Mistakes in sexual recognition among sympatric Zygoptera vary with time of day and color morphism (Odonata: Coenagrionidae)

Abstract

In odonates, female specific color polymorphisms appear to be an evolutionary response to sexual harassment, but we know little about the decision rules males use when searching for variable females. For two sympatric species of Enallagma, we measured male responses to live female variants under field conditions, early and later in the day. In the morning, when the operational sex ratio was the most male-biased and female density the lowest, males of the polymorphic E. civile did not discriminate among conspecific female morphs, and reacted sexually to the andromorphic females of E. aspersum, a monomorphic species. ‘Then, male E. aspersum did not favor conspecific females over E. civile morphs. Both morph types were more confusing for males than were conspecific male signals. However, after 13:00 h, males of both species made few mistakes, and E. civile males reacted sexually relatively less often to conspecific andromorphs, the minority morph in this population. The changes in a male's sexual response suggested that they cued to female-specific traits when females were scarce, increasing their detection of potential mates at the expense of making mistakes with heterospecific females. When females of both species were more abundant, a male's behavior was consistent with cueing to morph-specific features. Analyses of comparative data suggested that for several genera, males of polymorphic species were more likely to mistake heterospecific females as mates than males of monomorphic congeners. Our results best support the learned mate recognition hypothesis for the evolution and maintenance of female-specific polymorphisms.

Key words:

• Odonata
• dragonfly
• female polymorphism
• learned mate recognition
• heterospecific pairing