Susceptibility of eight larval anurans to trematode parasites across ecological contexts

Background/Question/Methods

Understanding the relationship between biodiversity and disease is of vital importance for predicting the emergence of infectious diseases and evaluating the role of parasites within food webs. Many disease agents affect multiple species, and these effects often differ among species and depend on community context. In particular, the presence of predators may differentially affect the interactions between different species and parasites, which can have important consequences for community structure and disease dynamics. Here, I examined the effects of trematode (Digenea: Echinostomatidae) parasites and the presence of predator chemical cue on eight species of larval frogs which overlap in habitat use. I hypothesized that the separate and combined effects of parasites and predators would differ among species, due to trait differences. I conducted two aquaria experiments: 1) I measured infection rates in each species in the presence and absence of larval dragonfly predator cue. 2) I measured post-infection survival, growth rates, and behavior of each species relative to uninfected controls in the presence and absence of predator cue.

Results/Conclusions

In support of my hypothesis, species differed in their susceptibility to parasites, including their behavioral avoidance response to trematode cercariae (infective stages), infection rates, and the effects of infection on traits and survival. Species also differed in their response to predator cue. Species’ behavioral responses to parasites correlated with habitat use, in line with a similar documented relationship between plastic responses to predators and habitat use. Species’ avoidance behavior was also negatively correlated with infection intensity, suggesting that the avoidance response contributes to species-level differences in infection rates. Interestingly, species’ behavioral responses to parasites and predators were correlated, potentially due to covariance among amphibian, parasite, and predator distributions in natural ponds. The observed differences among species may facilitate important interactions in multi-species communities, such as apparent competition or dilution effects, and have conservation implications.