GENERAL PATTERNS OF AGE-BY-STAGE DISTRIBUTIONS

1 The methods of Cochran & Ellner (1992) make it possible to calculate the within-stage stable age distributions for populations modelled wi th a stage-projection (Lefkovitch) matrix. 2 Applying these methods, I found a general pattern in the form of these distributions across a b road range of taxa: with increasing stage category, the stable age dis tributions become lower, more symmetric, and flatter. 3 This pattern i s found in most but not all populations, and thus is not simply an art efact of the method. Exceptions tend to be populations with multiple n ew-born types (e.g. with both vegetative and sexual reproduction). 4 T he pattern remains qualitatively the same when the number of stage cla sses is varied, despite quantitative differences, When the number of s tages is large, the skewness and kurtosis of the within-stage age dist ributions appear to decline exponentially with stage. 5 The cause of t he pattern seems to be the accumulation of lag times in individuals' p rogressing to larger stages. 6 This result can be used to test for sta bility, when populations can be aged directly; to modify methods for e stimating age from stage, when they cannot; and to suggest the need to look for vegetative reproduction in the field, when it does not hold.