Data from: A life-history perspective on sexual selection in a polygamous species

Background: Ever since Darwin, evolutionary biologists have studied sexual
selection driving differences in appearance and behaviour between males
and females. An unchallenged paradigm in such studies is that one sex
(usually the male) signals its quality as a mate to the other sex (usually
the female), who is choosy in accepting a partner. Here, we hypothesize
that in polygamous species these roles change dynamically with the mating
status of males and females, depending on direct reproductive costs and
benefits of multiple matings, and on sperm competition. We test this
hypothesis by assessing fitness costs and benefits of multiple matings in
both males and females in a polygamous moth species, as in moths not males
but females are the signalers and males are the responders. Results: We
found that multiple matings confer fitness costs and benefits for both
sexes. Specifically, the number of matings did not affect the longevity of
males or females, but only 67 % of the males and 14 % of the females mated
successfully in all five nights. In addition, the female’s reproductive
output increased with multiple matings, although when paired with a new
virgin male every night, more than 3 matings decreased her reproductive
output, so that the Bateman gradient for females fit a quadratic model
better than a linear model. The male’s reproductive success was positively
affected by the number of matings and a linear regression line best fit
the data. Simulations of the effect of sperm competition showed that
increasing last-male paternity increases the steepness of the male Bateman
gradient and thus the male’s relative fitness gain from additional mating.
Irrespective of last-male paternity value, the female Bateman gradient is
steeper than the male one for up to three matings. Conclusion: Our results
suggest that choosiness in moths may well change throughout the mating
season, with males being more choosy early in the season and females being
more choosy after having mated at least three times. This life-history
perspective on the costs and benefits of multiple matings for both sexes
sheds new light on sexual selection forces acting on sexual signals and
responses.