Functional traits explain variation in plant lifehistory strategies

Ecologists seek general explanations for the dramatic variation inspecies abundances in space and time. An increasingly popularsolution is to predict species distributions, dynamics, and responsesto environmental change based on easily measured anatomical andmorphological traits. Trait-based approaches assume that simplefunctional traits influence fitness and life history evolution, butrigorous tests of this assumption are lacking, because they requirequantitative information about the full lifecycles of many speciesrepresenting different life histories. Here, we link a global traitsdatabase with empirical matrix population models for 222 speciesand report strong relationships between functional traits and plantlife histories. Species with large seeds, long-lived leaves, or densewood have slow life histories, with mean fitness (i.e., populationgrowth rates) more strongly influenced by survival than by growth orfecundity, compared with fast life history species with small seeds,short-lived leaves, or soft wood. In contrast to measures of demographic contributions to fitness based on whole lifecycles, analysesfocusedonrawdemographic rates may underestimate the strengthof association between traits and mean fitness. Our results helpestablish the physiological basis for plant life history evolution andshow the potential for trait-based approaches in population dynamics.