Interpretation of elasticity matrices as an aid to the management of plant populations for conservation

Population projection (Lefkovitch) matrices are now a standard method for quantifying and analyzing the demography and population dynamics of plants. Elasticity analysis of such a matrix indicates the relative effect on the population growth rate (lambda) of small changes to matrix elements representing different transitions in the life cycle. In a comparison of elasticity matrices for 84 species of plants we show that the relative importance of recruitment from seed (measured by composite elasticity F), stasis (measured by composite elasticity L), and growth (measured by composite elasticity G) varies systematically between the groups semelparous herbs, iteroparous herbs of open habitats, forest herbs, shrubs, and trees. We discuss how this result might be used to construct rules of thumb useful in plant conservation. By looking in detail at how lambda covaries with the composite elasticities F, L, and G among 16 populations of the semelparous herb Cirsium vulgare and among 15 populations of the rare iteroparous herb Pedicularis furbishiae, we show that a naive interpretation of elasticities can give a misleading prescription for management. Instead, we show that elasticity analysis supports management prescriptions based upon the successional status of a species or upon its response to disturbance.