Eco-evolutionary dynamics - admixture and global change

Global change, including phenomena such as climate change, pollution, habitat loss and other stressors, is proceeding at an ever-faster pace and threatens organisms, communities, ecosystems and, ultimately, human wellbeing. It is unclear if and how species and ecosystems will be able to cope with this rapid environmental changes. However, we urgently need to understand how species, communities and ecosystems respond to global change for accurate risk assessment and the implementation of targeted mitigation and conservation measures. In recent years, we have learned that ecological and evolutionary changes can be rapid and if they occur on contemporary timescales they can influence each other an interaction known as eco- evolutionary dynamics. Understanding these eco-evolutionary interactions and feedbacks is essential for assessing how past disturbances changing these interactions may affect todays responses to ecological changes. Likewise, identification of the traits of organisms mediating these interactions is necessary for a mechanistic understanding. I will use water fleas, small crustaceans in the Daphnia longispina species complex system, and peri-Alpine lake ecosystems and the biological communities in those lakes as a model system to tackle these questions. Daphnia water fleas feed on microbes (algae, bacteria, protists) which they filter from the lake water and are an important prey for invertebrates and fish and thus an important organism in lake food webs - a so-called keystone species. Eutrophication, an ecological change in lakes caused by anthropogenic increase of nutrients, has resulted in invasions and admixture in the Daphnia longispina complex, that is, secondary contact and interbreeding among several species. I hypothesize that this evolutionary change in response to an ecological change has changed important traits in Daphnia such as body size and filter apparatus and has thus affected how the interact with their biotic and abiotic environment. To summarize, a previous stressor, here eutrophication, has changed eco-evolutionary interactions among Daphnia, lake community and ecosystem. In this project, I will characterize these changes and interactions and then assess whether and how they affect the response of the water fleas, community and ecosystem to a new, emerging stressor heat waves in lakes. Heat waves are one aspect of climate change and have recently been shown to constitute a major stressor for lake ecosystems with direct and indirect effects on organism and communities. I will use experiments and field studies to explore how two ecological stressors, eutrophication and heat waves, interact through time via their effects on eco-evolutionary dynamics and investigate how such interactions shape the outcome of global change.