Age × Stage-Classified Models

Abstract

The first step in developing any kind of structured population model is choosing one or more variables in terms of which to describe the population structure. The job of these i-state variables is to encapsulate all the information about the past experience of an individual that is relevant to its future behavior (Metz and Diekmann 1986; Caswell 2001). Classical demography (for both humans and for non-human animals and plants) uses age as a i-state, but other, more biologically relevant criteria (e.g., size, developmental stage, parity, physiological condition, etc.) are now widely used in ecology, with age-classified models viewed as a special case. However, it has long been recognized that cases exist where it is important to classify individuals by both age and stage. This chapter is modified, under a Creative Commons Attribution License, from Caswell, H. 2012. Matrix models and sensitivity analysis of populations classified by age and stage: a vecpermutation matrix approach. Theoretical Ecology 5:403-417.