LAUSR

Abstract Functional redundancy is considered a major component of the insurance mechanism, which theoretically maintains ecosystem stability by preventing the loss of ecosystem functions with species loss. Over the past decades, examination of functional trait patterns to elucidate processes of community stability and ecosystem functioning have stimulated considerable amount of research in ecology. As a result, a multitude of indices have been developed, describing community functional structure with various levels of overlap in their methodology. Here, we review the set of indices that have been suggested to measure the level of redundancy in traits among species in ecological communities. We first evaluate the correlations among redundancy indices and classical indices of community taxonomic and functional structure (species richness, Simpson diversity, functional richness, evenness and divergence). Second, we estimate the predictive power of these indices in terms of community vulnerability to species loss. Finally, we assess the sensitivity of the results to scenarios with different species loss orders. We simulated communities with different levels of taxonomic and functional structure (richness, evenness and divergence). Then, we simulated four scenarios of species loss order (abundance, functional uniqueness, environmental sensibility and random). The vulnerability of communities was estimated by the changes in community structural parameters (functional richness, functional divergence and biomass) as species were progressively removed from the initial communities. Our results showed that four out of the five redundancy indices tested were strongly correlated (Pearson R > ∣0.6∣) with at least one of the classical indices of community structure. Those correlations partly explained why the redundancy indices did not outperform classical indices in predicting community vulnerability to species loss. The fifth redundancy index (FredD) was the least correlated with classical indices of community structure (Pearson R