Evidence for limited intercontinental gene flow in the cosmopolitan mushroom, Schizophyllum commune
The genetic structure of populations of Schizophyllum commune was inferred from electrophoretic variation among 136 individuals at 11 polymorphic allozyme loci to determine the extent of geographic differentiation in this widespread mushroom species. The majority of the genetic variation was contained within populations; however, considerable genetic differentiation was observed among populations (global G(ST) = 0.214). Clustering analysis demonstrated that genetic distance was correlated with geographic distance and that a large component of the genetic variation was due to allele frequency differences among populations from the eastern and western hemispheres. Our results also suggest that populations are large and geographically widespread. The lack of fixed genetic differences among intercontinental populations at any of the allozyme loci suggests that long-distance spore dispersal may counter the effects of genetic drift in this cosmopolitan species. These results are contrasted with a previous description of the same collection, in which the mating allele distribution of the species displayed no population substructure at any geographic scale (Raper et al. 1958). Broader implications of this study are that both species and mating allele distributions may not be correlated with long-distance gene flow in basidiomycete fungi.