Intraspecific trait variation shows that functional diversity decreases in tropical forest natural edges compared to forest interiors

Functional traits are characteristics associated with the growth, reproduction, and survival of individuals. Studying them helps us understand how species traits drive ecosystem functioning. Thus, we evaluated the differences in traits and functional diversity between forest edges and interiors, and how the inclusion of intraspecific trait variation affects the assessment of functional diversity in these habitats. We sampled 10 representative forest patches, and, in each patch, we established five plots on the edge and five inside the forest, collecting leaf functional traits, allometric and wood density for all species. We assessed functional diversity using functional richness (FRic), divergence (FDiv), and dispersion (FDis). To assess the impact of incorporating intraspecific variation when comparing trait values and functional diversity indices, we established two scenarios: one that excludes intraspecific variation and another that includes it. We found that the edge and interior harbor individuals with distinct functional traits that alleviate the inherent stress of each habitat. The edge was also found to be more selective in terms of the range of functional traits, resulting in lower functional diversity. Our findings demonstrated that habitats play an important role in intraspecific trait variation (ITV) and that statistically significant differences between habitats, in relation to traits and functional diversity, were better observed with the inclusion of intraspecific variation. Our study highlights the potential of using natural forest patches to understand the edge effect, regardless of habitat loss. Additionally, we emphasize the importance of incorporating ITV into functional diversity studies, especially those on a smaller scale that incorporate quantitative variables, to better understand and predict ecological patterns.