Sexual Selection in Dung Beetles .1. A Multivariate Study of the Morphological Variation in 2 Species of Onthophagus (Scarabaeidae, Onthophagini)

Abstract

Sexual dimorphism in horned beetles reflects a history of different selection pressures operating on males and females. A multivariate morphometric analysis was carried out on two scarabaeine dung beetles, Onthophagus binodis Thunberg and O. ferox Harold. There is clear structural polymorphism within O. binodis; horned males, females and hornless males were separated on the basis of body shape. Sexual dimorphism within O. ferox was established; sexes were separated according to the size of pronotal and cephalic horns. The effect of differential selection is discussed within the context of sexual selection.