Past and current gene flow in the selfing, wind‐dispersed species Mycelis muralis in western Europe

Abstract

The distribution of genetic diversity in Mycelis muralis , or wall lettuce, was investigated at a European scale using 12 microsatellite markers to infer historical and contemporary forces from genetic patterns. Mycelis muralis has the potential for long‐distance seed dispersal by wind, is mainly self‐pollinated, and has patchily distributed populations, some of which may show metapopulation dynamics. A total of 359 individuals were sampled from 17 populations located in three regions, designated southern Europe (Spain and France), the Netherlands, and Sweden. At this within‐region scale, contemporary evolutionary forces (selfing and metapopulation dynamics) are responsible for high differentiation between populations (0.34 F ST H E ) (0.24 H E A = 2.38) than populations from southern Europe ( A = 3.34). In light of postglacial colonization hypotheses, these results suggest that rare alleles may have been lost during recolonization northwards. Our results further suggest that mutation has contributed to genetic differentiation between southern and northern Europe, and that Sweden may have been colonized by dispersers originating from at least two different refugia.

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