 'Book review: Introduction to Plant Population Biology', New Phytologist, vol. 155, pp. 201-202.
Murray, B.R. 2001, 'Acacia species and rhizobial interactions: Implications for restoration of native vegetation', Ecological Management and Restoration, vol. 2, no. 3, pp. 213-219.
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For successful restoration of native vegetation on nitrogen-depauperate soils, an understanding of nitrogen-fixing relationships between plant host species and their bacterial symbionts is critical. Each of three geographically restricted Acacia species (A fulva, A. nano-dealbata, and A. trachyphloia) and three widely distributed species (A. dealbata, A. implexa, and A. melanoxylon) were inoculated with 20 different rhizobial (Bradyrhizobium spp.) strains. The strains comprised two obtained from each of 10 different host species, including the six Acacia species listed above plus a further four species, A. cangaiensis, A. cincinnata, A. deanei, A. mearnsii. Neither restricted nor widely distributed species grew more effectively with their own strains than with strains isolated from other species. Thus, host species with restricted geographical ranges did not demonstrate greater specialization in their symbiotic associations with rhizobia than widespread species. Highly significant variation was observed between the strains obtained from each host species with respect to their ability to promote effective plant growth across all host species. In many cases, strains that were highly effective at promoting growth for one host species, were comparatively ineffective in combination with other host species. Strains thus exhibited host specificity in their ability to fix nitrogen. These findings indicate that choosing appropriate rhizobial strains for inoculation prior to revegetation is critical and should be made carefully for both restricted and widespread species.
Thrall, P.H., Murray, B.R., Watkin, E.L.J., Woods, M.J., Baker, K., Burdon, J.J. & Brockwell, J. 2001, 'Bacterial partnerships enhance the value of native legumes in rehabilitation of degraded agricultural lands', Ecological Management and Restoration, vol. 2, no. 3, pp. 233-235.
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Leishman, M.R. & Murray, B.R. 2001, 'The relationship between seed size and abundance in plant communities: Model predictions and observed patterns', Oikos, vol. 94, no. 1, pp. 151-161.
Recent studies have suggested that seed size and plant abundance in communities are associated. However, inconsistent patterns have emerged from these studies, with varying mechanisms proposed to explain emergent relationships. We employ a theoretical framework, based on key theory lineages of vegetation dynamics and species coexistence, to examine relationships between species abundance and seed size. From these theory lineages, we identified four models and their predictions: the Seed size/number trade-off model (SSNTM), the Succession model (SM), the Spatial competition model (SCM), and the Lottery model (LM). We then explored empirical evidence from ten diverse plant communities for seed size and abundance patterns, and related these patterns to model predictions. The SSNTM predicts a negative correlation between seed size and abundance. The SM predicts either a negative, positive or no correlation dependent on time since disturbance, while the SCM and LM make no predictions for a relationship between seed size and abundance. We found no evidence for consistent relationships between seed size and abundance across the ten communities. There were no consistent differences in seed size and abundance relationships between communities dominated by annuals compared to perennials. In three of the ten communities a significant positive seed size and abundance correlation emerged, which falsified the SSNTM as an important determinant of abundance structure in these communities. For sites in coastal woodland, the relationships between seed size and abundance were consistent with the predictions of the SM (although generally not significant), with fire being the disturbance. We suggest that the significant positive seed size and abundance correlations found may be driven by the association between large seeds and large growth forms, as large growth forms tend to be dominant. It seems likely that patterns of seed size and abundance in communities are determined by a comp...
Falster, D.S., Murray, B.R. & Lepschi, B.J. 2001, 'Linking abundance, occupancy and spatial structure: An empirical test of a neutral model in an open-forest woody plant community in eastern Australia', Journal of Biogeography, vol. 28, no. 3, pp. 317-323.
