We analyzed mate recognition and the cooperative behavior of male–female pairs in Canthon cyanellus cyanellus LeConte (Coleoptera: Scarabaeidae), a carrion-feeding scarab, during food ball rolling among five populations found in tropical forest fragments on the eastern coastal plains of Mexico. Sexual recognition in this species is mostly mediated by chemical cues. Intrapopulation and male–female pairs formed with individual from populations <400 km apart showed cooperative behavior (joint rolling of the food ball by both members). However, male–female pairs from populations >400 km apart showed no cooperative behavior (individual food ball rolling by one of the partners and fights), although they also rolled food balls together. In male–female pairs from the more distant populations (≥600 km apart), >50% fought for food balls. Brood ball production by females and the number of eclosed beetles from the northern population and from the crosses between individuals from the most distant populations were lower than those of other intra- or interpopulation combinations. Gas chromatograph mass spectroscopy of cuticular extract showed that the southern population had 48 surface compounds, 18 of them not present in the northern or intermediate populations. The intermediate population had 41 compounds, 11 of them exclusive. However, the northern population had 24 compounds and only one was exclusive. The lack of cooperative interaction among male–female pairs from distant populations, along with their reduced reproductive success and the differences in cuticular composition between populations, suggest that extreme populations of Canthon c. cyanellus are in a process of incipient speciation.
Annals of the Entomological Society of America
Vol. 99 • No. 6
Vol. 99 • No. 6