Developmental Rate and Competitive Ability in Tribolium. II. Changes in Competitive Ability Following Further Selection for Developmental Rate

Further tests of a genetic model for the relationship between developmental rate and competitive ability in flour beetles Tribolium castaneum (CS) and T. confusum (CF) were carried out using beetles from later generations of selection for fast and slow development in CS and fast development in CF. The CS-slow and CF-fast strains performed as expected-competitive ability was reduced in comparison with that of beetles taken from earlier generations. On the other hand, competitive ability of the CS-fast strain improved considerably with continued selection. Further studies indicated that the observed improvement may have been the result of an increased cannibalistic activity of larvae (and perhaps adults) of this strain. The possibility of cannibalism having played a role in the evolution of CF from CS is briefly discussed.