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  non-scriptus was moved from the genus Hyacinthus to the genus Hyacinthoides, its name had to be changed to Hyacinthoides non-scripta. Likewise moving a variety from one species to another causes a name change. Names below the rank of genus include an inherent classification: a species named Hyacinthoides non-scripta belongs to the genus Hyacinthoides, but a genus named Hyacinthoides can belong to any family, e.g. to Aspara­gaceae, Hyacinthaceae, or Liliaceae. This does not mean that nomenclature mandates a particular classification. Taxonomy and nomenclature are quite different things. The taxonomist uses evidence from research to arrive at a particular classification and then uses the rules of nomenclature to apply the correct name to the taxa recognized.

RULES FOR BIOLOGICAL NOMENCLATURE

The purpose of having rules for biological nomenclature is to provide a stable method of naming organisms, avoiding and rejecting the use of names that may cause error, ambiguity, or confusion. The current rules for the scientific nomenclature of plants, as well as for fungi and algae, are contained in the International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code; Turland & al., 2018). Unless otherwise qualified, “Code” in this guide refers to the Shenzhen Code. The title was formally changed at the XVIII International Botanical Congress in Melbourne in 2011, whereas previously it was the International Code of Botanical Nomenclature, or ICBN. The acronym “ICN”, standing for “International Code of Nomenclature”, is best avoided because it could refer to any one of five biological codes, of which more below. Note that the current edition of the Code supersedes all previous editions. Using a previous edition is therefore very risky because you could follow rules that have been changed or fail to follow new rules.

The Code governs the nomenclature of all organisms traditionally treated as algae, fungi, or plants, whether fossil or non-fossil, including blue-green algae (Cyanobacteria, chytrids, oomycetes, slime moulds, and photosynthetic protists with their taxonomically related non-photosynthetic groups (but excluding Microsporidia). The nomenclature of hybrids is also covered, but that of cultivated plants is dealt with separately by the International Code of Nomenclature for Cultivated Plants (ICNCP or Cultivated Plant Code), prepared under the authority of the International Commission for the Nomenclature of Cultivated Plants and now in its 9th edition (Brickell & al., 2016). Three additional codes govern the nomenclature of animals, prokaryotes (bacteria etc.), and viruses. They are, respectively, the International Code of Zoological Nomenclature (ICZN or Zoological Code; International Commission on Zoological Nomenclature, 1999); the International Code of Nomenclature of Prokaryotes (Parker & al., 2019); and the International Code of Virus Classification and Nomenclature (International Committee on Taxonomy of Viruses, 2018).

Unlike most modern sciences, e.g. ecology, the nomenclature of algae, fungi, and plants still makes full use of literature dating back to 1753, and in this respect it seems more like history than science. This strong historical element persists because the rules of the Code, except where expressly limited, are retroactive to 1753. Retroactive means that they 12