Towards a global list of accepted species I. Why taxonomists sometimes disagree, and why this matters

Abstract

Taxonomy-the delimitation, naming, classification and documentation of species and other taxa-is an often-misunderstood discipline. Complex and at times contested, taxonomy occupies a sometimes discomforting intermediate position on a continuum from descriptive to hypothetico-deductive science. Two aspects of taxonomy that are striking to many observers and users are the degree to which taxonomists often disagree, and the degree of taxonomic revisionism (the replacement of one taxonomic classification with another, exemplified by the phrase 'taxonomists are always changing the names of things'). Disagreements between taxonomists do not usually indicate taxonomic confusion or chaos, but rather often represent valid disagreements over the best, most effective and most meaningful way to interpret, describe and classify one of the most complex systems that scientists seek to describe and characterise-the patterns of variation of life on Earth. One way to partially manage disagreements among taxonomists is to develop a mechanism to synthesise the flux of taxonomic activity into agreed, broadly accepted, authoritative and scientifically robust global lists of the world's species and other taxa. A sound understanding of some aspects of the nature of taxonomy is needed to appreciate the opportunities, complexities and limitations of the development and maintenance of such lists.This article is part of the Special Issue and Topical Collection Towards a global list of accepted species

Towards a global list of accepted species V. The devil is in the detail

“…But taxa are represented by many more individual organisms in nature than the type specimen(s). The full set of organisms regarded by a taxonomist as comprising a taxon depends on a variety of factors, ranging from alternative species concept definitions to purely subjective interpretations by different taxonomists (Thiele et al, 2021). The link between a particular scientific name and the taxon it is intended to represent is, at best, imprecise.…”

“…Inevitably, disputes in how some taxa should be represented on the global list will emerge. Such disputes are an inherent and not necessarily undesirable aspect of taxonomic practice (Thiele et al, 2021). Mechanisms for the arbitration of such disputes depend on which fundamental model is adopted for content creation and curation.…”

“…For example, whether or not a name is correctly published and available under the relevant Code of Nomenclature, or whether it has the correct Code-compliant spelling is, in most cases, a matter that can be determined objectively. By contrast, taxonomy is necessarily rife with opinion, much of which is legitimately subjective (Thiele et al, 2021). Most arbitration will involve selecting from among two or more alternative opinions about circumscription and classification.…”

“…This debate led to the formation of a Working Group on the governance of taxonomic lists, supported by the International Union of Biological Sciences (IUBS), and focused on developing a consensus view on the issues that initiated the debate (Garnett et al, 2020a(Garnett et al, , 2020b. Other papers in this Special Issue discuss the taxonomic context (Thiele et al, 2021), governance (Lien et al, 2021), case studies (Thomson et al, 2021), issues related to independence and stakeholder inclusion (Conix et al, 2021), and role of the Catalogue of Life (Hobern et al, 2021) for creating a global list of accepted species.…”

Towards a global list of accepted species II. Consequences of inadequate taxonomic list governance

“…A key problem is that taxonomists necessarily divide the complex patterns of variation into simplified, discrete, and named units (taxa), which governments and the community then use to manage and understand biodiversity, one of the most complex systems we know. This has three consequences (Thiele et al, 2021): firstly, some diversity necessarily gets lost in the system; secondly, there are sometimes several to many possible taxonomies, none of which is entirely correct; and thirdly, many users are unaware of these nuances. A potential solution is to subdivide the taxa even further into evolutionarily significant units (Moritz, 1994)populations or groups of populations definable by measurably different allele frequencies-and use these as the basis for conservation etc.…”