Extrinsic versus intrinsic factors in the decline and extinction of Australian marsupials

Diana O. Fisher*, Simon P. Blomberg, Ian P.F. Owens

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    177 Citations (Scopus)

    Abstract

    Recent attempts to explain the susceptibility of vertebrates to declines worldwide have largely focused on intrinsic factors such as body size, reproductive potential, ecological specialization, geographical range and phylogenetic longevity. Here, we use a database of 145 Australian marsupial species to test the effects of both intrinsic and extrinsic factors in a multivariate comparative approach. We model five intrinsic (body size, habitat specialization, diet, reproductive rate and range size) and four extrinsic (climate and range overlap with introduced foxes, sheep and rabbits) factors. We use quantitative measures of geographical range contraction as indices of decline. We also develop a new modelling approach of phylogenetically independent contrasts combined with imputation of missing values to deal simultaneously with phylogenetic structuring and missing data. One extrinsic variable - geographical range overlap with sheep - was the only consistent predictor of declines. Habitat specialization was independently but less consistently associated with declines. This suggests that extrinsic factors largely determine interspecific variation in extinction risk among Australian marsupials, and that the intrinsic factors that are consistently associated with extinction risk in other vertebrates are less important in this group. We conclude that recent anthropogenic changes have been profound enough to affect species on a continent-wide scale, regardless of their intrinsic biology.

    Original languageEnglish
    Pages (from-to)1801-1808
    Number of pages8
    JournalProceedings of the Royal Society B: Biological Sciences
    Volume270
    Issue number1526
    DOIs
    Publication statusPublished - 7 Sept 2003

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