Molecular systematics of the Agkistrodon complex
Knight, Ralph Alexander
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This Study focused on the evolution and systematics of the pitviper genus Agkistrodon and other genera traditionally allied with Aakistrodon: Calloselasma. Deinagkistrodon and Hypnale. One aim was to complement traditional work by providing the first molecular systematic data sets for the Aakistrodon complex, based on restriction fragment and sequence analyses of mitochondrial DNAs. Restriction fragment analysis showed low genetic variation among A. contortrix populations, suggesting a recent radiation of the modern races. Geographic distribution of mitochondrial DNA genotypes among A. contortrix populations was discordant with distribution of morphological variation. The divergence between eastern and western A. piscivorus was of a degree greater than that observed between some species, and suggested that populations were isolated in refugia since the onset of the Pleistocene. New World Aakistrodon is a monophyletic group. Restriction fragment and 16S ribosomal gene sequence data suggested an A. bilineatus-A. piscivorus association, with A. contortrix the basal lineage of New World Agkistrodon. A relatively large degree of independent evolution has occurred along the A. contortrix lineage. Results of both analyses showed that the inclusion of Asian and New World species together forms a polyphyletic group, thereby supporting recognition of genus the Gloydius for the Asian species. Sequence obtained for Hypnale was different from other pitvipers and was not useful for phylogenetic purposes. Calloselasma rhodostoma and Deinagkistrodon acutus appeared to be remnants of an early pitviper radiation, and the validity of their independent generic status was confirmed.