Abstract:
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.
