Genetic effects of chronic habitat fragmentation in a wind-pollinated tree

Abstract

Habitat fragmentation poses a serious threat to plants through genetic changes associated with increased isolation and reduced population size. However, the longevity of trees, combined with effective seed or pollen dispersal, can enhance their resistance to these effects. The European beech (Fagus sylvatica) dominates forest over large regions of Europe. We demonstrate that habitat fragmentation in this species has led to genetic bottlenecks and the disruption of the species' breeding system, leading to significantly elevated levels of inbreeding, population divergence, and reduced genetic diversity within populations. These results show that, in contrast with the findings of previous studies, forest fragmentation has a negative genetic impact, even in this widespread, wind-pollinated tree. The identification of significant effects of forest fragmentation in beech demonstrates that trees are not at reduced risk from environmental change. This should be accounted for in the management of remaining natural and seminatural forest throughout the world.

Fig. 1.

Genetic distance (23) based on six microsatellite loci, vs. linear geographic distance for all possible pairwise combinations of F. sylvatica samples within each group. A significant positive correlation is observed for forest fragments only: regression analysis y = 0.0574 + 1.65 × 10⁻⁵x, r = 0.401, P = 0.0422. A significant positive correlation indicates that samples are spatially genetically structured, with isolation by distance playing an important role.

Fig. 2.

Location of F. sylvatica samples taken within the Montseny Natural Park, Catalonia, northeast Spain. Grid lines are marked with Universal Transverse Mercator coordinates in kilometers.