Intraspecific trade-offs in competitive ability and the coexistence of competitors

Background/Question/Methods

Understanding the forces allowing multiple species to coexist remains a central focus of community ecology. Building evidence suggests that evolutionary changes may frequently occur on timescales relevant for ecological dynamics, and thus a complete understanding of the maintenance of diversity is likely to require incorporating evolutionary dynamics. In this talk I will explore how a genetic trade-off between intra- and interspecific competitive ability can promote stable coexistence by providing an evolutionary advantage to species as they become rare. I will discuss evidence from two related plant systems (Brassica nigra and its competitors in California and Alliaria petiolata invasions into forest understories) where this trade-off is mediated by allelochemical production and interactions with soil microbial communities

Results/Conclusions

For both B.nigra and A. petiolata, genotypes that invest heavily in the allelochemical sinigrin are strong competitors against other species, but weak competitors against conspecifics. In both cases this phenomenon seems to be driven by the allelochemical's effect on the mycorrhizal mutualists of the competitor species. Simulations parameterized with field data suggest that this trade-off can buffer coexistence of B. nigra and three competitors across a wide range of ecological conditions. In A. petiolata, evidence suggests that this trade-off is playing an important role in shaping the invasion dynamics. Over time, this trade-off may prevent the invader from dominating communities indefinitely, and aid in the resurgence of displaced native species.