Podostemaceae (riverweed family), a
family in the
order Malpighiales, 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 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 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
dams 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 (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'', '' Ossubtus'', '' Tometes'' 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, Hypericaceae (the St. John's wort family, which is sometimes treated as a subfamily of Clusiaceae), and Bonnetiaceae.[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.
See also
* Eugenius Warming, a botanist who studied the family
References
Further reading
*
{{Authority control
Malpighiales families