P9

Modelling the causes and consequences of intraspecific plant chemodiversity in a changing world

Plant chemodiversity is shaped by a complex set of molecular, ecological, and evolutionary processes. The goal within the first funding period was to start building a quantitative modelling framework for the evolutionary emergence and maintenance of plant chemodiversity. In collaboration with P5, we reviewed the literature for existing models that explain how plant chemodiversity arises and is maintained. While there are many verbal models, there are so far few mathematical models and computer simulations. To fill this gap, we developed two complementary modelling approaches for the evolution of intraspecific plant chemodiversity. First, with P3 and P8, we developed a simple proof-of-concept model where the absence or presence of metabolites is directly encoded in the genome. We showed that temporal variation in herbivore pressure can maintain substantial intraspecific chemodiversity, both within and between plants, if the genetic dominance of the metabolite presence alleles for anti-herbivore activity is larger than their genetic dominance for costs. Second, we developed a more mechanistic individual-based simulation model where a plant individual’s metabolite profile emerges from a detailed model of its genome, its proteome and the kinetics of the reaction network. We again found a large role for temporal variation in selection pressures, and also substantial historical contingency. Finally, with P5, P6 and P8, we developed a first version of the virtual Tanacetum, a simulation model synthesising all currently available information on the genetic basis of leaf terpenoid chemodiversity and on the interactions of this chemodiversity with herbivores and pollinators. A first virtual Solanum (with P3, P4) will likewise be prepared in the first funding phase.

In the proposed second funding period, we aim to extend our models for the causes of chemodiversity and explore the consequences of plant chemodiversity in a variable biotic and abiotic world. First, we will explore the role of chemodiversity for the responses of plant populations in a variable pollinator and herbivore environment. Second, we will investigate the role of intraspecific chemodiversity for plant populations under climate change (with input from P10 and COR). For both work packages, we hypothesise that there is a portfolio or buffering effect whereby in a changing environment more chemodiverse populations fluctuate less strongly and are potentially also larger on average. Third (with P1-P8), we will develop the virtual Populus and extend the virtual Tanacetum and the virtual Solanum using newly generated data from the genomes, new crossing experiments and common garden data. Fourth, we will contribute to the common chemodiversity-plasticity experiment (COR) by feeding the short-term experimental results into our virtual plant models to derive long-term predictions for the effects of chemodiversity under recurrent episodes of drought stress and herbivory.