Genetic diversity and population systematics of hydrophiine sea snakes from the Ryukyus Archipelago, Japan

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To revise the long-confusing taxonomy of hydrophiine(i. e., viviparous) sea snakes from the Ryukyu Archipelago, Japan, and adjacent regions, morphological and molecular phylogenetic analyses were conducted using newly collected specimens, as well as specimens deposited in museums and other comparable institutions. As a result, distribution of Emydocephalus ijimae proved to be geographically strictly confined to the Ryukyu-Taiwan region. There was a prominent inconsistency in the species' delimitations of Hydrophis melanocephalus and H. cyanocinctus against each other between morphological and molecular approaches. Therefore, morphological re-definitions of the two species were strongly needed. Sea snake specimens referred to as voucher in the previous records of Lapemis curtus from the Ryukyus were not detected, and the other specimen from this region, identified as L. curtus and deposited in a museum, proved to represent a different species of Hydrophis in reality. These findings strongly suggest that actually L. curtus does not occur in the Japanese territory.