Interspecific contact and competition may affect the strength and direction of disease-diversity relationships for directly transmitted microparasites

With global declines in species diversity, understanding the effects of host species loss on disease dynamics, and parasite transmission, is vital.  In recent reviews by Civittello et al. (2015) and Johnson et al. (2015), the authors call for a more mechanistic understanding of disease diversity relationships, which generally posit that increases in host diversity result in a decrease in disease risk to host species.

We’ve developed a framework to explore the disease diversity relationships for directly transmitted, multi-host microparasites, integrating host regulation through intra- and interspecific competition, which can be dependent or independent on interspecific contact rates.

The results of our study show that

  • a decrease in parasite fitness does not necessarily result from host regulation via interspecific competition
  • an increase in host diversity does not necessarily result in a decrease of frequency dependent parasite transmission

Overall, we highlight that species identity and their ecological interactions jointly determine the outcome of microparasite transmission in multihost communities.