Morphological aspects of reproduction in the ant genus Cardiocondyla
The ant genus Cardiocondyla is an ideal system for studying questions concerning sexual selection and sexual conflict in social insects. Several species of this genus exhibit a male dimorphism. Winged, large-eyed males occur, which are typical for most ant species. Furthermore, so-called “ergatoid” males are produced, which are wingless and possess only small eyes. These differences in male morphology are also reflected in male reproductive tactics, which show variation not only between different morphs within a species but also between species.
In some species ergatoid males kill their ergatoid rivals. In other species, ergatoid males tolerate each other. In both cases, virgin queens may not only mate with ergatoid males, but also with winged males, as the latter stay for several days in the nest after eclosion. They do not receive aggressive behavior from ergatoid males. Finally, there are several Cardiocondyla species in which only ergatoid males occur. These are mutually tolerant in some of these species, in others they behave aggressively against other ergatoid males.
Furthermore, the dimorphism of male Cardiocondyla ants is well-suited for gaining insight in the processes underlying genital evolution. Predictions of several hypotheses of genital evolution (e.g. lock-and-key, sexual selection) may be tested to resolve the question of how genitalia evolved.
Male genital morphology in different Cardiocondyla species:
Thanks go to PD Dr. S. N. Gorb for providing the opportunity to use his SEM.