Nutrient uptake-related trait variability and trade-offs - adaptive evolution and community functioning in competing phytoplankton species

• Applicants: Dr. Birte Matthiessen; Professor Dr. Thorsten Reusch, Ph.D.
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Evolution, Anthropology ; Oceanography
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257416234

Marine phytoplankton communities are largely regulated by nutrient regime. Both nutrient concentration and stoichiometry select for nutrient uptake-related traits such as maximum uptake rate (Vmax) and the half saturation constant (Kn). Jointly these traits and associated trade-offs determine phytoplankton ecological niche, competitive ability and ultimately the conversion of dissolved nutrients into phytoplankton primary production as one major component of ecosystem functioning. The role of standing intra- and interspecific variability of nutrient uptake-related traits and trade-offs as predictors for adaptive eco-evolutionary dynamics remains to be understood, and equally unknown are consequences for realized primary production under different nutrient regimes. Here we target two major phytoplankton groups differing in fundamental ways to acquire nutrients, affinity vs. velocity-adapted for both nitrate and phosphate, exemplified by a diatom and a coccolithophore species. We follow eco-evolutionary dynamics over time as a function of nutrient regime and diversity, and study the consequences for phytoplankton community functioning. This is particularly important in the light of increasing nutrient limitation owing to enhanced water column stratification in many oceanic regions. In this project, we span experimental eco-evolution, molecular approaches and predictive modelling to test the following hypotheses: (1) adaptive evolution towards new optimal nutrient acquisition in the target species is slowed down due to pre-occupied trait space by a competitor; (2) phytoplankton community functioning is jointly determined by eco-evolutionary dynamics of nutrient uptake-related trait diversity within- and among species, and depend on the range of occupied niche space by each species. Our planned experiments will be supported by predictive nutrient-related trait-based modeling and by investigations of nutrient uptake-related gene expression.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1704: Flexibility Matters: Interplay Between Trait Diversity and Ecological Dynamics Using Aquatic Communities as Model Systems (DynaTrait)