Intestinal helminths of lesser scaup ducks: patterns of association

Abstract

The helminth communities of the small intestines of 45 lesser scaup ducks sampled from 13 lakes in Alberta, Canada, were examined for patterns of association among species. A core of eight frequent, numerous, and positively associated species provided a basic similarity across all host individuals. Six of these core species are specialists in lesser scaup, and the other two are generalists in waterfowl. A group of eight moderately frequent and numerous species, which were positively associated with the core species but not with each other, also contributed to this similarity; these secondary species included two specialists in scaup and three generalists in waterfowl. The 36 remaining "satellite species" appeared to be distributed randomly among birds. Variations among communities in individual birds were due largely to (i) differences in the numbers of two suites of helminth species, one using Hyalella azteca and the other Gammarus lacustris as intermediate host; (ii) differences in the numbers of the Hyalella suite, and in the presence or absence of some secondary or satellite species, associated with the lake from which the duck was taken; and (iii) differences in the total numbers of helminths per duck, which may be associated with differential susceptibility of individual ducks.