Acknowledging more biodiversity without more species

Abstract

Delimiting and naming biodiversity is a vital step toward wildlife conservation and research. However, species delimitation must be consistent across biota so that the limited resources available for nature protection can be spent effectively and objectively. To date, newly discovered lineages typically are either left undescribed and thus remain unprotected or are being erroneously proposed as new species despite mixed evidence for completed speciation, in turn contributing to the emerging problem of taxonomic inflation. Inspired by recent conceptual and methodological progress, we propose a standardized workflow for species delimitation that combines phylogenetic and hybrid zone analyses of genomic datasets (“genomic taxonomy”), in which phylogeographic lineages that do not freely admix are ranked as species, while those that have remained fully genetically compatible are ranked as subspecies. In both cases, we encourage their formal taxonomic naming, diagnosis, and description to promote social awareness toward biodiversity. The use of loci throughout the genome overcomes the unreliability of widely used barcoding genes when phylogeographic patterns are complex, while the evaluation of divergence and reproductive isolation unifies the long-opposed concepts of lineage species and biological species. We suggest that a shift in conservation assessments from a single level (species) toward a two-level hierarchy (species and subspecies) will lead to a more balanced perception of biodiversity in which both intraspecific and interspecific diversity are valued and more adequately protected.