Food density drives diet shift of the invasive mysid shrimp, .

Understanding the diet preferences and food selection of invasive species is crucial to better predict their impact on community structure and ecosystem functioning. , a Ponto-Caspian invasive mysid shrimp, is one of the most successful invaders in numerous European river and lake ecosystems. While existing studies suggest potentially strong trophic impact due to high predation pressure on native plankton communities, little is known of its food selectivity between phyto- and zooplankton, under different food concentrations. Here, we therefore investigated the feeding selectivity of .  on two commonly occurring prey organisms in freshwaters, the small rotifer zooplankton together with the microphytoplankton sp. present in increasing densities. Our results demonstrated a clear shift in food selection, with switching from to sp. already when the two prey species were provided in equal biomasses. Different functional responses were observed for the two food types, indicating somewhat different foraging mechanisms for each food type. These findings provide experimental evidence on the feeding flexibility of invasive mysid shrimps and potential implications for trophic interactions in invaded ecosystems.