Food-web-based comparison of the drivers of helminth parasite species richness in coastal fish and bird definitive hosts

Abstract

Studies on the factors determining parasite richness in hosts are typically performedusing data compiled for various sets of species from disparate habitats. However, parasite transmissionis embedded within local trophic networks, and proper comparisons among host speciesof the drivers of parasite richness should ideally be conducted among hosts belonging to the samelocal network. Here, we used data from 6 well-resolved coastal food webs that include parasites toinvestigate patterns and drivers of species richness of trophically transmitted helminths in coastalfish and bird definitive hosts. We first investigated whether previous notions that birds harbourmore trophically transmitted parasite species than fish hold true for food-web-based comparisons;then we investigated the roles of host prey range, trophic level and body size in driving parasiterichness patterns in coastal birds and fish. Our analyses indicated that bird hosts, on average, harbouredhigher parasite richness than fish hosts. While there was no consistent driver of parasiterichness at the level of entire food webs, host prey range and host trophic level were positively correlatedwith parasite richness in birds within individual food webs. For fish hosts, the effect of hostprey range was less consistent and trophic level had no effect on parasite richness. Host body sizedid not affect parasite richness for either host type. These results suggest that host prey range andtrophic level seem to be more consistent drivers of parasite richness for coastal bird than for fishhosts.