Podostemaceae Explained

Podostemaceae (riverweed family), a family in the order Malpighiales, comprise about 50 genera and species^[1] of more or less thalloid aquatic herbs.

Distribution and habitat

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.^{[2] [3]} Because of their small range, many species are seriously threatened, especially from habitat loss (for example, due to dams flooding their habitat).^{[3] [4]}

Riverweeds adhere to hard surfaces (generally rock) in rapids and waterfalls of rivers. 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.^[5]

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,^[6] and in South America several serrasalmid fish (Mylesinus, Ossubtus, Tometes and Utiaritichthys) mainly feed on Podostemaceae.^[7]

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.^{[8] [9]} 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 (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.^[10]

Genera

52 genera are accepted.^[11]

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

Further reading

• Kato . Masahiro . The vague form created by the environment: Podostemaceae . Biohistory . 40 . Spring . 2003 . https://web.archive.org/web/20220316191318/https://www.brh.co.jp/en/publication/journal/040/research_11.html . 16 March 2022.

Notes and References

1. Christenhusz, M. J. M. . Byng, J. W. . 2016 . The number of known plants species in the world and its annual increase . Phytotaxa . 261 . 201–217 . 10.11646/phytotaxa.261.3.1 . 3 . free .
2. Web site: Podostemaceae . Institute of Systematic Botany, University of Zurich . dead . https://web.archive.org/web/20070703100515/http://www.systbot.unizh.ch/podostemaceae/index.htm . 2007-07-03 .
3. Bove, C.P. . C.T. Philbrick . Rediscovery of a Neotropical rheophyte (Podostemaceae) after 160 years: Implications for the location of conservation unit boundaries (Tocantins, Brazil) . 2014 . Check List . 10 . 5 . 1170–1173 . 10.15560/10.5.1170 . free .
4. News: Hettiarachchi, K. . S. Daniel . Now vital aquatic plants face similar fate as fish . 7 August 2011 . . 4 November 2017 .
5. American Journal of Botany . 2006 . 93 . 5 . 682–692 . Comparative anatomy of root meristem and root cap in some species of Podostemaceae and the evolution of root dorsiventrality . Satoshi Koi . Rieko Fujinami . Namiko Kubo . Ikue Tsukamoto . Rie Inagawa . Ryoko Imaichi . Masahiro Kato . 10.3732/ajb.93.5.682 . 21642132.
6. Web site: Conraua goliath . AmphibiaWeb . 4 November 2017 .
7. Book: van der Sleen, P. . J.S. Albert . 2017 . Field Guide to the Fishes of the Amazon, Orinoco, and Guianas . Princeton University Press . 173–196 . 978-0691170749 .
8. 10.1086/342521 . Phylogeny of Clusiaceae Based on rbcL sequences . 2002 . Gustafsson, Mats H. G. . International Journal of Plant Sciences . 163 . 1045–1054 . 3080291 . 6 . 85307271 .
9. Web site: Malpighiales . .
10. 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
11. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77126691-1 Podostemaceae Rich. ex Kunth