Relationships among North American and Japanese Laetiporus isolates inferred from molecular phylogenetics and single-spore incompatibility reactions.

Relationships were investigated among North American and Japanese isolates of Laetiporus using phylogenetic analysis of ITS sequences and single-spore isolate incompatibility. Single-spore isolate pairings revealed no significant compatibility between North American and Japanese isolates. ITS analysis revealed 12 clades within the core Laetiporus clade, seven of which are known to occur in North America (including Hawaii and the Caribbean), three in Japan, two in South America, three in Europe and one in South Africa. The identity of L. sulphureus s.s. has yet to be determined and could be either L. "sulphureus" (clade C), which appears to be restricted to Europe and occurs on angiosperms and gymnospersm, or L. "sulphureus" (clade E), which is found in Europe, North America and South America exclusively on angiosperms. Three clades, one from the Caribbean, one from Hawaii and one from South Africa, have yet to be named formally. Of the three Laetiporus species found in Japan two have been named recently (L. cremeiporus and L. montanus) and one has been epitypified (L. versisporus). The single-spore incompatibility and ITS data support recognition of the three Japanese taxa as distinct biological and evolutionary species.