In biology , a monotypic taxon is a taxonomic group ( taxon ) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. 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 where a genus and a single species are simultaneously described.
17-424: Hagenia is a monotypic genus of flowering plant with the sole species Hagenia abyssinica , native to the high-elevation Afromontane regions of central and eastern Africa . It also has a disjunct distribution in the high mountains of East Africa from Sudan and Ethiopia in the north, through Kenya , Uganda , Rwanda , Burundi , Democratic Republic of Congo , and Tanzania , to Malawi and Zambia in
34-602: A common ancestor ) or paraphyletic (excluding some descendants), these concepts do not apply to monotypic taxa because they contain only a single member. Monotypic taxa are part of a broader challenge in biological classification known as aphyly – situations where 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. The German lichenologist Robert Lücking suggests that
51-482: A hierarchical system. 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. Some taxonomists argue against monotypic taxa because they reduce
68-475: A family. Some examples of monotypic groups are: Synapomorphies In phylogenetics , an apomorphy (or derived trait ) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy ). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have evolved in their most recent common ancestor . In cladistics , synapomorphy implies homology . Examples of apomorphy are
85-553: A natural classification. From a cladistic perspective, which focuses on shared derived characteristics to determine evolutionary relationships, the theoretical status of monotypic taxa is complex. Some argue 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. However, others contend that while most taxonomic groups can be classified as either monophyletic (containing all descendants of
102-477: A synapomorphy is the marker for the most recent common ancestor of the monophyletic group consisting of a set of taxa in a cladogram. What counts as a synapomorphy for one clade may well be a primitive character or plesiomorphy at a less inclusive or nested clade. For example, the presence of mammary glands is a synapomorphy for mammals in relation to tetrapods but is a symplesiomorphy for mammals in relation to one another—rodents and primates, for example. So
119-420: Is dominant, or in mixed stands of Hagenia and Juniperus procera . It is often found near the upper limit of forest growth, giving way to giant heather zones above it. Hagenia is used as a food plant by the larvae of some Lepidoptera species including turnip moth . Monotypic taxon Monotypic taxa present several important theoretical challenges in biological classification . One key issue
136-402: 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
153-775: Is known in English as African redwood , East African rosewood , brayera , cusso , hagenia , or kousso , in Amharic as kosso , and in Swahili as mdobore or mlozilozi . Synonyms of the species include Banksia abyssinica , Brayera anthelmintica , Hagenia abyssinica var. viridifolia and Hagenia anthelmintica . It is generally found from 2000–3000 m elevation, in areas receiving 1000–1500 mm of rainfall annually. It can be found growing in mixed afromontane forest with Podocarpus , Afrocarpus , and other trees, and in drier afromontane forests and woodlands where Hagenia
170-407: Is particularly associated with island species. Among 25 documented extinct monotypic genera studied, 22 occurred on islands, with flightless animals being particularly vulnerable to human impacts. 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
187-557: The Ancient Greek words σύν ( sún ), meaning "with, together"; ἀπό ( apó ), meaning "away from"; and μορφή ( morphḗ ), meaning "shape, form". Lampreys and sharks share some features, like a nervous system, that are not synapomorphic because they are also shared by invertebrates . In contrast, the presence of jaws and paired appendages in both sharks and dogs, but not in lampreys or close invertebrate relatives, identifies these traits as synapomorphies. This supports
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#1732797753131204-745: 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. Species in monotypic genera tend to be more threatened with extinction than average species. Studies have found this pattern particularly pronounced in amphibians , where about 6.56% of monotypic genera are critically endangered , compared to birds and mammals where around 4.54% and 4.02% of monotypic genera face critical endangerment respectively. Studies have found that extinction of monotypic genera
221-531: The concept can be understood as well in terms of "a character newer than" ( autapomorphy ) and "a character older than" ( plesiomorphy ) the apomorphy: mammary glands are evolutionarily newer than vertebral column, so mammary glands are an autapomorphy if vertebral column is an apomorphy, but if mammary glands are the apomorphy being considered then vertebral column is a plesiomorphy. These phylogenetic terms are used to describe different patterns of ancestral and derived character or trait states as stated in
238-510: The hypothesis that dogs and sharks are more closely related to each other than to lampreys. The concept of synapomorphy depends on a given clade in the tree of life. Cladograms are diagrams that depict evolutionary relationships within groups of taxa. These illustrations are accurate predictive device in modern genetics. They are usually depicted in either tree or ladder form. Synapomorphies then create evidence for historical relationships and their associated hierarchical structure. Evolutionarily,
255-427: 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". When monotypic taxa are sister to a single larger group, they might be merged into that group; however, when they are sister to multiple other groups, they may need to remain separate to maintain
272-492: The presence of erect gait , fur , the evolution of three middle ear bones , and mammary glands in mammals but not in other vertebrate animals such as amphibians or reptiles , which have retained their ancestral traits of a sprawling gait and lack of fur. Thus, these derived traits are also synapomorphies of mammals in general as they are not shared by other vertebrate animals. The word synapomorphy —coined by German entomologist Willi Hennig —is derived from
289-536: The south. A member of the rose family , its closest relative is the Afromontane genus Leucosidea . It is a tree up to 20 m in height, with a short trunk, thick branches, and thick, peeling bark. The leaves are up to 40 cm long, compound with 7-13 leaflets, each leaflet about 10 cm long with a finely serrated margin, green above, silvery-haired below. The flowers are white to orange-buff or pinkish-red, produced in panicles 30–60 cm long. It
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