GENETIC-STRUCTURE OF BLACK SPRUCE ON 2 CONTRASTING SITES

Several hundred dominant and co-dominant individuals in two populations of black spruce, located within 2 km of each other and representing upland and lowland site types, were sampled and mapped. Multilocus isozyme genotypes were determined and the genetic organization of the two populations examined by means of nearest-neighbor analysis and spatial autocorrelation of alleles. On the upland site type, population density was much higher and variation in age considerably less than on the lowland site type, which was interpreted as evidence for fire origin in the former. On the upland site, the mature trees were more inbred, possibly due to the conditions under which regeneration occurred and because of weak selective pressure. On the lowland site, clustering of similar genotypes was detectable on a local scale but the mature trees were not inbred. The two populations were very similar in terms of allozyme frequencies.