Relative Realized Life Span and Delayed Cost of Parental Care

Abstract

Many iteroparous animals delay full reproductive effort past the age of reproductive maturity. According to a life history model, this delay is likely to be selected for when the costs of reproductive effort (e.g., parental care) are low and/or the number of reproductive episodes is high, all other things being equal. Benefit increases as reproductive effort increases from its lowest level at the onset of reproduction through its peak. If this benefit increases while the number of reproductive episodes stays constant, selection favors full-scale effort from the start. The model fails to predict the change in parental defense of broods with age in two avian species, the great tit (Parus major) and the California gull (Larus californicus), and an insect, the eggplant lace bug (Gargaphia solani, Tingidae), assuming a similar benefit/cost ratio across all three species. By contrast, a simple life history measure, the ratio of the mean number of reproductive episodes in a lifetime to the maximum number of thos...