Female control over multiple matings increases the opportunity for postcopulatory sexual selection

It is widely acknowledged that in most species sexual selection continues after mating. Although it is generally accepted that females play an important role in generating paternity biases (i.e., cryptic female choice), we lack a quantitative understanding of the relative importance of female-controlled processes in influencing variance in male reproductive fitness. Here we address this question experimentally using the guppy Poecilia reticulata, a polyandrous fish in which pre- and postcopulatory sexual selection jointly determine male reproductive fitness. We used a paired design to quantify patterns of paternity for pairs of rival males across two mating contexts, one in which the female retained full control over double (natural) matings and one where sperm from the same two males were artificially inseminated into the female. We then compared the relative paternity share for a given pair of males across both contexts, enabling us to test the key prediction that patterns of paternit...