Phylogeny-based delimitation of species boundaries and contact zones in the trilling chorus frogs (Pseudacris)

Although the trilling chorus frogs (subclade within Pseudacris: Hylidae) have been important in studies of speciation, continental patterns of genetic diversity within and among species have not been elucidated. As a result, this North American clade has been the subject of substantial taxonomic debate. In this study, we examined the phylogenetic relationships among the trilling Pseudacris and tested previously hypothesized scenarios for speciation using 2.4 kb of mitochondrial 12S and 16S rRNA genes from 253 populations. Bayesian phylogenetic analyses, in combination with published morphological and behavioral data, support recognition of at least nine species, including an undescribed species from the south-central United States. Evidence is presented for substantial geographic subdivision within P. brachyphona (northern and southern clades) and P. feriarum (coastal and inland clades). Discordance between morphology/behavior and molecular data in several individuals suggests occasional hybridization between sympatric species. These results require major revision of range limits for several taxa, in particular, P. maculata, P. triseriata, and P. feriarum. Hypothesis tests using parametric bootstrapping strongly reject previously proposed scenarios for speciation in the group. The tests also support recognition of the geographically restricted taxon P. kalmi as a distinct species. Results of this study provide both a firm phylogenetic basis for future studies of speciation in the trilling Pseudacris and a taxonomic framework for conservation efforts.