Genetic variation of Central European oaks shaped

Authors: Charalambos Neophytou Stefanie M Gärtner Rodrigo VargasGaete HansGerhard Michiels

Publish Date: 2015/07/12

Volume: 11, Issue: 4, Pages: 79-

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Abstract

Oak species Quercus spp in Central Europe grow on a relatively wide range of sites Due to the economic importance of oak for its wood and other products oak forests have long been managed by humans This raises the question whether adaptation and/or human activities—especially the moving of propagules—have left their footprints on the genetic variation of oak populations To address this question we focused on the Upper Rhine Valley a densely populated area today that was settled by humans early on Here the three most common native Central European oak species can be found We studied their genetic variation across a large number of oak stands growing on different sites and having different silvicultural histories using neutral and ESTderived microsatellite markers At the interspecific level we showed that Quercus robur is relatively well delimited while Quercus petraea and Quercus pubescens are more closely related Natural hybridization might explain the increased genetic introgression between these two species Within species we found a low differentiation among populations of Q robur and Q petraea In spite of forest fragmentation we detected no spatial genetic barriers However we found that populations of Q pubescens a species with a marginal distribution in the study area were spatially structured Genetic drift but also unidirectional introgressive hybridization with Q petraea may account for this Regarding the question of adaptation we considered soil flooding texture drainage and calcium carbonate in the upper horizons as physiologically important site condition variables But with multivariate statistics we could not find any significant effects of these parameters on genetic differentiation Although there was no evidence for natural selection due to adaptation in stands of Q robur we demonstrated that age had a significant effect on their genetic variation and that stands established after the end of the Second World War had higher genetic diversity We interpret these findings as being the result of an increase in largescale transfers of reproductive materials during this time period and discuss arguments supporting this hypothesis Finally we consider the implications of these results for forest managementThe current study has been conducted within the framework of the InterregIV project “The regeneration of the oaks in the Upper Rhine lowlands” funded by the European Regional Development Fund ERDF the regional government authority of BadenWürttemberg in Freiburg Regierungspräsidium Freiburg RPF the National Office of Forests Office National des Forêts ONF in France and the Regional Directory of Food Agriculture and Forestry of Alsace Direction Régionale de l’Alimentation de l’Agriculture et de la Forêt d’Alsace DRAAF We express our gratitude to all of the people from the ONF RPF and the FVA who worked for the project in the field in the lab or in the office We thank three anonymous reviewers for providing valuable comments on this article We thank Bernhard Thiel for improving the English of the manuscript

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