Optimization of the taxonomic resolution of an indicator taxon for cost-effective ecological monitoring: Perspectives from a heterogeneous tropical coastline

Abstract

An important requirement towards formulating appropriate management and conservation measures for biological diversity is to devise efficient and cost-effective monitoring protocols that yield coherent data. Environmental monitoring investigations have been typically based on species level responses of biodiversity to environmental disturbances. Considering that this exercise is cost-intensive and the species identification keys are unavailable for some geographical areas, efforts are now afoot to test the efficacy of supra-specific taxa in resolving distribution patterns of biota, analogous to that of species. This study was aimed at testing the efficacy of Taxonomic Sufficiency (TS), a data reduction technique, in deciphering spatio-temporal variations of macrobenthos in the tropical coastal waters of northwest India. The macrobenthic indicator taxon, Polychaeta, was analyzed at five transects that included two marine protected areas, during the three major seasons. The consistency of spatio-temporal trends of polychaete assemblages, derived from four taxonomic levels and subjected to five types of data transformation was scrutinized. Univariate indices indicated that coarser taxonomic levels except order, maintained the indicative responses spatio-temporally, similar to the species level. Spatial variability was appropriately indicated by all data matrices. Temporal variation was evident only with family data subjected to fourth root or log data transformations. The TS approach succeeded in this tropical ecoregion owing to the consistent and sizable proportion of monotypic polychaete taxon and uniformity in responses of the constituents of higher polychaete taxon. CCA results revealed that a similar set of environmental variables influenced the polychaete distribution at all the taxonomic levels; however, spatial variations detected at species level diminished with reduced taxonomic breadth. Results indicated that meaningful robust data for deriving coastal management initiatives can be achieved cost-effectively by the adoption of TS approach for the ecologically and economically important 2360 km long northwest Indian coastline.