Population density, not host competence, drives patterns of disease in an invaded community

Catherine L. Searle, Michael H. Cortez, Katherine K. Hunsberger, Dylan C. Grippi, Isabella A. Oleksy, Clara L. Shaw, Solanus B. de la Sern, Chloe L. Lash, Kailash L. Dhir, Meghan A. Duffy

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Generalist parasites can strongly influence interactions between native and invasive species. Host competence can be used to predict how an invasive species will affect community disease dynamics; the addition of a highly competent, invasive host is predicted to increase disease. However, densities of invasive and native species can also influence the impacts of invasive species on community disease dynamics. We examined whether information on host competence alone could be used to accurately predict the effects of an invasive host on disease in native hosts. We first characterized the relative competence of an invasive species and a native host species to a native parasite. Next, we manipulated species composition in mesocosms and found that host competence results did not accurately predict community dynamics. While the invasive host was more competent than the native, the presence of the native (lower competence) host increased disease in the invasive (higher competence) host. To identify potential mechanisms driving these patterns, we analyzed a two-host, one-parasite model parameterized for our system. Our results demonstrate that patterns of disease were primarily driven by relative population densities, mediated by asymmetry in intra- and interspecific competition. Thus, information on host competence alone may not accurately predict how an invasive species will influence disease in native species.

Original languageEnglish (US)
Pages (from-to)554-566
Number of pages13
JournalAmerican Naturalist
Issue number5
StatePublished - Nov 2016
Externally publishedYes

Bibliographical note

Funding Information:
We would like to thank R. W. Bilich, A. M. Bromilow, and M. R. Christie for their assistance, S. R. Hall for providing code to calculate reproductive rates, and R. M. Penczykowski for logistical advice. We also thank the anonymous reviewers, who provided valuable feedback on our manuscript. This project was funded by a National Science Foundation CAREER grant to M.A.D. (DEB-1305836).

Publisher Copyright:
© 2016 by The University of Chicago.


  • Biodiversity
  • Daphnia
  • Dilution effect
  • Invasive species
  • Multi-host parasites
  • Pathogen


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