COMPARATIVE ANALYSES OF EFFECTIVE POPULATION SIZE WITHIN AND AMONG SPECIES: RANID FROGS AS A CASE STUDY

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Abstract

It has recently become practicable to estimate the effective sizes (Ne) of multiple populations within species. Such efforts are valuable for estimating Ne in evolutionary modeling and conservation planning. We used microsatellite loci to estimate Ne 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 Ne for populations of each species, compare Ne estimates among the species, and test for correlations between several geographic variables and Ne within species. We used single-sample linkage disequilibrium (LD), approximate Bayesian computation (ABC), and sibship assignment (SA) methods to estimate contemporary Ne for each population. Three of the species—Rana pretiosa, R. luteiventris, and R. cascadae— have consistently small effective population sizes (<50). Ne 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 Ne 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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