Species limits for Phellinus weirii.
Isolates of populations of Phellinus weirii from Japan (causing root and butt rot), Siberia (possibly a saprophyte), and North America (2 types, Douglas fir causing root rot, and cedar causing root and butt rot) were tested for mating compatibility and subjected to various tests of relatedness. Pairings between Asian and North American Douglas fir isolates appeared incompatible from visual observation but both backpairing and hybrid enzyme patterns indicated compatibility. Three populations were differentiated by isoenzyme and total protein electrophoresis, and M13 DNA fingerprinting and ITS DNA sequences distinguished the cedar types from the others. Differences between cedar type isolates and both Douglas fir and Asian type isolates were greater then those between Asian and Douglas fir types in most tests. Three reproductively isolated taxa are indicated - cedar, Douglas fir and Asian (Japan and Siberia) types.