Ecological specialization and population size in a biodiversity hotspot: how rare species avoid extinction

Williams, Stephen, Williams, Yvette M., VanDerWal, Jeremy, Isaac, Joanne L., Shoo, Luke P., and Johnson, Christopher N. (2009) Ecological specialization and population size in a biodiversity hotspot: how rare species avoid extinction. Proceedings of the National Academy of Sciences, 106. pp. 19737-19741.

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Species with narrow environmental niches typically have small geographic ranges. Small range size is, in turn, often associated with low local abundance. Together, these factors should mean that ecological specialists have very small total populations, putting them at high risk of extinction. But some specialized and geographically restricted species are ancient, and some ecological communities have high proportions of rare and specialized endemics. We studied niche characteristics and patterns of distribution and abundance of terrestrial vertebrates in the rainforests of the Australian Wet Tropics (AWT) to identify mechanisms by which rare species might resist extinction. We show that species with narrow environmental niches and small geographic ranges tend to have high and uniform local abundances. The compensation of geographic rarity by local abundance is exact, such that total population size in the rainforest vertebrates of the AWT is independent of environmental specialization. This effect would tend to help equalize extinction risk for specialists and generalists. Phylogenetic analysis suggests that environmental specialists have been gradually accumulating in this fauna, indicating that small range size/environmental specialization can be a successful trait as long as it is compensated for by demographic commonness. These results provide an explanation of how range-restricted specialists can persist for long periods, so that they now form a major component of high-diversity assemblages such as the AWT.

Item ID: 5577
Item Type: Article (Research - C1)
ISSN: 1091-6490
Keywords: abundance, range size, rarity, tropical biology
Date Deposited: 19 Nov 2009 22:51
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060207 Population Ecology @ 50%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060208 Terrestrial Ecology @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960810 Mountain and High Country Flora, Fauna and Biodiversity @ 70%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960509 Ecosystem Assessment and Management of Mountain and High Country Environments @ 30%
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