Comparative Analyses of Effective Population Size Within and Among Species: Ranid Frogs as a Case Study

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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.



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