Population structure of the endangered wood decay fungus Phellinus nigrolimitatus (Basidiomycota)

The population structure of five Fennoscandian geographic populations of the endangered wood-decay fungus Phellinus nigrolimitatus (Romell) Bourdot et Galzin was examined by analyses of nuclear ribosomal DNA (nrDNA) spacer sequences (ITS and IGS1) and a partial sequence of the elongation factor 1α gene (efa). A high level of sequence variation was observed in ITS and IGS1, suggesting restrictions in nrDNA homogenization in this taxon. Six polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) markers, five located in nrDNA and one in efa, suggest that the geographic populations are genetically very similar, presumably owing to recent gene flow. However, linkage disequilibria were obtained in 50% of the cases in tests between the five nrDNA PCR-RFLP markers. The calculated FST values from the linked nrDNA markers and the unlinked efa marker were congruent, ranging from 0.006 to 0.042. In one geographic population, the efa locus showed significant deviation from Hardy– Weinberg expectations. Somatic incompatibility tests demonstrated that isolates derived from different basidiocarps and different logs belonged to different genets. In a microscale study including three logs, the independent assays of PCRRFLP analysis and somatic incompatibility tests distinguished 10 genets. Life history traits and conservation status of P. nigrolimitatus are discussed in light of the results.