The Elaborate Postural Display of Courting Drosophila persimilis Flies Produces Substrate-Borne Vibratory Signals

Journal of Insect Behavior, Sep 2016

Sexual selection has led to the evolution of extraordinary and elaborate male courtship behaviors across taxa, including mammals and birds, as well as some species of flies. Drosophila persimilis flies perform complex courtship behaviors found in most Drosophila species, which consist of visual, air-borne, gustatory and olfactory cues. In addition, Drosophila persimilis courting males also perform an elaborate postural display that is not found in most other Drosophila species. This postural display includes an upwards contortion of their abdomen, specialized movements of the head and forelegs, raising both wings into a “wing-posture” and, most remarkably, the males proffer the female a regurgitated droplet. Here, we use high-resolution imaging, laser vibrometry and air-borne acoustic recordings to analyse this postural display to ask which signals may promote copulation. Surprisingly, we find that no air-borne signals are generated during the display. We show, however, that the abdomen tremulates to generate substrate-borne vibratory signals, which correlate with the female’s immobility before she feeds onto the droplet and accepts copulation.

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The Elaborate Postural Display of Courting Drosophila persimilis Flies Produces Substrate-Borne Vibratory Signals

The Elaborate Postural Display of Courting Drosophila persimilis Flies Produces Substrate-Borne Vibratory Signals Mónica Vega Hernández 0 Caroline Cecile Gabrielle Fabre 0 0 Department of Zoology, University of Cambridge , Downing Street, Cambridge CB2 3EJ , UK Sexual selection has led to the evolution of extraordinary and elaborate male courtship behaviors across taxa, including mammals and birds, as well as some species of flies. Drosophila persimilis flies perform complex courtship behaviors found in most Drosophila species, which consist of visual, air-borne, gustatory and olfactory cues. In addition, Drosophila persimilis courting males also perform an elaborate postural display that is not found in most other Drosophila species. This postural display includes an upwards contortion of their abdomen, specialized movements of the head and forelegs, raising both wings into a Bwing-posture^ and, most remarkably, the males proffer the female a regurgitated droplet. Here, we use high-resolution imaging, laser vibrometry and air-borne acoustic recordings to analyse this postural display to ask which signals may promote copulation. Surprisingly, we find that no air-borne signals are generated during the display. We show, however, that the abdomen tremulates to generate substrate-borne vibratory signals, which correlate with the female's immobility before she feeds onto the droplet and accepts copulation. Biotremology; drosophila; persimilis; pseudoobscura; courtship; behavior; abdomen; tremulation; substrate-borne vibrations; female stationary; quivering; feeding; copulation Introduction A variety of animals perform courtship displays to attract a mate. The complexity of these displays is driven by sexual selection, which in some species has led to extraordinary patterns of male courtship (Andersson 1994) . For example, during courtship, the male bird of paradise presents an iridescent chest and snaps its tail feathers rhythmically while hopping on its legs (Cooper and Forshaw 1977) . In jumping spiders and wolf spiders, courting males raise their abdomen and/or legs to attract the female’s attention (Waldock 1993; Hebets and Uetz 2000; Girard and Endler 2014; Girard et al. 2015) . These behaviors provide visual signals to the females (Cooper and Forshaw 1977; Amundsen et al. 1997; Bennett et al. 1997; Pearn et al. 2001; Hausmann et al. 2003; Li et al. 2008; Lim et al. 2008; Uhl and Elias 2011) , but, at the same time, they may also generate cues such as air-borne or substrate-borne signals (Edwards 1981; Gwynne and Dadour 1985; Maddison and Stratton 1988a, 1988b; Read and Weary 1992; Elias et al. 2003; Sivalinghem et al. 2010; Girard et al. 2011; Uhl and Elias 2011) . The females use all of these pieces of information to assess males and to decide whether to accept copulation. It was long thought that the jumping spider females assessed the courting display of the males mainly visually (Foelix 1996). In some species, courting males were shown to also produce air-borne sounds [see for example (Edwards 1981; Gwynne and Dadour 1985) ]. Later, the abdominal movements of the males were shown to produce substrate-borne vibrations; the transfer of these vibrations through the ground is essential for the copulation success of the males (Elias et al. 2003, 2005, 2006, 2010; Sivalinghem et al. 2010) . Substrate-borne vibrational communication is widely used by animals, in particular by invertebrates, and has recently received increased attention in the literature (Virant-Doberlet and Cokl 2004; Cocroft and Rodríguez 2005; Polajnar et al. 2014; Hill and Wessel 2016; Polajnar et al. 2016; Rebar and Rodríguez 2016) . Identifying and monitoring these vibrations that are imperceptible to humans requires sophisticated technologies, such as laser vibrometry (Elias et al. 2003; Cocroft and Rodríguez 2005; Girard et al. 2011) . Drosophila persimilis flies are a typical wild inhabitant of the western United States, where they breed on the infected sap of trees. Although their behaviour and ecology are not completely understood, D. persimilis flies are usually found together with the almost morphologically indistinguishable species Drosophila pseudoobscura (Carson 1951) . Like other Drosophila species the D. persimilis males produce Bstandard^ courtship behaviors, including the wing fluttering that produces an air-borne sound involved in species recognition (Spieth 1952; Brown 1965; Greenspan and Ferveur 2000) . Remarkably, Drosophila persimilis is one of the few Drosophila species, in which males also exhibit an elaborate postural display in addition to the standard courtship steps (Spieth 1952) . Some parts of this postural display were noted previously, including the upward movement of the wings (Bwing-posture^), the rowing of one leg, and the dramatic rise of the abdomen and the forelegs (Brown 1965) . Nevertheless, several aspects of the description and signals produced by this postural displ (...truncated)


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Mónica Vega Hernández, Caroline Cecile Gabrielle Fabre. The Elaborate Postural Display of Courting Drosophila persimilis Flies Produces Substrate-Borne Vibratory Signals, Journal of Insect Behavior, 2016, pp. 578-590, Volume 29, Issue 5, DOI: 10.1007/s10905-016-9579-8