Assessment of genetic structure within and among Bulgarian populations of the common ash (Fraxinus excelsior L.).

We analysed genetic variation within and between populations of the common ash from Bulgaria in order to extract biological information useful in the context of conservation management of eastern European genetic resources of noble hardwood species. A total of 321 trees from three regions of Bulgaria were typed at six highly polymorphic microsatellite loci. Analysis of within-population inbreeding suggests an upper boundary value of 2.7% for the selfing rate. Significant spatial genetic structure consistent with models of isolation by distance was detected within four out of 10 populations as well as among populations. Estimates of neighbourhood size in the range 38-126 individual trees were obtained based on spatial genetic structure analyses at either the intrapopulation or interpopulation level. Differentiation among populations explained only about 8.7% of total genetic diversity. These results are discussed in comparison with data from social broad-leaved species such as oak and beech.