Senescence in Organisms with Clonal Reproduction and Complex Life Histories

Abstract

A population genetics model is developed predicting the fate of alleles affecting life-history attributes in organisms with complex life histories, including clonal reproduction and indeterminate growth. Such organisms are widespread and found in many ecologically important groups, including marine invertebrates such as corals and sponges, and most higher plant taxa. The evolution of senescence (here defined as a decrease in fitness components with age or stage) by the action of alleles having negatively pleiotropic stage effects is investigated in such organisms. The spread of these alleles depends on the sensitivity of the population growth rate, a measure of fitness, to changes in life-history parameters that for this model are the entries of the stage transition matrix. Examples from a published demographic study show that, for several cases examined, alleles increasing early survival or early reproduction at the cost of decreased late survival will not be favored. Clonal reproduction acts to retard the evolution of senescence, although by itself the existence of clonal reproduction in an organism does not preclude the evolution of senescence.