LAUSR

Abstract English yew (Taxus baccata L.) is a strictly outcrossing and dioecious species with small and isolated populations, which has led to its endangered species status within its natural range in Europe. In the present study, we determined the level of genetic variation and genetic differentiation of thirty-one natural T. baccata populations in Poland (2725 individuals) and focused on the impact of demographic processes on the species’ population structure using five nuclear microsatellite loci. The populations demonstrated generally moderate to high levels of genetic diversity (AR = 2.4–12.5; Ho = 0.262–0.593; He = 0.441–0.839). The genetic differentiation between populations was geographically structured and occurred at a moderate level (Fst = 0.155). A Bayesian analysis identified a significant north-south population structure. Additionally, populations showed significant isolation by distance, suggesting the recent isolation and fragmentation of local T. baccata populations. All the examined populations experienced a demographic bottleneck and significant fluctuations in size. The improved understanding of genetic variation has practical implications for developing conservation strategies for this rare and endangered forest species. Our study supplements the limited knowledge regarding the fine-scale genetic structure of T. baccata; thus, the Polish populations are now among the most-surveyed stands of this species in Europe. Based on our findings, we suggest that the gene pools of T. baccata should be actively preserved and that local populations should be prioritized according to their potential significance for in situ or ex situ conservation.