AGE-SPECIFIC LIFE-HISTORY TACTICS IN ORGANISMS WITH DETERMINATE GROWTH - OPTIMAL MODELS FOR NONOPTIMAL BEHAVIOR

Among organisms with determinate growth, optimization models predict t hat reproductive effort should increase as individuals approach old ag e, but the assumptions of these models may be inappropriate because th e senescence that generates the necessary selective pressure may be no t itself be optimal. Population genetics models were constructed to ex amine whether genes for age-specific changes in reproductive effort co uld invade a population in which senescence was maintained at equilibr ium levels by a balance between mutation and selection. In asexually r eproducing organisms, it was found that strategies of increasing repro ductive effort could not normally invade the population. In sexually r eproducing organisms, however, recombination was found to be important and genes for age-specific changes in effort could spread in the popu lation under most circumstances.