Phylogenetic relationships and divergence times of reptiles inferred by mitochondrial DNA sequences

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During the granted period, we have sequenced mitochondrial DNAs of various reptiles. These data have been characterized in both the evolution of mitochondrial genome organization and the pattern and timing of phylogenetic divergences. We found that mtDNAs of some reptile groups (e.g., snakes, varanids, agamids, and cordylids) have distinct gene organizations from the typical organization found in most vertebrates. We then addressed when and how these gene rearrangements took place on ancestral lineages of each group by comparing sequences of the corresponding mtDNA region among relevant taxa. With respect to phylogenetic matters, the following implications were obtained. 1) Lacertilia can be divided into four groups mostly corresponding to infraorders suggested by morphological studies, 2) Amphisbaenia is nested within Lacertilia and is the most closely related to Lacertidae, 3) Among the four lizard infraorders, Gekkota rather than Iguania diverged first, 4) Snakes are not closely related to Varanoidea, and 5) Lizard families have deep divergences extending to Triassic and Jurassic.