Correct procedure for citing taxonomic works in non-taxonomic scientific papers

Many studies require or rely on identification of taxa as part of the methodology (Bortolus 2008; Franz and Peet 2009; Meier 2017; Packer et al. 2018). Such studies cover a wide range of fields that include many taxa, from assessing biodiversity of local and alien species, estimating the impact of global change on biodiversity loss, and ecological studies, whereas others might consider single model organisms that frequently come from longstanding laboratory cultures or single species used in behavioural or physiological studies (e.g. Bortolus 2008; Meier 2017; Packer et al. 2018). However, very often the names applied to species reflect regional, temporal and individual bias that is reflected in the source of the names (Franz and Peet 2009). Such bias is usually not immediately evident, because taxonomic research is seldom cited by the broader scientific community. For example, Bortolus (2008) found that 62.5% of the ecological papers that he examined did not provide any information as to how the authors identified the taxa named in their studies. Similarly, Packer et al. (2018) found that 29% of the entomological publications they examined did not cite identification methods, such as identification keys and monographs. Such poor citation of taxonomic works has had several consequences. The first relates to citation metrics (e.g. Krell 2002; Wägele et al. 2011; Steiner et al. 2015) and will not be considered further here. However, more serious consequences relate to the violation of the scientific method; not providing identification methodology essentially renders the study irreproducible (Packer et al. 2018), because species identification cannot be validated. To overcome this, the Latin binomial names should always be accompanied by the authority when first mentioned in an article, and the literature used for identification, be it identification keys, monographs or taxonomic revisions should be cited (Meier 2017). The original description might be cited (e.g. Wägele et al. 2011), but only if it is informative and aids identification (Meier 2017). Consider the hypothetical Species α Author A, 1880 with a distribution range along the coast of South Africa. Two simple scenarios illustrate the importance of citing taxonomic revisions in addition to (or instead of) original species descriptions, when reporting a species in any scientific article (more complicated, but equally realistic scenarios exist, Franz and Peet (2009)). In Scenario 1, Author B revises Species α in 2000 and finds that the species, as originally described, actually comprises two species, Species α Author A, 1880 and Species β Author B, 2000. Consequently, if only Author A is acknowledged as the authority of Species α by Author C in 2010, it disregards the fact that the original definition of Species α refers to two separate species. This implies that Author C identified Species α as defined only by Author A, and therefore also includes Species β. In Scenario 2, Author D records Species α in Australia in 1910. Author D provides a description that highlights a consistent, albeit minor, difference from Species α, as described from South Africa, which is ascribed to intraspecific variation. Subsequent to this, many other authors record Species α in Australia, but without acknowledging the publications of either Author A or D as the source of identification. Consequently, when Author E determines, in 2012, that Species α sensu Author D is in fact NOT equivalent to Species α sensu Author A or Author B, and describes it as Species γ Author E, 2012, it will be almost impossible to determine, retrospectively, whether records of Species α in Australia actually refer to Species α, Species β or Species γ, without examining deposited material (if such material exists, see 3 below). Acknowledging the method of identification better enables later researchers to validate these identifications. Some might argue that this is not necessary if the species is “well-established”, a model organism or sourced from a laboratory culture (Wägele et al. 2011; Packer et al. 2018). However, some species, such as the malaria vector Anopheles gambiae (Giles 1902), are members of species complexes that can only be distinguished using molecular data (Coetzee et al. 2013), whereas others, such as the widely used ecotoxicology model species Eisenia fetida (Savigny 1826), had been misidentified in some laboratory cultures in South Africa (Voua Otomo et al. 2013).