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Ecol Lett. 2013 Apr;16(4):461-8. doi: 10.1111/ele.12068. Epub 2013 Jan 10.

Sex differences in host defence interfere with parasite-mediated selection for outcrossing during host-parasite coevolution.

Author information

1
Department of Evolutionary Ecology and Genetics, Zoological Institute, Christian-Albrechts-University of Kiel, Kiel, Germany.

Abstract

The Red Queen hypothesis proposes that coevolving parasites select for outcrossing in the host. Outcrossing relies on males, which often show lower immune investment due to, for example, sexual selection. Here, we demonstrate that such sex differences in immunity interfere with parasite-mediated selection for outcrossing. Two independent coevolution experiments with Caenorhabditis elegans and its microparasite Bacillus thuringiensis produced decreased yet stable frequencies of outcrossing male hosts. A subsequent systematic analysis verified that male C. elegans suffered from a direct selective disadvantage under parasite pressure (i.e. lower resistance, decreased sexual activity, increased escape behaviour), which can reduce outcrossing and thus male frequencies. At the same time, males offered an indirect selective benefit, because male-mediated outcrossing increased offspring resistance, thus favouring male persistence in the evolving populations. As sex differences in immunity are widespread, such interference of opposing selective constraints is likely of central importance during host adaptation to a coevolving parasite.

PMID:
23301667
PMCID:
PMC3655609
DOI:
10.1111/ele.12068
[Indexed for MEDLINE]
Free PMC Article

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