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Aims: We implemented a neutral model of a positive relationship between abundance and distribution (occupancy) to examine how spatial structure influences abundance-occupancy relationships. The spatially explicit neutral model distributes individuals of species randomly and independently of one another in space to produce a positive abundance-occupancy relationship. Using empirical data, we tested whether abundance-occupancy relationships diverged significantly from the theoretical neutral model, and determined whether significant divergences emerged through intraspecific aggregation or over-dispersion of individuals. Location: Field work was conducted in open-forest vegetation of the Black Mountain region in south-eastern Australia. Methods: At eight floristically similar sites in open-forest vegetation, we established a 20 20 m census plot and spatially mapped all individuals of each woody species. The abundance and distribution of each species was determined at each site at three spatial scales within the census plot. Observed abundance-occupancy relationships were compared with the spatially explicit neutral model using linear regression techniques. Monte-Carlo methods using a two dimensional Poisson process were then used to classify the spatial structure of species as random, aggregated or over-dispersed. Results: We found consistent evidence among the eight sites for abundance-occupancy relationships to diverge significantly from the neutral model at the three spatial scales within each community. The direction that the slopes of relationships diverged from the neutral model provided consistent evidence that aggregation of individuals within species was responsible for modifying the form of abundance-occupancy associations in this vegetation, a feature most evident with increasing scale. Main conclusions: Aggregation is not a mechanism that causes positive abundance-occupancy relationships. Under the neutral model of a positive abundance-occupancy relati...
Murray, B.R. & Gill, A.M. 2001, 'A comparative study of interspecific variation in fruit size among Australian Eucalypts', Ecography, vol. 24, no. 6, pp. 651-658.
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We examined variation in woody fruit size among 362 Australian Eucalyptus species with respect to predictions relating fruit size to fire exposure and rainfall. Predictions for fruit size variation were established that focussed on selection for small or large seeds, given a positive allometric relationship between fruit and seed size within the genus, and on the potential for fruits to protect their valuable seed contents. Comparatively smaller fruits were found in species that continually experience frequent disturbance by fire, while both small and large fruits were found among species subjected to both short and long fire intervals. In the latter case where a broad range of fire intervals is possible, some species have adopted a strategy of producing small seeds that provide superior colonisation ability in disturbed conditions, while other species have adopted a strategy of producing large seeds which are more competitive during longer intervals between disturbance by fire. Only when taxonomic membership at the subgeneric level was accounted for in analyses across all species, did a significant relationship emerge between fruit size and rainfall independently of fire interval and plant height: comparatively larger fruits were found in species experiencing lower average annual rainfall in the subgenera Eucalyptus and Symphyomyrtus. In contrast to previous studies, larger fruits were found only in short species, while small fruits were found in both short and tall species. Many short species have adopted a strategy of protecting their seeds from high fire intensity by producing larger fruit. Since tall species can elevate their fruit far above high fire intensity, they make considerable energy savings by producing smaller fruit. It remains an open question as to why small fruit size occurs in some short species, but we suggest that these species may invest more heavily in vegetative regrowth after fire than in re-establishment by seed.
Thrall, P.H., Murray, B., Watkin, E.L., Woods, M.J., Baker, K., Burdon, J.J. & Brockwell, J. 2001, 'Bacterial partnerships enhance the value of native legumes in rehabilitation of degraded agricultural lands', Ecological Management & Restoration, vol. 2, pp. 233-235.
A consequence of the generally low nutrient levels of Australian soils is that relationships between plants and their microbial symbionts (mycorrhizal fungi as well as nitrogen-fixing bacteria) have particular significance for conservation management, sustainable agriculture, and ecosystem rehabilitation. Shrubby legumes in the Fabaceae (e.g. Acacia, Daviesia, Dillwynia, Oxylobium, Hovea and Pultenaea) constitute a major group of plants that form nitrogen- fixing (N2-fixing) partnerships with root-nodule bacteria (species of rhizobia). These taxa are found throughout Australia, and are frequently a dominant part of undisturbed ecosystems, both in terms of abundance as well as overall biomass.
