Population matrix models enable us to derive population statistics that describe the life history characteristics of species or populations such as life expectancy, elasticity and population growth rate. We developed a new population statistic, inter-stage flow matrix, which explicitly describes the inter-stage flows of individuals derived from projection matrices and stable stage distributions. We compared the inter-stage flows of four groups based on life history and functional traits (semelparous herbs, iteroparous herbs, shrubs, and trees) using projection matrices from the Plant Matrix Database, COMPADRE version 4.0.1. First we categorized inter-stage flow matrix elements into stasis, fecundity, or growth. Then we analyzed how the pattern of summed inter-stage flows for stasis, fecundity and growth varied across functional groups using best-fitted Dirichlet regression models.
Results/Conclusions
Each functional group and population growth rate affected inter-stage flows in fundamentally different ways. Semelparous herbs had large flow of growth and small flow related to stasis. Trees had large flow related to stasis but small flow of growth. Iteroparous herbs and shrubs had relatively similar flows. Species with large inter-stage flows related to fecundity have high population growth rate. Inter-stage flows describe distinct demographic properties compared to elasticity and other population statistics. Elasticity describes how a perturbation will influence future population growth rate. In contrast, inter-stage flow directly describes current contributions to population growth rate (at present). Inter-stage flow matrices have potential to provide unique ecological insights that complement other population statistics.