biological taxonomy In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given ...

, a combinatio nova (abbreviated comb. nov. or n. comb.) refers to the formal renaming of an organism's

scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

when it is transferred to a different

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

, reclassified within a different

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, or its

taxonomic rank In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of or ...

is altered. Unlike the naming of a new species (), a ''combinatio nova'' does not describe a previously unknown organism but reorganizes an existing name to reflect updated understanding of its relationships or classification. For example, when a species is moved to a new genus, its

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

is retained and combined with the new genus name, forming the new combination. This process ensures consistency and accuracy in naming while adhering to the rules established by

nomenclature codes Nomenclature codes or codes of nomenclature are the various rulebooks that govern the naming of living organisms. Standardizing the scientific names of biological organisms allows researchers to discuss findings (including the discovery of new s ...

. The concept of ''combinatio nova'' plays a vital role in maintaining the stability and traceability of scientific names as taxonomic classifications evolve. Creating a valid ''combinatio nova'' requires proper citation of the original name, known as the

basionym In the scientific name of organisms, basionym or basyonym means the original name on which a new name is based; the author citation of the new name should include the authors of the basionym in parentheses. The term "basionym" is used in both botan ...

, and compliance with strict publication standards. These rules differ between taxonomic groups, such as animals, plants and fungi, and bacteria, and are integral to preventing ambiguities in name usage. Superseded names, resulting from these changes, preserve the historical record of taxonomy and facilitate the integration of updated names into

biological database Biological databases are libraries of biological sciences, collected from scientific experiments, published literature, high-throughput experiment technology, and computational analysis. They contain information from research areas including geno ...

s. This systematic approach supports the self-correcting nature of taxonomy, where scientific names are continually revised to reflect new discoveries and evidence.

Overview

''Combinatio nova'' (abbreviated as ''comb. nov.'' or ''n. comb.'') is a

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

term used when creating a new scientific name based on a previously published legitimate name. The term literally means "new combination" in

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

and is essential in

biological nomenclature Nomenclature codes or codes of nomenclature are the various rulebooks that govern the naming of living organisms. Standardizing the Binomial nomenclature, scientific names of biological organisms allows researchers to discuss findings (including ...

when taxonomists need to transfer a species to a different

based on new research indicating different relationships, change the

rank A rank is a position in a hierarchy. It can be formally recognized—for example, cardinal, chief executive officer, general, professor—or unofficial. People Formal ranks * Academic rank * Corporate title * Diplomatic rank * Hierarchy ...

of a

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

, or move an

infraspecific taxon In botany, an infraspecific name is the scientific name for any taxon below the rank of species, i.e. an infraspecific taxon or infraspecies. The scientific names of botanical taxa are regulated by the ''International Code of Nomenclature for al ...

to a different species. A ''combinatio nova'' consists of two key elements: the new name being proposed and its

(the original name on which the new combination is based). The basionym provides the final

epithet An epithet (, ), also a byname, is a descriptive term (word or phrase) commonly accompanying or occurring in place of the name of a real or fictitious person, place, or thing. It is usually literally descriptive, as in Alfred the Great, Suleima ...

, name, or

stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...

of the new combination. For example, when transferring a species to a new genus, the specific epithet from the basionym is retained and combined with the new genus name. The new name supersedes the older one, which is then classified as a "superseded combination". Superseded combinations specifically denote cases where a species' name changes due to its transfer to a different genus or reclassification within the same hierarchical rank. This is distinct from

synonyms A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

preoccupied name In biology, a homonym is a name for a taxon that is identical in spelling to another such name, that belongs to a different taxon. The rule in the International Code of Zoological Nomenclature is that the first such name to be published is the s ...

s, which arise from different taxonomic circumstances. This taxonomic procedure differs from describing a new species (''

species nova In biological taxonomy, a ' (plural: '; abbreviation: ' plural abbreviation: ') is a new species. The phrase is Latin, and is used after a binomial name that is being published for the first time. The equivalent for a new genus name is genus novu ...

'') or creating a replacement name (''

nomen novum In biological nomenclature, a ''nomen novum'' (Latin for "new name"), replacement name (or new replacement name, new substitute name, substitute name) is a replacement scientific name that is created when technical, nomenclatural reasons have mad ...

''). Unlike a new

species description A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it diff ...

, a new combination does not require a new diagnostic description but must include a clear reference to its basionym. The validity of a new combination depends on proper citation of the basionym and adherence to the relevant nomenclatural codes. Recent analyses of taxonomic practices in

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

s have highlighted gaps in reporting for new combinations. To enhance clarity,

best practice A best practice is a method or technique that has been generally accepted as superior to alternatives because it tends to produce superior results. Best practices are used to achieve quality as an alternative to mandatory standards. Best practice ...

s include explicitly stating whether the

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

material has been examined and including detailed ecological and distributional data in the publication. These steps ensure that new combinations remain well-grounded in taxonomic evidence.

