Cold Snails in Hot Springs: Observations from Patagonia and the Tibetan Plateau

ABSTRACT Patagonia and the Tibetan Plateau both harbor various freshwaters with relatively low temperatures. Pulmonate freshwater gastropods are widely distributed in these water bodies. Both regions, however, also possess a number of geothermal hot springs. Such springs might have served as refugia for freshwater taxa during the Pleistocene. In the present study, two hot spring systems, one in Patagonia and one at the Tibetan Plateau, were examined. Individuals of Chilina patagonica (in Patagonia) as well as Radix cf. auricularia and Gyraulus sp. (at the Tibetan Plateau) were found living in the warm water. These taxa typically live at much lower water temperatures. At the Patagonian hot spring system, gastropods occurred continuously from warm to cold water. Analyses of mitochondrial DNA sequence data revealed very close relationships of Tibetan Plateau hot spring gastropods to cold water populations. Acclimatization and not adaptation is thus probably the main thermal adjustment process involved. Given these findings, it is plausible that hot springs have served as glacial refugia for these freshwater gastropods.