A morphometric analysis of environmental dependences between ultraviolet patches and wing venation patterns in Gonepteryx butterflies (Lepidoptera, Pieridae)

Abstract

It has been suggested that structural ultraviolet (UV) patches on the wings of butterflies play a role in sexual selection. UV patches may be condition-dependent signals of mate quality. In the current study, we investigated associations between the morphological properties of two male wing patterns (one signalling and one non-signalling trait) and between these patterns and various environmental variables in seven species of the genus Gonepteryx (G. rhamni, G. nepalensis, G. maxima, G. amintha, G. aspasia, G. niphonica and G. cleopatra). We collected UV photographs of a total of 320 male specimens and analysed them using geometric morphometrics. Our results show that the shape of UV patches (a signalling trait) is more asymmetric than the wing venation (a non-signalling trait). In both examined traits, however, relationship between the environment and fluctuating asymmetry is significant only in a minority of species. Our results thus do not support the hypothesis that fluctuating asymmetry is a reliable indicator of an individual’s quality, in other words, that UV patches are condition-dependent trait. Examination of correlations between the two investigated shapes and the environment yielded similar results, and while the shape of UV patterns tended to be more strongly associated with the environment than the venation patterns, the correlation reached a level of significance only in a minority of cases. Due to the ambiguity of our findings, we cannot corroborate the hypothesis that UV patches act as biological signals of male quality in Gonepteryx butterflies, which is the case in various other related butterfly species. Finally, we found that UV patches discriminate among various Gonepteryx species better than the venation patterns do, which indicates that UV patches play a role in species recognition. It also suggests that UV patterns could be a useful taxonomic trait.