Taxonomic distinctness in Mediterranean marine nematodes and its relevance for environmental impact assessment

Taxonomic distinctness has been applied successfully for the exploration of biodiversity patterns, yet its relevance in environmental impact assessment is far from being unquestioned. In this study, we assessed the potential of taxonomic distinctness to discern perturbed and unperturbed sites by analysing Mediterranean nematode assemblages. Geographic and habitat-related effects on the performance of the index were also explored. Above all, our findings do not corroborate the conjecture that taxonomic distinctness could be largely unaffected by natural variability, habitat features, and biogeographic context, casting doubts on potential generalization concerning its application as an indicator of environmental stress. Taxonomic distinctness represents an excellent metric to identifying taxonomic properties of ecological systems but, as for other ecological indices, it should be viewed as a complementary tool in environmental impact assessment, due to its sensitiveness to specific environmental features of systems being investigated.

► The performance of Δ+ using Mediterranean marine nematodes was investigated. ► The index did not clearly distinguish perturbed and unperturbed sites. ► The performance of the index was influenced by habitat features. ► The spatial scale of the taxonomic list affected randomization tests on Δ+. ► Δ+ Did not seem to be related to the trophic structure of assemblages.