Female sperm storage mediates postcopulatory costs and benefits of ejaculate anticipatory plasticity in the guppy

Males of many species evolved the capability of adjusting their ejaculate phenotype in response to social cues to match the expected mating conditions. When females store sperm for prolonged time, the expected fitness return of plastic adjustments of ejaculate phenotype may depend on the interval between mating and fertilization. While, prolonged female sperm storage (FSS) increases the opportunity for sperm competition, as a consequence of the longer temporal overlapping of ejaculates from several males, it may also create variable selective forces on ejaculate phenotype, for example by exposing trade-offs between sperm velocity and sperm survival. We evaluated the relationship between the plasticity of ejaculate quality and FSS in the guppy, Poecilia reticulata, a polyandrous livebearing fish in which females store sperm for several months and where stored sperm contribute significantly to a male’s lifelong reproductive success. In this species, males respond to the perception of futu...