{{Short description|Taxonomic group with only one subordinate taxon}} {{Redirect|Monotypic|the conservation biology term|Monotypic habitat|other uses|Monotype (disambiguation)}} {{Redirect|Monospecific|the immunology term|Monospecific antibody}}
[[File:Leptosomus discolor 3402120 (cropped).jpg|thumb|The cuckoo-roller is the sole member of its genus, family, and order.]] In biology, for ranks such as genus or family, a '''monotypic taxon''' is a taxonomic group (taxon) that contains only one immediately subordinate taxon.<ref name=Been10>{{Cite book |last=Beentje |first=Henk |year=2010 |title=The Kew Plant Glossary |publication-place=Richmond, Surrey |publisher=Royal Botanic Gardens, Kew |isbn=978-1-84246-422-9 |page=73}}</ref><ref>Mayr E, Ashlock PD. (1991). ''Principles of Systematic Zoology'' (2nd ed.). McGraw-Hill. {{ISBN|0-07-041144-1}}</ref> In the case of genera, the term "unispecific" or "monospecific" is sometimes preferred. In botanical nomenclature, a '''monotypic genus''' is a genus in the special case in which a genus and a single species are simultaneously described.<ref>{{cite book|author1=McNeill, J. |author2=Barrie, F.R. |author3=Buck, W.R. |author4=Demoulin, V. |author5=Greuter, W. |author6=Hawksworth, D.L. |author7=Herendeen, P.S. |author8=Knapp, S. |author9=Marhold, K. |author10=Prado, J. |author11=Reine, W.F.P.h.V. |author12=Smith, G.F. |author13=Wiersema, J.H. |author14=Turland, N.J. |year=2012|title=International Code of Nomenclature for algae, fungi, and plants (Melbourne Code) adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011|volume=Regnum Vegetabile 154|publisher=A.R.G. Gantner Verlag KG|isbn=978-3-87429-425-6 |chapter=Article 38 |chapter-url=https://www.iapt-taxon.org/melbourne/main.php?page=art38 }}</ref> The term ''monotypic'' may be used somewhat differently for species, where a '''monotypic species''' may be the only one in its genus.<ref name=Been10/>
==Theoretical implications== {{Biological classification}}
Monotypic taxa present several important theoretical challenges in biological classification. One key issue is known as "Gregg's Paradox": if a single species is the only member of multiple hierarchical levels (for example, being the only species in its genus, which is the only genus in its family), then each level needs a distinct definition to maintain logical structure. Otherwise, the different taxonomic ranks become effectively identical, which creates problems for organizing biological diversity in a hierarchical system.<ref name="Ebach & Williams 2010">{{cite journal |last1=Ebach |first1=Malte C. |last2=Williams |first2=David M. |title=Aphyly: A Systematic Designation for a Taxonomic Problem |journal=Evolutionary Biology |volume=37 |issue=2–3 |year=2010 |doi=10.1007/s11692-010-9084-5 |pages=123–127 |bibcode=2010EvBio..37..123E |url=https://www.researchgate.net/publication/225388188}}</ref>
When taxonomists identify a monotypic taxon, this often reflects uncertainty about its relationships rather than true evolutionary isolation. This uncertainty is evident in many cases across different species. For instance, the diatom ''Licmophora juergensii'' is placed in a monotypic genus because scientists have not yet found clear evidence of its relationships to other species.<ref name="Ebach & Williams 2010"/>
Some taxonomists argue against monotypic taxa because they reduce the information content of biological classifications. As taxonomists Backlund and Bremer explain in their critique, {{" '}}Monotypic' taxa do not provide any information about the relationships of the immediately subordinate taxon".<ref name="Backlund 1998">{{cite journal |last1=Backlund |first1=Anders |last2=Bremer |first2=Kåre |title=To Be or Not to Be. Principles of Classification and Monotypic Plant Families |journal=Taxon |year=1998 |volume=47 |issue=2 |pages=391–400 |doi=10.2307/1223768|jstor=1223768 |bibcode=1998Taxon..47..391B }}</ref> When a monotypic taxon is sister to a single larger group, it might be merged into that group; however, when it is sister to multiple other groups, it may need to remain separate to maintain a natural classification.<ref name="Backlund 1998"/>
