Abstract
The hispid pocket mouse (Chaetodipus hispidus) is one of the most genetically and morphologically divergent species within the heteromyid genus Chaetodipus. Four subspecies of C. hispidus currently are recognized, C. h. hispidus, C. h. paradoxus, C. h. spilotus, and C. h. zacatecae, ranging from North Dakota south through the Great Plains and Texas to central Mexico. We investigated the phylogeographic structure within C. hispidus by examining mitochondrial DNA from both freshly collected and museum specimens from localities distributed throughout the range of the species. We also examined 11 cranial characters in 303 specimens to assess morphological variation within the species. Although morphometric analyses were unable to differentiate the subspecies, phylogenetic analyses of molecular data indicated that the 4 currently recognized subspecies of C. hispidus are not genetically distinct. Instead, our results indicate that there are 4 distinct mitochondrial clades of C. hispidus that do not correspond to the currently recognized subspecies, but whose geographic limits instead coincide with major geographical features in the southern United States and northern Mexico. The Southern Coahuila filter-barrier (Durango and Coahuila), the Deming Plains (New Mexico), and the Balcones Escarpment (Texas) likely have acted as intermittent physical barriers to gene flow among the distinct mitochondrial clades, which we recognize as subspecies within C. hispidus.
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