A Reframing of Trait–Demographic Rate Analyses for Ecology and Evolutionary Biology

The relationship between plant functional traits and demographic performance forms the foundation of trait-based ecology. It also serves as the natural linkage between trait-based ecology and much of evolutionary biology. Despite these important aspects, plant trait–demographic performance relationships reported in the literature are typically weak or nonexistent, and a synthetic picture of how traits are related to ecological and evolutionary patterns remains underdeveloped. Here, we begin by presenting an overview of the shortcomings in functional trait–demographic performance research and why weak results are more common than trait-based ecologists like to admit. We then discuss why there should be a natural synthesis between trait-based ecology and evolutionary ecology and potential reasons for why this synthesis has yet to emerge. Finally, we present a series of conceptual and empirical foci that should be incorporated into future trait–demographic performance research that will hopefully solidify the foundation of trait-based ecology and catalyze a synthesis with evolutionary ecology. These include (1) focusing on individuals as the fundamental unit of study instead of relying on population or species mean values for traits and demographic rates; (2) placing more emphasis on phenotypic integration, alternative designs, and performance landscapes; (3) coming to terms with the importance of regional- and local-scale context on plant performance; (4) an appreciation of the varied drivers of life-stage transitions and what aspects of function should be linked to those transitions; and (5) determining how the drivers of plant mortality act independently and in concert and what aspects of plant function best predict these outcomes. Our goal is to help highlight the shortcomings of trait–demographic performance research as it stands and areas where this research could course correct, ultimately, with the hope of promoting a trait-based research program that speaks to both ecologists and evolutionary biologists.