From a cladistic perspective, which focuses on shared derived characteristics to determine evolutionary relationships, the theoretical status of monotypic taxa is complex. Some argue that they can only be justified when relationships cannot be resolved through synapomorphies (shared derived characteristics); otherwise, they would necessarily exclude related species and thus be paraphyletic.<ref name="Platnick 1976">{{cite journal |last=Platnick |first=Norman I. |title=Are Monotypic Genera Possible? |journal=Systematic Zoology |year=1976 |volume=25 |issue=2 |pages=198–199 |doi=10.2307/2412749|jstor=2412749 }}</ref> However, others contend that while most taxonomic groups can be classified as either monophyletic (containing all descendants of a common ancestor) or paraphyletic (excluding some descendants), these concepts do not apply to monotypic taxa because they contain only a single member.<ref name="Potter 2005">{{cite journal |last1=Potter |first1=Daniel |last2=Freudenstein |first2=John V. |title=Character-based phylogenetic Linnaean classification: taxa should be both ranked and monophyletic |journal=Taxon |year=2005 |volume=54 |issue=4 |pages=1033–1035 |doi=10.2307/25065487|jstor=25065487 |bibcode=2005Taxon..54.1033P }}</ref>
Monotypic taxa are part of a broader challenge in biological classification known as ''aphyly'' – situations in which evolutionary relationships are poorly supported by evidence. This includes both monotypic groups and cases where traditional groupings are found to be artificial. Understanding how monotypic taxa fit into this bigger picture helps identify areas needing further research.<ref name="Ebach & Williams 2010"/>
The German lichenologist Robert Lücking suggests that the common application of the term monotypic is frequently misleading "since each taxon by definition contains exactly one type and is hence 'monotypic', regardless of the total number of units", and suggests using "monospecific" for a genus with a single species, and "monotaxonomic" for a taxon containing only one unit.<ref>{{cite journal |last1=Lücking |first1=Robert |title=Stop the abuse of time! Strict temporal banding is not the future of rank-based classifications in Fungi (including lichens) and other organisms |journal=Critical Reviews in Plant Sciences |year=2019 |volume=38 |issue=3 |pages=199–253 [216] |doi=10.1080/07352689.2019.1650517|bibcode=2019CRvPS..38..199L }}</ref>
==Conservation implications==
Species in monotypic genera tend to be more threatened with extinction than average species. Studies have found this pattern to be particularly pronounced in amphibians, of which about 6.56% of monotypic genera are critically endangered, compared to birds and mammals, of which around 4.54% and 4.02%, respectively, of monotypic genera face critical endangerment.<ref name="Vargas 2023">{{cite journal |last1=Vargas |first1=Pablo |title=Exploring 'endangered living fossils' (ELFs) among monotypic genera of plants and animals of the world |journal=Frontiers in Ecology and Evolution |date=2023 |volume=11 |article-number=e1100503 |doi=10.3389/fevo.2023.1100503|doi-access=free |bibcode=2023FrEEv..1100503V |hdl=10261/353582 |hdl-access=free }}</ref>
Studies have found that extinction of monotypic genera is particularly associated with island species. Among 25 documented extinctions of monotypic genera studied, 22 occurred on islands, with flightless birds being particularly vulnerable to human impact.<ref name="Vargas 2023"/>
==Examples== Just as the term ''monotypic'' is used to describe a taxon including only one subdivision, the contained taxon can also be referred to as monotypic within the higher-level taxon, e.g., a genus monotypic within a family. Some examples of monotypic groups are:
