The Evolutionary Significance of Lifetime Reproductive Success

Abstract

Recent studies have reported lifetime reproductive success (LRS) as empirical counts of fledglings, yearlings, or breeders produced by individuals during their lifetimes. In this paper, I show how the mean LRS of the breeding individuals of a population can be calculated from age-specific probabilities of survival and fecundity. An analysis of a simulated population shows that the LRS of males and females from the same population can be different, even though the rates of change in numbers of males and females are identical. Thus, although LRS may be a measure of individual fitness, differences in LRS, even among individuals with different phenotypes and genotypes, cannot be construed to have evolutionary significance. The proper measure of fitness is the Malthusian parameter (mij).