Individual differences and survival during competition: a simple theoretical model and empirical evidence for flour beetles Tribolium castaneum (Herbst)

1 Population stability and persistence in discrete time units is related to the survival function k(N), where N is the number of individuals before competition and k is the number of individuals after competition. The shape of the function k(N) depends on resource partitioning among individuals within a population. This still holds under conditions of scramble competition, i.e. when resources are not monopolized by some individuals. 2 Individual differences among Tribolium larvae, due to differences in their age (eggs laid over 7 days as compared with those laid on the same day for the control), were used to test the theoretical model. Such differences led to the predicted results, i.e. better survival of the larvae at high densities but a worse survival at intermediate densities.