VALIDITY OF AN ESTIMATOR OF REPRODUCTIVE SUCCESS

Lifetime reproductive success is a major component of individual fitne ss and a central dependent variable for the study of natural selection . For long-lived animals, such as apes or baboons, assessment of lifet ime reproductive success requires observations of identified individua ls in continuous, long-term studies from which it is difficult and oft en impossible to obtain an adequate sample of necessary reproductive a nd survival data. This situation can be alleviated by the availability of a valid measure that uses incomplete reproductive histories to est imate the lifetime reproductive success of individuals. The validity o f one such estimator was tested by determining if, after 10.5 years of studying free-ranging female baboons, it predicted lifetime reproduct ive success obtained from full reproductive histories after 21.5 years . Validity was evaluated for seven criteria of success, ranging from t he number of a female's live births to the number of her offspring tha t reached the age of 72 months. Moderate to good prediction of lifetim e reproductive success by the estimator was found for criteria of offs pring living to 36 months or more, After 10.5 years, complete reproduc tive life spans were available for only eight females. Using the estim ator, analytic potential, via sample representativeness and size, was improved at 10.5 years by an increase from a sample of eight to betwee n 34 and 62, depending upon the criterion used, and at 21.5 years from 39 to 70. With a valid estimator, the opportunity to study lifetime r eproductive success of a long-lived species is substantially improved without having to depend upon rarely available, uninterrupted data col lection for 20-60 years. (C) 1998 Wiley-Liss, Inc.