Higher taxa are sufficient to represent biodiversity patterns

The scarcity of knowledge about both biodiversity (Linnean shortfall) and the geographic distributions of species (Wallacean shortfall) makes it hard to conduct biomonitoring programs and studies that seek to explain biodiversity patterns. One way to overcome this difficulty consists in the utilization of data with a lower taxonomic resolution, an approach called taxonomic sufficiency or Higher Taxon Approach (HTA). The main aim of this study was to evaluate, through a systematic review and meta-analysis, whether the HTA is reliable. We also evaluated whether the strength of the HTA (i.e., the relationship between datasets at high and low taxonomic resolutions) depended on different factors such as taxonomic level (genus, family, order and class), ecosystem type (aquatic and terrestrial), biological group (e.g., invertebrates, vertebrates and plants), spatial extent and higher taxa to species richness ratio (phi). We found that the HTA was a reliable approach in revealing species richness and compositional patterns independently of biological groups and ecosystem types. As expected, the strength of the HTA in describing biodiversity patterns decreased as the taxonomic resolution decreased. The strength of the HTA increased with the spatial scale of the studies. The phi was the main predictor of the HTA. Therefore, the use of higher taxonomic level (e.g., genera) is a reliable approach to save time and resources in biomonitoring programs and differs in this regard from other approaches that have already been tested in other studies (e.g., biological surrogacy). While the high HTA efficacy do not replace refined species level information which is crucial for basic and applied ecological studies, we advocate the use of the HTA especially for biological groups with high phi and for biomonitoring programs targeting large spatial extents.