Staying close: short local dispersal distances on a managed forest of two Patagonian Nothofagus species

Understanding the impact of management on the dispersal potential of forest tree species is pivotal in thecontext of global change, given the implications of gene flow on species evolution. We aimed to determine theeffect of logging on gene flow distances in twoNothofagusspecies from temperate Patagonian forests havinghigh ecological relevance and wood quality. Therefore, a total of 778 individuals (mature trees and saplings) ofNothofagus alpinaandN. obliqua,from a single plot managed 20 years ago (2.85 hectares), were mapped andgenotyped at polymorphic nuclear microsatellite loci. Historical estimates of gene dispersal distance (basedon fine-scale spatial genetic structure) and contemporary estimates of seed and pollen dispersal (based onspatially explicit mating models) were obtained. The results indicated restricted gene flow (gene distance<=45m, both pollen and seed), no selfing and significant seed and pollen immigration from trees located outsidethe studied plot but in the close surrounding area. The size of trees (diameter at breast height and height) wassignificantly associated with female and/or male fertility. The significant fine-scale spatial genetic structure wasconsistent with the restricted seed and pollen dispersal. Moreover, both estimates of gene dispersal (historicaland contemporary) gave congruent results. This suggests that the recent history of logging within the study areahas not significantly influenced on patterns of gene flow, which can be explained by the silviculture applied to thestand. The residual tree density maintained species composition, and the homogeneous spatial distribution oftrees allowed the maintenance of gene dispersal. The short dispersal distance estimated for these two specieshas several implications both for understanding the evolution of the species and for defining management,conservation and restoration actions. Future replication of this study in otherNothofagusPatagonian forestswould be helpful to validate our conclusions