Males learn to prefer gynochrome females in a polymorphic damselfly (Odonata: Coenagrionidae)

The existence of different female colour morphs in odonates has been explained as the result of conflict between the sexes over mating frequency. Several hypotheses have been proposed to explain the maintenance of this colour polymorphism. Some of them assume that the androchrome female is a male-mimicking morph and suggest that androchromes obtain benefits when males mistake them with other males. By contrast, other hypotheses explicitly reject the imitation and propose that males learn to recognize the most common female colour morph in the population. In this study we tested the male preference of Ischnura elegans for the three female colour morphs. Preference was evaluated by sequential and binary trial presentations, using naïve isolated males (reared in the laboratory) and males from populations with contrasting frequencies (high, medium and low androchrome frequencies). Our results indicate that I. elegans males show preference toward the gynochrome morph, and this preference is learned. Nevertheless, they behave indiscriminately when the androchrome is the majority morph in the population. We also underline that androchrome females are not only mimicking male-coloration but also male-behaviour, and this male-behaviour mimicry is playing an important role in the evolution of the colour polymorphism in odonates.