BELDEN, L.K.; BLAUSTEIN, A.R.: Population differences in sensitivity to UV-B radiation for larval long-toed salamanders

Due to ozone depletion, the intensity of ultraviolet-B radiation (UV-B; 280 – 315 nm) at the Earth’s surface is increasing. UV-B penetrates some aquatic habitats to biologically significant depths and can alter life histories of aquatic organisms, including algae, zooplankton, fish and amphibians. UV-B has also been suggested as one factor that could be contributing to current worldwide amphibian population declines. While major interspecific differences have been documented for UV-B sensitivity in amphibians, few studies have examined differences between populations of the same species. Previous work has suggested that larval long-toed salamanders, Ambystoma macrodactylum, from valley populations (approximately 100 m elevation) were more sensitive to UV-B exposure than individuals from mountain populations (above 500 m elevation). To test this hypothesis, we brought early stage embryos into the laboratory from three valley populations and five mountain populations and raised them under identical conditions without UV-B for two months after hatching. Larvae from each population were then placed under UV-B lighting and growth and survivorship was recorded for three weeks. Larvae from all populations had higher mortality when exposed to UV-B than when shielded from UV-B. However, UV-B exposed individuals from low elevation populations had significantly lower survivorship than those from high elevation, suggesting an elevational difference in UV-B sensitivity. In all populations, UV-B exposed individuals were smaller than shielded individuals after one week. If UV-B is a factor in determining the long-term persistence of some amphibian species, an understanding of within species variation is critical.