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.

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Aim The aim of our study was to reconstruct ancestral geographic distributions from time‐calibrated phylogenies generated from phylogenomic data to answer three broad questions about the biogeography of skinks in the Plestiodon brevirostris group: (1) Are biogeographic patterns correlated with the formation of the Trans‐Mexican Volcanic Belt? (2) Do different methods of phylogenetic estimation result in different topologies? If so, (3) are biogeographic reconstructions impacted by the use of different phylogenetic trees? Location Mexico. Methods We used target enrichment of ultraconserved elements (UCEs) to obtain sequence data from 58 skinks representing 11 of the 13 described species in the group. We estimated time‐calibrated phylogenies using concatenated and multispecies coalescent phylogenetic approaches. We used these phylogenies to reconstruct ancestral geographic distributions. Results The final dataset contained 3,282 UCEs from each skink. Samples of each putative species formed well‐supported clades in phylogenetic trees. Time‐calibrated phylogenies estimated using concatenated and multispecies coalescent methods were generally congruent, but differed in the placement of one basal relationship. Divergences in the P. brevirostris group were temporally and spatially congruent with the pre‐Pleistocene formation of the Trans‐Mexican Volcanic Belt. The group most likely colonized the Mexican highlands from east to west during the Late Miocene and Pliocene. Inferences about the early biogeographic history of the group were confounded by the unresolved placement of a key phylogenetic relationship deep in the phylogeny. Conclusions Skinks in the P. brevirostris group represent another example of a widespread montane Mexican taxon with a long history of pre‐Pleistocene diversification associated with the primary formation of the Trans‐Mexican Volcanic Belt. This mountain range seems to have been both a cradle of diversification for P. brevirostris group species and a land bridge facilitating dispersal across the Mexican highlands. Our results highlight the probable existence of new species within the P. brevirostris complex and suggest that querying a large portion of the genome may be critically important for studying the biogeographic history of these skinks. However, inferred differences between the concatenated and multispecies coalescent phylogenies, and the different biogeographic histories of the P. brevirostris group reconstructed from these phylogenies, caution that methods of estimating phylogenetic trees used in biogeographic reconstructions need to be carefully considered.

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A new species of the Rhadinaeadecorata group is described based on two specimens from the Sierra Madre del Sur, Guerrero, Mexico. The new species differs from all other members of the genus Rhadinaea by having: eight supralabials; 149–151 (male) ventrals; 63–77 (male) subcaudals; two large pale nuchal blotches, forming an incomplete collar that occupies two scales laterally and is bissected along the dorsal midline; a postocular pale marking consisting of a well-defined, narrow line beginning behind the upper posterior margin of the eye and extending posteriorly nearly horizontally until connecting with the nuchal blotches; and the dark ground color of the flanks extending to the lateral portion of the ventrals. The large nuchal blotches distinguish the new species from the other members of the R.decorata group, except for R.cuneata and some individuals of R.hesperia (pale nuchal marking one-scale wide in R.marcellae, absent in the other species). The condition of the postocular pale marking distinguishes it from R.cuneata and R.hesperia (postocular pale marking wedge-shaped in R.cuneata, not connected with the pale post-cephalic markings in R.hesperia). Furthermore, the number of subcaudals and the coloration of the lateral portion of the ventrals distinguish it from R.omiltemana and R.taeniata, the remaining congeners found in Guerrero (85–90 in males of R.omiltemana and 91–121 in R.taeniata; dark color of the flanks not reaching ventrals in the former species, occasionally and faintly in R.taeniata). Additionally, a new combination for R.stadelmani is proposed. The new species is the first described in the genus Rhadinaea in more than 40 years.

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How biotic and abiotic factors act together to shape biological diversity is a major question in evolutionary biology. The recent availability of large datasets and development of new methodological approaches provide new tools to evaluate the predicted effects of ecological interactions and geography on lineage diversification and phenotypic evolution. Here, we use a near complete phylogenomic-scale phylogeny and a comprehensive morphological dataset comprising more than a thousand specimens to assess the role of biotic and abiotic processes in the diversification of monitor lizards (Varanidae). This charismatic group of lizards shows striking variation in species richness among its clades and multiple instances of endemic radiation in Indo-Australasia (i.e., the Indo-Australian Archipelago and Australia), one of Earth's most biogeographically complex regions. We found heterogeneity in diversification dynamics across the family. Idiosyncratic biotic and geographic conditions appear to have driven diversification and morphological evolution in three endemic Indo-Australasian radiations. Furthermore, incumbency effects partially explain patterns in the biotic exchange between Australia and New Guinea. Our results offer insight into the dynamic history of Indo-Australasia, the evolutionary significance of competition, and the long-term consequences of incumbency effects.

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