Phellinus laevigatus s. l. (Hymenochaetales): a ring species
Phellinus laevigatus s. l. has evolved as a ring species, which was distributed in Paleocene from the eastern part of Asia via North America to Europe and further to West Siberia. As a result of clinal variation of basidiospores, three allopatric taxa in two species evolved. Of the two species (European–West Siberian Ph. laevigatus s. str. and Ph. betulinus (Murrill) Parmasto, comb. nova), latter is composed of two subspecies (ssp. betulinus and ssp. orienticus Parmasto ssp. nova), one distributed in North America and the other in East Asia.