On Measuring the Intrinsic Rate of Increase of Populations with Heterogeneous Life Histories

Abstract

A method is developed for determining the exact value of the intrinsic increase rate of populations with heterogeneous life histories. The method works whenever the life history can be represented by a finite set of reproductive paths taken by individuals of the population. The finite rate of increase is the largest real root of a generalized Lotka equation. This generalized equation is easily obtained by summing the overlapping reproductive contributions of each life history path to population growth. These contributions are readily identified and quantified from a simple graphical representation of the life history. In the case of patchy environments, the dominant root of the generalized Lotka equation may be complex, giving rise to oscillatory intrinsic rates of increase.