PLOS BIOLOGY
on Migratory Species; CoL, Catalogue of Life; EoL, Encyclopedia of Life; GBIF, Global Biodiversity Information Facility; GSD, Global Species Database; ICSU, International Council for Science; IPBES, Intergovernmental Platform for Biodiversity and Ecosystem Services; ISC, International Science Council; IUBS, International Union of Biological Sciences; IUCN, International Union for Conservation of Nature; WoRMS, World Register of Marine Species.
possible, (vii) a global list must balance conflicting needs for currency and stability by having archived versions, (viii) contributors need appropriate recognition, (ix) list content should be traceable, and (x) a global listing process needs both to encompass global diversity and to accommodate local knowledge of that diversity. We conclude by outlining issues that must be resolved if such a system of taxonomic list governance and a unified list of accepted scientific names generated are to be universally adopted.
Introduction
Lists of species matter. Whether a species (or any other taxon) is included on a list may affect conservation (e.g., by affecting investment in threatened species), trade (e.g., through the Convention on International Trade in Endangered Species of Wild Fauna and Flora [CITES] or listing as an invasive pest), development (through national threatened species legislation), local livelihoods (through species-specific conservation programs, ecotourism, etc.), or evolutionary and ecological research (e.g., in diversification analyses and macroecological studies). In the face of an unfolding global extinction crisis, global lists of accepted species are foundational to managing biodiversity in an era of accelerating global change.
In view of the importance and wide usage of lists of accepted species, there has been a push to create a unified, authoritative, comprehensive, and global list that is accepted by both the scientific community and key users[1][2][3]. The current lack of such a list has 4 main negative consequences. First, it means that some of the world's named species are effectively invisible to those who lack the resources to access or navigate specialist taxonomic literature. Second, the lack of a unified list means that scientific contributions towards improving the quality of taxonomic and nomenclatural knowledge are scattered and can often be missed. Third, it forces other users, who may lack relevant taxonomic expertise, to choose between competing lists and taxonomic treatments of groups even though they rarely understand the rationale why competing lists exist and are confused by the differences between alternate taxonomic concepts and classifications. Fourth, users may follow regional or other species identification guides or lists without realising that they are outdated and should be checked against authoritative sources[4].
One of the difficulties of creating a unified global list of accepted species is that the circumscription of a taxon is not a fully objective decision. It includes a judgement as to whether a set of specimens or populations is best regarded as one or more than one species[5][6][7][8][9]. Different taxonomists may legitimately judge the limits of taxa differently even when using the same data, and there are many alternative sources of data and methods for delimiting taxa (e.g., using molecular or morphological phylogenetics, morphometrics, or ecological or physiological traits).
All lists of accepted species are founded on the efforts of taxonomists describing and classifying new taxa, revising existing taxa, and, often using new data and methods, relegating to history taxa that are shown to be poorly justified or defined. Taxonomic research often involves reviewing the merits of existing taxa[10], a process that includes reviews of larger taxonomic groupings such as genera, families, orders, classes, phyla, and kingdoms at global scales. At high taxonomic levels, for all but the least species-rich groups, it is usual for consolidated global lists to combine the work of multiple taxonomists.
Traditionally, consolidated species lists consisted of formal publications that were produced at irregular intervals and not updated for decades. Increasingly, they are actively curated online
PLOS Biology | https://doi.org/10.1371/journal.pbio.3000736 July 7, 2020
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