Samples from subdivided populations yield biased estimates of effective size that overestimate the rate of loss of genetic variation.
Bottom Line: Many empirical studies estimating effective population size apply the temporal method that provides an estimate of the variance effective size through the amount of temporal allele frequency change under the assumption that the study population is completely isolated.We studied how gene flow affects estimates of effective size obtained by the temporal method when sampling from a population system and provide analytical expressions for the expected estimate under an island model of migration.This phenomenon might partially explain the frequently reported unexpectedly low effective population sizes of marine populations that have raised concern regarding the genetic vulnerability of even exceptionally large populations.
Affiliation: Division of Population Genetics, Department of Zoology, Stockholm University, SE-106 91, Stockholm, Sweden.Show MeSH
Mentions: The dependence of on global effective size introduces a bias when estimating local effective size and measuring genetic change over multiple generations. Our analytical results on the expected estimate of NeV refer to estimates obtained when measuring allele frequency changes in consecutive generations, and we used computer simulations to assess the effect of estimating NeV from changes accumulated over multiple generations. Similar to Fig.2, we set local effective size to NeV = N = 50 and simulated the sampling of the same (k = l = 1) and the same four (k = l = 4) subpopulations T = 1–10 generations apart, mimicking different sizes of the global population by setting the total number of subpopulations to s = 2, 10, and 500 with migration rates m = 0.1 and m = 1 (Fig.3).
Affiliation: Division of Population Genetics, Department of Zoology, Stockholm University, SE-106 91, Stockholm, Sweden.