Reproductive isolation in Damselflies

Abstract

Experiments were perfomied in the field on males of five species and females of ten species of damselflies (Odonata: Zygoptera: Coenagrionidae) to determine the relative importance of visual and mechanical reproductive isolating mechanisms. Males of all five species did not distinguish visually their own female from heterospecific females of the same genus, but they were slightly less responsive to females of other genera, probably because of size differences. When the males attempted to mate with females of other species, they were usually prevented from doing so because their abdominal appendages were unable to secure a firm grip on the appropriate thoracic structures in the females. In only one species pair was the male able to achieve the tandem position successfully most of the time, and the reciprocal was unable to do so. Mechanical isolation is clearly very important in this group of odonates, and it is hypothesized that it will be found to be important in all odonates in which male appendages differ substantially between species while female coloration does not.