Downstream changes in the composition of the parasite community of fishes in an Appalachian stream

The spatial distribution of 6 parasite species (Myxobolus sp.. Dactylogyrus sp., Sterliadochona ephemeridarum, Plagioporus sinitsini. Allopodocotyle c hiliticorum, Allocreadium lucyae) was studied in 5 species of fishes (Oncor hynchus mykiss. Clinostomus funduloides. Notropis chiliticus. Rhinichthys a tratulus. Semotilus atromaculatus) in Basin Creek, an Appalachian stream in North Carolina. Nonmetric multidimensional scaling and vector fitting were used to determine if the proximity of sampling sites was related to commun ity similarity. Position along Basin Creek was significantly related to par asite community structure. Breaks in parasite community composition were im posed by waterfalls at upstream areas of Basin Creek that restricted distri butions of C. funduloides. N. chiliticus. and S. atromaculatus and at the d ownstream limit of the study area by a break in the distribution of S. ephe meridarum coincident with the existence of a dam but were independent of su itable piscine host distributions. These discontinuities in parasite commun ity composition imply that the relationship between proximity of sites and community similarity is predictive because distance between sites is relate d to the probability that fish at different sampling sites recruit parasite s from different species pools. This relationship is not the same for all c omponent communities.