Two New Species of Russula (Stirps Atropurpurea) Associated with Alnus crispa in Alaska

Basidiomata of two species of Russula were observed frequently during the summer and fall of 1987 in two study plots in a homogeneous Alnus crispa stand near Fairbanks, Alaska. Russula subarctica and R. alnicrispae belong to the section Russula (subsection Russula, stirps Atropurpurea) and are described as new species. Both are distinguished from other members of st. Atropurpurea associated with alders by a brown component of the pileus color, smaller spores, and different hosts and host ranges. In addition, R. subarctica has an unusual greyish red to deep red stipe color. Spore size analysis between members of st. Atropurpurea associated with alders results in diagnostic values for R. subarctica and R. alnicrispae when compared to R. alnetorum, R. pumila, and R. alnijorullensis. Fruiting of both R. subarctica and R. alnicrispae seems to be dependent on a high amount of precipitation. However, fruiting of R. subarctica began one month later than that of R. alnicrispae. Within the plots, the two species show a slight positive interspecific association.