LAUSR

Key message Taxus baccata remnants established recently tend to contribute less to the species’ overall genetic variation than historical populations because they are subjected to a greater impact of the founder effect and genetic isolation. As tree trunk perimeter is a rough indicator of genetic variation in a population, this measure should be considered in conservation programs. Genetic variation within Taxus baccata (L.) populations is not associated with the current census size but correlates well with the effective size, suggesting that genetic drift intensity reflects variation in demographic histories. We hypothesize that recently established populations are subjected to greater bottleneck than old remnants. Using the mean trunk perimeter as a surrogate of tree age, we test whether the demographic history and genetic variation are associated with the mean tree age. Using 18 microsatellite markers, we analyze the genetic diversity and demographic history of 11 yew populations in Poland to assess the relationship between the mean trunk perimeter and the inferred genetic parameters. Populations reveal significant differences in levels of genetic variation and in the intensity and time of genetic bottleneck. After excluding an apparent outlier, the genetic variation is significantly greater while the bottleneck intensity lower in populations with a greater perimeter. Due to continuous species decline and increasing fragmentation, the non-uniform contribution of yew remnants to the overall genetic variation tends to decrease together with the mean tree age. Germplasm collections for the species should take into account tree perimeter as a rough indicator of the genetic variation of a population.