Title |
Ecological specialization and population size in a biodiversity hotspot: How rare species avoid extinction
|
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Published in |
Proceedings of the National Academy of Sciences of the United States of America, November 2009
|
DOI | 10.1073/pnas.0901640106 |
Pubmed ID | |
Authors |
S. E. Williams, Y. M. Williams, J. VanDerWal, J. L. Isaac, L. P. Shoo, C. N. Johnson |
Abstract |
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. |
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Geographical breakdown
Country | Count | As % |
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United States | 11 | 2% |
Spain | 6 | 1% |
Brazil | 6 | 1% |
United Kingdom | 5 | 1% |
Switzerland | 2 | <1% |
France | 2 | <1% |
India | 2 | <1% |
Bulgaria | 1 | <1% |
Ireland | 1 | <1% |
Other | 17 | 4% |
Unknown | 407 | 88% |
Demographic breakdown
Readers by professional status | Count | As % |
---|---|---|
Researcher | 110 | 24% |
Student > Ph. D. Student | 91 | 20% |
Student > Master | 60 | 13% |
Student > Bachelor | 37 | 8% |
Professor > Associate Professor | 31 | 7% |
Other | 87 | 19% |
Unknown | 44 | 10% |
Readers by discipline | Count | As % |
---|---|---|
Agricultural and Biological Sciences | 281 | 61% |
Environmental Science | 88 | 19% |
Biochemistry, Genetics and Molecular Biology | 10 | 2% |
Earth and Planetary Sciences | 9 | 2% |
Mathematics | 3 | <1% |
Other | 14 | 3% |
Unknown | 55 | 12% |