Nuclear Markers (AFLPs) and Chloroplast Microsatellites Differ Between Fagus sylvatica and F. orientalis

Former studies based on chloroplast markers and allozymes suggested that postglacial recolonization of central Europe by Fagus sylvatica L. occurred from one or a few undifferentiated refuges. Here, we examine F. sylvatica from Germany and Greece and different provenances of F. sylvatica ssp. orientalis (Lipsky) Greut & Burd. (F. orientalis Lipsky) with chloroplast microsatellites and AFLP markers. Only such AFLP markers were selected that had shown a differential amplification in F. sylvatica and F. orientalis in a preliminary analysis. UPGMA cluster analysis of AFLP data distinguished one F. sylvatica group and one F. orientalis group from northern Turkey. Low structuring in the neighborjoining analysis and the lack of diagnostic bands for either taxon suggests a relatively recent differentiation in Fagus orientalis and F. sylvatica. High bootstrap values were only found for a separate cluster that comprises F. orientalis from two different forest botanical gardens. Four of these samples have a unique chloroplast type and are genetically very similar (bootstrap value 96) mostly likely due to clonal replication. Only two different chloroplast types (type 1 in Germany, type 1 and type 2 in Greece) could be detected for F. sylvatica. In contrast, F. orientalis from northern Turkey showed different chloroplast types even within one provenance pointing to a glacial refuge in northern Turkey and a bottleneck at the time of postglacial recolonization of central Europe. The classification of ten samples from northern Turkey as F. sylvatica by AFLP data, chloroplast markers and morphology questions the interpretation of F. orientalis and F. sylvatica as two geographically separated (allopatric) taxa.