Summary: BRIEF COMMUNICATION
ASSORTATIVE MATING BY FITNESS
AND SEXUALLY ANTAGONISTIC GENETIC
G ¨oran Arnqvist1,2
Department of Ecology and Genetics, Animal Ecology, Uppsala University, Norbyv¨agen 18D, SE-752 36 Uppsala, Sweden.
Received October 13, 2010
Accepted February 9, 2011
Recent documentations of sexually antagonistic genetic variation in fitness have spurred an interest in the mechanisms that may
act to maintain such variation in natural populations. Using individual-based simulations, I show that positive assortative mating by
fitness increases the amount of sexually antagonistic genetic variance in fitness, primarily by elevating the equilibrium frequency
of heterozygotes, over most of the range of sex-specific selection and dominance. Further, although the effects of assortative
mating by fitness on the protection conditions of polymorphism in sexually antagonistic loci were relatively minor, it widens the
protection conditions under most reasonable scenarios (e.g., under heterozygote superiority when fitness is averaged across the
sexes) but can also somewhat narrow the protection conditions under other circumstances. The near-ubiquity of assortative mating
in nature suggests that it may contribute to upholding standing sexually antagonistic genetic variation in fitness.