Phylogeographic inference can determine the timing of population divergence, historical demographic processes, patterns of migration, and when extended to multiple species, the history of communities. Single-locus analyses can mislead interpretations of the evolutionary history of taxa and comparative analyses. It is therefore important to revisit previous single-locus phylogeographic studies, particularly those that have been used to propose general patterns for regional biotas and the processes responsible for generating inferred patterns. Here, we employ a multilocus statistical approach to re-examine the phylogeography of Lampropeltis zonata. Using nonparametic and Bayesian species delimitation, we determined that there are two well-supported species within L. zonata. Ecological niche modelling supports the delimitation of these taxa, suggesting that the two species inhabit distinct climatic environments. Gene flow between the two taxa is low and appears to occur unidirectionally. Further, our data suggest that gene flow was mediated by females, a rare pattern in snakes. In contrast to previous analyses, we determined that the divergence between the two lineages occurred in the late Pliocene (c. 2.07 Ma). Spatially and temporally, the divergence of these lineages is associated with the inundation of central California by the Monterey Bay. The effective population sizes of the two species appear to have been unaffected by Pleistocene glaciation. Our increased sampling of loci for L. zonata, combined with previously published multilocus analyses of other sympatric species, suggests that previous conclusions reached by comparative phylogeographic studies conducted within the California Floristic Province should be reassessed.
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