Cheadle Center for Biodiversity and Ecological Restoration

The disparate global range of Plethodontid salamanders in the Batrachoseps subgenus Plethopsis is unique, and implicates perplexing historical biogeographic scenarios.  Using uncorrelated relaxed molecular clock methods and fossil-calibrated divergence estimates from Shen et al. (2016), we present a time-scaled phylogeny for the genus Batrachoseps in order to test hypotheses concerning the diversification of the subgenus Plethopsis.  Our estimated divergence time intervals detract support from a hypothesis that Batrachoseps robustus diverged as the flow of the Owens river changed course at ca. 3.2 Ma, as evidenced by sediment deposits at Searles Lake (Phillips, 2008).  Instead, our estimates support that diversification of the known Plethopsis species began earlier, in the late Miocene to early Pliocene, as extensional activity formed the proto-Owens Valley and led to ensuing hydrological and climatic changes, driving vicariance between populations in the proto-southern Sierra Nevada and Inyo Mountains.  Moreover, our estimates support a scenario wherein B. campi and B. wrighti diverged in the Pliocene as ancestral populations of B. wrighti expanded northward to Oregon via a corridor of relatively mesic habitat in the western Great Basin.