Genes determine an organism’s phenotype, which influences its trophic interactions with other species. The strength and organization of trophic interactions define food-web structure, which plays an important role in determining the stability and persistence of ecological communities. Despite these obvious links between biological scales, we do not know how genetic change will rewire food webs, and thus community persistence. It is also unknown how these processes will change in response to the warmer temperatures we expect from ongoing climate change. To gain insight into these processes, we used a multi-trophic community comprising the plant Arabidopsis thaliana, two species of aphids, and a parasitoid wasp. The genomic resources available for Arabidopsis allowed us to manipulate the presence/absence of functional alleles at genes (MAM1, AOP2, and GSOH) that control its metabolic defenses against insect herbivores. We then created experimental plant populations that varied in genetic diversity under two different temperature regimes (20 C or 23 C). To measure community persistence, we quantified the time until species went extinct in each experimental community. We also quantified the abundance of each species over time to measure the strength of inter- and intraspecific interactions (food-web structure), and thus, the mechanisms underlying community persistence.
Results/Conclusions
We found that higher genetic diversity enhanced the persistence of the multi-trophic community. This enhanced persistence resulted from a decrease in the strength of aphid-aphid and aphid-parasitoid interactions. There was also evidence that specific genes influenced community persistence. For example, the presence of a functional AOP2 gene decreased community persistence because of its pleiotropic effects on plant growth, which reduced resource availability for upper trophic levels. Temperature, on the other hand, had conflicting effects on community persistence. For example, temperature enhanced the persistence of the faster-growing aphid species (Lipaphis erysimi), but this resulted in a more rapid exclusion of the slower-growing aphid (Brevicoryne brassicae). Taken together, our results show that genetic diversity in plant defense metabolism can enhance the persistence of multi-trophic communities in the face of climate change. Given that the current rate of population extinction, and subsequent loss of genetic diversity, is orders of magnitude higher than the rate of species extinction, our results highlight the pressing need to understand how the loss of genetic diversity within species will affect the stability and functioning of ecosystems.