Postmating Female Control: 20 Years of Cryptic Female Choice

Cryptic female choice (CFC) represents postmating intersexual selection arising from female-driven mechanisms at or after mating that bias sperm use and impact male paternity share. Although biologists began to study CFC relatively late, largely spurred by Eberhard's book published 20 years ago, the field has grown rapidly since then. Here, we review empirical progress to show that numerous female processes offer potential for CFC, from mating through to fertilization, although seldom has CFC been clearly demonstrated. We then evaluate functional implications, and argue that, under some conditions, CFC might have repercussions for female fitness, sexual conflict, and intersexual coevolution, with ramifications for related evolutionary phenomena, such as speciation. We conclude by identifying directions for future research in this rapidly growing field. In 1996, Eberhard crystallized the idea of CFC as an engine of sexual selection and initiated the study of female-driven processes.Demonstrating CFC, which is defined as female-mediated morphological, behavioral, or physiological mechanisms that operate to bias fertilization toward the sperm of specific male(s), requires dissecting male and female variance components of sperm retention or paternity.Technologies developed over the past 20 years have helped elucidate the proximate mechanisms underpinning fertilization and have accelerated the field of CFC.Females may bias sperm use at successive stages of the reproductive process, including shortly after mating, during sperm transit and/or storage, and at fertilization.CFC can have fundamental repercussions for sexual selection on males, female fitness, and, consequently, sexual conflict and intersexual coevolution, with ramifications for related evolutionary phenomena (e.g., speciation).