Predicting functional indices in Asteroidea and Echinoidea assemblages of the Mexican Pacific from measures of structural and taxonomic diversity

Useful indicators of anthropogenic impacts on the function and structure of marine communities are needed. Traditionally, changes in marine biodiversity have been evaluated using ecological indices such as species richness and evenness. However, these indices overlook potential ecological differences. Indeed, these differences are more accurately reflected using functional diversity, which is likely more representative of key ecosystem processes, including resilience and resistance. However, calculating functional diversity is complex due to a lack of available information on the natural history of many marine species. To address this problem, we used the information on Echinoidea and Asteroidea in the Mexican Pacific to examine the relationship between the Rao's quadratic entropy index (FD_Q), a commonly used functional diversity index, and indicators of community and taxonomic structure: richness (S), abundance (N), Shannon-Wiener diversity (H′), Pielou evenness (J'), taxonomic distinctness (Δ*), and average taxonomic distinctness (Δ+). We generated a set of equations to determine if these commonly used indices could be used as proximal indicators of FD_Q. We obtained good correlations between functional diversity and structural diversity, although the significant correlations were between FD_Q and J' (r = 0.975) and H′ (r = 0.965). These two ecological indices are very good indirect indicators of the local functional diversity of Echinoidea and Asteroidea in the Mexican Pacific and can be used as simple, inexpensive, and powerful tools to assess the complex effects of human-induced or natural perturbations in rocky reef ecosystems.