title: Controls of spatial variation in the prevalence of trematode parasites infecting a marine snail.
abstract: Geographic variability in abundance can be driven by multiple physical and biological factors operating at multiple scales. To understand the determinants of larval trematode prevalence within populations of the marine snail host Littorina littorea, we quantified many physical and biological variables at 28 New England intertidal sites. A hierarchical, mixed-effects model identified the abundance of gulls (the final hosts and dispersive agents of infective trematode stages) and snail size (a proxy for time of exposure) as the primary factors associated with trematode prevalence. The predominant influence of these variables coupled with routinely low infection rates (21 of the 28 populations exhibited prevalence <12%) suggest broad-scale recruitment limitation of trematodes. Although infection rates were spatially variable, formal analyses detected no regional spatial gradients in either trematode prevalence or independent environmental variables. Trematode prevalence appears to be predominantly determined by local site characteristics favoring high gull abundance.
authors.affiliation: Departinent of Zoology, University of New Hampshire, Durham, New Hampshire 03824, USA. jebyers@unh.deu
authors.forename: James E
authors.initials: JE
authors.lastname: Byers
authors.forename: April M H
authors.initials: AM
authors.lastname: Blakeslee
authors.forename: Ernst
authors.initials: E
authors.lastname: Linder
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Cooper
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Maguire
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D044822:Biodiversity; D005843:Geography; D006790:Host-Parasite Interactions; D007814:Larva / Q000254:growth & development; D008390:Markov Chains; D009010:Monte Carlo Method; D009792:Oceans and Seas; D011156:Population Density; D011157:Population Dynamics; D015995:Prevalence; D012908:Snails / Q000469:parasitology*; D013045:Species Specificity; D014200:Trematoda / Q000254:growth & development*