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Homage To Bateman: Sex Roles Predict Sex Differences In Sexual Selection
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
2013 (English)In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 67, no 7, 1926-1936 p.Article in journal (Refereed) Published
Abstract [en]

Classic sex role theory predicts that sexual selection should be stronger in males in taxa showing conventional sex roles and stronger in females in role reversed mating systems. To test this very central prediction and to assess the utility of different measures of sexual selection, we estimated sexual selection in both sexes in four seed beetle species with divergent sex roles using a novel experimental design. We found that sexual selection was sizeable in females and the strength of sexual selection was similar in females and males in role-reversed species. Sexual selection was overall significantly stronger in males than in females and residual selection formed a substantial component of net selection in both sexes. Furthermore, sexual selection in females was stronger in role-reversed species compared to species with conventional sex roles. Variance-based measures of sexual selection (the Bateman gradient and selection opportunities) were better predictors of sexual dimorphism in reproductive behavior and morphology across species compared to trait-based measures (selection differentials). Our results highlight the importance of using assays that incorporate components of fitness manifested after mating. We suggest that the Bateman gradient is generally the most informative measure of the strength of sexual selection in comparisons across sexes and/or species.

Place, publisher, year, edition, pages
2013. Vol. 67, no 7, 1926-1936 p.
Keyword [en]
Bateman gradient, mating system, sexual dimorphism, sperm competition
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-204985DOI: 10.1111/evo.12086ISI: 000321184500009OAI: oai:DiVA.org:uu-204985DiVA: diva2:641329
Available from: 2013-08-16 Created: 2013-08-13 Last updated: 2016-04-05Bibliographically approved
In thesis
1. Sexual selection and the evolution of sex-role reversal in honeylocust beetles
Open this publication in new window or tab >>Sexual selection and the evolution of sex-role reversal in honeylocust beetles
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sexual selection is the prime evolutionary force that makes males and females different. This process has long been viewed as one where male compete with one another and where females choose. However, since the discovery that multiple mating by females is common in animals, sexual selection theory has been expanded to include mate competition between females and mate choice by males. However, empirical studies addressing these themes are scarce. In my thesis, I explore the evolution of sex role reversed mating systems using the honey locust beetles (Megabruchidius dorsalis and M. tonkineus). I used these species to shed light on (1) how closely sexual selection in females resembles its better‑studied male counterpart, (2) the implications of male mating costs for mating system evolution and (3) the effects of reproductive competition between females on the evolution of female courtship behaviour. By manipulating male mating rate, I found that males that mated more lived shorter lives, showing that mating is costly for males. I also demonstrated that males are choosy about whom they mate with and prefer vigorously courting females (Paper II). In contrast to males, previous studies suggested that female honey locust beetles benefit nutritionally from mating due to the large ejaculates provided by males. I manipulated male condition to show that male adult feeding had significant effects on female reproduction. Females that mated with males of good condition lived longer and produced more offspring than females whose mates were in poor condition (Paper III). When mating is costly for males, theory predicts that sexual selection in females can be strong. I compared sexual selection in honey locust beetles to that in two other species of seed beetles with conventional sex roles. I found substantial sexual selection in honey locust beetle females, which was comparable in strength to that in males (Paper I). I also measured the evolutionary effects of altered sex ratios on mating system parameters in both honey locust beetle species, using an experimental evolution design. Under female-biased sex ratios, representing strong sexual selection in females, females of M. dorsalis rapidly evolved elevated courtship intensity, thereby intensifying the reversal of sex roles (Paper V). In M. tonkineus, males evolved under male-biased sex ratios to transfer larger ejaculates, demonstrating the role of male-male reproductive competition for the evolution of male provisioning (Paper IV). My thesis highlights the essential, and often overlooked, role that females play in mating system evolution and that their contribution cannot simply be reduced to mate choice.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 46 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1240
National Category
Evolutionary Biology
Research subject
Animal Ecology
urn:nbn:se:uu:diva-246715 (URN)978-91-554-9209-0 (ISBN)
Public defence
2015-05-13, Zootissalen, Evolutionary Biology Centre, Norbyvägen, Gamla Zoologen (Hus 1), Uppsala, 10:00 (English)
Available from: 2015-04-22 Created: 2015-03-09 Last updated: 2015-07-07

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