Tropics, trophics and taxonomy: the determinants of parasite-associated host mortality

Authors


D. L. Murray, Dept of Biology, Trent Univ., 1600 West Bank Drive, Peterborough, ON, K9J 7B8, Canada. E-mail: dennismurray@trentu.ca

Abstract

Empirical studies often reveal deleterious effects of parasites on host survival, but the ecological and environmental processes modulating parasite-associated host mortality are not well understood. We conducted meta-analysis of experimental studies assessing parasite-associated mortality (n = 52) to evaluate broad-scale patterns in host mortality risk relative to host or parasite taxon, parasite life cycle, or local environmental conditions. Overall, likelihood of host mortality was ∼2.6 times higher among infected individuals when compared with hosts that either lacked parasites or had experimentally-reduced parasite burdens. Parasites with complex life cycles reliant on predation-mediated transmission generally were associated with higher mortality risk than those exploiting other transmission strategies. We also detected a negative relationship between parasite-associated host mortality and latitude; host mortality risk declined by ∼2.6% with each degree increase in latitude. This result indicated the likely importance of abiotic factors in determining parasite effects. Host taxonomy further influenced parasite-associated mortality risk, with amphibian, fish, and mollusc hosts generally having higher hazard than arthropod, mammal, and bird hosts. Our results suggest patterns that conform to the predicted link between host mortality and parasite transmissibility, and pathogenicity. The relationship between host mortality and latitude in particular may portend marked shifts in host–parasite relationships pursuant to ongoing and projected global climate change.

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