engleski

High molecular diversity in the true service tree (Sorbus domestica) despite rareness : data from Europe with special reference to the Austrian occurrence

Sorbus domestica L. is one of the rarest deciduous tree species in Europe and characterized by a scattered distribution. Until now, there is no population genetic study on a large geographical scale. Our aims were to infer levels of molecular diversity covering the major part of its European distribution, its population differentiation and structure as well as spatial genetic structure and pattern of historic and recent gene flow among two nearby located populations. We used eight nuclear microsatellites and one chloroplast minisatellite. Our sample frame included 17 populations covering an area from north-west France to south-east Bulgaria. Allelic richness was unexpectedly high for both markers within populations (mean per locus: 3.868 for nssr and 1.647 for cp- DNA). Moreover, there was no evidence of inbreeding (mean Fis: -0.047). The Apennine peninsula could be characterized as genetic hotspot for both genomes. Overall population differentiation was moderate (FST: 0.138) and it was obvious that S.domestica formed three groups in Europe (France, Mediterranean/Balkan, Austria). Historic gene flow showed strong asymmetry on a small geographical scale while recent gene flow seemed to be disrupted. We conclude that molecular mechanisms as self incompatibility as well as high gene flow distances are responsible for the observed level of allelic richness as well as for population differentiation. However, a human influence could have contributed to the present genetic pattern, especially in the Mediterranean region. Comparison of historic and recent gene flow may mirrors the progress of habitat fragmentation in eastern Austria.

chloroplast DNA; genetic variability; habitat fragmentation; historic gene flow; metapopulation dynamics; nuclear microsatellites; Sorbus domestica L.

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