The Role of Plant Trait Variation in Community Assembly and Plant Diversity at Local to Continental Scales

The trait based approach has been proposed as a way to reconcile community ecology. Despite recent advances in trait based ecology, such as the development of global trait databases and standardized methodology for trait collections, it remains unclear to what degree traits vary across individuals, species, and communities. In addition, the drivers of trait variation may shed light on the underlying processes that maintain species diversity and community assembly at local to continental scales yet these have been poorly studied. In this study, I examine both the magnitude of trait variation as well as the patterns of trait variation at local to continental scales in order to understand the drivers of diversity patterns across environmental gradients. First, I quantified the magnitude of trait variation at local scales in a dry tropical forest and determined that intraspecific variation is not negligible and can be quite large for compound-leaved species. However, I showed that the sample sizes necessary for quantifying trait variation are tractable and should encourage the adoption of trait variation in trait based ecology. Second, I tested whether climatic variables are predominantly responsible for observed trait variation across dry tropical forests in the Americas. I showed that climatic variability, specifically variability in precipitation, explained a large degree of observed trait variation across dry tropical forests and may provide a unique approach for classifying dry tropical forests based on their inherent degree of climatic seasonality. Third, I quantified patterns of trait variation at continental scales across elevational gradients at high to low latitudes. I showed that climatic variables largely drive patterns of trait variation at high latitudes while biotic factors largely drive patterns of trait variation at low, tropical latitudes. This finding has implications for understanding large-scale patterns of species diversity across elevational and latitudinal gradients. Finally, I apply trait variation to life history theory by quantifying variation in two life history traits (growth and reproduction) in a tropical tree species using a legacy dataset. I showed that variation in these two life history traits is due to both resource availability and allometric related effects on both traits. In sum, this study advances our understanding of the magnitude and underlying drivers of trait variation at local to continental scales