Triggers of the Postural Display of Courtship in Drosophila persimilis Flies

Journal of Insect Behavior, Sep 2017

D. persimilis courtship shows some flexibility and courting males sometimes perform an elaborate postural display in addition to the standard courtship behaviours shared by most Drosophila species. This postural display includes the acrobatic contortion and tremulation of their abdomen, accompanied by the generation of substrate-borne vibrations, and they proffer a nutritional droplet to the female. Here, we use courtship and choice assays to ask what triggers this display and what advantages males may gain from it during courtship. In pair assays, we found no differences in the courtship duration and copulation success between displaying and non-displaying males. In trio assays, however, the female always mated with the male who performed the display. To investigate what promotes the male display, we varied the level of receptivity of the female and studied the impact of a second male. We found that rejection by the female does not induce the male to display, contrary to what was previously suggested. We present evidence that the male display is in fact promoted by the presence of an attentive and sexually receptive female and the absence of male competition, with the greatest exhibition rate obtained if the courted female is starved. These findings provide valuable information about the social ecology of flies, and how internal and external cues influence sexual behaviours and mate choice.

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Triggers of the Postural Display of Courtship in Drosophila persimilis Flies

J Insect Behav Triggers of the Postural Display of Courtship in Drosophila persimilis Flies Mónica Vega Hernández 0 Caroline Cecile Gabrielle Fabre 0 0 Department of Zoology, University of Cambridge , Downing Street, Cambridge CB2 3EJ , UK D. persimilis courtship shows some flexibility and courting males sometimes perform an elaborate postural display in addition to the standard courtship behaviours shared by most Drosophila species. This postural display includes the acrobatic contortion and tremulation of their abdomen, accompanied by the generation of substrate-borne vibrations, and they proffer a nutritional droplet to the female. Here, we use courtship and choice assays to ask what triggers this display and what advantages males may gain from it during courtship. In pair assays, we found no differences in the courtship duration and copulation success between displaying and non-displaying males. In trio assays, however, the female always mated with the male who performed the display. To investigate what promotes the male display, we varied the level of receptivity of the female and studied the impact of a second male. We found that rejection by the female does not induce the male to display, contrary to what was previously suggested. We present evidence that the male display is in fact promoted by the presence of an attentive and sexually receptive female and the absence of male competition, with the greatest exhibition rate obtained if the courted female is starved. These findings provide valuable information about the social ecology of flies, and how internal and external cues influence sexual behaviours and mate choice. Drosophila; persimilis; pseudoobscura; courtship; behaviour; biotremology; tremulation; competition; receptivity; rejection; feeding; copulation Introduction In many animals, courtship behaviours are important traits for reproductive success (Andersson 1994) . Sexual selection has influenced the complexity of the courtship displays that a variety of animals use to attract a mating partner and advertise their desire to mate [see for example (Pruett-Jones and Pruett-Jones 1990; Frith and Beehler 1998) . Darwin implied that this complexity is a consequence of the Bconstantly recurring struggle between the males for the possession of the females^ with constraints that include direct competition between males (intrasexual selection) and the choice of a mate by the females (intersexual selection). This has sometimes led to complex behaviour patterns of male courtship in some species. Examples of spectacular displays are found in birds and mammals [see for example (Cooper and Forshaw 1977; CluttonBrock and Albon 1979; Frith and Beehler 1998; Scholes 2006) ], as well as arthropods, including some species of flies (Brown 1964, 1965; Spieth 1952, 1966, 1981, 1987; Kaneshiro 1983; Setoguchi et al. 2014; Hernandez and Fabre 2016) . In most Drosophila flies, the males display Bstandard^ courtship behaviours that often show only subtle variations between species. The males follow the females, they flutter one wing to produce a species-specific song, they gather gustatory information by licking and tapping the female, they tremulate the abdomen up-and-down to produce substrate-borne vibrational signals and finally they curve the abdomen and attempt copulation (Spieth 1952; Ewing and Bennet-Clark 1968; Fabre et al. 2012; Bontonou and Wicker-Thomas 2014) . Males of the species Drosophila persimilis perform most of these standard behaviours but they are also one of the few Drosophila species in which males sometimes exhibit an additional postural display of high complexity (Brown 1965; Spieth 1981; Kaneshiro 1983; Setoguchi et al. 2014; Hernandez and Fabre 2016) , which we call the postural display of courtship (PDC). The PDC is about 20 s long and the male usually performs it twice to the female during his 2 min long courtship (Hernandez and Fabre 2016); the PDC includes the acrobatic contortion and tremulation of the male abdomen, the production of substrate-borne vibratory signals, the upwards movement of the wings as well as the offering of a droplet to the female (Brown 1964, 1965; Hernandez and Fabre 2016) . We previously reported that the PDC is in fact exhibited in only ~ half of the D. persimilis courting pairs (the other half relying exclusively on the standard courtship behaviours) but it is not clear why this is the case and which contexts may favour the PDC exhibition in males (Hernandez and Fabre 2016) . This flexibility in the male behaviour was also surprising because Drosophila courtship is usually described as being largely stereotyped [see for example (Spieth 1952; Greenspan and Ferveur 2000) ] and, to our knowledge, the finding that ~ half of the D. persimilis courting pairs behave differently to the other half had not previously been reported. In most animals performing complex courtship displays, it is difficult to analyse the effect of social interaction (...truncated)


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Mónica Vega Hernández, Caroline Cecile Gabrielle Fabre. Triggers of the Postural Display of Courtship in Drosophila persimilis Flies, Journal of Insect Behavior, 2017, pp. 582-594, Volume 30, Issue 5, DOI: 10.1007/s10905-017-9641-1