Colourful male guppies do not provide females with fecundity benefits

The phenotype-linked fertility hypothesis (PLFH) predicts that males with elaborated sexual ornaments signal their high fertilizing efficiency to females and that female preferences for ornamented males are driven by direct fecundity benefits. Although some studies have demonstrated that attractive males produce more or higher quality sperm, there is limited experimental evidence that females derive fecundity benefits by mating with attractive males. Some of the best indirect evidence for the PLFH comes from work on guppies (Poecilia reticulata), an internally fertilizing species of freshwater fish in which phenotypically attractive males produce larger and relatively higher quality ejaculates than their less attractive counterparts. We used artificial insemination to impregnate female guppies using known numbers of sperm from a range of males with different phenotypes and related female fecundity (brood success, time from insemination to parturition, and brood size) to sperm numbers and male phenotype (body size and the relative area of color spots). We found no evidence that male phenotype or experimentally adjusted "ejaculate" size influenced any of our measures of female fecundity. These results highlight the importance of experimentally investigating potential fecundity benefits associated with female mating preferences before concluding that the maintenance of these preferences is driven by the pursuit of such benefits.