title: Evolutionary associations between host traits and parasite load: insights from Lake Tanganyika cichlids.
abstract: Parasite diversity and abundance (parasite load) vary greatly among host species. However, the influence of host traits on variation in parasitism remains poorly understood. Comparative studies of parasite load have largely examined measures of parasite species richness and are predominantly based on records obtained from published data. Consequently, little is known about the relationships between host traits and other aspects of parasite load, such as parasite abundance, prevalence and aggregation. Meanwhile, understanding of parasite species richness may be clouded by limitations associated with data collation from multiple independent sources. We conducted a field study of Lake Tanganyika cichlid fishes and their helminth parasites. Using a Bayesian phylogenetic comparative framework, we tested evolutionary associations between five key host traits (body size, gut length, diet breadth, habitat complexity and number of sympatric hosts) predicted to influence parasitism, together with multiple measures of parasite load. We find that the number of host species that a particular host may encounter due to its habitat preferences emerges as a factor of general importance for parasite diversity, abundance and prevalence, but not parasite aggregation. In contrast, body size and gut size are positively related to aspects of parasite load within, but not between species. The influence of host phylogeny varies considerably among measures of parasite load, with the greatest influence exerted on parasite diversity. These results reveal that both host morphology and biotic interactions are key determinants of host-parasite associations and that consideration of multiple aspects of parasite load is required to fully understand patterns in parasitism.
authors.affiliation: Centre for Ecology and Conservation, University of Exeter, Penryn, UK.
authors.forename: A
authors.identifier: 0000-0001-7413-718X
authors.initials: A
authors.lastname: Hayward
authors.affiliation: Department of Animal Ecology, Uppsala University, Uppsala, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Tsuboi
authors.affiliation: Department of Animal Ecology, Uppsala University, Uppsala, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Owusu
authors.affiliation: Department of Zoology, Stockholm University, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Kotrschal
authors.affiliation: Department of Zoology, Stockholm University, Stockholm, Sweden.
authors.forename: S D
authors.initials: SD
authors.lastname: Buechel
authors.affiliation: IFM Biology, Linköping University, Linköping, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Zidar
authors.affiliation: Department of Ecology, Lund University, Lund, Sweden.
authors.forename: C K
authors.initials: CK
authors.lastname: Cornwallis
authors.affiliation: IFM Biology, Linköping University, Linköping, Sweden.
authors.forename: H
authors.identifier: 0000-0003-4352-6275
authors.initials: H
authors.lastname: Løvlie
authors.affiliation: Department of Zoology, Stockholm University, Stockholm, Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Kolm
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D023681:Cichlids / Q000469:parasitology*; D006790:Host-Parasite Interactions; D060106:Lakes; D059208:Parasite Load; D010802:Phylogeny; D013636:Tanzania
keywords: endoparasite; evolution; fish; helminth; parasitic worm