Systematic status of Peromyscus boylii ambiguus based on morphologic and molecular data

Recent chromosomal and allozymic studies suggest that Peromyscus boylii ambiguus is aligned more closely to P. levipes than to P. b. rowleyi. To clarify taxonomic and systematic status of this taxon, univariate and multivariate morphometric analyses were conducted on representative specimens of P. b. rowleyi, P. b. ambiguus, P. levipes, and P. beatae (hereafter referred to as rowleyi, ambiguus, levipes, and beatae). In addition, DNA sequences of the mitochondrial D-loop region were examined in exemplars representing each taxon to further assess the phylogenetic relationship of ambiguus to other members of the P. boylii species group. The morphological study revealed a consistent pattern of increasing size from north to south. Most multivariate analyses separated ambiguus and beatae from rowleyi and showed phenetic affinities between ambiguus and levipes. DNA-sequence data revealed a sister-taxon relationship between ambiguus and levipes to the exclusion of rowleyi and beatae. Morphological and DNA-sequence data are in agreement with previous karyotypic and allozymic studies supporting affinities between ambiguus and levipes. Based on concordance of these four data sets, it is apparent that these two taxa represent subunits within levipes, the ranges of which are divided approximately at the Tropic of Cancer in northeastern Mexico. The appropriate taxonomic designation for ambiguus is as a subspecies of levipes.