No evidence of population structure across three isolated subpopulations of Russula brevipes in an oak/pine woodland.

Russula brevipes is common ectomycorrhizal (EM) fungus that is associated with several hosts across temperate forest ecosystems. A previous study has demonstrated that substructuring across large geographic distances (1500 km) occurs in the western USA. To examine genetic structure over a more localized scale, basidiocarps of Russula brevipes from three subpopulations, separated by distances of 230-1090 m, were collected over two consecutive years in an oak/pine woodland. Microsatellite loci were used to test for population differentiation both among subpopulations and by year. No significant population differentiation was detected between subpopulations (theta(ST) = 0.01) or between years (theta(ST) = 0.01). Most loci were consistent with a Hardy-Weinburg equilibrium and 82% of the genets between seasons from similar sampling localities constituted new genotypes. These results indicate that R. brevipes constitutes a randomly mating population with no genetic differentiation between locations or across successive fruiting seasons.