High resources and infectious disease facilitate invasion by a freshwater crustacean
It is well-established that both resources and infectious disease can influence species invasions, but little is known regarding interactive effects of these two factors. We performed a series of experiments to understand how resources and parasites can jointly affect the ability of a freshwater invasive zooplankton to establish in a population of a native zooplankton. In a life history trial, we found that both species increased offspring production to the same degree as algal resources increased, suggesting that changes in resources would have similar effects on both species. In a microcosm experiment simulating an invasion, we found that the invasive species reached its highest densities when there was a combination of both high resources and the presence of a shared parasite, but not for each of these conditions alone (i.e., a significant resource x parasite interaction). This result can be explained by changes in native host population density; high resource levels initially led to an increase in the density of the native host, which caused larger epidemics when the parasite was present. This high infection prevalence caused a subsequent reduction in native host density, increasing available resources and allowing the invasive species to establish relatively dense populations. Thus, in this system, native communities with a combination of high resource levels and parasitism may be the most vulnerable to invasions. More generally, our results suggest that parasitism and resource availability can have interactive, non-additive effects on the outcome of invasions.
KeywordsDaphnia dentifera Daphnia lumholtzi Eutrophication Invasive species Pathogen
We would like to thank M.A. Duffy and M.R. Christie for feedback on the manuscript. This project was funded by the Department of Biological Sciences at Purdue University, Purdue Honors College research funds for JKI, a McAtee stipend for BRH, and a Cable-Silkman award to BRH.
Author contribution statement
CLS designed the experiments and analyzed the data. BRH, AMM, JKI, and MAW performed the experiments. CLS wrote the manuscript; all other authors provided editorial advice.
- Brooks JL (1957) The systematics of North American Daphnia. Mem Conn Acad Arts Sci 13:1–180Google Scholar
- Ebert D (1993) The trade-off between offspring size and number in Daphnia magna: the influence of genetic, environmental and maternal effects. Arch Hydrobiol 4(Suppl. 90):453–473Google Scholar
- Hebert P (1995) The Daphnia of North America: an illustrated fauna. University of Guelph, CyberNatural SoftwareGoogle Scholar
- Hiskey RM (1996) The occurrence of the exotic Daphnia lumholtzi in Grand Lake St Marys, Ohio. Ohio J Sci 96:100–101Google Scholar
- Prior NH, Washington CN, Housley JM, Hall SR, Duffy MA, Cáceres CE (2011) Maternal effects and epidemiological traits in a planktonic host–parasite system. Evol Ecol Res 13:401–413Google Scholar
- R Core Team (2017) R: A language and environment for statistical computing. R Foundation for Statistical Computing. Vienna, Austria. https://www.R-project.org
- Therneau T (2015) A package for survival analysis in S. Version 2.38. Url: https://CRAN.R-project.org/package=survival. Accesed 6 June 2017