Spatial distribution of ectomycorrhizal Basidiomycete Russula subsect. Foetentinae populations in a primary dipterocarp rainforest.

The spatial distribution of basidiocarps of the ectomycorrhizal Basidiomycete Russula subsect. Foetentinae was assessed in a primary forest in the Western Ghâts (India) dominated by the ectomycorrhizal tree species Vateria indica and Dipterocarpus indicus. Over a 7,700-m(2) sampling area, both trees and basidiocarps of Russula subsect. Foetentinae were mapped during the first month of the 2002 rainy season. First-order spatial analysis revealed that the distribution of the 45 collected carpophores was highly aggregated, with 60% of all basidiocarps located at a distance lower than 1 m from the nearest one. The genetic structure of the Russula subsect. Foetentinae population was studied by inter-simple sequence repeat polymorphism analysis using three primers. Eighteen of the 45 genotypes were represented by single basidiocarps. Twenty-seven basidiocarps were identified as belonging to 11 genets or separated ramets. Five genets were small, with diameters ranging from 0.5 to 5 m. The six others were large, with a diameter ranging from 31 m to a maximum measured distance of 70 m. In spite of the lack of data concerning the reproductive biology of this species, the presence of large genets suggests that mature stands may shelter well-spread underground mycelium, crucial for durable interaction with plant partner.