Murray, B.R. & Westoby, M. 2000, 'Properties of species in the tail of rank-abundance curves: The potential for increase in abundance', Evolutionary Ecology Research, vol. 2, no. 5, pp. 583-592.
It has recently been shown that most low-abundance species at a location are substantially more abundant somewhere else within their geographical range (somewhere-abundant). Fewer than 10% are everywhere-sparse. Here, two everywhere-sparse species from dry sclerophyll woodland were compared with phylogenetically contrasted somewhere-abundant species, at sites where both were at low abundance. In each pair, everywhere-sparse species produced approximately ten-fold fewer seeds per area of canopy cover than the somewhere-abundant species, consistently across replicate sites. Around individuals, a significantly larger proportion of the immediately colonizable neighbourhood was already occupied by the same species, for the everywhere-sparse compared to the somewhere-abundant species, in each pair and across replicate sites. Together, these differences amount to a much lower potential rate of increase in everywhere-sparse species compared with somewhere-abundant species, and are consistent with their having low capacity for opportunistic increase to high abundance. Our findings suggest novel differences between species that differ in local abundance patterns across geographical ranges, and provide a basis for further exploration of life-history and demographic differences between everywhere-sparse and somewhere-abundant species.
Murray, B.R. & Dickman, C.R. 2000, 'Relationships between body size and geographical range size among Australian mammals: Has human impact distorted macroecological patterns?', Ecography, vol. 23, no. 1, pp. 92-100.
Extinction and artificial reduction in the size of geographical ranges of many species have occurred extensively across the globe because of human activities. In particular, Australian mammals have suffered heavily in the last two hundred years, with the highest number of reported cases of mammal extinctions anywhere. In the present study, we investigated the extent to which human impact has affected contemporary macroecological patterns in Australian terrestrial mammals. After examining patterns relating to body size and range size among the contemporary mammal fauna, we removed the effects of the last two hundred years of human impact by exploring patterns in the pre-European assemblage. This permitted us to determine whether contemporary macroecological patterns are distortions of pre-European patterns. In contrast to the expected pattern of a significant positive relationship between body size and range size, our results showed no significant association for the complete fauna in both cross-species and phylogenetic analyses, even when data were corrected for species extinctions and range reductions. Analyses within families and among species with the same dietary strategy revealed three significant positive relationships (Macropodidae, Peramelidae, and herbivores) and one significant negative relationship (insectivores) within the contemporary assemblage that disappeared when the pre-European assemblage was analysed. A positive relationship also emerged in the pre-European assemblage for the Vombatidae that was not apparent in the contemporary fauna. Thus, correcting for human impact revealed important distortions among contemporary macroecological relationships that have been brought about by human-induced range reduction and extinction. These findings not only provide further evidence that the Australian continent presents a unique and valuable opportunity with which to test the generality of macroecological patterns, but they also have important ramificati...
Murray, B.R., Rice, B.L., Keith, D.A., Myerscough, P.J., Howell, J., Floyd, A.G., Mills, K. & Westoby, M. 1999, 'Species in the tail of rank-abundance curves', Ecology, vol. 80, no. 6, pp. 1806-1816.
At focal sites within dry sclerophyll woodland and temperate rain forest, species were identified that were of low local abundance and hence in the tail of the rank-abundance curve. We then asked the question: What proportion of tail species within a given community are constitutive members of the tail everywhere throughout their geographical range, versus what proportion are found as substantially more abundant somewhere within their range? Out of 55 tail species identified from dry sclerophyll woodland and 116 tail species identified from temperate rain forest, 91% and 95%, respectively, were significantly more abundant at other locations ('somewhere-abundant' species), versus 9% and 5% 'everywhere-sparse' species. Among eight attributes in dry sclerophyll woodland and nine attributes in temperate rain forest compared between somewhere-abundant and everywhere-sparse species, none discriminated consistently between the two groups of species. The size and dispersal morphology of seeds, flowering and fruiting durations and seasons, regeneration strategy after fire, size of geographical ranges, maximum plant height, and size class revealed no consistent distinctions. For the small minority of species that are everywhere-sparse, some general explanation may exist as to why they are in the tail of rank-abundance curves, though none was located among the attributes compared in this paper. For the majority of tail species that are somewhere-abundant, any explanation as to why they are in the tail will need to account for different outcomes in different places.
