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Mitochondrial DNA phylogeography of the polytypic north American Rat Snake (Elaphe obsoleta):
a critique of the subspecies concept

Evolution, 54(6), 2000, pp. 2107-2118

Frank T. Burbrink1, Robin Lawson2, and Joseph B. Slowinski3
1Museum of Natural Science and Departement of Biology, 119 Foster Hall, Louisiana State University, Baton Rouge, Louisiana 70803
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2Osher Foundation Laboratory for Molecular Systematics and Department of Herpetology, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118
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3Departement of Herpetology, California Academt of Sciences, Golden Gate Park, San Francisco, California 94118
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Abstract

Subspecies have been considered artificial subdivisions of species, pattern classes, or incipient species. However, with more data and modern phylogenetic techniques, some subspecies may be foun to represent true species. Mitochondrial DNA analysis of the polytypic snale, Elaphe obsoleta, yields well-supported clades that do not conform to any of the currently acceptes subspecies Complete nucleotide sequences of the cytochrome b gene and the mitochondrial control region produced robust maximum-parsimony and maximum-likelihood trees that do not differ statistically. Both trees were sgnificantly shorter that a most parsimonious tree in which each subspecies was constrained to be monophyletic. Thus, the subspecies of E. obsoleta do not represent distinct genetic lineages. Instead, the evidence points to three well-supported mitochondrial DNA clades confined to particular geographic areas in the eastern United States. This research underscore the potential problems of recognizing subspecies based on one or a few characters.

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Un ringraziamento a Judy Stone, segretaria di The Society for the Study of Evolution, per aver concesso il permesso di pubblicare l'articolo completo su www.elaphe.it.