Size, distribution, and persistence of genets in local populations of the late-stage ectomycorrhizal basidiomycete, Russula brevipes

The spatial mapping of genets from sporocarps allows determination of the primary modes of reproduction of ectomycorrhizal fungi. The goals of this research were to determine the relative size, density, and persistence of genets of Russula brevipes, a late successional basidiomycete, in mature stands of lodgepole pine (Pinus contorta) and Sitka spruce (Picea sitchensis). Sporocarps were mapped and genets were identified using species-specific hypervariable microsatellite markers. Most of the sporocarps sampled in clumped aggregations were the same genet and occupied areas less than 3 m. The largest distance measured between two sporocarps of the same genet was 18 m. In local populations of R. brevipes associated with Sitka spruce, genets were comprised of largely related individuals, whereas in lodgepole pine, most genets appeared unrelated. High genotypic diversity in Sitka spruce stands suggests frequent mating and recombination between local inhabitants from primary establishment of basidiospores. In lodgepole pine, fewer, unrelated genotypes of R. brevipes indicates that multiple sources of colonization arose from infrequent, long distance spore dispersal events.