Sib competition in Tribolium A test of the elbow-room model

Abstract

The elbow-room model of sib competition predicts that sexually reproducing parents could have a fitness advantage over asexual parents if competition within more diverse, sexually producedoffspring was less intense than within more homogeneous, asexually produced ones. To test theassumption empirically that genetic homogeneity implies stronger competition, we compared theproductivity of sib groups and random groups of the flour beetle Tribolium castaneum maintainedat very high densities. For larval production, we found an initial advantage of sib groups but it didnot result in an advantage in total adult production, because high initial densities increasedmortality in the long run, such that the adult production was the same in both groups. We discusshow some changes in our experimental design could produce very different results, and concludethat sib competition is unlikely to be a general explanation for the widespread presence of sexualreproduction in nature. © 1992 The Genetical Society of Great Britain.