Division is ataxonomic rank inbiological classification that is used differently in zoology and in botany.
Inbotany andmycology,division is the traditional name for a rank now considered equivalent tophylum. The use of either term is allowed under theInternational Code of Botanical Nomenclature.[1]
The main Divisions ofland plants are theMarchantiophyta (liverworts),Anthocerotophyta (hornworts),Bryophyta (mosses),Filicophyta (ferns),Sphenophyta (horsetails),Cycadophyta (cycads),Ginkgophyta (ginkgo)s,Pinophyta (conifers),Gnetophyta (gnetophytes), and theMagnoliophyta (Angiosperms, flowering plants). The Magnoliophyta now dominate terrestrialecosystems, comprising 80% ofvascular plant species.[2]
Inzoology, the termdivision is applied to an optional rank subordinate to theinfraclass and superordinate to thelegion andcohort. A widely used classification (e.g. Carroll 1988[3]) recognisesteleost fishes as a Division Teleostei within ClassActinopterygii (the ray-finned fishes). Less commonly (as in Milner 1988[4]), livingtetrapods are ranked as DivisionsAmphibia andAmniota within theclade of vertebrates with fleshy limbs (Sarcopterygii).
In 1978, a group of botanists includingHarold Charles Bold,Arthur Cronquist andLynn Margulis proposed replacing the term "division" with "phylum" in botanical nomenclature, arguing that maintaining different terms for the same taxonomic rank across biological kingdoms created unnecessary confusion. This was particularly problematic for unicellulareukaryotes, whereheterotrophic organisms were classified under zoological nomenclature (using "phylum") whileautotrophic organisms fell under botanical nomenclature (using "division"). They proposed updating the International Code of Botanical Nomenclature to use "phylum" and "subphylum" throughout, while maintaining that names originally published as divisions would be treated as if they had been published as phyla.[5]
The use ofmolecular methods, particularly16S ribosomal RNA analysis, helped establish major bacterial divisions in the 1980s. In 1985,Carl Woese and colleagues identified ten major groups of eubacteria througholigonucleotide signature analysis, noting that these groupings were "appropriately termed eubacterial Phyla or Divisions." This work provided early molecular evidence for the equivalence of bacterial divisions with phyla and helped establish aphylogenetic basis for high-level bacterial classification.[6]
In 2020, theInternational Committee on Taxonomy of Viruses (ICTV) formalised a 15-rank hierarchical classification system, ranging from the highest rank "realm" (rather thandomain) down through the lower ranks, notably using "phylum" rather than "division". Under this system, the first viral realm established wasRiboviria, encompassing allRNA viruses that encode anRNA-directed RNA polymerase.[7]
In 2021, theInternational Code of Nomenclature of Prokaryotes (ICNP) formally included the rank of phylum for the first time, adopting thesuffix "-ota" for phylum names. This led to the publication of names for 46 prokaryotic phyla withcultured representatives, replacing some established names withneologisms – for example, "Proteobacteria" became "Pseudomonadota" and "Firmicutes" became "Bacillota".[8]
