4 - Reproduction Curves and Their Utilities

Summary

A reproduction curve is the size of a population in a given generation plotted against its size in the preceding generation. Here I introduce its utility as an analytical tool in the study of animal population processes. As an example, I apply it to re-interpret the US census data to which Pearl and Reed fitted their logistic model. My analysis reveals some problems in the way Pearl and Reed envisaged the logistic nature of the US population. In particular, I reveal that the iconic sigmoid curve of the logistic model has no ecological significance but a mere consequence of the mathematical attribute that a population is a non-negative entity. I show an alternative way to conceive the actual nature of the logistic law and reinterpret the US census data. In particular, I introduce the notions of endogenous process (as intrinsic to the population) and exogenous (environmental) influences on it.