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.
16-462: Anastatica is a monotypic genus of plants in the family Brassicaceae containing the single species Anastatica hierochuntica . The plant is a small gray annual herb that rarely grows above 15 centimetres (6 in) high, and bears minute white flowers. It is a tumbleweed capable of hygroscopic expansion and retraction. However, it is not a true resurrection plant , because the plant's dead tissues do not revive and turn green. This species
32-602: 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
48-465: 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 the information content of biological classifications. As taxonomists Backlund and Bremer explain in their critique, "'Monotypic' taxa do not provide any information about
64-529: Is found in arid areas in the Middle East and the Sahara Desert, including parts of North Africa and regions of Iran, Egypt, Israel, Saudi Arabia, Iraq, Jordan and Pakistan. A plant with great resistance to desiccation , its branches have the property of contracting with dryness, remaining closed and dry for many years, reopening with moisture or contact with water, regaining all its freshness and beauty. After
80-428: Is not to be confused with Selaginella lepidophylla , also sometimes referred to as "rose of Jericho", or "false rose of Jericho", which is a true resurrection plant that can revive from a dried state and regain the processes of respiration and photosynthesis. Common names include Maryam's flower , flower of St Mary , St. Mary's flower , Mary's flower , white mustard flower and rose of Jericho . Anastatica
96-407: 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
112-425: The rainy season , the plant dries up, dropping leaves and curling branches into a tight ball, and aestivates . Within the ball, the fruits remain attached and closed, protecting the seeds and preventing them from being dispersed prematurely. The seeds are very hardy and can remain dormant for years. Moistened again in a later rainy season, the ball uncurls and the plant wakes up from its dormant state, which causes
128-445: The ball is said to become detached and is dispersed by wind. This tumbleweed habit has been interpreted as a mechanism of avoiding burial in dunes . However, Anastatica may possess this habit only in the literature, or tumble only rarely, if uprooted by accident. Since ancient times it was used as an element to guess the climate, since being a vegetable hygrometer , the wise man or shaman , predicted it with success. In dry weather
144-455: The capsular fruits to open to disperse the seeds. If water is sufficient, the dispersed seeds germinate within hours. After it curls, it is easy for the wind itself to lift and drag it large distances, making them obligatory travellers through steppes and deserts crossing the borders of various countries in Asia and disseminating their seeds for all of them. A fraction of the seeds are dispersed in
160-745: 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
176-469: 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. When taxonomists identify a monotypic taxon, this often reflects uncertainty about its relationships rather than true evolutionary isolation . This uncertainty
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#1732859414476192-457: The plant remains completely closed; in wet weather, it opens slowly; if it threatens rain, it opens in a very showy way and with more or less speed according to the proximity of discharge of the clouds. Monotypic 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
208-423: The presence of trehalose , a disaccharide sugar involved in several mechanisms of cryptobiosis . Although the rehydrated plant sometimes is described as putting out new leaves, flowers, and fruits, this is disputed; instead, the seeds may sometimes germinate and sprout new plants while still seated in the fruit on the dead parent plant. Anastatica has been described as the most famous tumbleweed . Once dry,
224-405: 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 a natural classification. From a cladistic perspective, which focuses on shared derived characteristics to determine evolutionary relationships,
240-403: 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
256-411: The vicinity of the parent plant by raindrops hitting a spoon-like appendix on the seeds. The seeds have a sticky coat that helps them adhere to the soil, but they also may be carried downstream by surface wash. However, seeds swept downstream do not survive. The process of curling and uncurling is completely reversible and can be repeated many times. The ability of the plant to do this is attributed to
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