Evolution between two competing macrophyte populations along a resource gradient leads to collapse in a bistable lake ecosystem

While it is known that shallow lake ecosystems may experience abrupt shifts (ie tipping points) from a clear water state to a contrasting turbid alternative state as a result of eutrophication, the role of evolutionary processes and the impact of trait variation in this context remain largely unexplored. It is crucial to elucidate how eco-evolutionary feedbacks affect abrupt ecological transitions in shallow lakes and more in general in bistable ecosystems. These feedbacks can significantly alter the dynamics of aquatic plants competition, community structure, and species diversity, potentially affecting the existence of alternative states or either delay or expedite the thresholds at which these ecological shifts occur. In this paper, we explore the eco-evolutionary dynamics of submerged and floating macrophytes in a shallow lake ecosystem under asymmetric competition for nutrients and light along a gradient of nutrient diffusion. We use Adaptive Dynamics and a structured population model to analyze the evolution of the growth depth of the submerged and floating macrophytes populations, which influences their competitive ability for the two resources. We show how trait evolution can result in complex dynamics including evolutionary oscillations, extensive diversification and evolutionary suicide. Furthermore, we find that the co-evolution of the two competing populations plays a stabilizing role, but does not significantly alter the dynamics compared to when only one of the two populations is evolving. Overall, our study contributes to the understanding of the effects of evolution on the ecological dynamics of bistable ecosystems.