Nomenclatural stability and longevity

The stability of taxonomic names plays a critical role in ensuring effective communication and the reliability of

s. However, names often undergo revision due to improved understanding of relationships among taxa.

Superseded combination In taxonomy, a superseded combination is a notice of change to the binomial nomenclature of the accepted name of a species. This happens when a species is moved to a new genus after the initial species description. The original name is called a ...

s are one of the most common outcomes of these revisions, as species are reassigned to different genera or reclassified based on new evidence. Studies show that superseded combinations account for two-thirds to three-quarters of all unaccepted species names in some taxonomic groups, such as

helminth Parasitic worms, also known as helminths, are a polyphyletic group of large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other par ...

s. The longevity of superseded combinations varies widely. On average, unaccepted species names persist in scientific use for about 29 years before being replaced, but this can range from just a few years to over a century. Older names proposed before the mid-20th century tend to have greater longevity, often remaining in use for decades before their invalidation. In contrast, names proposed more recently are revised or replaced more quickly, reflecting advances in

molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

methods and taxonomic practices. This pattern highlights the self-correcting nature of taxonomy, where names are systematically revised to align with the latest scientific understanding. Superseded combinations, while no longer valid, are an important part of this process, preserving the historical record of taxonomic decisions and facilitating the traceability of name changes. Many nomenclatural challenges can lead to uncertainty or a proliferation of invalid species names. Amid these difficulties, the concept of ''combinatio nova'' serves as a vital tool for preserving clarity. By ensuring that taxonomic revisions—such as transferring a species to a different genus—are formalized under established rules, ''combinatio nova'' prevents ambiguities and maintains a consistent historical record of name changes. This structured process allows researchers to trace the lineage of scientific names, understand their taxonomic context, and avoid confusion caused by informal or unsystematic name changes. Over time, the self-correcting nature of taxonomy, supported by ''combinatio nova'', helps align nomenclature with evolving scientific understanding.

Requirements for valid publication

The requirements for validly publishing a new combination have evolved significantly over time. Before 1 January 1953, a new combination could be established simply by adopting a previously published name or epithet for the same taxon, even without explicit reference to the basionym. Stricter standards were introduced after this date, requiring authors to clearly indicate the basionym and provide a complete, direct reference to its original publication, including the author, place of publication, page or plate reference, and date. These changes ensured clear links between new combinations and their original names, preventing ambiguities. The importance of explicitly indicating new combinations was further emphasized in 1968, when the

International Code of Nomenclature of Bacteria The International Code of Nomenclature of Prokaryotes (ICNP) or Prokaryotic Code, formerly the International Code of Nomenclature of Bacteria (ICNB) or Bacteriological Code (BC), governs the scientific names for Bacteria and Archaea.P. H. A. Sneath ...

(ICNP) mandated that names "merely mentioned incidentally" without clear indication of their new status would not be valid. This requirement aimed to prevent confusion and ensure that readers could distinguish newly proposed names from older references. Since 2007, explicit citation of the basionym has been mandatory. The basionym must meet specific rank requirements and cannot itself have a basionym. In cases where a name change is based on an illegitimate name, it is treated as a replacement name (''nomen novum'') rather than a ''combinatio nova''. These requirements differ from those for new taxa, as new combinations do not require a new description or diagnosis but must adhere to citation and reference rules outlined in Article 33 of the nomenclatural code. Across all fields governed by the ICN, ICNP, and ICZN, a new combination involves reassigning a species to a different genus or changing its rank while retaining the type of the original name (basionym). This principle is universal, though codes differ in implementation details. For example, the ICZN requires that the original authority's name be placed in parentheses to denote its relationship to the new combination. These shared rules ensure taxonomic stability, allowing revisions to reflect updated classifications while preserving historical and typological continuity. In fungal taxonomy, including lichen-forming fungi, tools such as

MycoBank MycoBank is an online database, documenting new mycological names and combinations, eventually combined with descriptions and illustrations. It is run by the Westerdijk Fungal Biodiversity Institute in Utrecht. Each novelty, after being screene ...

provide registration systems to ensure valid publication and traceability of names. Similarly, databases like WoRMS integrate taxonomic records across groups, enhancing accessibility and consistency in nomenclature. A key principle is that new combinations are only valid when made at identical ranks. Changes in rank, such as elevating a

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

to species status or reducing a species to subspecies level, do not constitute new combinations and follow separate rules.

Nomenclatural rules and restrictions

Taxonomic nomenclature follows specific rules governing how new combinations can be created and validated. A fundamental principle is that true new combinations can only be made between taxa of identical ranks. When taxonomic rank changes occur, such as elevating a subspecies to species status, these are denoted by the term ''status novus'' (stat. nov.), indicating a change in rank rather than a new combination. For prokaryotic nomenclature, when changing ranks between species and subspecies, the epithet from the original name must be maintained unless this would create an illegitimate name. While the

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN or ICNafp) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all tho ...