Murray, B.R., Dickman, C.R., Watts, C.H.S. & Morton, S.R. 1999, 'The dietary ecology of Australian desert rodents', Wildlife Research, vol. 26, no. 4, pp. 421-437.
Very little systematic information has been collected on the diets of Australian rodents in arid and semiarid regions. The information that is available is restricted generally to short periods of sampling and small sample sizes. Here we review the diets of 15 extant and one extinct species of Australian desert rodents, and provide new results of dietary analyses for (1) Leggadina forresti, Pseudomys desertor and Rattus villosissimus from the Simpson Desert, south-western Queensland, (2) P. albocinereus and P. bolami from the western goldfields of Western Australia, and (3) Notomys alexis, P. desertor and P. hermannsburgensis from the Tanami Desert, Northern Territory. Overwhelmingly, omnivory is the predominant dietary strategy, with most species (II) taking substantial amounts of invertebrate, seed and green plant material. Of the other five species, four can be considered herbivores and one a granivore. Of the four herbivores, however, one is extinct (Leporillus apicalis), one is restricted to an offshore island (Lep. conditor), while another (P. fieldi) is classified as a herbivore from a diet sample of four individuals only. Similarly, P. occidentalis is classified as a granivore on the basis of dietary sampling of two individuals alone. These findings indicate that omnivory, over and above any other dietary strategy including granivory, is predominant among rodents inhabiting Australian deserts.
Murray, B.R. 1998, 'Density-dependent germination and the role of seed leachate', Austral Ecology, vol. 23, no. 5, pp. 411-418.
While density dependence is a central issue in much of plant ecology, it is often overlooked during the crucial seed germination period of the plant life-cycle. Here, patterns of germination in relation to initial seed density for 12 phylogenetically-diverse perennial plant species are described from laboratory experiments. When each of the 12 species was analysed individually, seeds of Alysicarpus rugosus, Callistemon citrinus, Eragrostis curvula and Panicum miliaceum showed a significant decrease in the proportion of seeds germinating at high densities of conspecifics. A meta-analysis carried out by grouping 11 of the 12 species together revealed an overall significant effect for a decrease in the proportion of seeds germinating at high conspecific densities compared with low conspecific densities. Significant decreases in the proportion of seeds germinating are interpreted as risk reappraisal by seeds through dormancy in response to potentially hazardous conditions imposed by high density clusters of seeds all germinating at once. The four species that responded significantly to high densities individually were each treated at low densities with a leachate solution obtained from high density conspecifics. For Alysicarpus rugosus and Panicum miliaceum, this resulted in a significant decrease in the proportion of seeds germinating at simulated high densities implicating the leachate as a causative agent. Heterospecific effects were investigated similarly for A. rugosus and E. curvula by the addition of leachate from high density clusters of seeds of one species upon the other. Only A. rugosus decreased germination significantly through the addition of leachate. These results demonstrate the ability of seeds to predict environmental conditions of the habitat into which they will emerge in terms of potential competitive interactions from neighbouring seedlings.
Murray, B.R., Fonseca, C.R. & Westoby, M. 1998, 'The macroecology of Australian frogs', Journal of Animal Ecology, vol. 67, no. 4, pp. 567-579.
