Introduced predator elicits population-specific responses from prey

Abstract

Predator induced responses by prey can reduce risk, however, newly introduced predators may not elicit the same predator responses, thus making prey more vulnerable to these new predators. Therefore, examining responses of different prey populations of the same species to a non-native predator may provide novel insights for the evolution of predator recognition. Here, we tested the response of three populations of a low-dispersing marine gastropod (Littorina saxatilis) to chemical cues from a native crab predator (Dyspanopeus sayi) and a newly introduced crab predator (Hemigrapsus sanguineus). Using geometric morphometrics to study shell shape changes, we found that snails from all populations responded similarly to the native predator but differed in their response to the non-native predator. Snails from two of the three populations elicited no response to H. sanguineus, while the other population produced a more rotund shell, similar to their response to the native predator. Shell shape response in snails exposed to the native predator was different from those fed a reduced diet, suggesting that these anti-predator responses are active changes to shell morphology and not a by-product of reduced feeding in the presence of predators as suggested by other studies. Lastly, there were innate population shell shape differences, suggesting possible distinct ecotypes for Littorina saxatilis in North America as seen in European populations. Overall, populations differed in their response to an invasive predator indicating that evolution of predator recognition can differ between populations of the same species with similar co-existent history with the invader.