Sexual dimorphism in the dark-winged damselfly Calopteryx maculata.

Abstract

Pronounced sexual dimorphisms are suggestive of sexual selection (McKinney, 1971). In Calopteryx maculata, a pronounced sexual dimorphism is seen in the degree of wing pigmentation, with males having significantly darker wings than females. Territoriality in C. maculata confounds the ability to discern the function which the sexual dimorphism serves. Previous studies of have suggested that degree of male wing pirmentation in a related species C. haemoroidalis may serve as a sexual signal to females or other males indicating their genetic quality (Siva-Jothy, 2001). Various studies showed that males with a higher degree of wing pigmentation were more likely to defend a territory, obtain more matings, have fewer gut parasites, and have larger fat reserves. In contrast, we found that degree of wing pigmentation was not correlated to male mating or territorial success. We found that females were choosy of territories but not of males. Our results suggest that the degree of wing pigmentation may play a role in species recognition by females. This was supported by the fact that the C. maculata population we studies co-inhabited the Maple River with Calopteryx maculata. Due to great variation in explanantions for sexual dimorphisms in dark-winged damselflies in both published literature and our study, further investigation into the sexual dimorphism of Calopteryx maculata is needed.