The diversity and spacing of plant functional traits along environmental gradients provides insight into community assembly and species coexistence mechanisms. Surprisingly, empirical studies relating trait diversity in tropical dry forests are limited. On the one hand, increased seasonality and decreased precipitation are strong environmental filters for drought-adaptive traits which should limit trait variation. On the other hand, if seasonality leads to increased spatio-temporal environmental variation then we might expect an increase in functional diversity in more seasonal forests. To determine the link between climatic and functional trait variability, first, the magnitude of functional diversity of tropical dry forests was quantified across major tropical and sub-tropical ecosystems (encompassing arid, semi-arid, and tropical forests) using published trait datasets. Second, values of functional diversity were related to climatic variables using downscaled climate data for each study location. Finally, this approach is extended to tropical dry forests within the Caribbean Basin to predict patterns of functional diversity and to identify functional hotspots in this understudied region.
Most notably, functional diversity increased with increasing climatic variability, supporting the hypothesis that increased spatio-temporal environmental variability allows for the coexistence of functionally diverse species. The relationship between climatic variability and functional diversity can aid in the identification of key functional hotspots within the Caribbean. However, functional hotspots within the Caribbean tended to be located in regions situated on unique soil substrates (e.g. serpentine and limestone). This study demonstrates 1) tropical dry forests harbor high levels of functional diversity and 2) the role of edaphic variation may be overlooked in climate models predicting ecosystem level response.