A system for designating taxonomic certainty in mammals and other taxa

Taxonomy and systematics are fundamental to the success of conservation actions. A robust and accurate classification of living organisms is vital for understanding biodiversity, using limited resources wisely, prioritising conservation action, and for legal protection and regulation of trade. However, all too often current taxonomies are not based on the latest science and reflect traditional classifications developed in the nineteenth and early twentieth centuries. Understanding of the numbers of species has also changed dramatically with the widespread, but patchy, adoption of the phylogenetic species concept for many vertebrate groups. This has led to a situation where taxonomies are constantly changing in the light of new, mostly genetic, studies. Therefore, the need for a global list of accepted taxa has been recognised by the conservation community as a way of overcoming the uncertainties caused by this dynamic situation. Here, we propose a traffic-light system that may assist the efforts towards the global list of accepted taxa. The traffic-light system indicates the level of certainty in support of the recognition of each taxon, which mainly comprises morphological, genetic and biogeographical lines of evidence. So far, this approach has been adopted by the IUCN Cat Specialist Group to revise felid taxonomy, and the resulting classification has been adopted by the IUCN Red List of Threatened Species and CITES. We discuss the applicability of the approach to other species groups.