title: The measure and significance of Bateman's principles.
abstract: Bateman's principles explain sex roles and sexual dimorphism through sex-specific variance in mating success, reproductive success and their relationships within sexes (Bateman gradients). Empirical tests of these principles, however, have come under intense scrutiny. Here, we experimentally show that in replicate groups of red junglefowl, Gallus gallus, mating and reproductive successes were more variable in males than in females, resulting in a steeper male Bateman gradient, consistent with Bateman's principles. However, we use novel quantitative techniques to reveal that current methods typically overestimate Bateman's principles because they (i) infer mating success indirectly from offspring parentage, and thus miss matings that fail to result in fertilization, and (ii) measure Bateman gradients through the univariate regression of reproductive over mating success, without considering the substantial influence of other components of male reproductive success, namely female fecundity and paternity share. We also find a significant female Bateman gradient but show that this likely emerges as spurious consequences of male preference for fecund females, emphasizing the need for experimental approaches to establish the causal relationship between reproductive and mating success. While providing qualitative support for Bateman's principles, our study demonstrates how current approaches can generate a misleading view of sex differences and roles.
authors.affiliation: Department of Zoology, Edward Grey Institute, University of Oxford, , Oxford OX1 3PS, UK, School of Biological Sciences, University of Queensland, , Brisbane, Queensland 4072, Australia, Department of Genetics, Evolution and Environment, University College London, , The Darwin Building, Gower Street, London WC1E 6BT, UK, Department of Evolutionary Biology, Uppsala University, , Norbyvägen 18D, Uppsala 752 36, Sweden, Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich Research Park, , Norwich NR4 7TJ, UK.
authors.forename: Julie M
authors.initials: JM
authors.lastname: Collet
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: Dean
authors.forename: Kirsty
authors.initials: K
authors.lastname: Worley
authors.forename: David S
authors.initials: DS
authors.lastname: Richardson
authors.forename: Tommaso
authors.initials: T
authors.lastname: Pizzari
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics* / Q000502:physiology*; D005260:Female; D005298:Fertility; D008297:Male; D052586:Mating Preference, Animal; D008954:Models, Biological; D012098:Reproduction / Q000235:genetics* / Q000502:physiology*; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal
keywords: Bateman principles; Gallus gallus; polyandry; sex roles; sexual dimorphism; sexual selection