Data from: Sperm competition generates evolution of increased paternal investment in a sex role-reversed seed beetle

When males provide females with resources at mating they can become the
limiting sex in reproduction, in extreme cases leading to the reversal of
typical courtship roles. The evolution of male provisioning is thought to
be driven by male reproductive competition and selection for female
fecundity enhancement. We used experimental evolution under male- or
female-biased sex ratios and limited or unlimited food regimes to
investigate the relative roles of these routes to male provisioning in a
sex role-reversed beetle, Megabruchidius tonkineus, where males provide
females with nutritious ejaculates. Males evolving under male-biased sex
ratios transferred larger ejaculates than did males from female-biased
populations, demonstrating a sizeable role for reproductive competition in
the evolution of male provisioning. Although larger ejaculates elevated
female lifetime offspring production, we found little evidence of
selection for larger ejaculates via fecundity enhancement: males evolving
under resource-limited and unlimited conditions did not differ in mean
ejaculate size. Resource limitation did, however, affect the evolution of
conditional ejaculate allocation. Our results suggest that the resource
provisioning that underpins sex role reversal in this system is the result
of male-male reproductive competition rather than of direct selection for
males to enhance female fecundity.