Population Genetics of the Red-listed Wood-decay Fungus Phlebia centrifuga

The aim of this licentiate thesis was to study the population genetic structure of the wood-decay fungus Phlebia centrifuga P. Karst. in northern Europe. The fungus, which is red-listed in Sweden, is dependent on dead wood of Norway spruce (Picea abies) and therefore rare in managed forest stands. The isolates used in the studies included in this licentiate thesis were sampled from both continuous and fragmented populations of P. centrifuga in eight European countries and six North American states. The first study included development of seven polymorphic microsatellite markers specific to P. centrifuga, using two different techniques. Of the seven primers, two varied only on a worldwide scale, whereas the other five varied both on a worldwide and a European scale. In the second study, microsatellite markers and arbitrary primed PCR using the core sequence of the M13 minisatellite DNA as marker were used to study the genetic structure of eight populations of P. centrifuga in northern Europe. Here, the question studied was whether the dispersal of out-crossing basidiospores of the fungus manage to overcome the genetic isolation of populations that occur in fragmented habitats. No significant inbreeding was detected in any of the populations. The pair-wise comparisons of the fixation index (FST) generally revealed little to moderately low genetic differentiation. However, all comparisons with the southern-most population, on the edge of the distribution of the species, showed moderately high or even great genetic differentiation. The results suggest that the basidiospores of the fungus do not completely overcome genetic isolation between fragmented populations, which might eventually lead to inbreeding. Different ways of assisting the persistence of these populations were discussed.