The importance of spore dispersal over short and long distances is discussed in terms of risk for infection and population differentiation, respectively. Spore dispersal gradients were calculated from literature data. Most of the spores are spread over very short distances but some may travel for at least 500km. Indirect measures of spore dispersal were obtained from literature data on the distribution of mating alleles within and between populations. Results show a high degree of local similarities and a low degree of similiarity over 100s of km. Moreover, the regional distribution of genetic variation in Heterobasidion annosum (Fr.) Bref. was studied with DNA techniques. DNA from samples of 20 populations was amplified using the core sequence of the M 13 hypervariable region as primer. Genetic similarity of populations decreased with increasing geographic distance. Distances larger than 500km were needed for clear signs of isolation effects to occur. Evidences from the literature also suggest that differentiation has occurred between northern and southern Europe in the S intersterility group in interfertility with the F group. Results are compared with the history of conifer colonization of the European continent.
