UC Davis

The building evidence that evolution can be extremely rapid leads us to consider the convergence of ecological and evolutionary timescales. The convergence of timescales implies that evolution has the potential to significantly affect ecological processes and vice versa. The models and experiments presented here fall under this shared framework of eco-evolutionary feedbacks. Chapter 1 uses a general model to consider one way in which evolution affects ecology. It asks the question how rapid evolution affects short-term population dynamics and extinction risk in a population facing extreme climate events. We found that evolution can increase extinction risk if the extreme event is short-lived. Chapters 2 and 3 consider the other direction: how ecological contexts drive evolutionary change. In a controlled laboratory experiment using the common freshwater zooplankton Daphnia, we explored two selective mechanisms through which predators can cause prey life-history evolution. We found that both density-dependent selection and size selection are important drivers of life-history evolution. Then, in an outdoor experiment, we explored to what extent rapid evolution in Daphnia is predictable in a natural environment. We found consistent changes across replicate populations that are potentially driven by the ability of different clones to utilize resources. Finally, Chapter 4 documents a purely ecological feedback. In a lab experiment, we exposed multiple naturally diverse communities of phytoplankton to zooplankton grazing and showed that the composition of primary producers was altered as a result of the changes they imposed on the composition and feeding behavior of consumers.