Gene flow and drift shape the distribution of neutral genetic diversity in\ud metapopulations, but their local rates are difficult to quantify. To identify gene\ud flow between demes as distinct from individual migration, we present a\ud modified Bayesian method to genetically test for descendants between an\ud immigrant and a resident in a nonmigratory life stage. Applied to a\ud metapopulation of pond-breeding European newts (Triturus cristatus,\ud T. marmoratus) in western France, the evidence for gene flow was usually\ud asymmetric and, for demes of known census size (N), translated into\ud maximally seven reproducing immigrants. Temporal sampling also enabled\ud the joint estimation of the effective demic population size (Ne) and the\ud immigration rate m (including nonreproductive individuals). Ne ranged\ud between 4.1 and 19.3 individuals, Ne/N ranged between 0.05 and 0.65 and\ud always decreased with N; m was estimated as 0.19–0.63, and was possibly\ud biased upwards. We discuss how genotypic data can reveal fine-scale\ud demographic processes with important microevolutionary implications
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