Preferential consumption of invasive over native prey by rocky intertidal predators

Abstract Invasive species have broad scale impacts on recipient ecosystems, and are one of the major drivers of the currently observed biodiversity decline. Invasive prey species can disrupt native food webs through altering trophic interactions between predators and prey. Despite the potentially wide-ranging consequences of these changes, the dynamics of such interactions are yet to be explored in-depth. Here we assessed the frequency dependent predation towards invasive and native bivalve prey ( Xenostrobus securis and Brachidontes variabilis , respectively) by different native predator types – a crab ( Hemigrapsus penicilatus ) and a predatory gastropod ( Reishia clavigera ). Greater absolute consumption of the invasive compared to native prey was shown by both predators. Further, there was a clear preference for invasive prey over native prey by both predators, even when invader availability was scarce. These results show that the predators are able to readily consume, and potentially restrict the spread of, the invasive prey species. However, the patterns of consumption observed experimentally here and the subsequent suggested biotic resistance to invasion are not reflected in field populations as the invasive bivalve prey continues to spread locally. We highlight the need to incorporate multiple types of investigation – both laboratory and field based – to provide a comprehensive understanding of trophic interactions, and the broader impacts invasive prey species may exert on recipient communities.