Taxonomic surrogacy, numerical resolution and responses of stream macroinvertebrate communities to ecological gradients: Are the inferences transferable among regions?

It is typically at the species level where the responses of organisms to natural environmental gradients are the most clearly visible. However, due to the fact that many organismal groups are poorly resolved at the species level in various geographical regions, many studies have to still rely on supra-specific taxa when analyzing community–environment relationships. This study examined the community–environment and richness–environment relationships of stream macroinvertebrates at three taxonomic levels (i.e., species, genus, family) in three high-latitude drainage basins. Despite the fact that species-to-genus and species-to-family ratios were low and of similar magnitude in all drainage basins, each region showed different rankings in terms of the species-, genus- and family-level data being best explained by environmental variables. Furthermore, within each region the three taxonomic levels did not respond similarly to the underlying environmental gradients, which was evident with taxonomic richness and taxonomic composition based on both quantitative and qualitative data (adjusted R2 of models varied from 0 to 0.604 for taxonomic richness and from 0.068 to 0.307 for taxonomic composition). The present findings thus do not support the views: (i) taxonomic surrogacy in stream macroinvertebrate communities is transferable among regions and (ii) that higher taxon taxonomic surrogates can be used without restraints to infer species-level community–environment and richness–environment relationships in studies of community ecology, conservation biology and environmental assessment.