Aim We used inferences of phylogeographical structure and estimates of divergence times for three species of gophersnakes (Colubridae: Pituophis) distributed across the Mexican Transition Zone (MTZ) to evaluate the postulated association of three Neogene geological events (marine seaway inundation of the Isthmus of Tehuantepec, formation of the Transvolcanic Belt across central Mexico, and secondary uplifting of the Sierra Madre Occidental) and of Pleistocene climate change with inter-and intraspecific diversification.Location Mexico, Guatemala, and the western United States.Methods We combined range-wide sampling (67 individuals representing three putative species distributed across northern Middle America and western North America) and phylogenetic analyses of 1637 base pairs of mitochondrial DNA to estimate genealogical relationships and divergence times. The hypothesized concordance of inferred gene trees with geological histories was assessed using topology tests. ResultsWe identified three major lineages of Middle American gophersnakes, and strong phylogeographical structure within each lineage. Gene trees were statistically congruent with hypothesized geological histories for two of the three postulated geological events. Estimated divergence dates and the geographical distribution of genetic variation further support mixed responses to these geological events. Considerable phylogeographical structure appears to have been generated during the Pleistocene.Main conclusions Phylogenetic and phylogeographical structure in gophersnakes distributed across northern Middle America and western North America highlights the influence of both Neogene vicariance events and Pleistocene climate change in shaping genetic diversity in this region. Despite the presence of two major geographical barriers in southern Mexico, extreme geological and environmental heterogeneity in this area may have differentially structured genetic diversity in highland taxa. To the north, co-distributed taxa may display a more predictable pattern of diversification across the warm desert regions. Future studies should incorporate nuclear data to disentangle inferred lineage boundaries and further elucidate patterns of mitochondrial introgression.

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que, hasta octubre de 2013, en México existen 864 especies de reptiles, descritas en 159 géneros y 40 familias que representan el 8.7% de los reptiles del mundo. De las 864 especies, 417 son lagartijas, 393 serpientes, 48 tortugas, 3 anfisbénidos y 3 cocodrilos. Se registraron 493 taxones endémicos para el país. Los estados con un mayor número de especies son: Oaxaca (262), Chiapas (220) y Veracruz (200), mientras que los estados con una fauna de reptiles menos diversa son: Tlaxcala (36 especies), Distrito Federal (39) y Guanajuato (43).

Aim: Multiple geological and climatic events have created geographical or ecological barriers associated with speciation events, playing a role in biological diversification in Mexico. Here, we evaluate the influence of Neogene geological events and of Pleistocene climate change in the diversification of the genus Gerrhonotus using molecular dating and ancestral area reconstruction. Location: Mexico and south-central United States.Methods: A multilocus sequence dataset was generated for 86 individuals of Gerrhonotus from most Mexican biogeographical provinces and belonging to five of the seven currently recognized species, as well as two putative undescribed species. Phylogeographical structure was explored using Poisson-Tree-Processes molecular species delimitation. Divergence events were estimated based on the fossil record using a relaxed uncorrelated lognormal clock. Ancestral areas were estimated at divergence events across the tree using a probabilistic Bayesian approach.Results: Extensive geographical structure was evident within three well-supported clades. These clades probably diverged from each other in the early to mid-Miocene, and their divergence was followed by six divergences in the late Miocene and eight divergences in the Pliocene. The ancestral origin of Gerrhonotus with keeled dorsal scales (keeled-scale Gerrhonotus) was reconstructed to be across the Pacific Coast Province. Our phylogenetic analyses did not support the monophyly of Gerrhonotus. Main conclusions: Miocene and Pliocene geomorphology, perhaps in conjunction with climate change, appears to have induced allopatric divergence on a relatively small spatial scale in this genus. The late Miocene-Pliocene reduction in the highlands along the Tehuantepec fault probably created a large marine embayment that led to an early divergence in a clade of Gerrhonotus. Our analysis suggests uplifting of the Trans-Mexican Volcanic Belt during this same time period resulted in additional diversification. This was followed by more recent, independent colonization events in the Pliocene from the Mexican Plateau to the Sierra Madre Oriental, Sierra Madre Occidental, Tamaulipas and Edwards Plateau provinces. A genus Gerrhonotus with the keeled-scale species in addition to Coloptychon rhombifer (= G.