The impact of infection on host competition and its relationship to parasite persistence in a Daphnia microparasite system
- 190 Downloads
Evolutionary studies often estimate fitness components with the aim to make predictions about the outcome of selection. Depending on the system and the question, different fitness components are used, but their usefulness for predicting the outcome of selection is rarely tested. Here we estimate host fitness components in different ways with the aim to test how well they agree with each other and how well they predict host fitness at the population level in the presence of the parasite. We use a Daphnia magna-microparasite system to study the competitive ability of host clones in the absence and presence of the parasite, the infection intensity of the parasite in individuals of twelve host clones (an estimate of both host resistance and parasite reproductive success), and parasite persistence in small host populations (an estimate of R 0 of the parasite). Analysis of host competitive ability and parasite persistence reveals strong host genotype effects, while none are found for infection intensity. Host competitive ability further shows a genotype-specific change upon infection, which is correlated with the relative persistence of the parasite in the competing hosts. Hosts in which the parasite persists better suffer a competitive disadvantage in the parasite’s presence. This suggests that in this system, parasite-mediated selection can be predicted by parasite persistence, but not by parasite infection intensity.
KeywordsCompetition Fitness components Red Queen Resistance Virulence
We thank N. Basieux, J. Hottinger, S. Lass and L. Sygnarski for technical assistance, M. Kölliker for statistical advice, and H. K. Alexander for polishing the language. The manuscript benefitted from comments by J. Bull, J. Jokela, C. Kost, S. Lass, M. Zbinden, two anonymous reviewers, and the handling editor. The authors were supported by the Swiss National Science Foundation.
- Dieckmann U (ed) (2002) Adaptive dynamics of infectious disease. Cambridge University Press, CambridgeGoogle Scholar
- Ebert D (2005) Ecology, epidemiology, and evolution of parasitism in Daphnia [Internet]. National Library of Medicine (US), National Center for Biotechnology Information, Bethesda, MD. Available from http://www.ncbi.nlm.nih.gov/books/NBK2036. (Accessed Feb 2011)
- Hartl DL (1987) A primer of population genetics. Sinauer, SunderlandGoogle Scholar
- Rolff J, Joop G (2002) Estimating condition: pitfalls of using weight as a fitness correlate. Evol Ecol Res 4:931–935Google Scholar
- SAS Institute Inc (1989) JMP, Version 8. SAS Institute Inc., CaryGoogle Scholar
- Stearns SC (1992) The evolution of life histories. Oxford University Press, OxfordGoogle Scholar
- Thompson JN (1994) The coevolutionary process. University of Chicago Press, ChicagoGoogle Scholar