Cryptic species in Sigmodon hispidus: Evidence from DNA sequences

Phylogenetic relationships among 8 subspecies of Sigmodon hispidus from Nor th, Central, and South America were examined using DNA-sequence data from t he mitochondrial cytochrome-b gene. The magnitude of DNA-sequence variation detected among these subspecies, in some cases, exceeded levels of intersp ecific variation observed among currently recognized species of Sigmodon. T hese data suggest that S. hispidus is paraphyletic and that a minimum of 3 species exist within the currently recognized taxon. Consequently, the taxo nomy should be revised to recognize the following samples as distinct speci es: those from the United States and north-central Mexico, those from south ern Mexico, and those from Central and South America.