Will estimates of lifetime recruitment of breeding offspring on small-scale study plots help us to quantify processes underlying adaptation?

Reviewing 22 long-term studies of birds that provide information on the ind ividual lifetime recruitment of breeding offsprings in local study plots, w e estimated local replacement rates of adults by breeding offspring (LRR) o n these plots. The studies indicate that on average two thirds of the offsp ring emigrate to breed outside the study plots and are replaced by immigran ts. Because recent studies show that individuals that disperse can differ f rom those that stay, and parents may produce dispersers and non-dispersers in different proportions, recruitment of breeding offspring in local study plots may not reflect the total recruitment of breeding offspring in the wh ole population. It is concluded that the identification of adaptations usin g estimates of lifetime recruitment of breeding offspring in study plots ma y be misleading and conclusions concerning adaptations are most often prema ture and extremely complicated to demonstrate quantitatively.