Mesozoic continental fragmentations and lizard radiations

完整的或近乎完整的线粒体DNA序列已经从不同种类的蜥蜴中确定，这些蜥蜴代表了鳞目的主要家族。与先前发表的其他脊椎动物分类群的有丝分裂基因组序列一起，我们进行了分子系统发育分析。通过最大似然方法建立了可靠的系统发育关系，并使用贝叶斯方法估计了发散时间，而不假设分子钟。根据这些分子结果和独立的地质和古生物学数据，对生物地理学假设进行了评估。1)主要蜥蜴科之间的分化早于白垩纪大规模大陆碎裂期，但蜥蜴科与变色龙科之间的分化可能发生在白垩纪中期。2)另一方面，大多数蛇的家族辐射发生在白垩纪/第三纪界线之后。(3)泛大陆分裂为Laurasia和Gondwanaland可能与蜥蜴的一些较浅的分化有关，例如Eublepharinae和Gekkoninae之间的分化。其他发现还包括首次在脊椎动物线粒体基因组中发现龙蝇脯氨酸tRNA基因的基因倒置。

Complete or nearly complete mitochondrial DNA sequences have been determined from various species of lizards that represent major families of the order Squamata. Together with previously published mitogenomic sequences of other vertebrate taxa, we have conducted molecular phylogenetic analyses. Reliable phylogenetic relationships have been established by the maximum-likelihood method and divergence times were estimated using a Baysian method without assuming the molecular clock. Biogeographic hypotheses were evaluated in light of these molecular results and independent geological and paleontological data Our major findings are the following. 1) Divergences between major lizard families predate the large-scale continental fragmentation during Cretaceous time, except for the divergence between Agamidae and Chamaeleonidae that likely occurred in the mid-Cretaceous. 2) On the other hand, most familial radiations of snakes postdate the Cretaceous/Tertiary boundary. 3) The break-up of Pangea into Laurasia and Gondwanaland may have been correlated with some shallower divergences of lizards, e.g., between Eublepharinae and Gekkoninae. Other findings include the first characterization of gene inversion in vertebrate mitochondrial geneomes in the proline tRNA gene of Draconinae agamids.