The Effect of Energy Trade-Offs on Life History and Fitness in the Rice Weevil, Sitophilus oryzae

The weevil populations had been reared for >50 generations on either wheat, sorghum or yellow split-pea. The selective forces operating in the three environments had resulted in the evolution of different, presumably adaptive, life histories. Yellow split-pea and probably also sorghum contain toxic phytochemicals. The need to detoxify these chemicals favoured higher investment in detoxification mechanisms to maintain survival (in the sorghum and pea populations) at the expense of other fitness characters, such as development rate and fecundity. Fitness was calculated using two methods which made different assumptions concerning the oviposition behaviour of the insects in response to old grain. Only in the yellow split-pea environment did the pea population have a higher fitness than the other two populations. No significant fitness differences were found between populations in the wheat environment. -from Authors