Comparison of fine-scale genetic structure using nuclear microsatellites within two British oakwoods differing in population history

Two oak woods in northern Britain which contained both Quercus robur and Quercus petraea were selected for study. The woods differed in the degree of human interference they had experienced; Roudsea, in the Lake District, is a native wood with no record of planting but has experienced coppicing; Dalkeith, in southern Scotland, has experienced extensive planting and management. All the trees in a selected area of each wood (nearly 700 trees) were mapped and genotyped using six nuclear microsatellite loci. A range of statistical methods was used to assess the diversity and degree of spatial genetic structure present in each wood, and results are compared with published results for a natural oakwood in central France (Petite Charnie). For the unplanted wood at Roudsea, significantly higher genetic diversity and greater spatial genetic structure, at relatively short distances, was detected in the Q. petraea component of the wood relative to that of Q. robur. These observations agree with those from Petit Charnie and indicate that native oak woods across Europe maintain similar levels and structure of genetic variation, and is probably due to differences in seed dispersal mechanism and regeneration dynamics of the species. At Dalkeith, however, significant spatial structure of genetic variation occurred in both species examined, and the additional influence of planting is offered to account for increased genetic structure within this wood. At Roudsea, the influence of coppicing is also discussed to explain the lack of population genetic equilibrium and increased genetic diversity at this site. (C) 2002 Elsevier Science B.V. All rights reserved.