The effects of interspecific biodiversity on intraspecific genetic diversity: a community genomics approach

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Evolutionary and ecological processes interact on contemporary timescales. This results in eco-evolutionary dynamics, in which ecological processes influence the selective environment (eco-to-evo feedbacks) and within-species changes in abundance and composition influence community interactions (evo-to-eco feedbacks). On the evo-to-eco side, standing genetic variation (= intraspecific diversity) constitutes the raw material for adaptation. Adaptation affects population persistence and thus represents an important component for long-term ecosystem functioning at the community level. On the eco-to-evo side, species diversity (= inter-specific diversity) constitutes a significant aspect of the selective environment that influences the population structure of any focal species and thus impacts on standing genetic variation within species. Intriguingly, inter- and intraspecific genetic diversity often covary positively in natural populations (a phenomenon known as species-genetic diversity correlations SGDC), but the causes for this covariation are largely elusive. One reason for the lack of knowledge is the paucity of long-term experimental studies that manipulate species diversity and thus allow an assessment of the eco-to-evo feedbacks on intraspecific genetic diversity. Our project pioneers in uniting population genetics and community ecology in an approach that has become known as community genetics. Community genetics allows us to understand the eco-evolutionary dynamics at all levels of diversity from species assemblages to populations to individuals. Unlike most previous studies, we will use the experimental setting of the Jena Experiment and will cover all species of the plant community. Specifically, we address the following questions: (1) Does plant species diversity influence the maintenance of intraspecific standing genetic variation of plant populations? (2) Does plant species diversity influence the distribution of genetic variation across individuals? (3) Did plant species systematically change in their genetic composition across the 18 years of experimental manipulation of the Jena Experiment? We will study intraspecific and inter-individual genetic diversity in a set of 12 focal plant species (three species per functional group) across the full species-diversity gradient of the Jena Experiment using modern genotyping-by-sequencing approaches. We will then replicate and generalize to the full set of 60 species, including samples from the founding population from 2002 (stored as seed materials) and species-specific samples taken from contemporary high and low diversity communities. This approach allows us to test for the first time in a field experimental setting how species diversity of the community affects intra-specific genetic diversity and thus the potential for future adaptation.