Ecological determinants of parasite acquisition by exotic fish species

Disease-mediated threats posed by exotic species to native counterparts are not limited to introduced parasites alone, since exotic hosts frequently acquire native parasites with possible consequences for infection patterns in native hosts. Several biological and geographical factors are thought to explain both the richness of parasites in native hosts, and the invasion success of free-living exotic species. However, the determinants of native parasite acquisition by exotic hosts remain unknown. Here, we investigated native parasite communities of exotic freshwater fi sh to determine which traits infl uence acquisition of native parasites by exotic hosts. Model selection suggested that fi ve factors (total body length, time since introduction, phylogenetic relatedness to the native fi sh fauna, trophic level and native fi sh species richness) may be linked to native parasite acquisition by exotic fi sh, but 95% confi dence intervals of coeffi cient estimates indicated these explained little of the variance in parasite richness. Based on R 2 -values, weak positive relationships may exist only between the number of parasites acquired and either host size or time since introduction. Whilst our results suggest that factors infl uencing parasite richness in native host communities may be less important for exotic species, it seems that analyses of general ecological factors currently fail to adequately incorporate the physiological and immunological complexity of whether a given animal species will become a host for a new parasite. Oikos 121: 1889–1895, 2012 doi: 10.1111/j.1600-0706.2012.20143.x © 2012 Th e Authors. Oikos © 2012 Nordic Society Oikos Subject Editor: Hamish McCallum. Accepted 19 January 2012