Tracking the evolution of thermal niches in Palearctic lacertid lizards

我们提出了一项整合系统基因组学、生理学、骨学和古生物学方法的创新研究，以了解lacertid蜥蜴的热生理适应进化。蜥科蜥蜴是欧洲主要的蜥蜴，在化石记录中有广泛的代表性。它们包括微地方性和极其广泛的物种。从它们的生态偏好来看，我们可以假设lacertid分支可能对温度和湿度有不同的特异性。因此，乳虫类可能是理解当前和过去气候变化对生物影响的理想模型群。我们将使用从转录组中获得的DNA序列的超矩阵，锚定杂交富集测序和传统的Sanger测序来产生一个高度支持的，时间校准的这些蜥蜴的系统发育树，具有近乎完整的物种覆盖，特别关注主要分布在古北西部的Lacertini分支。基于所有现存124种Lacertini物种骨骼的微ct扫描，我们将定义骨骼特征状态，通过结合分子形态系统发育分析优化这些特征状态，并使用它们将化石分配给进化支。通过实验评估所有Lacertini物种的最佳、首选、野外和临界最低和最高温度，将用于模拟它们现在和过去的潜在分布范围。热生理生态位将被重建为沿着系统发育的特征，以定义专门针对特定生态位的进化枝，这些进化枝的化石分布将验证古模型。使用设想的广泛数据集，我们将测试以下假设：(a)系统发育学和骨骼学数据的结合可以快速解决新生代辐射，如Lacertini，包括许多化石分类群的可靠位置；(b)基于对骨骼的详细检查和特征状态的分支定义，可以将相当一部分lacertid化石分配给特定的Lacertini分支；(c)热生理特征通常是进化枝特异性的，有助于从化石组合推断过去的气候；(d)热耐受性的变化与蜥蜴的纬度范围大小相关；(e)基于化石的古分布可以为基于生理的模型提供严格的验证，以预测气候变化的影响。通过选择合适的外群来确定转录组，我们的数据将进一步有助于解决鳞片动物的深层系统发育问题，并且基于热生理学的分布模型将直接用于爬行动物灭绝风险的全球评估。

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.