© Universität Bielefeld
P7
Intraspecific chemodiversity in Tanacetum vulgare shapes above- and belowground plant-associated communities
In the first funding phase, our goal was to manipulate chemodiversity of Tanacetum vulgare at the plant community level, to study the interactions between these plants and aphids. Therefore, we created a chemodiversity field experiment - totaling 84 plots and 504 plants - in which the plot-level chemotype richness of Tanacetum vulgare terpenoid chemotypes (determined by P5 and P6) ranged from one to six. We sampled insect communities (focusing on aphids and predators) and plant growth parameters as well as headspace volatile organic compounds (with P1 and P2). Field insect and volatile data are currently under analysis, but preliminary analyses show effects of plot-level chemotype richness on aphid colonisation, particularly a positive effect on Metopeurum fuscoviride abundance. Under laboratory conditions, we performed pairwise choice assays for the used chemotypes, using two aphid species specialised on T. vulgare, Macrosiphoniella tanacetaria and Uroleucon tanaceti (with P5). We found that chemotypes affect choice behaviour in both species and that terpenoid diversity tends to repel, while total terpenoid concentration tends to attract M. tanacetaria. Bottom-up and top-down pot studies on the T. vulgare chemotypes revealed that M. tanacetaria colonies grow significantly faster on two out of six chemotypes, while colony survival when exposed to natural predators was significantly lower on one (different) chemotype. We showed that chemodiversity mediates – at least partly – aphid attraction or repellence, bottom-up and top-down processes in T. vulgare and its insect communities, and our current focus is to link these individual processes in the study system.
In the second funding period, our goal is to continue to investigate aphid communities in relation to chemodiversity (with P5) with a focus on its effects on the dynamics between the specialist ant-tended aphid M. fuscoviride and Lasius niger ants. We will combine field observations in our common garden with pot experiments to unravel the role of chemodiversity, and particularly volatiles (with P1, P2), in driving ant visitation and consequences for M fuscoviride performance and interspecific competition with other aphid species. In addition, our aim is to use the field experiment to investigate consequences of chemodiversity belowground. We will study the consequences of plot-level chemotype richness on soil communities, i.e. soil-dwelling nematodes, micro- and macro-arthropods and endophytic fungi (with P4). In a pot experiment, we will test the consequences of soils from plots differing in plot-level chemotype richness and conspecific response plants differing in chemodiversity for plant-soil feedbacks, herbivores and pollinators (with P5). P7 will contribute to the chemodiversity-plasticity experiment by quantifying herbivory and herbivore fitness.
