August 1, 2005
New Amphibian Species Result from Exploration, Not from Rule Changes
Researchers have discovered amphibian species at an accelerating rate in recent decades, with over 1,000 new ones recognized between 1992 and 2003. At the same time, amphibians are, for reasons not entirely clear, declining more rapidly than either mammals or birds, underscoring the importance of an accurate evaluation. An analysis published in the August 2005 issue of BioScience, the monthly journal of the American Institute of Biological Sciences, indicates that, contrary to some published expert opinions, new amphibian discoveries are a consequence of increasing exploratory effort, not of changing criteria for recognizing a species, or "taxonomic inflation." The authors of the new analysis, Jörn Köhler of the Hessisches Landesmuseum Darmstadt, Germany, and colleagues, conclude that "Taxonomic exploration is still desperately needed to avoid misinterpretations in global conservation policy."
Köhler and his coauthors reached their conclusions after examining genetic data on a Madagascan frog family, the Mantellidae, that grew from 143 to 203 species between 1992 and 2003. The investigators compared the sequence of a particular mitochondrial gene in mantellid species recognized at various times from the 19th century to the present. The gene sequences were no more similar in recently recognized species than in long-recognized species, a result that argues again taxonomic inflation as the explanation for the growth. Moreover, the Mantellidae include few subspecies that could complicate an analysis. Köhler and colleagues credit the boost in the number of amphibian species descriptions to new bioacoustic and genetic tools, and urge the continuation and expansion of efforts to identify further examples. They acknowledge, however, that taxonomic inflation might explain the growing number of species in some other animal groups, such as primates and birds.
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