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

Author(s): Masri, Leila; Schulte, Rebecca D; Timmermeyer, Nadine; Thanisch, Stefanie; Crummenerl, Lena L; Jansen, Gunther; Michiels, Nico K; Schulenburg, Hinrich
Article Title: Sex differences in host defence interfere with parasite-mediated selection for outcrossing during host-parasite coevolution
Affiliation IST Austria
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.
Keywords: sexual selection; Host-parasite coevolution; Bacillus thuringiensis; Bateman's principle; Caenorhabditis elegans; Ecological immunology; Red Queen hypothesis
Journal Title: Ecology Letters
Volume: 16
Issue 4
ISSN: 1461-023X
Publisher: Wiley  
Date Published: 2013-04-04
Start Page: 461
End Page: 468
Copyright Statement: CC BY
Sponsor: German Science Foundation for funding within the priority programme SPP1399 on host–parasite coevolution (grant SCHU 1415/8).
DOI: 10.1111/ele.12068
Notes: We thank Nils Anthes, Marsha Bundman, Sylvia Cremer, Thomas D'Souza, Dieter Ebert, Patrick Günther, Barbara Hasert, Martina Hohloch, Gerrit Joop, Joachim Kurtz, Carsten Makus, David Lähnemann, Olivia Roth, Anna Sheppard, Paul Schmid-Hempel, Gregor Schulte, Thorsten Reusch and Henrique Teotónio for support and advice; Curt Lively, Olivier Restif, several anonymous referees and one editor for valuable comments on the manuscript.
Open access: yes (OA journal)