Local founding events as determinants of genetic structure in a plant metapopulation

The genetic structure of a metapopulation of the weedy plant, Silene alba, was quantified by calculating F-ST, Wright's measure of the among-deme component of genetic variance, for seven polymorphic allozyme loci and a chloroplast DNA (cpDNA) polymorphism. Specifically, F-ST was estimated separately for 12 recently founded demes and 11 demes that had been established in the same area for at least six years, in order to assess the influence of founding events on genetic structure. The F-ST value for the recently established populations was the larger of the two estimates for six of the seven allozyme polymorphisms and for the cpDNA polymorphism, showing that the metapopulation dynamics of extinction and colonization enhance genetic structure. Combined with an estimate of k, the size of colonizing groups, the F-ST values were also used to estimate phi, the probability that two alleles found in a colonizing group originated in the same source population. Information from allozymes and cpDNA resulted in estimates of phi of 0.73 and 0.89, respectively, suggesting that relatively little mixing of individuals from diverse source populations occurs during colonization.