Meeting Abstract
55.6 Sunday, Jan. 5 14:45 Salt and the Rough-skinned Newt: Investigations of Adaptation to a Natural and Anthropogenic Stressor HOPKINS, G.R.*; BRODIE, JR., E.D.; FRENCH, S.S.; Utah State University; Utah State University; Utah State University gareth.hopkins@usu.edu
Amphibians are osmotically sensitive organisms, and tolerance of saline environments is rare (some coastal species have adapted to natural sources of salt). Due to anthropogenic factors, freshwater habitats are becoming increasingly saline, and osmotically sensitive organisms will be forced to adapt. We investigated the ability of the rough-skinned newt (Taricha granulosa) to adapt to natural and anthropogenic sources of salt. Increasing salt concentrations resulted in higher newt egg mortality, incidence of developmental deformities, reduced size and developmental stage at hatching, and significantly compromised post-hatching larval survival. Survival was also dependent on the type of salt used, and whether or not newts had an evolutionary history of regulating it. MgCl2 was more toxic to larvae than NaCl, which larvae were able to regulate with Na+ pumps. We also found in a salt-naïve population of newts there exists significant interfamily variation in salt tolerance, providing the raw material for natural selection and evolutionary change. We have discovered that newt populations along the Oregon coast have adapted to naturally elevated sources of NaCl. Newts located in the tidal area of a stream were significantly less stressed (lower corticosterone levels) and their immune system (bacterial killing ability) less affected by NaCl than newts located upstream. Thus, adaptation to salt can occur in this amphibian species, and such adaptive potential may be more common than originally thought. We provide some preliminary evidence, however, that the affect of salt on newts may interact with other environmental factors, namely temperature, with possible consequences for the adaptive potential of amphibian populations in a warming world.
