Tracking the evolution of thermal niches in Palearctic lacertid lizards

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We propose an innovative study integrating approaches in phylogenomics, physiology, osteology and paleontology to understand the evolution of thermophysiologial adaptations in lacertid lizards. Species in the family Lacertidae are the predominant lizards in Europe and widely represented in the fossil record. They comprise both microendemic and extremely widespread species. From their ecological preferences, it can be hypothesized that lacertid clades might be differentially specialized to temperature and humidity regimes. Lacertids therefore might constitute an ideal model group to understand biotic impacts of present and past climatic change. We will use a supermatrix of DNA sequences obtained from transcriptomes, anchored hybrid enrichment sequencing, and traditional Sanger sequencing to produce a highly supported, time-calibrated phylogenetic tree of these lizards with near-complete species coverage, focusing in particular on the Lacertini clade which is distributed mainly in the Western Palearctic. Based on micro-CT scans of the skeletons of all 124 extant Lacertini species we will define osteological character states, optimize these via combined molecular-morphological phylogenetic analysis, and use them to assign fossils to clades. Experimentally assessed optimum, preferred, field, and critical minimum and maximum temperatures for all Lacertini species will be used to model their present and past potential distribution ranges. Thermophysiological niches will be reconstructed as traits along the phylogeny to define clades specialized to particular niches, and the fossil distribution of these clades will validate paleomodels. Using the envisaged extensive data set we will test the hypotheses that (a) a combination of phylogenomic and ostelogical data allows resolving fast Cenozoic radiations such as the Lacertini, including a reliable placement of many fossil taxa, (b) a substantial portion of lacertid fossils can be assigned to particular lacertid clades based on a detailed examination of skeletons and cladistic definitions of character states, (c) thermophysiological traits are often clade-specific and help inferring past climates from fossil assemblages, (d) variation in thermal tolerances correlates with latitudinal range size of lizards, (e) paleodistributions based on fossils can provide a stringent validation of physiology-based models to predict climate-change effects. By appropriate choice of outgroups for transcriptome determination our data will further considerably contribute to resolving deep phylogeny of squamates, and the thermophysiology-informed distribution models will directly feed into a global assessment of reptile extinction risks.