Effect of habitat fragmentation on the genetic diversity of peripheral populations of beech in Central Italy

Fragmentation can affect the demographic and genetic structure of populations near the boundary of their bio-geographic range. Higher genetic differentiation among populations coupled with lower level of within population variability is expected as a consequence of reduced population size and isolation. The effects of these two factors have been rarely disentangled. Given their high gene flow, anemophilous forest trees should be more affected, in terms of loss of genetic diversity, by small population size rather than geographic isolation alone. We studied the impact of distance from the main range (a measure of isolation) and reduced population size on the within and among population components of genetic variability. We assayed 11 isozyme loci in 27 marginal populations of European beech (Fagus sylvatica L.) in Central Italy. Populations were divided in three groups with an increasing level of fragmentation. In the most fragmented group the within population genetic variability was sl...