Wikipedia:WikiProject Protista/Article guidelines

When choosing a name for the article on a taxon, the informal (vernacular) name that is most commonly used is preferred. This follows the general guidelines for article titles of Wikipedia. In absence of a popular informal name, the most common formal (scientific) name is used. If the taxon is monotypic, the formal name with the lowest rank is preferred; this is consistent with the naming conventions for monotypic flora and fauna. If there are multiple formal names (synonyms) of relatively similar popularity for the same rank, the least controversial formal name is used (i.e., with highest taxonomic priority, such as by date of publication or by date of first accurate circumscription).

Example: Apusomonad (vernacular) > Apusomonadidae (family) > Apusomonadida (monotypic order).

The Tree of Life project maintains a unified system of classification through the automated taxobox system. However, whereas animal, fungal, plant and prokaryotic taxonomists work under relatively coherent classification systems, there are two mutually exclusive approaches to protist classification.

• The traditional or ranked approach maintains a hierarchy that does not necessarily follow natural evolutionary groups (clades), and instead employs artificial (paraphyletic or polyphyletic) groups to sort protists. This system, developed primarily by evolutionary biologist Thomas Cavalier-Smith (1942–2021),^[1] proposes five kingdoms of eukaryotes: Plantae, Animalia, Fungi, "Protozoa" and "Chromista"^[2] (both non-clades). It provides a detailed categorization for most eukaryotes through ranks equivalent to those used for other organisms (kingdoms, phyla, classes, orders...), but many of the taxa are not clades.^[3][4] This is contrary to the classification of other organisms, as evolutionary relatedness is the basis of categorizing animals, fungi, plants, and even prokaryotes. In addition, this scheme has been unstable throughout its lifespan, with many scientific names being repurposed for different circumscriptions after hypotheses were rejected (e.g., Archezoa,^[5] Opalozoa, Corticata)^[6] and others changing spelling altogether as a result of being moved into a different rank.^[7] Consequently, it has very limited use in the larger scientific community.^[8]

• The cladistic or phylogenetic approach embraces the abandonment of traditional concepts (e.g., protozoa, algae) brought by molecular phylogenetics, and prioritizes a hierarchy based on clades. It was initiated by authors such as David J. Patterson^[5] and developed collectively by the International Society of Protistologists (ISOP) through periodical publications that represent the consensus of the scientific community.^[7][9][10] This system uses clade names without formal rank designations, to avoid issues caused by ranks (such as name changes); as such, it remains stable across time. Instead of artificially separated kingdoms, this system recognizes monophyletic supergroups that contain both the "higher" eukaryotes (animals, fungi, plants) and the protists from which they evolved.^[11] Still, some artificial taxa are maintained in this system because there is no cladistic alternative yet (e.g., "Colponemida", "Monothalamea").^[10]

This WikiProject and its parent Tree of Life project prioritize the cladistic approach, as it represents the scientific consensus and is compatible with the automated taxobox system. For consistency with the ranked classifications of other organisms, ranks are still used whenever possible, as long as they are not in conflict with the cladistic scheme.

Plants, animals and fungi are well-defined kingdoms of life whose classifications are directly regulated by separate codes of nomenclature, namely the International Code of Zoological Nomenclature (ICZN) and the International Code of Nomenclature for algae, fungi, and plants (ICNafp). Protists represent very different organisms that cannot be easily assigned to either code. Historically, protists known as "protozoa" (heterotrophs) were interpreted as more animal-like, and thus are mostly regulated by the ICZN. Similarly, those known as "algae" (phototrophs, with chloroplasts) were treated as plant-like, and are mainly ascribed to the ICNafp. However, the separation between alga and protozoon is artificial: some protozoa are also studied as "colorless algae", and some descendants of algae are studied as protozoa. The issue extends beyond the presence or absence of chloroplasts: fungus-like protozoa were historically interpreted as fungi, and thus were also considered under the ICNafp. These are known as ambiregnal protists, for which both ICZN and ICNafp formal names exist, each with different suffixes (class: -ea or -phyceae/-mycetes, order: -ida or -ales, family: -idae or -aceae).^[12]

Only one of these names can be displayed in titles and taxobox templates. For the sake of consistency, the following table determines the preferred nomenclatural code used for each group of ambiregnal protists within this WikiProject.