(ICN) treats such rank changes as new combinations, there is ongoing debate about this treatment in prokaryotic nomenclature. Author citations in parentheses track the origin of reused epithets during rank or genus changes, with formatting rules differing between the

botanical Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

and

zoological Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...

codes. For rank changes, taxonomists must follow distinct protocols. The epithet from the original name must be maintained in the new designation unless this would create an illegitimate name. For example, when elevating a subspecies to species status, the subspecific epithet becomes the new specific epithet. Similarly, when reducing a species to subspecies rank, its specific epithet becomes the new subspecific epithet. These rank-change procedures are governed by specific articles in various nomenclatural codes. In prokaryotic taxonomy, Rules 50a and 50b of the

International Code of Nomenclature of Prokaryotes The International Code of Nomenclature of Prokaryotes (ICNP) or Prokaryotic Code, formerly the International Code of Nomenclature of Bacteria (ICNB) or Bacteriological Code (BC), governs the scientific names for Bacteria and Archaea.P. H. A. Sneath ...

explicitly regulate the elevation of subspecies to species and the lowering of species to subspecies, respectively. Although the primary goal of ''combinatio nova'' is to formalize name changes, the inclusion of ecological, distributional, and morphological data can significantly improve their utility. A 2021 study revealed that over 70% of new combinations lack such information, emphasizing the need for more comprehensive taxonomic descriptions. Modern taxonomic databases, such as the

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive catalogue and list of names of marine organisms. Content The content of the registry is edited and maintained by scien ...

, incorporate tools to manage ''combinatio nova'' by linking new combinations to original names. In this database, "superseded combination" is a standardized term used to describe names replaced by a ''combinatio nova''. Such terminology helps ensure clarity in cases where species names are reassigned to new genera or taxonomic contexts.

Types of new combinations

New combinations in taxonomy typically occur in three main situations, each serving a different taxonomic purpose: #Generic reassignment: When research indicates a species belongs in a different genus, taxonomists create a new combination by transferring the species epithet to the new genus. The specific epithet remains unchanged while the genus name changes. #Rank changes: When modifying a taxon's hierarchical position, such as elevating a subspecies to species status or changing a subgenus to genus level. When changing ranks between species and subspecies, the epithet from the original name must be maintained unless this would create an illegitimate name. For example, when elevating a subspecies to species status, the subspecific epithet becomes the new specific epithet. Similarly, when reducing a species to subspecies rank, its specific epithet becomes the new subspecific epithet. #Infraspecific transfers: When moving varieties or subspecies between species while maintaining their infraspecific rank. The infraspecific epithet is preserved but associated with a different species name.

Examples

In taxonomic practice, new combinations occur across different biological domains. In bacteriology, when ''Calymmatobacterium granulomatis'' was reassigned to a different genus, it became ''

Klebsiella granulomatis ''Klebsiella granulomatis'' is a Gram-negative, rod-shaped bacterium of the genus ''Klebsiella'' known to cause the sexually transmitted infection granuloma inguinale (or donovanosis). It was formerly called ''Calymmatobacterium granulomatis''. ...

'' comb. nov., maintaining its specific epithet while changing its genus placement. Other bacterial examples demonstrate rank changes: ''Bifidobacterium pseudolongum'' became ''B. pseudolongum'' subsp. ''pseudolongum'' when reduced to

rank, while ''Lactobacillus bulgaricus'' was reclassified as ''L. delbrueckii'' subsp. ''bulgaricus'' when its taxonomic status changed. In botanical taxonomy, new combinations often result from genus reassessments. For instance,

Illiciaceae Illiciaceae A.C.Sm. was a family of flowering plants recognized in a number of systems of plant taxonomy. The Illiciaceae is not recognized as a distinct family by the APG III system of plant taxonomy, the most well accepted system in use today ...

represents a new combination based on Illicieae , demonstrating the transfer of a taxon while preserving its taxonomic root. Similarly,

Irvingiaceae Irvingiaceae is a small family of flowering plants, consisting of about 13 species; it was erected by Exell and Mendonça in 1951. The family and type genus were named after the Scottish naval surgeon, Edward George Irving.D. Gledhill. ''The Na ...

was established as a new combination from Irvingioideae , showing how family-level taxonomy can be adjusted through new combinations. Under Article 7.3 of the ICN, a new combination or a name at a new rank must retain the type of its basionym, even if it was erroneously applied to a different taxon. For instance, ''Pinus mertensiana'' Bong. was transferred to the genus ''Tsuga'' by Carrière, who (based on his description) was actually referring to ''Tsuga heterophylla'' (Raf.) Sarg. Nonetheless, the combination ''Tsuga mertensiana'' (Bong.) Carrière remains permanently linked to the original basionym, ''Pinus mertensiana'' Bong. The citation "(Bong.)" in parentheses under Article 49 indicates that Bongard's name is the basionym, and thus determines the type for the new combination—even though Carrière mistakenly applied it to a different species.

References

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