Environmental filtering limits functional diversity during succession in a seasonally wet tropical secondary forest

Aims: Successional shifts in biodiversity are key drivers of the recovery of ecosystem functioning following disturbances. Identifying mechanisms that enhance or limit the ecological processes that drive these successional patterns can strengthen efforts to manage biodiversity-dependent ecosystem functions across human-dominated landscapes. Here, we examine successional patterns of multiple aspects of functional diversity in a seasonally wet tropical secondary forest and changes in the strength of environmental filtering during secondary succession. Location: Central Panama. Methods: We calculate functional richness (FRic) and dispersion (FDis) across a secondary forest chronosequence (n = 51 0.1-ha plots) using nine functional traits related to resource acquisition and conservation. Functional diversity indices are calculated using all traits and each trait individually. Using a null model approach, we test the effects of environmental filtering during secondary succession. Results: FRic and FDis exhibit saturating relationships with time since abandonment, reaching their maxima after 7 and 10 years, respectively. Overall, we find evidence that environmental filtering reduces FDis to a greater extent than FRic and that the strength of environmental filtering on both FDis and FRic increases during succession. The impacts of environmental filtering on functional diversity of individual traits are consistent; the mean standardized effect sizes (SES) of FRic and FDis of at least six of the nine studied traits are lower than expected. Notably, environmental filtering on FRic and FDis of particular traits associated with light and nutrient acquisition increases significantly along the secondary forest chronosequence, suggesting that functional convergence of multiple resource acquisition strategies strengthens in parallel. Conclusions: We find that successional shifts in environmental conditions limit trait variation in seasonally wet tropical secondary forests. Our results suggest that the increasing strength of environmental filtering shifts abundance of trait combinations towards a subset of functionally convergent species that compete for light and nutrients in similar ways.