title: Diet quality determines interspecific parasite interactions in host populations.
abstract: The widespread occurrence of multiple infections and the often vast range of nutritional resources for their hosts allow that interspecific parasite interactions in natural host populations might be determined by host diet quality. Nevertheless, the role of diet quality with respect to multispecies parasite interactions on host population level is not clear. We here tested the effect of host population diet quality on the parasite community in an experimental study using Daphnia populations. We studied the effect of diet quality on Daphnia population demography and the interactions in multispecies parasite infections of this freshwater crustacean host. The results of our experiment show that the fitness of a low-virulent microsporidian parasite decreased in low, but not in high-host-diet quality conditions. Interestingly, infections with the microsporidium protected Daphnia populations against a more virulent bacterial parasite. The observed interspecific parasite interactions are discussed with respect to the role of diet quality-dependent changes in host fecundity. This study reflects that exploitation competition in multispecies parasite infections is environmentally dependent, more in particular it shows that diet quality affects interspecific parasite competition within a single host and that this can be mediated by host population-level effects.
authors.affiliation: Laboratory Aquatic Biology, Science & Technology-Kulak, KU Leuven Kortrijk, 8500, Belgium.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lange
authors.affiliation: Department of Genetics, Evolution & Environment, University College London London, WC1E 6BT, UK.
authors.forename: Max
authors.initials: M
authors.lastname: Reuter
authors.affiliation: Zoological Institute, University of Basel Basel, CH-4051, Switzerland.
authors.forename: Dieter
authors.initials: D
authors.lastname: Ebert
authors.affiliation: Laboratory Aquatic Biology, Science & Technology-Kulak, KU Leuven Kortrijk, 8500, Belgium.
authors.forename: Koenraad
authors.initials: K
authors.lastname: Muylaert
authors.affiliation: Laboratory Aquatic Biology, Science & Technology-Kulak, KU Leuven Kortrijk, 8500, Belgium.
authors.forename: Ellen
authors.initials: E
authors.lastname: Decaestecker
keywords: Daphnia magna; disease dynamics; food quality; host population demography; interspecific parasite competition; multispecies infections; parasite ecology; unicellular gut parasite; white bacterial disease