A Comparison of Genetic Diversity and Phenotypic Plasticity among European Beech (Fagus sylvaticaL.) Populations from Bulgaria and Germany under Drought and Temperature Manipulation

Premise of research. In the future, ecosystems will have to deal with climate warming in combination with increasing frequency and magnitude of extreme weather events such as drought. Adaptive phenotypic plasticity enables plants to respond to environmental variability and is likely to buffer impacts of climate change. Therefore, factors that influence the phenotypic plasticity of plant populations must be identified to assess climate change outcomes and support conservation measures. Genetic diversity in many temperate plant species is known to vary among regions and populations, largely as a result of their phylogeographic history during the late Pleistocene and Holocene. Here, we argue that high (neutral) genetic diversity of populations might represent increased probability of possessing alleles or allele combinations that are advantageous or more capable in terms of average response capacities to environmental change. Methodology. We test this idea for European beech (Fagus sylvatica) by investigating response patterns of plant growth and leaf phenology to drought and warming treatments in a common-garden experiment with seedlings of six populations from Bulgaria and Germany. Phenotypic plasticity of populations was assessed and correlated with allozyme diversity. Populations differed in their plasticity to warming with respect to timing of leaf unfolding and senescence as well as in their drought plasticity in terms of height increment (marginally not significant), with some populations showing consistently high plasticity among traits.Pivotal results. Measures of genetic diversity showed an interregional structure according to known phylogeographic patterns. Height increment plasticity showed a significant positive correlation with genetic variation (allelic diversity) at the population level.Conclusions. Our results suggest general differences in phenotypic plasticity among populations and a potential influence of genetic diversity on the average plasticity. Besides its evolutionary value, genetic diversity might thus be an important property of plant populations for their short-term response capability against adverse effects of climate change.