Comparative analyses of effective population size within and among species: ranid frogs as a case study

It has recently become practicable to estimate the effective sizes (N(e) ) of multiple populations within species. Such efforts are valuable for estimating N(e) in evolutionary modeling and conservation planning. We used microsatellite loci to estimate N(e) of 90 populations of four ranid frog species (20-26 populations per species, mean n per population = 29). Our objectives were to determine typical values of N(e) for populations of each species, compare N(e) estimates among the species, and test for correlations between several geographic variables and N(e) within species. We used single-sample linkage disequilibrium (LD), approximate Bayesian computation (ABC), and sibship assignment (SA) methods to estimate contemporary N(e) for each population. Three of the species-Rana pretiosa, R. luteiventris, and R. cascadae- have consistently small effective population sizes (<50). N(e) in Lithobates pipiens spans a wider range, with some values in the hundreds or thousands. There is a strong east-to-west trend of decreasing N(e) in L. pipiens. The smaller effective sizes of western populations of this species may be related to habitat fragmentation and population bottlenecking.