Finding hidden females in a crowd: Mate recognition in fig wasps

Antennae and the role of olfaction and contact stimulation in mate recognition by males of the pollinating fig wasp Ceratosolen gravelyi (Hymenoptera: Agaonidae)

“…The present study is the first to report fighting between Ceratosolen males competing for an individual female; however, the morphology of C. gravelyi males is not consistent with the fighting traits of aggressive males (Greeff et al 2003). Conversely, C. gravelyi males move more rapidly than males of the non-aggressive C. fusciceps, which move slowly when searching for females in the dark cavity of the fig (Krishnan et al 2014). During our observations of male behaviour, we observed that fighting between males typically occurred in the centre of figs (Supplementary material), where access to females is easy, and females have larger body-size, suggesting higher reproductive value and more mating opportunities, while fighting was not observed for the fertilisation of females in galls of difficult access located close to the fig wall (Dunn et al 2008;Yu and Compton 2012;Peng et al 2014).…”

“…In such a system, selection favours females producing cuticular chemicals that facilitate their recognition by conspecific males and limiting fertilisation by heterospecific males, thus ensuring pre-zygotic isolation through assortative mating (Lukhtanov et al 2005;Smadja and Butlin 2008;Langerhans and Makowicz 2013). In our experiments, the males were very active and moved more rapidly than do males of the non-aggressive, pollinating fig wasps (Krishnan et al 2014). This allowed monitoring of numerous choices made by the males.…”

“…Fig wasps constitute such an example as sometimes thousands of individuals from multiple species occur within a single breeding arena constituted by a fig (Weiblen 2002;Kjellberg et al 2005b; Krishnan et al 2014). not rely on visual cues to find potential mates in close proximity and they have to gnaw a hole into galls to reach the females (Greeff et al 2003;Kjellberg et al 2005b;Krishnan et al 2014;Ohyama et al 2015). Nevertheless, using acoustic songs to locate receptive females from a distance is particularly challenging in a fig as several hundreds of conspecific receptive females may be present within the enclosed cavity.…”

“…The cuticular hydrocarbons of the insect epicuticle compose a group of lipid compounds that contain various numbers of carbon atoms. These cuticular hydrocarbons are important in insect chemical communication and function in mate discrimination, kin discrimination and sexual discrimination in numerous insect taxa, including fig wasps (Howard and Blomquist 2005;Nagamoto et al 2005;Krishnan et al 2014;Ranganathan et al 2015). Cuticular hydrocarbons are relatively heavy and hence have limited volatility, a feature which is probably a favourable trait for efficient signalling within the closed fig cavity.…”

“…To determine whether male Ceratosolen wasps recognise conspecific females using olfactoryguiding and tactile-confirming chemicals that are emitted by females, we employed three biological tests using a method similar to that of Krishnan et al (2014). Each male was individually placedin themiddleof a cell cultureplate filled with 1% agarose gel and presented with a choice between two galls or extracts placed symmetrically on either side of the male at a distance of 3 mm.…”