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Australian Mammals (australian + mammal)

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Life Sciences100%

Selected Abstracts

Body Size and Risk of Extinction in Australian Mammals

CONSERVATION BIOLOGY, Issue 5 2001
Marcel Cardillo
For Australian terrestrial mammals this link is of particular interest because it is widely believed that species in the intermediate size range of 35,5500 g (the "critical weight range") have been the most prone to recent extinction. But the relationship between body size and extinction risk in Australian mammals has never been subject to a robust statistical analysis. Using a combination of randomization tests and phylogenetic comparative analyses, we found that Australian mammal extinctions and declines have been nonrandom with respect to body size, but we reject the hypothesis of a critical weight range at intermediate sizes. Small species appear to be the least prone to extinction, but extinctions have not been significantly clustered around intermediate sizes. Our results suggest that hypotheses linking intermediate body size with high risk of extinction in Australian mammals are misguided and that the focus of future research should shift to explaining why the smallest species are the most resistant to extinction. Resumen: El vínculo entre el tamaño del cuerpo y el riesgo de extinción ha sido el centro de mucha atención reciente. Para los mamíferos terrestres australianos este vínculo es de particular interés debido a que se cree ampliamente que las especies en un rango intermedio de tamaño de 35,5500 g (el rango de peso crítico) ha sido el más susceptible a extinciones recientes. Sin embargo, la relación entre extinciones, el tamaño y el riesgo de extinción en mamíferos australianos nunca ha sido sometida a un análisis estadístico robusto. Usando una combinación de pruebas aleatorizadas y análisis filogenéticos comparativos, encontramos que las extinciones y disminuciones de mamíferos australianos han sido no aleatorias con respecto al tamaño del cuerpo, pero rechazamos la hipótesis de un rango crítico a tamaños intermedios. Las especies pequeñas aparentan ser las menos susceptibles de extinción, pero las extinciones no se han agrupado significativamente alrededor de tamaños intermedios. Nuestros resultados sugieren que la hipótesis que vincula el tamaño intermedio de cuerpo con un alto riesgo de extinción en mamíferos australianos está mal planteada y que el centro de la investigación a futuro deberá enfocarse a explicar el porqué las especies más pequeñas son las más robustas a la extinción. [source]

Australian Mammals: Biology and Captive Management

AUSTRAL ECOLOGY, Issue 1 2005
JENNY MARTIN
No abstract is available for this article. [source]

Body Size and Risk of Extinction in Australian Mammals

CONSERVATION BIOLOGY, Issue 5 2001
Marcel Cardillo
For Australian terrestrial mammals this link is of particular interest because it is widely believed that species in the intermediate size range of 35,5500 g (the "critical weight range") have been the most prone to recent extinction. But the relationship between body size and extinction risk in Australian mammals has never been subject to a robust statistical analysis. Using a combination of randomization tests and phylogenetic comparative analyses, we found that Australian mammal extinctions and declines have been nonrandom with respect to body size, but we reject the hypothesis of a critical weight range at intermediate sizes. Small species appear to be the least prone to extinction, but extinctions have not been significantly clustered around intermediate sizes. Our results suggest that hypotheses linking intermediate body size with high risk of extinction in Australian mammals are misguided and that the focus of future research should shift to explaining why the smallest species are the most resistant to extinction. Resumen: El vínculo entre el tamaño del cuerpo y el riesgo de extinción ha sido el centro de mucha atención reciente. Para los mamíferos terrestres australianos este vínculo es de particular interés debido a que se cree ampliamente que las especies en un rango intermedio de tamaño de 35,5500 g (el rango de peso crítico) ha sido el más susceptible a extinciones recientes. Sin embargo, la relación entre extinciones, el tamaño y el riesgo de extinción en mamíferos australianos nunca ha sido sometida a un análisis estadístico robusto. Usando una combinación de pruebas aleatorizadas y análisis filogenéticos comparativos, encontramos que las extinciones y disminuciones de mamíferos australianos han sido no aleatorias con respecto al tamaño del cuerpo, pero rechazamos la hipótesis de un rango crítico a tamaños intermedios. Las especies pequeñas aparentan ser las menos susceptibles de extinción, pero las extinciones no se han agrupado significativamente alrededor de tamaños intermedios. Nuestros resultados sugieren que la hipótesis que vincula el tamaño intermedio de cuerpo con un alto riesgo de extinción en mamíferos australianos está mal planteada y que el centro de la investigación a futuro deberá enfocarse a explicar el porqué las especies más pequeñas son las más robustas a la extinción. [source]

