title: Paternal reproductive success drives sex allocation in a wild mammal.
abstract: Parents should bias sex allocation toward offspring of the sex most likely to provide higher fitness returns. Trivers and Willard proposed that for polygynous mammals, females should adjust sex-ratio at conception or bias allocation of resources toward the most profitable sex, according to their own body condition. However, the possibility that mammalian fathers may influence sex allocation has seldom been considered. Here, we show that the probability of having a son increased from 0.31 to 0.60 with sire reproductive success in wild bighorn sheep (Ovis canadensis). Furthermore, our results suggest that females fertilized by relatively unsuccessful sires allocated more energy during lactation to daughters than to sons, while the opposite occurred for females fertilized by successful sires. The pattern of sex-biased offspring production appears adaptive because paternal reproductive success reduced the fitness of daughters and increased the average annual weaning success of sons, independently of maternal allocation to the offspring. Our results illustrate that sex allocation can be driven by paternal phenotype, with profound influences on the strength of sexual selection and on conflicts of interest between parents.
authors.affiliation: Département de biologie and Centre d'Études Nordiques, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec, J1K 2R1, Canada. mathieu.douhard@gmail.com.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Douhard
authors.affiliation: Département de biologie and Centre d'Études Nordiques, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec, J1K 2R1, Canada.
authors.forename: Marco
authors.initials: M
authors.lastname: Festa-Bianchet
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
authors.forename: David W
authors.initials: DW
authors.lastname: Coltman
authors.affiliation: Département de biologie and Centre d'Études Nordiques, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec, J1K 2R1, Canada.
authors.forename: Fanie
authors.initials: F
authors.lastname: Pelletier
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D000835:Animals, Wild / Q000235:genetics / Q000502:physiology; D005260:Female; D007774:Lactation; D008297:Male; D052586:Mating Preference, Animal; D010375:Pedigree; D010641:Phenotype; D012098:Reproduction / Q000235:genetics*; D019849:Sex Determination Processes / Q000235:genetics*; D034581:Sheep, Bighorn / Q000235:genetics* / Q000502:physiology
keywords: Male quality; Trivers-Willard hypothesis; maternal resource allocation; paternity analysis; sex ratio