===Plants=== * The division Ginkgophyta is monotypic, containing the single class Ginkgoopsida. This class is also monotypic, containing the single order Ginkgoales, which has only the single family Ginkgoaceae, containing a single genus ''Ginkgo'' with a single species ''Ginkgo biloba''.<ref>{{cite journal |last1=Wu |first1=Chung-Shien |last2=Chaw |first2=Shu-Miaw |last3=Huang |first3=Ya-Yi |title=Chloroplast Phylogenomics Indicates that Ginkgo biloba Is Sister to Cycads |journal=Genome Biology and Evolution |date=2013 |volume=5 |issue=1 |pages=243–254 |doi=10.1093/gbe/evt001 |pmid=23315384 |pmc=3595029 }}</ref> * In the order Amborellales, there is only one family, Amborellaceae, there is only one genus, ''Amborella'', and in this genus there is only one species, ''Amborella trichopoda''. * The conifer ''Sciadopitys verticillata'' is the only species in the monotypic genus ''Sciadopitys'', and also the only member of the family Sciadopityaceae.<ref>{{cite web | title=Sciadopityaceae | website=Plants of the World Online | date=2020-11-19 | url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:330510-2 | access-date=2025-06-04}}</ref> Multiple other conifer genera are monotypic, but are members of larger families; examples include ''Cathaya, Diselma, Fitzroya, Glyptostrobus, Metasequoia, Microcachrys, Nothotsuga, Parasitaxus, Saxegothaea, Sequoia, Sequoiadendron, Sundacarpus, Tetraclinis, Thujopsis'' and ''Wollemia''. * The flowering plant ''Breonadia salicina'' is the only species in the monotypic genus ''Breonadia''. * The family Cephalotaceae includes only one genus, ''Cephalotus'', and only one species, ''Cephalotus follicularis'' – the Albany pitcher plant. * The water lily species ''Euryale ferox'' is the sole extant member of the monotypic genus ''Euryale''.<ref>{{cite POWO |id=27994-1 |title=''Euryale'' Salisb. |accessdate=15 February 2026}}</ref>
===Animals=== * The platypus is the only member of the monotypic genus ''Ornithorhynchus'', and the family Ornithorhynchidae. * The aye-aye is the only extant member of the genus Daubentonia, and the family Daubentoniidae. * The aardvark is the only extant member of the genus ''Orycteropus'', the family Orycteropodidae, and the order Tubulidentata.<ref>{{cite journal |last1=Schlitter |first1=D. A. |title=Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.) |journal=Johns Hopkins University Press |year=2005 |isbn=978-0-8018-8221-0 |page=86 |oclc=62265494 |url=https://books.google.com/books?id=JgAMbNSt8ikC&pg=PA86 }}</ref> * The madrone butterfly is the only species in the monotypic genus ''Eucheira''. However, there are two subspecies of this butterfly, ''E. socialis socialis'' and ''E. socialis westwoodi'', which means the species ''E. socialis'' is not monotypic.<ref>{{cite journal |last1=Kevan |first1=P. G. |last2=Bye |first2=R. A. |year=1991 |title=The natural history, sociobiology, and ethnobiology of Eucheira socialis Westwood (Lepidoptera: Pieridae), a unique and little-known butterfly from Mexico |journal=Entomologist |volume=110 |pages=146–165 }}</ref> * ''Delphinapterus leucas'', the beluga whale, is the only member of its genus and lacks subspecies.<ref>{{cite report |url=https://www.cosewic.ca/images/cosewic/pdf/beluga_whale_dus_en.pdf |title=Designatable Units for Beluga Whales (Delphinapterus leucas) in Canada |publisher=Committee on the Status of Endangered Wildlife in Canada |year=2016 }}</ref> * ''Dugong dugon'' is the only species in the monotypic genus ''Dugong''.<ref>{{cite book |doi=10.1016/B978-0-12-409542-7.50003-2 |chapter=Taxonomic Groupings Above the Species Level |title=Marine Mammals of the World |year=2015 |last1=Jefferson |first1=Thomas A. |last2=Webber |first2=Marc A. |last3=Pitman |first3=Robert L. |pages=17–23 |isbn=978-0-12-409542-7 }}</ref> * ''Homo sapiens'' (humans) are monotypic, as they have too little genetic diversity to have any accepted living subspecies.<ref>{{cite journal |last1=Premo |first1=L. S. |last2=Hublin |first2=J.