Does Carcinus maenas facilitate the invasion of Xenostrobus securis?

Abstract

Introduction of non-indigenous species can generate new trophic interactions that may facilitate or control their spread. The first recorded Atlantic population of the mytilid Xenostrobus securis, originally from New Zealand, offers an opportunity to examine how native predators may control the outcome of invasions. Laboratory experiments were done to evaluate the impact of the native crab, Carcinus maenas, on 2 species of mussels, X. securis and the native Mytilus galloprovincialis, at 3 different temperatures (15, 20 and 25 °C). In addition, we investigated handling time, breaking time and profitability for both species of mussel. We tested the hypotheses that (1) C. maenas exerts a greater predation pressure on the native mussel and (2) C. maenas increases its ingestion of the most profitable species of mussel at higher temperatures. The first hypothesis was supported because C. maenas consumed greater than twice as many native mussels as invasive ones at all temperatures. This greater consumption of M. galloprovincialis could be explained by its greater profitability and shorter handling and breaking time. These results are in concordance with the enemy release hypothesis suggesting that C. maenas might facilitate the invasion of X. securis. The consumer–prey relationship was not significantly affected by temperature although the number of X. securis ingested by C. maenas tended to decrease with increasing temperature, whereas the number of M. galloprovincialis consumed increased at the highest temperature. Results, therefore, suggest that global warming could enhance the facilitation of the invasion of X. securis due to its lower profitability and greater handling and breaking time.