Optimal size and number of offspring in a variable environment

Abstract

The effect of variable offspring survival is incorporated into the Smith-Fretwell (1974, Am. Nat. 108, 499–506.) model of optimal offspring size and number. When offspring survival varies, the optimal size of offspring, r′, is likely to be greater than or equal to the Smith-Fretwell optimum, r*, and hence the optimal number of offspring, n′, is less than or equal to the Smith-Fretwell optimum, n*. However, when n is large, and the probability of survivorship of individual offspring is small, n′ = n* and r′ = r*. Thus, as n increases the importance of variance in offspring survival on selection for the optimal size of offspring likely diminishes.