Female iridescent colour ornamentation in a butterfly that displays mutual ornamentation: is it a sexual signal?. (April 2017)

• Record Type: Journal Article
• Authors: Rutowski, Ronald L.; Kemp, Darrell J.
• Is Part Of: Animal behaviour. Volume 126(2017)
• Page Start: 301
• Page End: 307
• Publication Date: 2017-04
• Subjects: iridescence -- mutual ornamentation -- sexual signal -- sulphur butterfly -- ultraviolet; Animal behavior -- Periodicals; 591.5
• DOI: 10.1016/j.anbehav.2017.02.012
• Languages: English
• ISSNs: 0003-3472

Abstract

Abstract : In species wherein males display elaborate sexually selected traits or ornaments, conspecific females may also express these traits in full or partial form. This is called mutual ornamentation, and the co-occurrence of such traits in males and females remains poorly understood. In many sulphur butterflies (subfamily Coliadinae), males have a brilliant ultraviolet (UV) iridescence on their dorsal wing surfaces that functions as a sexual signal in courtship. In some of these sulphurs, such as the large grass yellow, Eurema hecabe, females also display dorsal iridescent patches, albeit smaller, restricted to the forewings and less bright than the male's, but the reasons for its occurrence in females are unknown. Here we present a study testing two functional hypotheses for the female UV-reflecting patch: an antiharassment hypothesis and a male mate choice hypothesis. The daily activity pattern of this species suggests that males are most likely to harass or choose among females from midday on. Observations made at this time of day on the characteristics of females related to male courtship duration suggest that males may preferentially court females with a large UV patch. Experiments with colour-manipulated models also suggest that males court with equal intensity females with and without a basal UV patch. Taken altogether the results provide no support for the antiharassment hypothesis. Because support for the male mate choice hypothesis was relatively weak and because of the limited potential for selection on female coloration due to male choice in these butterflies, the nonfunctional sexual correlation hypothesis remains a viable explanation for the female ornament. Highlights: We test two functional hypotheses for female UV wing patches in Eurema hecabe . Specifically, we tested whether female UV iridescent wing patches deter or attract males. Males were most likely to harass females or engage in mate choice in the afternoon. We found no evidence for deterrence and only very weak evidence for mate choice. The female UV wing patch is unlikely to have evolved as a sexual signal.