GENETIC-STRUCTURE OF ENGLISH YEW (TAXUS-BACCATA L)IN THE WIERZCHLAS RESERVE - IMPLICATIONS FOR GENETIC CONSERVATION

Genetic structure and mating patterns were studied in Taxus baccata L. in the Wierzchlas Reserve in Poland, using 18 allozyme loci as genetic markers. The population exhibited high levels of genetic variation, with expected heterozygosity estimated for all loci equal to 0.279. The effective number of alleles was 1.37, and 61.11% of loci were polymorphic. Expected heterozygosity calculated for polymorphic loci only was as large as 0.419. The level of inbreeding as measured by Wright's fixation index was generally low for parental trees. However, in progeny population an excess of homozygotes was observed compared with the Hardy-Weinberg equilibrium (F= + 0.049), which may be attributed to mating between relatives (biparental inbreeding). The effective population size calculated for both male and female trees was considerable and accounted for about 56 individuals. Allele frequencies in the pollen pool successful in fertilizing viable embryos were, in general, spatially homogeneous across the sampled trees. Considering the high genetic diversity and relatively large population size, the Wierzchlas Reserve represents a valuable gene pool for reforestation of Taxus baccata.