When Similar Individuals Don't Attract: Absence of Assortative Mating by Coloration in a Damselfly With Honest Signaling

ABSTRACT Ornaments are conspicuous traits used in intraspecific signaling, occurring in one or both sexes. In species with mutual ornamentation, male traits have traditionally received more attention, whereas female traits have frequently been assumed to evolve as byproducts of male ornamentation. However, other less explored processes, such as mutual mate choice, may explain ornamentation in both sexes. According to this hypothesis, when males and females prefer the same trait, selection reinforces it over generations, promoting ornament development in both sexes, especially when the trait signals individual quality. However, mate choosiness may vary according to the time available for the reproductive process to take place: the shorter the time, the lower the choosiness. We tested these patterns in a damselfly species ( Acanthagrion lancea ), in which both sexes possess blue ornamentation, and investigated two hypotheses: (i) blue coloration results from mutual mate choice, in which coloration signals quality; (ii) mate selectivity decreases over the course of the day, as time available for reproduction decreases. To investigate these hypotheses, we analyzed whether the color of male–female couples correlated, considering their visual spectrum, and whether this correlation decreased throughout the day, indicating less mate selectivity. We used lipid weight and dry body mass as indicators of quality. Coloration was positively correlated with individual dry mass. Surprisingly, a new red coloration, not visible in the human spectrum, was identified. However, there was no relationship between the colorations of couples, regardless of the time of day. These results suggest that, although coloration signals quality, it is not used in mutual mate choice, independent of the available time for reproduction.