The role of genetic diversity in biodiversity-ecosystem functioning relationships

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Genetic diversity is usually neglected in biodiversity-ecosystem functioning studies. However, functioning may depend on genetic diversity as well as on between-species diversity, and the two might interact. Also, variation in species diversity may affect genetic diversity. In four work packages (WP) we will explore the role of genetic diversity (GD) and the effects of species diversity (SD) on GD.WP1: The role of experimental genetic diversity and of its interaction with expe rimental species diversity for plant performanceIn the Main Experiment, we factorially crossed SD and GD (different numbers of seed families) on 24 1-mu plots. We will comprehensively assess plant performance (biomass, growth, herbivory, pathogen load) of all trees on these plots in relation to GD and its interaction with SD.WP2: Experimental SD effects on genetic variation of phytometer treesResident and additional phytometer trees of defined seed families allow us to assess genetic variation in plant performance and the relative roles of genetic variation and phenotypic plasticity in tree responses to diversity.Task 1: Assessing resident phytometer tree performance (seed families of 12 species regularly planted in the Main Experiment, totaling >45000 individuals)Task 2: Assessing additional phytometer tree performance (seed families of 1 species, Machilus thunbergii, in all plots, totaling >7000 individuals)We will assess plant performance (biomass production, growth, herbivory, pathogen load) of all phytometer trees to analyze genetic variation, phenotypic plasticity, and genetic variation in plasticity (i.e. seed family x environment interactions) in response to SD and composition in the plots.WP3: Natural SD effects on genetic variationWe established a common garden with hundreds of clones of ten clonal shrub species collected in the CSPs. We will use this experiment to address effects of SD and composition of the CSPs on quantitative genetic variation. Moreover, we will transplant clones (cuttings) to plots of low and high species diversity to address the relative importance of phenotypic plasticity and genetic variation for plant performance in the CSPs, and to test whether there is adaptation to diversity or specific CSPs. If transplantation to the CSPs should not be permitted, we will transplant to high and low diversity plots of the Main Experiment.WP 4: Flowering and reproductionGenetic diversity depends to an increasing degree on differential offspring recruitment in the plots. Diversity effects on reproduction and offspring growth and survival may deviate from diversity effects on established trees. As a first step towards assessing offspring performance in relation to SD we will assess flowering, fruit set and seed set in the seven species of the Main Experiment that have already entered the reproductive state. Overall, our subproject will comprehensively explore the effects of SD on GD and the role of GD for plant performance.