SYSTEMATICS

Here Now, Gone Later

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Science  22 Mar 2002:
Vol. 295, Issue 5563, pp. 2179
DOI: 10.1126/science.295.5563.2179b

Discussions about the disparity between current and past rates of species extinction and the varying estimates of the number of extant species (from 3 million to 30 million) have rarely touched on the issue of how often named species are found to be invalid (or synonymous with those already described). Using a database of 4861 North American fossil mammal species, Alroy analyzes this issue with a flux-ratio model that incorporates the movement of species from recognized to unrecognized taxa (invalidation) and the backward flux (revalidation). This model is used to assess two centuries of taxonomic effort covering approximately 65 million years of evolutionary time. He finds that about 27% of currently acknowledged mammalian species will become invalid, translating into an overestimate of about 38% in biodiversity, which may also be applicable to more abundant groups such as insects and fungi. Nevertheless, taxonomic reclassification is insufficient to alter values of modern-day extinction rates. — GJC

Proc. Natl. Acad. Sci. U.S.A.99, 3706 (2002).

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