Meeting Abstract
Salinity tolerance is a defining factor in shaping geographic range limits of many species. Nonetheless, the influence of salinity tolerance on patterns of dispersal and local adaptation are relatively understudied for most species. In aquatic environments, euryhaline species are capable of acclimating to a wide range of salinities; however, most species typically exhibit a preference for a particular salinity. For example, previous work in euryhaline teleosts indicates that crossing along a salinity gradient typically results in increased oxygen uptake, incurring an energetic cost for the organism. On the island of Trinidad, swamp guppies, Poecilia picta, are typically found in adjacent fresh and brackish water habitats, but the degree to which these populations are locally adapted to different salinities is unknown. We investigate the physiological responses to variations in salinity at different temporal scales as a means to determine whether the physiological response to salinity variation in these populations is locally adaptive. To do so, we split wild-caught individuals from each population and laboratory acclimated them to freshwater (0ppt) and brackish water (30ppt) conditions over a 3-month period. By gradually acclimating wild P. picta to alternate salinities, we simulated slow movement along the salinity gradient. We also tested the effect of a rapid acclimation through a fast-changing salinity titration to simulate conditions these fish might encounter during dispersal or flooding events. If the populations are locally adapted, then we predict that elevated metabolic rates will be higher when fish are exposed to their “away” salinity conditions.