1. The Australian continent provides an important test of macroecological patterns given its unique biota and long-term geographical isolation. However, macroecological contributions from the Australian continent are rare. We explored the relationship between abundance and geographical range for Australian frogs (Order Anura) across complete geographical ranges, and investigated how adult body size relates to both abundance and the size of geographical ranges. 2. Our analyses followed two complementary paths. First, we employed cross-species correlations at a number of taxonomic levels to analyse present-day ecological associations among the macroecological variables. Secondly, we tested whether there were correlated evolutionary divergences among the variables by use of the phylogenetic regression. In the event, cross-species patterns and correlated divergence patterns proved quite similar for this dataset. 3. For Australian frogs there is a strong, significant positive correlation between abundance and geographical range, that is not mediated through body size, and that is found for both cross-species correlations and as correlated evolutionary divergences. Among biological mechanisms that have been proposed, some can be rejected. Feasible explanations would invoke resource use or intrinsic rates of increase or both. 4. There is also a significant positive correlation between adult body size and geographical range. We were able to discard four of the five proposed mechanisms describing this relationship. The remaining mechanism relates to homeostasis and environmental variability. 5. Previous studies of the relationship between adult body size and abundance have revealed a strong negative correlation when studies are performed over areas that encompass most or all of the geographical ranges of the species in question. Contrary to these studies, a negative relationship was not found for Australian frogs. None of the eight explanations postulated from other studi...
Murray, B.R. & Dickman, C.R. 1997, 'Factors affecting selection of native seeds in two species of Australian desert rodents', Journal of Arid Environments, vol. 35, no. 3, pp. 517-525.
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The preferences for different species of native seeds by two species of Australian desert rodents, the sandy inland mouse, Pseudomys hermannsburgensis, and the spinifex hopping-mouse, Notomys alexis, were investigated. In two sets of cafeteria trials providing low and high numbers of different seed species, both rodent species showed discrimination, preferentially consuming certain seed species, while avoiding others. In one of the two trials, P. hermannsburgensis selected seeds with the highest free water content, while N. alexis showed no clear mechanism of seed choice in either trial. It is suggested that although both species of rodents are omnivorous, P. hermannsburgensis relies more on seeds than does N. alexis, and is thus the more efficient seed harvester.
Murray, B., Hume, I. & Dickman, C.R. 1995, 'Digestive tract characteristics of the spinifex hopping-mouse, Notomys alexis and the sandy inland mouse, Pseudomys hermannsburgensis in relation to diet', Australian Mammalogy, vol. 18, pp. 93-97.
Murray, B.R. & Dickman, C.R. 1994, 'Food preferences and seed selection in two species of Australian desert rodents', Wildlife Research, vol. 21, no. 6, pp. 647-655.
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Murray, B.R. & Dickman, C.R. 1994, 'Granivory and microhabitat use in Australian desert rodents: are seeds important?', Oecologia, vol. 99, no. 3-4, pp. 216-225.
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The diet and microhabitat use of two species of native Australian desert rodents, the spinifex hoppingmouse Notomys alexis and sandy inland mouse Pseudomys hermannsburgensis, were studied in the Simpson Desert, south-western Queensland. Contrary to expectation, both species were confirmed from analyses of their stomach contents to be omnivorous. The diets of both species varied through time in a similar manner; seeds were important in summer and especially in winter, but in autumn invertebrates constituted nearly 50% and 60% of the diet of N. alexis and P. hermannsburgensis, respectively. Other plant material (root, leaf, floral part, stem) was found in appreciable amounts in the stomach contents of both species, and fungi were identified from a small number of individuals. Both species showed a high degree of overlap in the broad types of food they ingested (seed, plant material, invertebrates); however, there was considerably less overlap in the species of seeds eaten. Analysis of microhabitat use suggested that this difference was due to differential foraging between the species; the larger, bipedal N. alexis forages in the open more than the smaller, quadrupedal P. hermannsburgensis, which is found more commonly in or under hummocks of spinifex grass. Although our findings parallel patterns of morphological specialisation and differential foraging on seeds that have been described within communities of North American heteromyid rodents, we found little evidence that the foraging economics of N. alexis or P. hermannsburgensis should depend solely or primarily on the distribution patterns of seeds. In the absence of dietary information, we suggest that ecological studies of desert rodents which focus solely on granivory, and neglect other important aspects of rodent foraging, can lead to a misinterpretation of species coexistence and community structure. &copy; 1994 Springer Verlag.