Abstract
BackgroundAlthough males and females need one another in order to reproduce, they often have different reproductive interests, which can lead to conflict between the sexes. The intensity and frequency of male-male competition for fertilization opportunities is thought to be an important contributor to this conflict. The nematode genus Caenorhabditis provides an opportunity to test this hypothesis because the frequency of males varies widely among species with different mating systems.ResultsWe find evidence that there is strong inter- and intra-sexual conflict within C. remanei, a dioecious species composed of equal frequencies of males and females. In particular, some C. remanei males greatly reduce female lifespan following mating, and their sperm have a strong competitive advantage over the sperm of other males. In contrast, our results suggest that both types of conflict have been greatly reduced within C. elegans, which is an androdioecious species that is composed of self-fertilizing hermaphrodites and rare males. Using experimental evolution in mutant C. elegans populations in which sperm production is blocked in hermaphrodites (effectively converting them to females), we find that the consequences of sexual conflict observed within C. remanei evolve rapidly within C. elegans populations experiencing high levels of male-male competition.ConclusionsTogether, these complementary data sets support the hypothesis that the intensity of intersexual conflict varies with the intensity of competition among males, and that male-induced collateral damage to mates can evolve very rapidly within populations.
Highlights
Males and females need one another in order to reproduce, they often have different reproductive interests, which can lead to conflict between the sexes
Sperm competition in C. remanei some males are more successful than others in terms of total offspring production when solely mated with a female, it is possible that reproductive success in the absence of competition trades off against competitive ability when other males are present
We investigate mating competition in both of these species and find results consistent with theoretical expectations: (1) C. remanei displays strain-specific sexual interaction traits that are indicative of an evolutionary history of interand intrasexual conflict; and (2) by shifting the mating system of C. elegans to resemble that of C. remanei, we are able to recapitulate these attributes in just 60 generations of experimental evolution
Summary
Males and females need one another in order to reproduce, they often have different reproductive interests, which can lead to conflict between the sexes. Males and females typically have different reproductive strategies [1, 2], which often result in conflicts surrounding control of fertilization [3,4,5]. The resulting antagonistic coevolution of Conflicts over control of fertilization are thought to explain the evolution of a wide variety of morphological, behavioral, and molecular traits related to fertilization success in both males and females (reviewed in [4]). Antagonistic coevolution is thought to explain the observation that male fruit flies transfer a complex suite of accessory-gland proteins to females during insemination, some of which can alter the reproductive patterns of their mates in ways that reduce female fitness while enhancing sperm competitive ability (reviewed in [7]). By generating flies lacking these proteins, it is possible to demonstrate benefits to males producing them (e.g., increased probability of paternity), and costs to females receiving them
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