Parasite communities of a rallid bird, Eurasian coot Fulica atra Linnaeus, 1758, in the Palaearctic.

Geographic distance is often recognized as a leading factor structuring the diversity of parasite communities. However, specific ecological and biogeographic mechanisms underlying the influence of this factor are not always evident. We used the material on the helminths of Fulica atra Linnaeus, 1758 (Rallidae) from seven areas in the Palaearctic to study geographic differentiation of the parasite communities at the level of both component communities and infracommunities. The analysis of spatial patterns of the parasite communities included (i) a reconnaissance study exploring the directions of variability of the communities using principal component analysis (PCA), and (ii) a careful disentanglement of the relationships identified in the reconnaissance study using metric scaling in Euclidean space. The component communities showed a clearer differentiation associated with geographic factors as compared to the infracommunities. The differences in the species composition of the parasite component communities of F. atra. increased consistently with increasing longitudinal distance between the localities, while the differences in prevalence increased with increasing latitudinal distance. The longitudinal trend of similarity decay of species composition of the component communities is probably determined by the directions of the seasonal migrations of F. atra., which promote or prevent the exchange of parasite species between geographically isolated areas. The latitudinal gradient in the variability of the component communities in terms of prevalence may be associated with the latitudinal patterns in the temperature regime of the water bodies and their impact on the species composition and biomass of the food objects of F. atra.