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  • New evidence backs up 'chance theory' of species abundance


A controversial theory – that patterns of species abundance arise due to chance – can help predict the number of rare species in an ecosystem, according to new research.

The so-called 'neutral theory', the brainchild of Stephen Hubbell of the University of Georgia, United States, suggests that species abundance is determined randomly, and is not related to factors such as such as habitat preferences or birth, growth and death rates.

Earlier this year, research by Brian McGill of the University of Arizona, United States, suggested that the theory did not accurately predict species abundance among tree species on Barro Colorado Island in Panama.

But in this week's issue of Nature, Hubbell and colleagues report that they have re-analysed McGill's data set and have found that the abundance of tree species within the rainforest does match the theory's predictions. The model may therefore help to forecast the number of rare species in other settings, they say.

These findings could be of great value to conservation biologists because "it is rare species that are most likely to disappear under habitat loss," writes John Harte of the University of California at Berkeley, United States in an accompanying article in Nature.

"It is difficult to include rare species in census counts, so having a theory that reliably predicts how many there are is of enormous value," he adds.

Link to John Harte's article in Nature

Link to research paper in Nature

Reference: Nature 424, 1006 (2003)/ Nature 424, 1035 (2003)

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