Study of genetic variation and differentiation of yew (Taxus baccata L.) stands using isozyme and DNA marker.

Yew (Taxus baccata L.) is a rare dioecious tree species in Europe. The object of this study is to characterize the genetic variation within and between 6 yew stands using isozyme and cpDNA (PCR-RFLPs and cpSSRs) markers. This study should enlarge the basis for the conservation measures of genetic resources of yew. Genotyping of individual trees has been carried out by analysis of bud material. For isozyme analysis, 6 isozyme genloci with altogether 19 alleles were investigated (Table 2). Results of data analysis revealed a high level of genetic variation within the investgated populations with a mean number of alleles per locus (A/L) of 2.6, a diversity (upsilon) of 1.48, an expected beterozygosity (H-e) of 31.6% and an observed heterozygosity (H-o) of 34.0%. The largest variation (1.6 less than or equal to upsilon less than or equal to 1.7, 36.4% less than or equal to H-e less than or equal to 41.4%) was found in the populations Hedemundener Gerneindewald (HM), Burgberg Thurnhosbach (TH) and Lohkopf (LK). The stands Naturwaldzelle Eichenberg (NZ, Abt. 249) and Naturwaldzelle Eichenberg (NWZ, Abt. 250) were genetically the least variable (1.2 less than or equal to upsilon less than or equal to 1.3, 19.6% less than or equal to H-c less than or equal to 24.2%) (Table 3). Comparisons between the genetic structures of male and female trees within stands indicated remarkable differences which were probably caused by genetic drift (Table 4). Variation between populations was measured using genetic distance d(o) and genetic differentiation D-j. The stands Burgberg Thurnhosbach (TH) and Lohkopf (LK) differed from the others substantially both in genetic distance (Table 5, Figure 1) and in genetic differentiation (Figure 3) concerning genetic structures. The mean differentiation 6 between stands amounted to 19.5% (Figure 3). Over all observed gene loci, the genetic structures of those stands which are located in the same geographical areas showed the smallest differences (Figure 1). Regarding the relatively high genetic variation within and the high differentiation between yew stands, it appears necessary to plan conservation measures on a broad basis of stands. The analysis of genetic variation within and between populations of yew was completed by cpDNA analysis at 5 trees per stand, respectively. As compared with other conifers like Abies alba and Picea abies with considerable variability, no cp-DNA variation has been observed for Taxus baccata L. in this study.