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AimWe quantify the degree to which co-distributed snakes across the Cochise Filter Barrier (CFB) have a shared history of population divergence and estimate the timing of divergence for each taxon pair.

LocationNorth America.

MethodsA single locus dataset was collected (n=747 individuals) for 12 snake taxon pairs. Phylogeographical structure was estimated for each taxon. Redundancy analyses were used to assess the importance of geographical distance, climate and putative barriers to gene flow in structuring genetic diversity. Hierarchical approximate Bayesian computation was used to estimate the magnitude of synchronicity in divergence times across a well-documented phylogeographical barrier. Lastly, gene divergence and population divergence times were estimated using multiple methods.

ResultsThere is substantial phylogeographical structure in many of the snake taxa, particularly at the CFB. A model containing distance, climate and barriers explained the greatest amount of genetic variation in nearly all taxa. When each variable was examined separately, climate explained the most variation. The hABC model testing indicates that there is overwhelming support for asynchronous phylogeographical histories within these co-distributed taxa. Estimated divergence times range throughout the Quaternary and Neogene.

Main ConclusionsWe demonstrate that the 12 snake taxon pairs studied here have diversified within the desert Southwest forming distinct Sonoran and Chihuahuan populations, illustrating the importance of this region in driving diversification in North American taxa. Although these groups exhibit the same pattern of lineage formation, there is strong support for asynchronous diversification and little concordance in divergence time estimates.