Klonale Ökologie der Flaumeiche (Quercus pubescens)

Klonale Ökologie Quercus pubescens

Quercus pubescens Willd. is widespread at low and middle altitudes throughout S Europe. In Central Europe the species is restricted to climatically favourable sites south of approx. 51 degrees latitude. Impressive, several square meter sized, domelike clusters of up to 4 m high oak stems or clusters of dense thickets of stunted growth, are scattered on shallow soils in the large seminatural dry grasslands on Monte Gargano on the Adriatic coast of S Italy. Similar clusters have been observed elsewhere in C Apennines (C Italy), in the Považský Inovec Mountains (Slovak Republic), and in Biokovo (S Croatia). For these patterns of stem emergence it is difficult to determine merely by observation whether they represent distinct individuals or if they are generated by clonal growth. We hypothesize that the observed clusters of stems represent single clones of Q. pubescens. To test our hypothesis we investigated the population genetic structure of these Q. pubescens stands using molecular markers. Clusters were located in two highland areas of southern and central Italy (Puglia and Marche). Individual stems were tagged and mature leaf tissue was collected for 11 clusters and in sum 135 stems, ensuring inclusion of all potential clonal groupings. DNA was extracted from leaf samples and amplified by PCR using 17 polymorphic microsatellite loci (simple sequence repeats, SSR) from Q. petraea. Allele frequencies were identified for each locus and subjected to population statistical analyses. Results on genetic differentiation patterns among sampled stems within clusters on Monte Gargano show identical genetic structure suggesting that they were generated by clonal growth. Field observations confirm the capability of clonal growth by resprouting from the base of the trunk as well as by sprouts from roots. This knowledge has implications for the persistence of Q. pubescens populations across a long time-span of climatic fluctuations (i.e. the last glacial cycle) as well as for their future development in a changing climate.