Molecular Evaluation of Phylogenetic Significances in the Highly Divergent Karyotypes of the Genus Gonocephalus (Reptilia: Agamidae) from Tropical Asia

The Oriental large-bodied crested dragons of the genusGonocephalusare known to includetwo distinct karyomorphs. To evaluate their phylogenetic significances, we conducted phylogenetic analysesof the genus together with other agamid genera on the basis of 862 base positions of mitochondrial12S and 16S rRNA genes. Results suggested the presence of two distinct lineages withinGonocephalus,of which one, represented byG. robinsoniithat has a 2n=32 karyotype, was closer to other Oriental agamidgenera than to the other congeneric lineage. Monophyly of the latter, characterized by unique chromosomalarrangement among agamid genera (2n=42 karyotype), was confirmed. It is thus likely that statesof morphological characters shared between the two lineages are derived through convergence, or representsymplesiomorphy. Our results also suggest that the karyological similarity betweenG. robinsoniiandseveral Australian agamids, pointed out in a previous study, is actually attributable to homoplasy ratherthan their recent common ancestry