Mitochondrial DNA sequences of five squamates: phylogenetic affiliation of snakes.

Complete or nearly complete mitochondrial DNA sequences were determined from four lizards (Western fence lizard, Warren's spinytail lizard, Terrestrial arboreal alligator lizard, and Chinese crocodile lizard) and a snake (Texas blind snake). These genomes had a typical gene organization found in those of most mammals and fishes, except for a translocation of the glutamine tRNA gene in the blind snake and a tandem duplication of the threonine and proline tRNA genes in the spinytail lizard. Although previous work showed the existence of duplicate control regions in mitochondrial DNAs of several snakes, the blind snake did not have this characteristic. Phylogenetic analyses based on different tree-building methods consistently supported that the blind snake and a colubrid snake (akamata) make a sister clade relative to all the lizard taxa from six different families. An alternative hypothesis that snakes evolved from a lineage of varanoids was not favored and nearly statistically rejected by the Kishino-Hasegawa test. It is therefore likely that the apparent similarity of the tongue structure between snakes and varanoids independently evolved and that the duplication of the control region occurred on a snake lineage after divergence of the blind snake.