Extensive genetic divergence associated with speciation in filamentous fungi.

Little is known about genetic differentiation during speciation in fungi. The Collybia dryophila complex (Basidiomycetes: Tricholomataceae) contains several closely related groups of fungi at various levels of evolutionary divergence. Mating compatibility studies show there are several intersterile groups within the complex, three of which are distributed over two or more continents. Genetic relationships among five intersterility groups were compared by the method of DNA.DNA hybridization. Clustering techniques were used to reconstruct phylogenetic relationships of these fungi. Genic identity based on DNA.DNA hybridization corresponds well with mating compatibility. Reduced genic identity was observed between geographically isolated populations of a single mating group. This evidence suggests an allopatric mode of evolution for the C. dryophila group. These results indicate extensive genic divergence is associated with the appearance of intersterility barriers in basidiomycetous fungi. The levels of divergence observed in these and in other fungi are significantly higher than that observed in many other eukaryotes, and this suggests that the rate of molecular or morphological evolution in fungi may differ from that found in other organisms.