S5-1.4 Thursday, Jan. 5 Distributional data helps to identify evolutionary challenges: Oceanic salinity as a major constraint during the transition to marine life in snakes BRISCHOUX, F*; TINGLEY, R; SHINE, R; LILLYWHITE, HB; CEBC-CNRS, France; University of Sydney, Australia; University of Sydney, Australia; University of Florida, USA email@example.com
Secondary transitions from terrestrial to marine life provide remarkable examples of evolutionary change. Maintenance of osmotic balance poses a particular challenge for secondarily marine vertebrates. However, its role during such evolutionary transition has not previously been assessed. Using large scale biogeographical analyses on the four independent lineages of marine snakes, we found that salinity significantly constrains their current distribution, and does so more profoundly in species which are presumably analogous to the early transitional forms between the land and the sea. Fine scale analyses at the species level suggest that a more efficient salt-secreting gland allows a species to exploit more saline, and hence larger, oceanic areas. These results, as well as the current ranges of marine snakes suggest that the Indonesian Basin has been a centre of origin for the four independent lineages of marine snakes. We emphasise that both the low salinity and high seasonal variation in salinity of the Indonesian Basin might have provided a favourable context for the evolutionary transition to marine life in snakes. More generally, salinity may have been an overlooked parameter in ecological and evolutionary studies of secondarily marine vertebrates (including turtles, birds and mammals) and should be incorporated into models assessing the impact of climate change on marine vertebrates. Supported by NSF IOS–0926802 to HB Lillywhite.