Pleomassaria siparia is composed of two biological species, both of which occur in dead twigs of Betula pendula and B-pubescens

The coelomycetes Prosthemium betulinum, Pr. asterosporum and the ascomycete Pleomassaria siparia are all common in the basal part of detached birch tw igs in Finland. The teleomorph of Pr. betulinum is Pl. siparia, but the tel eomorph of Pr. asterosporum is unknown. In denaturing gradient gel electrop horesis (DGGE) analysis, different internal transcribed spacer (ITS) allele s were observed among Pr. betulinum and Pr. asterosporum isolates. Both all eles were also observed among Pl. siparia isolates. We developed specific m arkers, which separated between Pr. betulinum and Pr. asterosporum. The all eles in these loci correlated to ITS alleles among Pl. siparia isolates. Th us we showed that Pl. siparia is composed of two separate biological specie s indistinguishable by teleomorph morphology, although they correlate to an amorphic species Pr. betulinum and Pr. asterosporum The in vivo studies wit h specific primers showed that both of these two species occur in dead twig s of Betula pendula and B. pubescens.