-J. |title=Culture, population structure, and low genetic diversity in Pleistocene hominins |journal=Proceedings of the National Academy of Sciences |date=6 January 2009 |volume=106 |issue=1 |pages=33–37 |doi=10.1073/pnas.0809194105 |pmid=19104042 |pmc=2629215 |bibcode=2009PNAS..106...33P |doi-access=free }}</ref> * The maned wolf, a large canid, is the only species in the monotypic genus ''Chrysocyon''<ref>{{cite web |last1=Costa Silva |first1=Bruno |last2=Alexander de Oliveira |first2=Luan |last3=Clauss |first3=Marcus |last4=Guimarães Costa |first4=Claudia |last5=de Oliveira Marques Alexandre |first5=Leandro |last6=J Duque-Correa |first6=María |title=Digestive anatomy and diet of free-ranging maned wolf (Chrysocyon brachyurus) |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC12287139/ |website=National Library of Medicine |publisher=Springer Nature}}</ref> * The narwhal, a medium-sized cetacean, is the only member of the monotypic genus ''Monodon''.<ref>{{cite report |url=https://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_narwhal_e.pdf |title=COSEWIC assessment and update status report on the narwhal Monodon monoceros in Canada |publisher=Committee on the Status of Endangered Wildlife in Canada |year=2004 }}</ref> * The palmchat is the only member of the genus ''Dulus'' and the only member of the family Dulidae.<ref name="iucn status 12 November 2021">{{cite iucn|title=''Dulus dominicus''|article-number=e.T22708129A94150155|author=BirdLife International|date=2016|volume=2016|access-date=12 November 2021|doi=10.2305/IUCN.UK.2016-3.RLTS.T22708129A94150155.en}}</ref> * The salamanderfish (''Lepidogalaxias salamandroides'') is the only member of the order Lepidogalaxiiformes, which is the sister group to the remaining euteleosts.<ref>[https://bmcecolevol.biomedcentral.com/articles/10.1186/s12862-018-1267-1 A phylogenomic approach to reconstruct interrelationships of main clupeocephalan lineages with a critical discussion of morphological apomorphies]</ref> * ''Ozichthys albimaculosus'', the cream-spotted cardinalfish, which is found in tropical Australia and southern New Guinea, is the type species of the monotypic genus ''Ozichthys''.<ref>{{cite journal |last1=Fraser |first1=Thomas H. |title=A new genus of cardinalfish from tropical Australia and southern New Guinea (Percomorpha: Apogonidae) |journal=Zootaxa |date=14 August 2014 |volume=3852 |issue=2 |pages=283–293 |doi=10.11646/zootaxa.3852.2.7 |pmid=25284398 |url=http://publication.plazi.org/id/46127B6C4D66FFD64E68FFEC5D149F08 }}</ref> * The bearded reedling is the only species in the monotypic genus ''Panurus'', which is the only genus in the monotypic family Panuridae; it does however have three subspecies so it is not strictly monotypic.<ref name="IOC">{{cite web | title=Nicators, Bearded Reedling, larks – IOC World Bird List | website=IOC World Bird List – Version 14.2 | date=2025-02-20 | url=https://www.worldbirdnames.org/new/bow/larks/ | access-date=2025-06-04}}</ref> * The reindeer is the only species in the monotypic genus ''Rangifer''. * The sloth bear is the only species in the monotypic genus ''Melursus''
<gallery widths="200" heights="200"> File:Amborella trichopoda.jpg|In the order Amborellales, there is only one family, Amborellaceae, and there is only one genus, ''Amborella'', and in this genus there is only one species, ''Amborella trichopoda''. File:Beluga Whale Kissing its trainer.jpg|Beluga "kissing" a human trainer; both are monotypical in their genera. File:Cephalotus follicularis Hennern 3 (cropped).jpg|The family Cephalotaceae has only one genus, ''Cephalotus'', which contains only one species, ''Cephalotus follicularis'', the Australian pitcher plant. </gallery>
=== Other ===
* ''Picomonas judraskeda'' is the only known species in the division ''Picozoa''.<ref name="Seenivasan2013">{{cite journal |vauthors=Seenivasan R, Sausen N, Medlin LK, Melkonian M |year=2013 |title=Picomonas judraskeda gen. et sp. nov.: the first identified member of the Picozoa phylum nov., a widespread group of picoeukaryotes, formerly known as 'picobiliphytes' |journal=PLOS ONE |volume=8 |issue=3 |article-number=e59565 |bibcode=2013PLoSO...859565S |doi=10.1371/journal.pone.0059565 |pmc=3608682 |pmid=23555709 |doi-access=free |veditors=Waller RF}}</ref>
== See also == {{Portal|Biology}} * Glossary of scientific naming * Monophyly
== References == {{Reflist}}
== External links == * {{Wiktionary-inline|monotypic}}
{{DEFAULTSORT:Monotypic Taxon}} Category:Monotypic taxa Category:Conservation biology Category:Speciation