S5-1.1 Thursday, Jan. 5 Marine Invasions by Non-Sea Snakes, With Thoughts on Terrestrial-Aquatic-Marine Transitions MURPHY, John; Field Museum of Natural History email@example.com
Oceans cover 71% of the earth’s surface with about 350,000 km of coastline yet only 2.5% (about 86 species) of the 3364 extant snakes are known to inhabit the oceans, but at least another 54 species are known to use the brackish and marine waters of coastal habitats. The physical environment and possibly marine predators appear to provide challenges for snakes. Yet there is evidence that evolution continues to tinker with snake adaptation to marine environments. A survey of life styles and habitats of 2552 althenophidian snakes in 459 genera revealed about 362 (14%) semi-aquatic and aquatic species; only 70 (2.7%) of these are sea snakes (Hydrophiinae and Laticaudinae). The ancient Acrochordidae contains three extant species, all of which have populations in brackish, marine and freshwater environments. A family that contains terrestrial, semi-aquatic and aquatic snakes, the Homalopsidae has another 14 species that have invaded brackish and marine waters. The specious Dipsadidae of the western hemisphere has an additional seven species with coastal-marine populations; while the cosmopolitan Natricidae has 24 species with populations that inhabit brackish waters; and the semi-aquatic, African Grayiinae has at least one species that uses brackish water. Geographically the most specious brackish water snake assemblages are concentrated in South East Asia and Australasia with distributions that correspond to the most diverse mangrove and salt marsh communities. Species with semi-aquatic lifestyles are compared with more aquatic and terrestrial (fossorial, cryptozoic, and arboreal) species for morphological and life history traits. Emergent morphological and life history characters are identified that may provide clues to the evolution of marine snakes.