GENETIC DIVERSITY, DIFFERENTIATION, AND INBREEDING IN PACIFIC YEW FROM BRITISH-COLUMBIA

Variation at 21 allozyme loci in Pacific yew( Taxus brevifolia Nutt.) from nine disjunct regions, representing three geographic areas of Bri tish Columbia, was measured to estimate the amount and pattern of gene tic variability. Pacific yew has moderate levels of genetic diversity compared to that present in associated temperate-rone species, with 1. 7 average number of alleles per locus, 42.3% polymorphic loci, and 0.1 66 mean expected within-region heterozygosity. Among-region genetic di fferentiation accounted for a significant 8% of the total variation. H igh gene flow (N-m = 2.99) was observed, and it is argued that the pri mary cause is seed, rather than pollen, subsequently producing low amo ng-region and high within-region genic differentiation. Wright's gene fixation index, F, averaged 0.472, indicating the presence of high lev els of inbreeding. Nei's genetic distances (D) among regions from the same geographic area averaged 0.004, which was significantly lower tha n the average among regions from different geographic areas (0.021), p roducing close agreement between genetic relationships and geography. The high levels of inbreeding detected may be attributable to both the ecology and reproductive strategies of the species.