Population genetics of Escherichia coli in a natural population of native Australian rats

ENVIRONMENTAL MICROBIOLOGY, Issue 6 2000
Gulietta M. Pupo
Escherichia coli, a normal inhabitant of the intestinal tract of mammals and birds, is a diverse species. Most studies on E. coli populations involve organisms from humans or human-associated animals. In this study, we undertook a survey of E. coli from native Australian mammals, predominantly Rattus tunneyi, living in a relatively pristine environment in the Bundjalung National Park. The genetic diversity was assessed and compared by multilocus enzyme electrophoresis (MLEE), sequence analysis of the mdh (malate dehydrogenase) gene and biotyping using seven sugars. Ninety-nine electrophoretic types were identified from the 242 isolates analysed by MLEE and 15 sequences from the mdh genes sequenced from 21 representative strains. The Bundjalung isolates extend the diversity represented by the E. coli reference (ECOR) set, with new MLEE alleles found in six out of 10 loci. Many of the Bundjalung isolates fell into a discrete group in MLEE. Other Bundjalung strains fell into the recognized E. coli ECOR set groups, but tended to be at the base of both the MLEE and mdh gene trees, implying that these strains are derived independently from ancestral forms of the ECOR groups and that ECOR strains represent only a subset of E. coli adapted to humans and human-associated animals. Linkage disequilibrium analysis showed that the Bundjalung population has an ,epidemic' population structure. The Bundjalung isolates were able to utilize more sugars than the ECOR strains, suggesting that diet plays a prominent role in adaptation of E. coli. [source]

Body size and extinction risk in Australian mammals: An information-theoretic approach

AUSTRAL ECOLOGY, Issue 6 2010
RYAN A. CHISHOLM
Abstract The critical weight range (CWR) hypothesis for Australian mammals states that extinctions and declines have been concentrated in species with body mass between 35 g and 5.5 kg. The biological basis for this hypothesis is that species of intermediate size are disproportionately impacted by introduced predators. The CWR hypothesis has received support from several statistical studies over the past decade, although the evidence is weaker or non-existent for certain groups such as mesic-zone mammals and arboreal mammals. In this study, we employ an information-theoretic model selection approach to gain further insights into the relationship between body mass and extinction risk in Australian mammals. We find evidence, consistent with the CWR hypothesis, that extinction risk peaks at intermediate body masses for marsupials, rodents and ground-dwelling species, but not for arboreal species. In contrast to previous studies, we find that the CWR describes extinction patterns in the mesic zone as well as the arid zone. In the mesic zone, there is also a weaker tendency for large species above the CWR to be more vulnerable, consistent with extinction patterns on other continents. We find that a more biological plausible Gaussian distribution consistently fits the data better than the polynomial models that have been used in previous studies. Our results justify conservation programmes targeted at species within the CWR across Australia. [source]

Body mass and extinction risk in Australian marsupials: The ,Critical Weight Range' revisited

AUSTRAL ECOLOGY, Issue 1 2009
CHRISTOPHER N. JOHNSON
Abstract Australian mammals have suffered an exceptionally high rate of decline and extinction over the last two hundred years. Body mass is linked to extinction risk in Australian mammals, but the nature of this association is controversial. A widely held view is that species of intermediate body mass (between 35 and 5500 g, the ,critical weight range', CWR) have declined most severely. However, the existence of the CWR has been disputed. In this paper we clarify the relationship of decline status and body mass in Australian marsupials. We show that the form of this relationship differs for ground-living versus arboreal species, and for species from low versus high rainfall areas. Among ground-living species and those from low-rainfall areas, declines were strongly size-selective and concentrated on species within the CWR. For the remaining species, decline was only weakly related to body mass with no evidence of heightened risk for species of intermediate size. We conclude that for terrestrial species in low rainfall areas, species within the CWR are most at risk of decline and extinction. [source]