Assessing the effectiveness of surrogates for species over time: Evidence from decadal monitoring of a Mediterranean transitional water ecosystem

Progress in 'taxonomic sufficiency' in aquatic biological investigations

The 'taxonomic sufficiency' (TS) approach has been applied to algae, protists, invertebrates, and vertebrates, generally by aggregating species-level abundance data to a higher taxonomic level, where genus-level data are often highly correlated with species-level data and are a valid proxy level. The TS approach offers the possibility of a comparison of data from different geographical areas and highlights the effects of contaminants. The TS approach is stable in the face of different researchers and in the comparison of long-term biological survey data. The effectiveness of the TS approach may increase with increasing environmental gradients or spatial area. The TS approach should be avoided when the spatial area is small and small differences in species-level data are considered important, so as not to cancel out the distribution patterns specific to the local environment of the biological taxa.

The efficiency of Taxonomic Sufficiency for identification of spatial patterns at different scales in transitional waters

Taxonomic Sufficiency (TS), the use of coarser taxonomic resolution in monitoring plans, has been receiving increasing attention in last years. A comprehensive dataset of macrobenthos from 18 Italian lagoons in a range of different latitude, typology, salinity and surface area, was analysed in order to test the efficiency of TS, in terms of correlation between patterns at level of species and patterns resulting from different levels of taxonomic aggregation. First, TS was applied on a range of univariate indices, providing complementary information on macrobenthic community, in order to test the efficiency, in a contest of different taxonomic composition, and different number of lower taxa belonging to the same higher taxon in each lagoon. Then, TS was applied on multivariate analyses, in order to test whether the efficiency changes between two different scales: local (comparison of sites nested within each lagoon) and regional (comparison among lagoons), and with different data transformation. The patterns resulting from univariate indices and multivariate analyses, at both local and regional scales, were retained till family level, despite the different levels of taxonomic composition and different number of lower taxa belonging to the same higher taxon of different lagoons. Nevertheless, the correlation values among matrices and the effect of data transformation differed between regional and local scales. Our results support the efficiency of TS until family level, but at the same time underline the need of scale- and region-specific baseline knowledge prior application of TS in lagoons.