Sex Combs are Important for Male Mating Success in Drosophila melanogaster

Section of Evolution and Ecology and Center for Population Biology, University of California-Davis, One Shields Ave, Davis, CA 95616, USA.
Behavior Genetics (Impact Factor: 3.21). 04/2008; 38(2):195-201. DOI: 10.1007/s10519-008-9190-7
Source: PubMed


The sex comb is one of the most rapidly evolving male-specific traits in Drosophila, making it an attractive model to study sexual selection and developmental evolution. Drosophila males use their sex combs to grasp the females' abdomen and genitalia and to spread their wings prior to copulation. To test the role of this structure in male mating success in Drosophila melanogaster, we genetically ablated the sex comb by expressing the female-specific isoform of the sex determination gene transformer in the tarsal segments of male legs. This technique does not remove the sex comb entirely, but simply restores the morphology of its constituent bristles to the ancestral condition found in Drosophila species that lack sex combs. Direct observations and differences in long-term insemination rates show that the loss of the sex comb strongly reduces the ability of males to copulate with females. Detailed analysis of video recordings indicates that this effect is not due to changes in the males' courtship behavior. Rapid evolution of sex comb morphology may be driven either by changes in female preferences, or by co-evolution between sex combs and female external genitalia.

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    • "It is known from earler studies that male sex combs are involved in the exchange of tactile stimuli during courtship and mounting (Spieth, 1952), and, in D. melanogaster, their loss (by either mechanical or genetic means) strongly reduced the ability of males to copulate (Ng and Kopp, 2008). In our study, significant difference in average number of sex comb teeth, as well as in their symmetry between mated and unmated males were not observed. "
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    ABSTRACT: The influence of three types of diets on the number and symmetry of sex comb teeth (male secondary sexual character) as well as on behavioral trait (mating success) was tested in fruit fly in laboratory conditions. Mating experiments were conducted with three Drosophila melanogaster strains reared more than one year on different food. The quality of the diet itself had no influence on the number of sex comb teeth, neither on their symmetry. The size of sex comb and levels of fluctuating asymmetry were similar in mated and unmated males. However, males developed on different substrates showed differences in mating success: males of the “banana strain” and of the “cornmeal strain” were more successful in achieving copulations than males of the “tomato strain”. It seems that some other traits (morphological, physiological, and behavioral) were more important for male mating success than tactile stimuli provided by sex combs during the courtship.
    Full-text · Article · Dec 2013 · Journal of Animal and Plant Sciences
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    • "Several studies in these two species have tested for associations between male mating success and the presence/absence of sex combs (Spieth, 1952; Cook, 1977; Ng & Kopp, 2008) by physical (Spieth, 1952; Cook, 1977) or genetic (Ng & Kopp, 2008) sex comb ablation. These studies found that the presence of the sex comb is necessary for males to successfully mate. "
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    ABSTRACT: Sexual selection can drive rapid evolutionary change in reproductive behaviour, morphology and physiology. This often leads to the evolution of sexual dimorphism, and continued exaggerated expression of dimorphic sexual characteristics, although a variety of other alternative selection scenarios exist. Here, we examined the evolutionary significance of a rapidly evolving, sexually dimorphic trait, sex comb tooth number, in two Drosophila species. The presence of the sex comb in both D. melanogaster and D. pseudoobscura is known to be positively related to mating success, although little is yet known about the sexually selected benefits of sex comb structure. In this study, we used experimental evolution to test the idea that enhancing or eliminating sexual selection would lead to variation in sex comb tooth number. However, the results showed no effect of either enforced monogamy or elevated promiscuity on this trait. We discuss several hypotheses to explain the lack of divergence, focussing on sexually antagonistic coevolution, stabilizing selection via species recognition and nonlinear selection. We discuss how these are important, but relatively ignored, alternatives in understanding the evolution of rapidly evolving sexually dimorphic traits.
    Full-text · Article · Mar 2013 · Journal of Evolutionary Biology
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    • "It consists of several, well defined phases during which visual, olfactory, acoustic, tactile, and gustatory stimuli are exchanged (Hall 1994; Greenspan & Ferveur 2000). Because of the possible importance of wing size and symmetry during courtship (in producing " love song " , since approximately 80 per cent of the sexual stimulation in D. melanogaster is provided by wing vibration, Ewing 1964), as well as size and symmetry of sex combs (which are involved in grasping the female's abdomen, Spieth 1952; Ng & Kopp 2008), it was supposed that larger and more symmetrical males could be more successful in mating. "
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    ABSTRACT: Are larger and/or more symmetrical Drosophila melanogaster (Diptera, Drosophilidae) males more successful in matings in nature? Sexual selection in Drosophila melanogaster, related to body size and fluctuating asymmetry in wing length and number of sex comb teeth in males, was tested in natural conditions. Males collected in copula were significantly larger than those collected as a single, while no difference in mean number of sex comb teeth between copulating and single males was observed. On the other hand, single males had greater asymmetry both for wing length and number of sex comb teeth than their mating counterparts. It looks like that symmetry of these bilateral traits also may play a role in sexual selection in this dipteran species in nature.
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