title: Explaining co-occurrence among helminth species of lesser snow geese (Chen caerulescens) during their winter and spring migration.
abstract: The digestive tracts of 771 lesser snow geese (Chen caerulescens) collected from January to May 1983 from 12 locations (27 samples) were examined for helminth parasites to determine whether parasite species present in wintering geese or in spring migrants occurred independently of each other. Nine helminth species were identified. Seven had mean prevalences >5% and were the focus of this study. Six of those species were waterfowl generalists, one was a goose specialist. Our primary objective was to assess the potential contribution of factors, other than species interactions, in determining patterns of co-occurrence between helminth species. There were few negative relationships between helminth species, regardless of whether presence-absence or abundance data were used. However, some species pairs showed recurrent and significant co-occurrences. There were similar and significant effects of timing of sampling, host gender, and host age, on prevalence and mean abundance of particular species. Co-occurrences were found for those species that showed seasonal declines in prevalence, for those expected to have high colonizing ability based on host age profiles (using abundance data), and for abundant species that may have shared vectors or environmental conditions favorable for transmission. Thus, similarities between parasites in their abundance, transmission biology, and phenology seem sufficient to explain species co-occurrences without invoking other processes such as species interactions.
authors.affiliation: Department of Biology, Carleton University, 1125 Colonel By Drive Ottawa, Ontario, KlS 5B6, Canada e-mail: mforbes@ccs.carleton.ca, Tel.: +1-613-5202600, Fax: +1-613-5204497, , , , , , CA.
authors.forename: M R
authors.initials: MR
authors.lastname: Forbes
authors.affiliation: Canadian Wildlife Service, Prairie and Northern Wildlife Research Centre, 115 Perimeter Road, Saskatoon, Saskatchewan, S7N OX4, Canada, , , , , , CA.
authors.forename: R T
authors.initials: RT
authors.lastname: Alisauskas
authors.affiliation: Department of Biology, Concordia University, Sir George Williams Campus, 1455 de Maisonneuve Blvd West, Montreal, Quebec, H3G lM8, Canada, , , , , , CA.
authors.forename: J D
authors.initials: JD
authors.lastname: McLaughlin
authors.affiliation: Department of Zoology, University of Guelph, Guelph, Ontario, NlG 2W1, Canada, , , , , , CA.
authors.forename: K M
authors.initials: KM
authors.lastname: Cuddington
keywords: Helminths; Key words Communities; Lesser snow geese; Parasites; Species interactions