PARENT SESSION
Contributed Oral Session 9: Marine Ecology: Disturbance; Dispersal; Recruitment
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 519 A, Level 5, Palais des congrès de Montréal
Recruitment limitation or environmental drivers: What controls occurrence of parasitic trematodes in a marine snail?
Byers, James*,1, Blakeslee, April1, Linder, Ernst2, Cooper, Andrew3, Maguire, Tim4, 1 Department of Zoology, Durham, NH, USA2 Dept. of Math & Statistics, Durham, NH, USA3 Dept. of Natural Resources, Durham, NH, USA4 Massachusetts Maritime Academy, Buzzards Bay, MA, USA
ABSTRACT- Parasitic trematodes typically have life cycles in which they progress through hosts at increasing trophic levels, e.g. from a snail to a fish to a shorebird. To understand the determinants of trematode infection within the snail host, Littorina littorea, we quantified the prevalence (and species richness) of trematodes within 28 snail populations throughout New England. We examined over 5000 snails from a wide range of coastal, estuarine, and island sites. Overall prevalence rates of snail infection varied between 0.6% and 47%. All five trematode species that had been identified in the literature were detected, although two species, Cryptocotyle lingua and Cercaria parvicaudata, accounted for over 98% of all infections. We concurrently sampled many physical and biological variables at each site to determine which factors most influenced observed patterns of infection across this regional scale. Eight sites at the Isles of Shoals near Portsmouth, NH, where aggregations of breeding shorebirds were an order of magnitude higher than anywhere in this study, were more efficiently modeled as a distinctly different group than mainland sites. A nested, hierarchical, mixed-effects model indicated that high abundance of gulls (the final host and dispersive agent of the trematodes) and larger snail body size (a proxy for length of exposure) are the primary factors associated with high infection rates in L. littorea everywhere. However, trematode prevalence was most sensitive to changes in gull abundance at mainland sites. Thus, trematodes seem to be more recruitment limited at mainland sites where birds are sparse, while limitation still occurs but is less pronounced in island populations where length of a snail's exposure plays a larger role because birds are already in high abundance.
Key words: dispersal, hierarchical models, macroecology, marine intertidal communities