Small effective population size in the long-toed salamander

The effective population sizes (N-e) of six populations of the long-toed salamander (Ambystoma macrodactylum) from Montana and Idaho, USA were estimated from allozyme data from samples collected in 1978, 1996 and 1997 using the temporal allele frequency method. Five of the six estimates ranged from 23 to 207 (mean = 123 +/- 79); one estimate was indistinguishable from infinity. In order to infer the actual N-e of salamander populations, we compared the frequency distribution of our observed N-e estimates with distributions obtained from simulated populations of known N-e. Our observed N-e estimate distribution was consistent with distributions from simulated populations with N-e values of 10, 25, and 50, suggesting an actual N-e for each of the six salamander populations of less than 100. This N-e estimate agrees with most other N-e estimates for amphibians. We conclude by discussing the conservation implications of small N-e values in amphibians in the context of increasing isolation of populations due to habitat fragmentation.