Pronounced ecological separation between two closely related lineages of the polyporous fungus Gloeoporus taxicola

Gloeoporus taxicola is a saprotrophic polypore that produces annual fruit bodies, in Scandinavia exclusively on coniferous wood. In this study, we demonstrate the existence of two ecotypes of G. taxicola in Norway; a coastal lowland form fruiting on dead logs and dying branches of standing Pinus sylvestris, and a highland form largely fruiting on trunks of Picea abies in moist, old-growth forests. Thus, a distinct ecological separation has happened between the two forms both concerning substrate and environmental requirements, leading to a rather distinct difference in distribution. Genetically, there seems to be a more stepwise transition between the two forms, as revealed by sequence analyses of two DNA regions. Genetic variation was significantly higher in the highland form compared with the lowland form, which could be due to disparate immigration histories in Scandinavia. Different evolutionary scenarios may explain the observed pattern, including a former allopatric distribution in isolated glacial refugia, succeeded by immigration into the same region. The partition of the genetic variation among the two forms suggests a recent or ongoing speciation event and possibly some ongoing introgression. Our findings have implications on the conservations status of the taxon, as their susceptibility to modern forestry seems to be different.