Comparative phylogeography of baileys' pocket mouse (Chaetodipus bailey) and the Peromyscus eremicus species group: Historical vicariance of the BajaCalifornia Peninsular desert

Phylogenetic analysis of 699 bp of the mitochondrial DNA (mtDNA) COIII and 450 bp of the cytochrome b genes among 14 species of coarse-haired pocket m ice (Heteromyidae: Chaetodipus) corroborated previous indications that gene tic divergence between species and species groups within the genus is gener ally very high, suggesting old times of divergence, and that the nominal sp ecies C. baileyi represents a highly divergent lineage within the genus, wi th no closely related extant sister species. Analysis of phylogeographic st ructure among 51 individuals from 12 localities throughout the geographic r ange of C. baileyi revealed three geographically separate mtDNA haplotype l ineages. The oldest split separates populations east and west of the Colora do River, a pattern that is congruent with chromosomal and allozyme electro phoretic evidence. We consider the western populations to represent a disti nct species, C. rudinoris. Within C. rudinoris, mtDNA haplotypes are furthe r subdivided into northern and southern lineages along the Baja California Peninsula. Comparison of phylogeographic structure in the baileyi species g roup and the codistributed Peromyscus eremicus species group implies two po ints of codivergence and thus supports two historical vicariance hypotheses proposed for biotas distributed across the peninsular and continental warm deserts: a late Neogene (3 Ma) northern extension of the Sea of Cortez and a mid-Pleistocene (1 Ma) mid-peninsular seaway across Baja California. (C) 2000 Academic Press.