Not-so-naïve: A native prey recognizes and responds specifically to a novel predator in a freshwater system

摘要: Native prey may be expected to lack the ability to detect and behaviorally respond to non-native predators due to a lack of shared evolutionary history, particularly in isolated systems like lakes. Nevertheless, seemingly adaptive responses by native prey to invasive predators have been observed. Four mechanisms can explain these observations. Native prey could perceive and respond to non-native predators:(1) through cue similarity between the non-native predator and pre-existing predators in the native system;(2) from cues from conspecifics eaten by the non-native predator;(3) through learning based on recent experience with the non-native predator; and (4) through constitutive cues produced specifically by the non-native predator. In the Great Lakes, the native cladoceran Daphnia mendotae responds in a seemingly adaptive manner to the invasive planktivore Bythotrephes longimanus; migrating to deeper, darker water in the presence of Bythotrephes, which helps it avoid detection and capture by this visual predator. We conducted a series of laboratory experiments designed to determine which of the above four mechanisms was responsible for Daphnia’s adaptive response to Bythotrephes.