What is Taxonomy?
Biological taxonomy is the scientific discipline of classifying and naming the organisms that compose present and past biodiversity as formal units or entities, the taxa. Its work consists of three steps: (1) the recognition, delimitation, and differential definition (or diagnosis) of the basic discrete units resulting from the evolutionary process (the species), (2) the establishment of a hierarchical classification of these taxa reflecting their evolutionary relationships, and (3) their naming according to nomenclatural rules relying on museum-kept voucher specimens (so-called ‘types’). The objects of taxonomy are not individuals but these supra-individual entities. It uses integrative operational and repeatable analyses relying on explicit taxonomic paradigms, concepts, and criteria, and on the production, testing, and refutation of data-based hypotheses concerning species and their phylogenetic and other relationships (supraspecific classification). On the other hand, biological nomenclature is a precise system, based on rules that ensure any recognised taxon bears a single scientific name – a label allowing unambiguous and universal communication about these taxa, but having no proper content or meaning. Taxonomists recognise and name taxa, i.e., scientific concepts based on data obtained from specimens—not individuals, photographs, molecular sequences, or ‘kinds’ of organisms traditionally recognised by local or regional human cultures.
This discipline is foundational for all comparative and evolutionary biology, as well as any other scientific and non-scientific domains, where there exists a need to designate organisms unambiguously and universally. It gives meaning to our world, allowing us to communicate clearly and efficiently about living and fossil organisms. It links data from various sources into a synthetic framework from which we can make powerful predictions and devise effective strategies, from biodiversity management or next-generation medicines to the origins of diversity or its responses to climate change.
Are there any misconceptions regarding taxonomy?
Taxonomy is an undervalued biological discipline. This is mainly due to several misconceptions that are widespread in the scientific community, including among evolutionary biologists and ecologists. Among these are the ideas that taxonomy (1) is outdated and frozen, relying only on morphology and typological, non-evolutionary concepts, (2) uses unnecessarily complex nomenclatural rules independent of evolutionary theory, and (3) is not a genuine science but an ancillary ‘service’ technique, merely providing names and identification of specimens used in other biological studies, such as molecular phylogeny, ecology, or conservation biology.
Like many other sciences, some of which are highly esteemed, taxonomy is indeed a descriptive discipline, but a lively one that permanently formulates and tests explicit hypotheses. It requires an integrative approach, synthesising information derived from many fields of inquiry. In this sense it is perhaps the most integrative of all biological disciplines. It constantly revises and re-evaluates its hypotheses about the content and relationships of taxa. The complexity of nomenclatural rules is inherent in the difficult task of providing stable references for permanently evolving concepts (the taxa and their hypothesised relationships) and dealing with a dynamic and complex reality (organic evolution). So-called ‘type’ specimens are just ‘name-bearers’, i.e., objective references for the allocation of names to taxa, and their use does not imply a ‘typological’ approach to classification based on a Platonist concept of ‘essence of the taxa’. Such a criticism is a red herring and based on an ignorance of the science. Finally, as for the identification of specimens, which some believe to be the only work of taxonomists, this is merely a practical, albeit critically useful, outcome of taxonomy, but not the core of the discipline, which instead consists of phylogenetic and biological research, taxonomic and nomenclatural revisions. The introduction of new names, as well as the synonymisation of others, are needed as the result of such research but are not the sole aim of taxonomy.
Biodiversity crisis vs taxonomic crisis… and what now?
In recent decades, this discipline has suffered various challenges, which have been collectively called a ‘taxonomic crisis’. The term ‘taxonomic impediment’ has been used to qualify one of the major dimensions of this crisis, which challenges our ability to address the current human-induced biodiversity crisis. However, from the start, this formula has been equivocal, designating both the insufficiency and inadequacy of the resources put to the service of taxonomy (the taxonomic impediment sensu stricto) and its main consequence, the wide discrepancy between the reality of species biodiversity and our knowledge of it (the ‘taxonomic gap’). As a matter of fact, the total number of species on our planet is unknown, but consensus exists that we are far from having inventoried half, and most likely one tenth, of the species still present on earth today. Meanwhile, the biodiversity crisis has developed, so that it is now doubtless that a large proportion of these species will become extinct in the current and coming decades due to anthropogenic actions, thus depriving us forever of the priceless information each embodies. This should put taxonomic urgency at the top of the priority list among biological sciences in our ‘century of extinctions’.
Thus far, the international scientific community has put emphasis mainly on the discipline of conservation biology. However, it is quite clear that most of the extinctions result from causes depending on the basic economic and social functioning of our society, which are beyond the reach of conservation biology or any other scientific discipline, and that, despite all the field’s efforts, its actions will not significantly reduce the rate of extinctions. The principal duty of scientists should be to reduce, as much as possible, the taxonomic gap and to store specimens and tissues that will testify to our planet’s vanishing biodiversity. Once safely stored, research on this material will remain possible even when species have become extinct in the interim.
References
Engel, M, et al. (2021). The taxonomic impediment: a shortage of taxonomists, not the lack of technical approaches, Zoological Journal of the Linnean Society, 193, 381–387
Wheeler Q. 2014. Are reports of the death of taxonomy an exaggeration? New Phytologist 201: 370‒371.
Wheeler QD, Raven PH, Wilson EO. 2004. Taxonomy: impediment or expedient? Science (New York, N.Y.) 303: 285.
Dubois A. 2010. Zoological nomenclature in the century of extinctions: priority vs. usage. Organisms, Diversity & Evolution 10: 259–274.
Dubois A. 2003. The relationships between taxonomy and conservation biology in the century of extinctions. Comptes Rendus Biologies 326 Suppl 1: S9–S21.
de Carvalho MR, et al. 2014. Does counting species count as taxonomy? On misrepresenting systematics, yet again. Cladistics 30: 322–329.
Figure 1: Gimo M. Daniel – a taxonomist from the National Museum Bloemfontein working on scarab beetles taxonomic revision at the Ditsong Museum of Natural History, Pretoria, South Africa (Photo by WP Strunmpher).
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