Population structure and responses to disturbance of the basidiomycete Resinicium bicolor

Resinicium bicolor (Alb. & Schw. ex Fr.) Parm. [=Odontia bicolor (Alb. & Schw. ex Fr.) Bres.] is an outcrossing resupinate basidiomycete associated with root and butt rots of trees, but is itself only very weakly pathogenic. The distribution of genets among every spruce stump in a 70-year-old 1250 m² spruce stand was analysed using somatic incompatibility testing. R. bicolor was present on 40% of 8-to 10-year-old stumps. Nineteen genets were found occupying 32 stumps; yielding probabilities of colonisation following establishment by basidiospores of 0.20-0.24 and by mycelial extension or dispersal of 0.16-0.20. The probability of colonisation decreased with increasing distance from a point of establishment. R. bicolor responded to both enrichment and destructive disturbances by the formation of an extensive cord system which enabled it to colonise discontinuously distributed resources and to overgrow fungi adjacent to it in a single resource unit, including Heterobasidion annosum.