Genetic differentiation among Long-Toed Salamander (Ambystoma macrodactylum) populations

We examined the genetic population structure of Long-Toed Salamanders (Amby stoma macrodactylum) from the Bitterroot Mountains of Idaho and Montana to better understand their evolutionary history and genetic population structu re. Populations show high levels of within-population genetic variation at sig polymorphic allozyme loci ((H) over bar(s) = 0.09 for all 18 loci exami ned; range 0.04-0.14). There is very little divergence among populations wi thin basins, suggesting panmixia within basins. In contrast, genetic differ entiation among all populations is high (G(st) = 0.30). We used computer si mulations to examine population structures that could have led to the obser ved distribution of genetic variation, assuming selective neutrality of the allozymes. To test the assumption of selective neutrality of the markers u sed in dais study, we compared the observed divergence among the allozymes to that expected from simulations of independently segregating and selectiv ely neutral markers. The observed genetic divergence among populations is c ompatible xith that expected for neutral genetic markers sampled from panmi ctic populations within basins that exchange less than one migrant among ba sins each generation.