Wing Pigmentation in Males of a Territorial Damselfly: Alternative Reproductive Tactics, Allometry and Mating Success

Abstract

Alternative reproductive tactics (ARTs) evolve to maximise fitness by favouring alternative phenotypes when high variance in relative fitness occurs amongst individuals. In the damselfly Hetaerina vulnerata males occur as either territorial or nonterritorial, depending on whether males acquire and defend an area to which females are attracted for copulation. Territorial males are usually larger, more pigmented and more successful in obtaining copulations than nonterritorial males. Several studies further suggest that territorial males are in overall better condition than nonterritorial ones. Other studies have investigated whether wing pigmentation, a sexual trait in damselflies, scales hyperallometrically with body size, and asked whether this pattern is related to fitness—nonetheless, a clear answer to this question remains elusive. Here we investigate whether i) territorial and nonterritorial males differed in body size and wing pigmentation; ii) body size, wing pigmentation and/or male status (male ART) predicted male mating success; and iii) the allometry of wing pigmentation in territorial and nonterritorial males, and amongst mated and unmated males. We first found that territorial and nonterritorial males did not differ in body size. Second, contrary to what occurs in other damselflies, territorial and nonterritorial males exhibited similar amounts of wing pigmentation. Third, only territory tenure, but not body size or wing pigmentation, predicted male mating success. Finally, with the exception of the relationship exhibited by mated males, which exhibited isometry, wing pigmentation was hyperallometric in all groups of males tested. The latter result suggests that hyperallometry of the sexual trait in this damselfly may not be selectively advantageous.