Host diet influences parasite diversity: a case study looking at tapeworm diversity among sharks

Abstract

In theory, animal diets may act as important filters for different parasite species. However, there is currently a lack of empirical research looking at host diet as a potential predictor of parasite diversity among different host species. The aim of this study was to assess the influence of several host diet features (including diet breadth, diet composition, and trophic level) on tapeworm diversity in sharks, relative to other key factors, including host size, habitat, phylogeny, latitude, and depth. Data on these host features were compiled from a comprehensive analysis of literature records including 91 different shark species, and 3 measures of tapeworm diversity were examined: tapeworm species richness, tapeworm taxonomic distinctness (TD), and variance in tapeworm TD. The diet breadth of a shark species was revealed to be a better predictor of tapeworm species richness than other host features examined to date. Host size, trophic level, diet TD, latitudinal range, and the mid-point of a shark’s depth range also significantly influenced tapeworm richness when analyses were adjusted to prevent confounding by phylogenetic relationships between hosts. The TD of tapeworm assemblages was influenced by diet breadth, diet TD, host size, and depth range when analysed independently of host phylogeny. Overall, our findings demonstrate that aspects of host diet have important consequences for parasite diversity in sharks. We emphasise that studies of parasite diversity in other systems should more seriously consider including aspects of host diet (particularly diet breadth) as potential key predictors of parasite diversity.