Podostemaceae (riverweed family), a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

in the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Malpighiales The Malpighiales comprise one of the largest Order (biology), orders of flowering plants. The order is very diverse, with well-known members including willows, Viola (plant), violets, aspens and Populus, poplars, Euphorbia pulcherrima, poinsett ...

, comprise about 50

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

and

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), ...

of more or less

thalloid Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entire ...

aquatic herbs.

Distribution and habitat

They are found mostly in

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

areas worldwide. Many species are found in a very small geographic area, often even just a single river or waterfall. Because of their small range, many species are seriously threatened, especially from

habitat loss Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

(for example, due to

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

s flooding their habitat). Riverweeds adhere to hard surfaces (generally rock) in rapids and waterfalls of

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s. They are submerged when water levels are high, but during the dry season they live a terrestrial existence, flowering at this time. Their root anatomy is specialized for the purpose of clinging to rocks, and in fact details of the root structure are one of the ways of classifying riverweeds.

Ecology

In many rivers, Podostemaceae are an important food source for a wide range of animals. For example, the tadpoles of the African

goliath frog The goliath frog (''Conraua goliath''), otherwise known commonly as the giant slippery frog and the goliath bullfrog, is a species of frog in the family Conrauidae. The goliath frog is the largest living frog. Specimens can reach up to about in ...

(world's largest frog) feed only on ''Dicraeia warmingii'', and in South America several

serrasalmid The Serrasalmidae (serrasalmids) are a family of characiform fishes native to freshwater habitats of South America. They include more than 90 species. The name means "serrated salmon family", which refers to the serrated keel running along the ...

fish (''

Mylesinus ''Mylesinus'' is a genus of serrasalmids from South America, where found in the eastern Amazon, Essequibo and Orinoco basins. They are rheophilic, typically found at rapids and mainly feed on Podostemaceae plants. Because of their habitat prefe ...

'', ''

Ossubtus ''Ossubtus'' is a genus of fish in the family Serrasalmidae. It contains a single species, ''Ossubtus xinguense'', the parrot pacu or eaglebeak pacu, The species is endemic to rapids in the Xingu River basin in the Brazilian Amazon. This vulner ...

'', ''

Tometes ''Tometes'' is a genus of fish in the family Serrasalmidae found in fast-flowing rivers in northern South America. Adults of all seven species in this genus are phytophagous, feeding primarily on aquatic plants in the family Podostemaceae. The ...

'' and ''

Utiaritichthys ''Utiaritichthys'' is a genus of serrasalmid fish found in the Amazon Basin, Amazon and Orinoco basins in tropical South America. The adults are typically found in rapidly flowing water where they feed on aquatic plants in the family Podostemace ...

'') mainly feed on Podostemaceae.

Taxonomy

The Podostemaceae are related to the families

Clusiaceae The Clusiaceae or Guttiferae Juss. (1789) (''nom. alt. et cons.'' = alternative and valid name) are a family (biology), family of plants including 13 genera and ca 750 species. Several former members of Clusiacae are now placed in Calophyllaceae ...

Hypericaceae Hypericaceae is a plant family in the order Malpighiales, comprising six to nine genera and up to 700 species, and commonly known as the St. John's wort family. Members are found throughout the world apart from extremely cold or dry habitats. ...

(the St. John's wort family, which is sometimes treated as a subfamily of Clusiaceae), and

Bonnetiaceae Bonnetiaceae is a family of flowering plants, consisting of 3 genera and 38 species. The family is Neotropical, with the exception of the genus '' Ploiarium'', which is found in Malesia. It is sister to the family Clusiaceae The Clusiaceae or ...

. In the classification system of Dahlgren Podostemaceae were placed as a single family in the Podostemales order, which was the only order in the

superorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

Podostemiflorae (also called Podostemanae). The family is divided into three subfamilies, Podostemoideae, Trisichoideae, and Weddellinoideae. Trisichoideae is the most basally diverged, and is sister to the other two subfamilies.Katayama, N., Koi, S., Sassa, A. et al. Elevated mutation rates underlie the evolution of the aquatic plant family Podostemaceae. ''Communications Biology'' 5, 75 (2022). https://doi.org/10.1038/s42003-022-03003-w

Genera

52 genera are accepted.Podostemaceae Rich. ex Kunth
''

Plants of the World Online Plants of the World Online (POWO) is an online taxonomic database published by the Royal Botanic Gardens, Kew. History Following the Convention on Biological Diversity, the Royal Botanic Gardens in Kew launched Plants of the World Online i ...

''. Retrieved 12 April 2024.

Moved to other families

* '' Hydrostachys'' from Madagascar. This genus seems to have relatively little in common with any other, and no affinity to the Podostemaceae except being aquatic; moved to its own family in the

Cornales The Cornales are an order of flowering plants, early diverging among the asterids, containing about 600 species. Plants within the Cornales usually have four-parted flowers, drupaceous fruits, and inferior to half-inferior gynoecia topped with d ...

Distribution and habitat

Ecology

Taxonomy

Genera

Moved to other families

See also

References

Further reading