Pre- and Post-Copulatory Mate Selection Mechanisms in an African Dung Beetle, Circellium bacchus (Coleoptera: Scarabaeidae)

Abstract

Females of most taxa mate selectively. Mate selection may be: (1) precopulatory,involving active female choice and male-male competition, and (2) postcopulatory,with cryptic female choice and sperm competition. Because female dungbeetles (Circellium bacchus) invest heavily in parental care by ball-rolling andremaining with developing larva they are, therefore, expected to be highly selectivewhen mating. Mate choice in this species was investigated via behavioralobservations and investigations of genital allometry of both sexes, leading toconclusions about the mechanisms of, and male characteristics important in, femalechoice. Male–male competition seems to be crucial in mate selection of C. bacchus,although the females appeared to show no active mate choice. There is a negativeallometric relationship between genital size and body size of males as predicted bythe ‘one size fits all’ hypothesis (where males have genitalia that fit average-sizedfemales). For the females, no relationship was found between genital size and bodysize. This might be as a result of the non-sclerotized nature of female genitalia,which may allow for greater morphological plasticity.