Populations of ectomycorrhizal Laccaria amethystina and Xerocomus spp. show contrasting colonization patterns in a mixed forest.

•  The knowledge of temporal and spatial structure of populations of ectomycorrhizal fungi, together with the origin and maintenance of their genetic variation, is critical to understanding how populations of these fungi establish, evolve and disappear at different stages of development of forest ecosystems. •  Identification and spatial delimitation of genets in populations of the ectomycorrhizal basidiomycetes, Laccaria amethystina, Xerocomus chrysenteron and X. pruinatus were inferred from the polymorphism of two codominant genetic loci, the nuclear rDNA internal transcribed spacers (ITS) and intergenic spacers (IGS), and anonymous dominant RAPD markers from basidiocarps collected in a mixed mature forest in the fungal reserve of La Chanéaz (Switzerland). •  The L. amethystina population showed numerous small, short lifespan genets; most closely spaced basidiocarps were genetically unique. Our results confirmed that sexual spore propagation is important in the life history of L. amethystina in undisturbed mature forests. By contrast, we found a single genet for each of the boletoid species colonizing a nearby plot indicating that clonal growth dominated. •  In La Chanéaz forest, the intrinsic biological features of the investigated species appear to play a higher role in colonization strategy than the features of local habitat.