title: The contrasting role of male relatedness in different mechanisms of sexual selection in red junglefowl.
abstract: In structured populations, competition for reproductive opportunities should be relaxed among related males. The few tests of this prediction often neglect the fact that sexual selection acts through multiple mechanisms, both before and after mating. We performed experiments to study the role of within-group male relatedness across pre- and postcopulatory mechanisms of sexual selection in social groups of red junglefowl, Gallus gallus, in which two related males and one unrelated male competed over females unrelated to all the males. We confirm theoretical expectations that, after controlling for male social status, competition over mating was reduced among related males. However, this effect was contrasted by other sexual selection mechanisms. First, females biased male mating in favor of the unrelated male, and might also favor his inseminations after mating. Second, males invested more-rather than fewer-sperm in postcopulatory competition with relatives. A number of factors may contribute to explain this counterintuitive pattern of sperm allocation, including trade-offs between male investment in pre- versus postcopulatory competition, differences in the relative relatedness of pre- versus postcopulatory competitors, and female bias in sperm utilization in response to male relatedness. Collectively, these results reveal that within-group male relatedness may have contrasting effects in different mechanisms of sexual selection.
authors.affiliation: Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, OX1 3PS, United Kingdom.
authors.forename: Cedric Kai Wei
authors.initials: CK
authors.lastname: Tan
authors.affiliation: Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, OX1 3PS, United Kingdom.
authors.forename: Philippa
authors.initials: P
authors.lastname: Doyle
authors.affiliation: Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, OX1 3PS, United Kingdom.
authors.forename: Emma
authors.initials: E
authors.lastname: Bagshaw
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: David S
authors.initials: DS
authors.lastname: Richardson
authors.affiliation: Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, OX1 3PS, United Kingdom.
authors.forename: Stuart
authors.initials: S
authors.lastname: Wigby
authors.affiliation: Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, OX1 3PS, United Kingdom.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Pizzari
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics / Q000502:physiology*; D003163:Competitive Behavior; D003307:Copulation; D005260:Female; D008297:Male; D052586:Mating Preference, Animal; D013094:Spermatozoa / Q000502:physiology*
keywords: Ejaculate expenditure; Gallus; kin recognition; kin selection; rare male effect; sperm competition