Genetic variation in northern marginal Taxus baccata L. populations. Implications for conservation

Abstract

Taxus baccata L. is a dioecious gymnosperm with a wide but scattered distribution in Europe. Small populations are inclined to genetic drift, and we therefore studied genetic structure in 13 T. baccata populations of the northern range margin in coastal areas of Norway by means of 13 isoenzyme loci. The average observed (Ho) and expected (He) heterozygosities were 0.143 and 0.150, respectively. The genetic differentiation was considerable (Fst = 0.166), and the derived gene flow was correspondingly modest (Nm = 1.26). The fixation index (Fis) across all populations was 0.039, but with consistently higher values (0.119-0.226) in the northernmost populations, suggesting inbreeding. The poor regeneration, associated with extensive browsing, may impede adaptation to environmental changes. If also the effective population sizes are reduced, drift and differentiation may increase in future generations. Implications for conservation are discussed in light of the genetic structure, longevity and the poor regeneration of the species. © Institute of Chartered Foresters, 2009.