Genetic diversity and mating system of post-fire and post-harvest black spruce: an investigation using codominant sequence-tagged-site (STS) markers

cDNA-based sequence-tagged-site (STS) markers were used to examine the gene tic composition of three mature, layer-origin populations of black spruce ( Picea mariana (Mill.) BSP), which were the result of logging operations in the first half of the 20th century, and compare them with four mature, seed ling-origin populations that regenerated naturally following fire. The amou nt of STS-marker variation revealed in these populations was very similar t o that previously observed in a rangewide panel of black spruce trees. Ther e was little differentiation among populations, and no significant differen ces in heterozygosities, numbers of alleles, or fixation indices were evide nt between layer-origin and fire-origin stands. Likewise, when mating-syste m parameters were estimated in one population of each of these two types, n o significant differences were found; outcrossing was essentially complete with no evidence of mating among relatives. The estimated correlation of pa ternity within progeny arrays was about 17 and 13% in the fire-origin and l ayer-origin stands, respectively, but again the observed difference was not statistically significant. At least at the current scale of sampling, silv icultural practices that result in stand replacement by layer-origin advanc e regeneration appear not to have had negative impact upon the genetic dive rsity or level of inbreeding in second-growth black spruce stands.