Leaf traits as predictors of climatic adaptation and distributional range in wide- and narrow-range species

Abstract

The distribution of species and their resistance to climate change can be predicted by examining the range of abiotic factors and the expression of intraspecific functional trait variation. Functional traits, such as specific leaf area (SLA) and total leaf surface area (LA), may vary in individuals according to their natural habitat conditions, improving plant performance. The genus Erythroxylum is a good model for understanding the vulnerability of tropical plants to climate change as it widely occurs from semiarid to humid tropical climates at different elevations, and many species now face the risk of extinction in response to climate change and other factors. In this study, we examined the relationship between leaf functional traits and climatic variables and how intraspecific variation in these traits and variables correlates with the distribution breadth of Erythroxylum species. We also aimed to identify which specific traits influence their distribution across Brazil's diverse climates and elevations. We found a negative correlation between specific leaf area (SLA) and precipitation and temperature, indicating that individuals with lower SLA are more common at higher temperatures and precipitation. In contrast, we observed a positive correlation between leaf area (LA) and precipitation. We also found higher intraspecific variability in SLA and LA across wide-range compared to narrow-range species. LA was a good predictor in estimating the area of occupancy and extension of occupancy in Erythroxylum species. We suggest that Erythroxylum has adapted to hotter and wetter environments using relatively slow investment strategies, prioritizing long-term survival over rapid growth, also known as a resource-conservative strategy. Additionally, the capacity to exhibit a wide range of leaf thickness and size has enabled these plants to expand their distribution, allowing for a broader range of environmental conditions.