Eco-evolutionary importance in competing marine phytoplankton communities

Ecosystems have always been exposed to environmental changes. During the past centuries, however, human activities have accelerated these processes vastly. The awareness that ecological and evolutionary changes happen on a similar timescale, and that these processes interact, and consequently jointly determine community structure, only arose over the past decades. This might be especially important for organisms such as phytoplankton, which have short generation times and vast population sizes, characteristics that favour rapid evolutionary changes. Phytoplankton communities form massive blooms and provide the basis of aquatic food webs. Thus, understanding and predicting future phytoplankton community structures is essential in the light of rapid climate changes. Empirical studies have demonstrated species frequency shifts and adaptive evolution in response to novel environments. To date, however, most studies have treated ecological and evolutionary changes in isolation, and their relative contributions to the overall community change were not quantified. In this thesis, I aim to close this knowledge gap by simultaneously studying ecological and evolutionary processes of a marine phytoplankton community under a climate change driver, to ultimately uncover their relative importance for future community changes.