Predicting the similarity of parasite communities in freshwater fishes using the phylogeny,ecology and proximity of hosts

Parasite communities tend to be dissimilar in hosts that are geographically, phylogenetically, ecologically and developmentally distant from one another. The decay of community similarity is a powerful and increasingly common method of studying parasite beta diversity, but most studies have examined only a single type of distance. Here, we evaluate distances based on the phylogeny, ecology, spatial proximity and size of hosts, as predictors of the similarity of parasite communities in individual hosts, host populations and host species. We surveyed parasites in six species of fish collected simultaneously from six localities in the St. Lawrence River, Canada, and species in a common group of larval parasites were discriminated using DNA sequences from barcode region of cytochrome c oxidase I. Distances based on the habitat use patterns of host species were good predictors of short‐term, ecological similarity of parasite communities, such as that operating at the scale of the individual host. The genetic distance between host species was associated with almost all types of similarity at all scales, particularly qualitative and phylogenetic similarity of parasite communities at the level of populations and meta‐populations of hosts. The trophic level, diet, spatial proximity and size of hosts were poor predictors of parasite community similarity. The increased taxonomic resolution provided by molecular data increased the explanatory power of regression models, and different factors were implicated when parasite species were distinguished with DNA barcodes than when larval parasites were lumped into morphospecies, as is commonly practiced.