Podostemaceae, a family in the orderMalpighiales, comprise about 46 genera and ca 300 species of more or less thalloid aquatic herbs. Riverweeds adhere to hard surfaces in rapids and waterfalls of rivers. They are found mostly in tropical 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. Riverweeds are submerged when water levels are high, but during the dry seasonthey 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. river in Colombia is famous for the bright red Macarenia clavigera, a species only found in Serranía de la Macarena The Podostemaceae are related to the families Clusiaceae, Hypericaceae, and Bonnetiaceae. 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 Podostemiflorae. In many rivers, Podostemaceae are an important food source for a wide range of animals. For example, the tadpoles of the African goliath frogfeed only on Dicraeia warmingii, and in South America several serrasalmid fish mainly feed on Podostemaceae.
Genera
Angolaea
Apinagia
Butumia
Castelnavia
Ceratolacis
Cipoia
Cladopus
Dalzellia
Devillea
Diamantina
Dicraeanthus
Dicraeia
Diplobryum
Djinga
Endocaulos
Farmeria
Griffithella
Heterotristicha
Hydrobryum
Indotristicha
Jenmaniella
Lebbiea
Ledermanniella
Leiothylax
Letestuella
Lonchostephus
Lophogyne
Macarenia
Macropodiella
Malaccotristicha
Marathrum
Mniopsis
Monostylis
Mourera
Oserya
Paleodicraeia
Podostemum
Pohliella
Polypleurella
Polypleurum
Rhyncholacis
Saxicolella
Sphaerothylax
Stonesia
Thelethylax
Torrenticola
Tristicha
Tulasneantha
Vanroyenella
Weddellina
Wettsteiniola
Willisia
Winklerella
Zehnderia
Zeylanidium
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.