A comparison of the helminth communities in Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii at Barberspan, South Africa.

Examination of the helminth communities in 25 yellow-billed ducks (Anas undulata), 21 red-billed ducks (Anas erythrorhyncha), ten Cape teal (Anas capensis) and seven Cape shovellers (Anas smithii) that had overwintered at Barberspan, revealed differences in community structure. Infracommunities in yellow-billed and red-billed ducks were characterized by low diversity and high eveness, and generally consisted of less than 100 helminths per duck. Similarity values (mean percent similarity and mean Jaccard's coefficients) were low. In contrast, infracommunities in Cape teal and Cape shovellers were more diverse, displayed low eveness values and consisted of far greater numbers of helminths. Mean similarity values for the infracommunities in Cape teal and Cape shovellers were much higher than those in yellow-billed or red-billed ducks. The component communities in all four duck hosts were species rich. Those in yellow-billed and red-billed ducks, however, consisted predominantly of satellite species and no core species were present, whereas those in Cape teal and Cape shoveller included several core species. Cape teal and Cape shovellers each had a group of recurrent species but there was not much of a tendency for species to co-occur in yellow-billed and red-billed ducks. Multivariate analysis revealed a greater similarity between the communities in Cape teal and Cape shovellers than between the latter and the communities in yellow-billed or red-billed ducks. Communities in Cape teal and Cape shovellers could be distinguished from each other by the presence or absence of particular cestode species. The communities in these two species could be distinguished from those in yellow-billed or red-billed ducks by a suite of cestode species that was absent in the latter two. Two recurrent groups, consisting of eight and two species, were identified in the compound community. Each group consisted of species found predominantly in Cape teal and Cape shovellers. Patterns seen in the helminth communities of the various hosts reflected differences in diet, but other factors, including feeding behaviour, spatial segregation and host specificity, may also have had an effect.