Intraspecific variation in fruiting phenology in an ectomycorrhizal Laccaria population under Douglas fir

Laccaria bicolor and L. laccata are ectomycorrhizal basidiomycetes which fruit abundantly over I or 2 months in autumn and sometimes in summer. We investigated the phenology of fruiting of the various Laccaria spp. genets in a Douglas fir plantation in the Nievre (France), in which all genets had been identified by molecular methods. During the fruiting period of the population, the genets did not fruit synchronously: some fruited early, others later, and some over the whole period. For some genets that survived over 2-3 years (1995-97), the fruiting phenology remained similar from year to year, even when fruiting occurred in summer. We took advantage of the presence of a L. bicolor genet, which had been used to artificially inoculate Douglas firs in this plantation, to assess whether the timing of fruiting was influenced by microsite differences in the plantation (soil, host tree, etc.). In summer 1997, fruit bodies of this genet appeared synchronously everywhere at the beginning of the fruiting period. We conclude that the timing of Laccaria fruiting may be genetically determined, rather than explained by the size and position of the genet or the environmental conditions. The consequences for population studies are discussed.