Trait-shift induced interaction modification: How individual variation affects ecosystem stability

Individual organisms of the same species can exhibit substantial variation in traits that are important for their interaction with the environment and other species. The distribution of such variable traits within a species can shift over time. For example, behavioral traits can change quickly in response to environmental change or species interactions. The dynamic shift of trait distribution within a species can modify the interaction patterns among species and ultimately affect the stability of ecosystems. However, the prevalence and significance of such effects have not been evaluated systematically. This research project aims to fill in the gap by integrating theoretical and empirical approaches. A mathematical framework will be developed to classify different types of interaction modification and identify conditions that would destabilize ecosystems. Additionally, a comprehensive survey of empirical studies will be conducted to assess the level of evidence for the various types of interaction modification identified above and provide criteria for evaluating past and future case studies. This project will train young researchers in the interdisciplinary area between mathematics and ecology to address important environmental and ecological problems facing the next generation. In addition, educational kits and programs will be designed to promote teaching of important ecological concepts and engage underrepresented groups in K-12 schools. Intraspecific trait variation has been increasingly recognized as an important factor in determining ecological and evolutionary dynamics. Although some work has examined how the variation of heritable traits affects eco-evolutionary dynamics, non-heritable variation caused by phenotypic plasticity, developmental differences, or species interactions has received less consideration. Ecosystems have traditionally been studied as dynamical systems with fixed interaction strengths, but these interaction strengths will no longer be constant if the trait distributions can shift within short timescales. Such “trait-shift induced interaction modification” (TSIIM) can lead to higher-order interactions among species, causing species extinction or coexistence that are otherwise unexpected. This project will develop a theoretical framework for studying TSIIM by generalizing traditional dynamical systems to incorporate intraspecific trait variation and categorizing these systems into different network motifs. The effect on large ecosystems will be studied using a disordered systems approach augmented by the new motifs. Meta-analysis of these motifs using empirical studies will provide insight on the mechanisms by which higher-order interactions arise from TSIIM, prompting experimental searches for such phenomena and their consequences. This project is jointly funded by the Mathematical Biology Program at the Division of Mathematical Sciences and the Population and Community Ecology Cluster in the Division of Environmental Biology at the Directorate for Biological Sciences. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.