Mate guarding and alternative reproductive tactics in the ant Hypoponera opacior

Abstract

In many animals, males have evolved weapons, elaborate courtship displays, or costly ornaments to increase their reproductive success. Ants, in contrast, commonly mate during nuptial flights, in which males do not profit from fighting or attempting to monopolize females. However, where mating occurs in the nest, males can use other reproductive tactics. We found that wingless (apterous) males of Hypoponera opacior sat on top of queen cocoons, inserted their genitalia into the cocoons and remained in copula with cocooned queens for up to 40h. These males were tolerant of each other; fighting was never recorded. Our observations therefore suggest that wingless males of H.opacior ensure reproduction by copulatory mate guarding. This strategy, although time consuming, presumably reduces the likelihood of subsequent inseminations by other males. Apterous H.opacior males have only a limited amount of sperm available: histological preparations showed that, in contrast to Cardiocondyla fighter males, the testes degenerate in early adult life. Males ofH.opacior have relatively few mating opportunities. Although some wingless males were reproductively active for more than 3 weeks, we observed a maximum of only six matings per male, with a mean slightly above one. SomeH.opacior males used an alternative reproductive tactic of dispersal and outbreeding. We found colonies headed by single, dealate queens, which did not rear wingless sexuals but presumably reproduced through winged reproductives that mate in nuptial flights. The social structure of those colonies contrasted with nests containing wingless reproductives, which were highly polygynous and polydomous.