XVI International Botanical Congess

The outcome of population studies are influenced by the biology of studied organisms, the scale at which they are studied and the variability of the markers used. In the outcrossing root infecting basidiomycete Heterobasidion annosum populations are structured at various hierarchical levels. In each substrate unit, interactions among homo- and heterokaryotic mycelia result in a high degree of relatedness among genets, while genets from substrate units at distances 10-100 meters are less similar. Furthermore, vegetative spread of individual mycelia forms groups of trees infected by the same genet. At a larger scale, the evidences are weak for isolation by distance among populations separated by less than 1000 km, although local spore sources contribute strongly to establishment. In contrast, in the homothallic wood-decaying basidiomycete, Stereum sanguinolentum, genetic markers indicate a clear effect of isolation by distance within somatically compatible groups on the scale of up to 500 km. The possibilities to detect fungal spread and gene flow at various scales are discussed.