Multidimensional coevolution drives predator coexistence

Understanding how multiple predators can coexist while relying on a single, ecologically homogeneous prey species has been a central question in community ecology, as classical theory predicts competitive exclusion unless niche differences or other stabilizing forces are present. While rapid evolution has been shown to facilitate coexistence among competing predators in some systems, most studies have largely focused on single-trait dynamics, often overlooking reciprocal predator-prey coevolution. Here, I develop an eco-evolutionary model in which two predator species and their shared prey coevolve in one or two traits. The results demonstrate that allowing two traits to evolve significantly broadens the parameter space for coexistence compared to one-trait systems, particularly when the prey evolves rapidly. Multidimensional coevolution promotes various forms of trait-space partitioning among predators by driving prey to adapt alternately to the predator posing the greatest threat, resulting in asynchronous trait dynamics that underlie coexistence. It also causes the relative advantages between species to alternate over time and tends to balance their long-term average R^*, the minimum resource requirement for population persistence, thereby potentially favoring otherwise subordinate species. Consequently, multidimensional coevolution simultaneously fosters both stabilizing and equalizing mechanisms, leading to fluctuation-driven coexistence. These findings unveil a richer and more diverse set of pathways to predator coexistence than previously recognized. This work highlights the need to integrate evolutionary complexity into coexistence theory and calls for empirical exploration of multivariate coevolution in predator-prey systems.