Genetic Differentiation among Long-Toed Salamander (Ambystoma macrodactylum) Populations
We examined the genetic population structure of Long-Toed Salamanders (Ambystoma macrodactylum) from the Bitterroot Mountains of Idaho and Montana to better understand their evolutionary history and genetic population structure. Populations show high levels of within-population genetic variation at six polymorphic allozyme loci (H̄s = 0.09 for all 18 loci examined; range 0.04–0.14). There is very little divergence among populations within basins, suggesting panmixia within basins. In contrast, genetic differentiation among all populations is high (Gst = 0.30). We used computer simulations to examine population structures that could have led to the observed distribution of genetic variation, assuming selective neutrality of the allozymes. To test the assumption of selective neutrality of the markers used in this study, we compared the observed divergence among the allozymes to that expected from simulations of independently segregating and selectively neutral markers. The observed genetic divergence among populations is compatible with that expected for neutral genetic markers sampled from panmictic populations within basins that exchange less than one migrant among basins each generation.Abstract
Long-toed salamander populations sampled in the main study area of the Bitterroot Mountains of eastern Idaho and western Montana. Dotted lines outline basins containing multiple populations (β). Dashed lines outline the four major ridges
Plot of the first two principal component scores of the most common allele at six polymorphic loci among 34 long-toed salamander populations in the Bitterroot Mountains. (The axes are scaled by the square root of the associated eigenvalue.) These 34 populations aggregate loosely into three clusters lettered A, B, and C
Mean and variance in divergence among populations (Gst) as a function of the number of migrants per generation (Nm) between populations. Effective population size is 100 for each population. (The dotted line indicates the observed mean level of divergence among long-toed salamander populations.)