Female mediation of competitive fertilization success in Drosophila melanogaster

Abstract

How females store and use sperm after remating can generate postcopulatory sexual selection on male ejaculate traits. Variation in ejaculate performance traits generally is thought to be intrinsic to males but is likely to interact with the environment in which sperm compete (e.g., the female reproductive tract). Our understanding of female contributions to competitive fertilization success is limited, however, in part because of the challenges involved in observing events within the reproductive tract of internally fertilizing species while discriminating among sperm from competing males. Here, we used females from crosses among isogenic lines of Drosophila melanogaster, each mated to two genetically standardized males (the first with green-and the second with red-tagged sperm heads) to demonstrate heritable variation in female remating interval, progeny production rate, sperm-storage organ morphology, and a number of sperm performance, storage, and handling traits. We then used multivariate analyses to examine relationships between this female-mediated variation and competitive paternity. In particular, the timing of female ejection of excess second-male and displaced first-male sperm was genetically variable and, by terminating the process of sperm displacement, significantly influenced the relative numbers of sperm from each male competing for fertilization, and consequently biased paternity. Our results demonstrate that females do not simply provide a static arena for sperm competition but rather play an active and pivotal role in postcopulatory processes. Resolving the adaptive significance of genetic variation in female-mediated mechanisms of sperm handling is critical for understanding sexual selection, sexual conflict, and the coevolution of male and female reproductive traits.cryptic female choice | heritability | sperm ejection

Sisters' curse: sexually antagonistic effects constrain the spread of a mitochondrial haplogroup superior in sperm competition

“…Whether or not the sperm competitive superiority of the B2 haplogroup is intrinsic or dependent on female haplogroup remains to be determined, since only A-haplogroup females were used in this experiment. Given the evidence of male and female genotype effects on sperm competition in other species [44,45], it is possible that sperm competitive ability in C. scorpioides may be influenced by female mitochondrial haplogroup. While haplogroup-dependent cryptic female choice favouring B2 sperm could theoretically account for the B2 male advantage in fertilization, this hypothesis is not consistent with the results of our assessment of possible haplotype effects on female reproductive function.…”

Retention of Ejaculate by Drosophila melanogaster Females Requires the Male-Derived Mating Plug Protein PEBme

“…A recent study identified female innervation that modulates MP ejection and showed that this behavior has an impact on fertility (Lee et al 2015). MP ejection may be important in postcopulatory sexual selection because the timing of ejection influences the fertilization success of competing males (Lüpold et al 2013).Some functions of the D. melanogaster AMP are known. Females that do not receive the SFP Acp36DE during mating do not form an AMP (Bertram et al 1996) and fail to store sperm at optimal levels (Neubaum and Wolfner 1999;Bloch Qazi and Wolfner 2003).…”

“…A recent study identified female innervation that modulates MP ejection and showed that this behavior has an impact on fertility (Lee et al 2015). MP ejection may be important in postcopulatory sexual selection because the timing of ejection influences the fertilization success of competing males (Lüpold et al 2013).…”

Social structure and indirect genetic effects: genetics of social behaviour

“…In mammals, paternally derived genes are thought to increase maternal investment (reviewed in Wilkins & Haig, 2003). However this focus on the male portion of reproduction manipulating the female can potentially obscure the female's role, as it is both sexes that contribute to the social environment (Lupold et al, 2013), where traits of one sex are both genetic contributions to the environment for the other sex and an evolving trait (Moore et al, 1997;Wolf et al, 1998;Wigby & Chapman, 2004;Pischedda et al, 2011).…”

“…Therefore, females provide an interactive rather than a static environment (Lupold et al, 2013). This could explain why heritability estimates of female fertility range from high (Long et al, 2009) to low (Fernandez et al, 2003).…”