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18-502: Gynerium is a monotypic genus of Neotropical plants in the grass family , native to Mexico and Colombia , Central America , South America , and the West Indies . It is classified in its own tribe Gynerieae . The sole species in the genus is Gynerium sagittatum , a tall grass that grows up to six metres (twenty feet) high. It is a very vigorous species that grows into a considerably dense mass of vegetation. The species

36-602: 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

54-468: A common ancestor, but evolved independently. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies ), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly . The word "mono-phyly" means "one-tribe" in Greek. These definitions have taken some time to be accepted. When the cladistics school of thought became mainstream in

72-427: A family. Some examples of monotypic groups are: Monophyletic In biological cladistics for the classification of organisms , monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of taxa which meets these criteria: Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A paraphyletic grouping meets 1. but not 2., thus consisting of

90-417: Is Gynerium sagittatum , widespread from northern Mexico to Paraguay . Three varieties are recognized: see Austroderia Cortaderia Chusquea Monotypic taxon 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

108-409: Is covered with "vainas" from the fallen leaves, while in the middle part the leaves are arranged in fan shaped groups. The upper part, round and thin, stiff on the outside and soft on the inside, develops a large bloom at the top. There are many varieties in the plant's stems. The bark zone, which is the main factor in the unusual height, functions as a water distribution system, transporting water from

126-465: 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

144-617: Is known as "cana-do-rio", "cana-flecha", "cana-frecha", "ubá" and "cana-brava" in Brazil , "caña brava" in Peru and Colombia , "chuchío" in eastern Bolivia , and "tañil" in Guatemala and other Spanish speaking countries. It is known in English as "wildcane" or "wild cane", while "arrow cane" is less common ( sagitta is Latin for arrow ). The stems are straight and erect, the lower part

162-407: 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

180-412: The 1960s, several alternative definitions were in use. Indeed, taxonomists sometimes used terms without defining them, leading to confusion in the early literature, a confusion which persists. The first diagram shows a phylogenetic tree with two monophyletic groups. The several groups and subgroups are particularly situated as branches of the tree to indicate ordered lineal relationships between all

198-745: 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

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216-415: The descendants of a common ancestor, excepting one or more monophyletic subgroups. A polyphyletic grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of a polyphyletic grouping are not inherited from

234-413: The fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a unique common ancestor. Conversely, the term polyphyly , or polyphyletic , builds on the ancient Greek prefix πολύς ( polús ), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. By comparison,

252-469: 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

270-431: The organisms shown. Further, any group may (or may not) be considered a taxon by modern systematics , depending upon the selection of its members in relation to their common ancestor(s); see second and third diagrams. The term monophyly , or monophyletic , derives from the two Ancient Greek words μόνος ( mónos ), meaning "alone, only, unique", and φῦλον ( phûlon ), meaning "genus, species", and refers to

288-405: 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,

306-403: 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

324-419: The underground roots to the superior part of the plant including the leaves. This vital function occurs at any season of the year. Being one of the first plants to colonise open areas, G. sagittatum is an important pioneer species that reaches new sites via wind-distributed seeds. Once established, it spreads vegetatively, and is found usually near rivers and lakes, and even beaches. The only known species

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