Sex Ratio Bias Leads to the Evolution of Sex Role Reversal in Honey Locust Beetles.
The reversal of conventional sex roles was enigmatic to Darwin, who suggested that it may evolve when sex ratios are female biased [1]. Here we present direct evidence confirming Darwin's hypothesis. We investigated mating system evolution in a sex-role-reversed beetle (Megabruchidius dorsalis) using experimental evolution under manipulated sex ratios and food regimes. In female-biased populations, where reproductive competition among females was intensified, females evolved to be more attractive and the sex roles became more reversed. Interestingly, female-specific mating behavior evolved more rapidly than male-specific mating behavior. We show that sexual selection due to reproductive competition can be strong in females and can target much the same traits as in males of species with conventional mating systems. Our study highlights two central points: the role of ecology in directing sexual selection and the role that females play in mating system evolution.
Department of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria. Electronic address: fritzsche.karoline@gmail.com.
Karoline
K
Fritzsche
Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Isobel
I
Booksmythe
Animal Ecology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden.
Göran
G
Arnqvist
D000818:Animals; D005075:Biological Evolution; D001517:Coleoptera / Q000502:physiology*; D005260:Female; D000071421:Life History Traits; D008297:Male; D052586:Mating Preference, Animal; D012098:Reproduction; D012737:Sex Factors; D012744:Sex Ratio; D012726:Sexual Behavior, Animal