Evol Ecol Res 9: 459-469 (2007)     Full PDF if your library subscribes.

Parasite transgenerational effects on infection

Tom Little,1* Jane Birch,1 Pedro Vale1 and Michelle Tseng2

1Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK and  2Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada

Author to whom all correspondence should be addressed.
e-mail: tom.little@ed.ac.uk


Question: Do past conditions experienced by parasites mediate current levels of infectivity and virulence in the host–parasite combination of Daphnia magna and Pasteuria ramosa?

Methods: We varied either temperature (three levels: 15, 20 or 25°C) or food supplied to the host (two levels) during a primary infection event, and then harvested parasites and measured their infectivity during a secondary infection event that was subject to the same environmental variation.

Result: Past temperatures did not influence any of the infection-related traits measured. By contrast, past food conditions appeared to impact infection, with parasite spores originating from well-fed hosts generally being more harmful. There was no indication that parasites had become specialized to their past environment. Four host genotypes were included in the experiment, and there was evidence that one of four was more sensitive to the environmental history of parasites than were the other hosts, i.e. there was an interaction between host genotype and parasite treatment effects.

Conclusion: Overall, parasite transgenerational effects appear to influence the level of harm parasites cause.

Keywords: Daphnia, genetic variation, genotype × environment interaction, maternal effect, parasitism, Pasteuria, pathogen, virulence.

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