Phyllanthus
Phyllanthus is the largest genus in the plant family Phyllanthaceae. Estimates of the number of species in this genus vary widely, from 750 to 1200. Phyllanthus has a remarkable diversity of growth forms including annual and perennial herbs, shrubs, climbers, floating aquatics, and pachycaulous succulents. Some have flattened leaflike stems called cladodes. It has a wide variety of floral morphologies and chromosome numbers and has one of the widest range of pollen types of any seed plant genus.
Despite their variety, almost all Phyllanthus species express a specific type of growth called "phyllanthoid branching" in which the vertical stems bear deciduous, floriferous, plagiotropic stems. The leaves on the main axes are reduced to scales called "cataphylls", while leaves on the other axes develop normally. Phyllanthus is distributed in all tropical and subtropical regions on Earth.
Phyllanthus was first described by Carl Linnaeus in 1753; the type species has subsequently been designated as Phyllanthus niruri.
Species
The circumscription of this genus has been a cause of much confusion and disagreement. Molecular phylogenetic studies have shown that Phyllanthus is paraphyletic over Reverchonia, Glochidion, Sauropus, and Breynia. A 2006 revision of the family Phyllanthaceae has subsumed all four of these genera into Phyllanthus. This enlarged version of Phyllanthus might eventually be divided into smaller genera, including 32 Chinese species. A complete overhaul of the genus, including a new classification is currently underway, following a recent indepth molecular treatment of major groups included.
Selected species
Phyllanthus abnormis Baill. – Drummond's leafflowerPhyllanthus acidus Skeels – Otaheite gooseberryPhyllanthus acuminatus Vahl – Jamaican gooseberry treePhyllanthus amarus SchumacherPhyllanthus anamalayanus G.L.WebsterPhyllanthus angustifolius Sw.Phyllanthus arbuscula J.F.Gmel.Phyllanthus axillaris Müll.Arg.Phyllanthus brasiliensis Poir.Phyllanthus caesiifolius Petra Hoffm. & CheekPhyllanthus caroliniensis Walt. – native to the AmericasPhyllanthus cauliflorus Griseb.Phyllanthus cladanthus Müll.Arg.Phyllanthus cochinchinensis Spreng.Phyllanthus coluteoides Baill. ex Müll.Arg.Phyllanthus cuneifolius CroizatPhyllanthus debilis Klein ex Willd.Phyllanthus distichus Hook. & Arn.Phyllanthus emblica L. – Indian gooseberry, also known as amla or amalaki.Phyllanthus engleri PaxPhyllanthus epiphyllanthus L.Phyllanthus ericoides Torr.Phyllanthus eximius G.L.Webster & ProctorPhyllanthus fadyenii Urb.Phyllanthus fluitans Benth. ex Müll.Arg. – red root floater, sometimes sold in aquarium shopsPhyllanthus fraternus G.L.WebsterPhyllanthus gentryi WebsterPhyllanthus grandifolius L.Phyllanthus gunnii Hook.f.Phyllanthus hakgalensisPhyllanthus hirtellus F.Muell. ex Mull.Arg. Phyllanthus juglandifolius Willd.Phyllanthus lacunarius F.Muell.Phyllanthus latifolius Sw.Phyllanthus liebmannianus Muell.Arg.Phyllanthus maderaspatensis L.Phyllanthus microcladus Muell.Arg.Phyllanthus millei Standl.Phyllanthus mirabilis Müll.Arg. – one of the four succulent species of this genusPhyllanthus montanus Sw.Phyllanthus myrtifolius Muell.Arg.Phyllanthus muellerianus ExellPhyllanthus niruri L. – Chanca piedra Phyllanthus nyale Petra Hoffm. & CheekPhyllanthus parvifolius Buch.-Ham. ex D.DonPhyllanthus pavonianus Baill.Phyllanthus pentaphyllus C.Wright ex Griseb.Phyllanthus phialanthoides Falcón & J.L.GómezPhyllanthus polygonoides Nutt. ex Spreng. – Smartweed leafflowerPhyllanthus polyspermus Shumach. & Thonn. – often misidentified as P. reticulatusPhyllanthus profusus N.E.Br.Phyllanthus pulcher Wallich ex Muell.Arg.Phyllanthus reticulatus Poir. – Asian sp. similar in appearance to P. polyspermusPhyllanthus revaughanii CoodePhyllanthus rufuschaneyi Welzen, R.W.Bouman & EntPhyllanthus saffordii Merr.Phyllanthus salviifolius KunthPhyllanthus sepialis Müll.Arg.Phyllanthus societatis Müll.Arg. Phyllanthus sponiifolius Müll.Arg. Phyllanthus stipulatus G.L. WebsterPhyllanthus taxodiifolius BeillePhyllanthus tenellus Roxb.Phyllanthus urinaria L. – chamberbitterPhyllanthus virgatus G.Forst.Phyllanthus warnockii G.L.WebsterPhyllanthus watsonii Airy ShawPhyllanthus welwitschianus Müll.Arg.
Fossil record
Two fossil seeds of a Phyllanthus species have been extracted from borehole samples of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland. The seeds are similar to seeds of the fossil species †Phyllanthus triquetra and †Phyllanthus compassica from the Oligocene and Miocene of West Siberia. Phyllanthus fossils are known from several Miocene and Pliocene sites in Poland.
Phyllanthus are of note in the fields of pollination biology and coevolution because some but not all species in the genus have a specialized mutualism with moths in the genus Epicephala, in which the moths actively pollinate the flowers. While ensuring that the tree may produce viable seeds, the moths also lay eggs in the flowers' ovaries where their larvae consume a subset of the developing seeds as nourishment. Other species of Epicephala are pollinators of certain species of plants in the genera Glochidion and Breynia, both of which are phylogenetically nested within Phyllanthus.
Particularly for its content of tannins, P. emblica fruit has a history of use in traditional medicine and is under study for its potential biological properties. Leaves, roots, stem, bark and berries of this genus contain lignans and other phytochemicals.