Role of constitutive and induced chemodiversity in Solanum dulcamara in plant-herbivore interactions

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The wet-loving plant Solanum dulcamara is found in very different habitats, including significantly drier ones, due to its high phenotypic plasticity. In the first funding period, our goal was to study populations of this plant for relationships between biotic and abiotic environmental factors and chemodiversity in leaf metabolites. Strong correlations indicated that the chemodiversity of phenolic substances is significantly higher in drier habitats with higher species numbers of plants and herbivores than in wet, species-poor sites. This suggests that complex communities may promote intraspecific chemodiversity and is consistent with the assumption that plant chemodiversity evolves under the pressure to cope with different stressors. In addition, the plants showed a high intra-individual chemodiversity, which was expressed in a pronounced change in leaf metabolite patterns over the course of a season. Analyses with P4 currently test these relationships for steroid alkaloids. Ongoing greenhouse experiments with clones of the same plant individuals are investigating the genotypically determined differences in constitutive and wound-induced leaf metabolite composition to subsequently experimentally test the consequences of chemodiversity with selected genotypes in plant-insect interactions. In a second funding period, we aim to analyse genetic variation within and between populations with molecular markers and use multivariate statistics to examine how it is related to chemodiversity. We will test whether there are differences in this relationship between constitutive and wound-induced chemodiversity and how genetic and chemical diversity are related to environmental factors in populations. We aim to extend the geographic range of the populations analysed for their genetic, chemical and ecological variation so that these relationships can also be investigated across macroclimatic gradients and across populations of larger genetic divergence. The results can be compared with P5 and provide clues for evaluating hypotheses on the evolution of plant chemodiversity together with P9. We further aim to investigate constitutive and induced intra-individual chemodiversity in different organs for genotypes from populations characterised by a dominance of either specialised or generalist herbivores. Chemically divergent genotypes will be used in the chemodiversity-plasticity experiment (COR) and all data on chemical variation in P10. Organ-specific patterns will be analysed comparatively across all three plant species with P1-P5 and the functional role of organ-specific chemodiversity in interaction with generalists and specialists will be investigated in bioassays and reciprocal transplant experiments.