Species Limits Based on mtDNA and Morphological Data in the Polytypic Species Plestiodon brevirostris (Squamata: Scincidae)

Abstract

The Mexican Plestiodon brevirostris species group (Squamata: Scincidae) is composed of seven nominal species. The wide-ranging P. brevirostris is a polytypic species composed of five subspecies: P. b. brevirostris, P. b. bilineatus, P. b. dicei, P. b. indubitus, and P. b. pineus. A tree-based approach for species delimitation with mtDNA data was used to test the traditional species-level taxonomy of P. brevirostris preliminarily. A haplotype phylogeny for all of the species and subspecies in the P. brevirostris group, except P. colimensis, was inferred. The mtDNA data consisted of sequences encompassing the genes encoding 16S rRNA (part), ND1, and associated tRNAs (1355 base pairs), which were analyzed with Bayesian methods. Then, a search for diagnostic morphological characters for the putative species delimited by this approach was performed. The results indicate that the P. brevirostris group is paraphyletic with respect to P. lynxe, and that P. brevirostris actually is composed of at least five distinct lineages disguised by traditional taxonomy: P. b. brevirostris, P. b. bilineatus, P. b. dicei, and the eastern populations of P. b indubitus (from Morelos, Guerrero, and Mexico) represent distinct species, whereas the western populations of P. b. indubitus (from Colima and Jalisco) represent an undescribed species. The data cannot resolve whether P. b. pineus is conspecific with P. b. dicei or P. b. dicei is a paraphyletic (5nonexclusive) species relative to an exclusive P. b. pineus. Thus, the status of P. b. pineus remains uncertain. The haplotype phylogeny also suggests that P. b. brevirostris may represent more than one species.