Geographic Variation in Sea Kraits of the 'Laticauda colubrina' Complex (Serpentes: Elapidae: Hydrophiinae: Laticaudini)

Abstract

The 'Laticauda colubrina' complex previously consisted of three species, 'Laticauda saintgironsi' from New Caledonia and the Loyalty Islands, 'Laticauda frontalis' from Vanuatu, and 'Laticauda colubrina', a widespread species ranging from the Andaman and Nicobar Islands and the Myanmar-Thai-Malaysian peninsula, through the Indonesian archipelago to New Guinea, north to Palau, the Philippines, Taiwan and the Ryukyu Islands, and southeastward along the island-chain of the Solomon Islands, Vanuatu, Fiji and Tonga. Their geographic variation, based on 1515 specimens involving 33 characters of coloration and scutellation, was analyzed in two different ways: (1) an hierarchical analysis and (2) an analysis of principal components and discriminant function. Sexual dimorphism occurred in many characters and for those, females and males were analyzed separately. The results confirmed the distinctiveness of the three original species. Within 'L. colubrina' different characters displayed slightly different geographic patterns of variation, but overall five general groupings of populations could be discerned: (1) a north-south axis from Sabah, north through the Philippines to Taiwan and the Ryukyus, (2) an east-west axis encompassing localities from the Andaman and Nicobar Islands in the west through New Guinea and the Solomon Islands in the east, (3) the eastern islands of Vanuatu, Fiji, and Tonga, (4) a partially isolated population in Palau, and finally (5) an isolate in southern Papua. Despite significant differences among these regions, different characters showed slightly different patterns of geographic variation across their boundaries; similarly, within each axis the pattern of variation among islands differed for different characters. Divergence was deemed sufficiently consistent to warrant taxonomic distinction only in the case of the population in southern Papua that was accorded recognition as a new species, Laticauda guineai. In some characters, widely peripheral populations were more similar morphologically to each other than to more central ones, and alternative hypotheses accounting for this are discussed. The observed distribution and the geographic patterns of variation are attributable to a combination of present and past ecological restrictions, directions of sea currents, and paleogeography.