Dynamic trait shift and its effects on biological populations

A biological population exhibits a distribution of traits among individuals that affect how they interact with other species and the environment. This distribution of trait values can shift under three types of influences: differential growth, phenotypic plasticity, and preferential consumption by the predator. Ecological models of population dynamics and species distributions often focus on "density effects", ignoring trait shifts. Through a simple predator-prey model that explicitly tracks the trait distribution of the prey, we explore the implications of trait shifts. We quantify "trait effects" resulting from the shift in trait distribution, first on the prey population itself, including the healthy herd effect and emergent promotion. We then show the back-reaction on the predator, which may reduce its population and possibly even result in its extinction. Our results suggest that including trait shifts in modeling ecological dynamics will be important for predicting species interactions and persistence.