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.

Pathogen Interactions, Population Cycles, and Phase Shifts

“…Nevertheless, while most forms of interspecific interaction are well documented, unequivocal evidence of the existence of interspecific pathogen interactions under field conditions is rare. This has led to suggestions that interspecific interactions are of little importance in shaping pathogen communities under natural conditions [6][7][8][9][10][11][12][13][14][15][16]. This debate continues despite the fact that the importance of pathogen interactions is becoming increasingly obvious in clinical settings [17][18][19][20][21].…”

Mixed infections and insect–pathogen interactions

“…2001; Cox 2001), bird (e.g. Forbes et al . 1999), reptile (Schall & Bromwich 1994; Lainson 2002) and fish (Sousa et al .…”

“…Nilssen et al 1998;Behnke et al 2001;Cox 2001), bird (e.g. Forbes et al 1999), reptile (Schall & Bromwich 1994;Lainson 2002) and fish (Sousa et al 1996;Barker et al 2002) host systems. Given that insects are subject to challenge from a diversity of parasites and pathogens [e.g.…”

Abundance patterns and coexistence processes in communities of fleas parasitic on small mammals

“…Much previous research on parasite communities has been conducted at the level of parasite infracommunities (assemblages of parasite species in an individual host) (e.g. Bush and Holmes 1986a,b, Haukisalmi and Henttonen 1993, Forbes et al 1999). On the contrary, component communities (=xenocommunities) of parasites (assemblages of parasite species in a host population) and compound communities (assemblages of parasite species in a host community) have received much less attention.…”