Data from: Quantitative genetic insights into the coevolutionary dynamics of male and female genitalia

The spectacular variability that typically characterizes male genital
traits has largely been attributed to the role of sexual selection. Among
the evolutionary mechanisms proposed to account for this diversity, two
processes in particular have generated considerable interest. On the one
hand, females may exploit postcopulatory mechanisms of selection to favour
males with preferred genital traits (cryptic female choice; CFC), while on
the other hand females may evolve structures or behaviours that mitigate
the direct costs imposed by male genitalia (sexual conflict; SC). A
critical but rarely explored assumption underlying both processes is that
male and female reproductive traits coevolve, either via the classic
Fisherian model of preference-trait coevolution (CFC) or through sexually
antagonistic selection (SC). Here, we provide evidence for this prediction
in the guppy (Poecilia reticulata), a polyandrous livebearing fish in
which males transfer sperm internally to females via consensual and forced
matings. Our results from a paternal half-sibling breeding design reveal
substantial levels of additive genetic variation underlying male genital
size and morphology—two traits known to predict mating success during
non-consensual matings. Our subsequent finding that physically interacting
female genital traits exhibit corresponding levels of genetic
(co)variation reveals the potential intersexual coevolutionary dynamics of
male and female genitalia, thereby fulfilling a fundamental assumption
underlying CFC and SC theory.