Aporosa octandra

A. octandra is in a clade with sisters Aporosa ficifolia, A. planchoniana, A. tetrapleura, and A. villosa, separated from other species within the Appendiculatae section of the Aporosa genus.[7]

The tree, sometimes shrub, which grows up to 15m tall, and up to 30cm in diameter.[8] In India the tree may grow some 9-12m tall, but is usually shrubby. The bark is a light-brown to grey or tan, can be either smooth, roughened, thickened, flaky or with narrow vertical ridges and cracks.[8] Inner bark is pink. The wood is cream in colour. The branchlets usually have a few small scars of fallen leaves. The leaves are narrow, ovate to elliptic in shape, some 5-23.5 by 2-8cm in size, base is rounded to cuneate, obtuse in shape, the margins are lowly undulate to lowly glandular-crenate or -serrate and are sometimes slightly recurved; the apex of the leaves is acuminate to cuspitate; the leave are thinnish and smooth, not brittle and dull or slightly shiny; when dry they are grey-brown to green-brown above, greenish to brownish below. Inflorescences occur axillary or just below leaves. Staminate inflorescences occur as 1-5 cluster together, with 6-8 laxly set flowers, staminate flowers have 4 sepals and two stamens. Pistillate inflorescences occur as 1 to 3 clustered together, with up to 11 densely arranged flowers along the rachis, 4 sepals, occasionallyy staminodes, slightly raised and elongated stigmas, perpendicular to the sides of the ovary. The fruit are ovoid to ellipsoid in shape, rarely globose; slightly stiped and beaked young fruit are 9-13 x 6-10mm in size, punctate; they dry to dark brown/black, with sparse hairs. Terete, ellipsoid seeds (1 maybe 2 per fruit) are 7-8 x 5-6 x 3-4mm.

Like other species in the Appendiculatae section of the Aporosa genus, this species has: glands that are basal and adaxial; disc-like glands scattered unevenly within arches of marginal veins throughout the abaxial surface of the leaf/lamina; stigma that are papillate; and theovary has pubescent septae and column.[7]

Noting the caveat given above by Schot, the varieties are described as follows:[8]

The species is found in from Queensland, Australia to New Guinea, through Southeast Asia to southern Zhōngguó/China and India.[2] Countries and regions in which it is native to include: Australia (Queensland); Papua Niugini (eastern New Guinea); Indonesia (West Papua, Sulawesi, Kalimantan, Jawa, Sumatera); Philippines; Malaysia (Sabah, Sarawak, Peninsular Malaysia); Thailand; Cambodia; Vietnam; Zhōngguó/China (Hainan, South-Central, Southeast); Laos; Myanmar; India (Nicobar Islands, Andaman Islands, Assam, Nagaland, Manipur, Mizoram, Tripura, Meghalaya, Sikkim, West Bengal, Odisha, Uttarakhand); Bangladesh; East and West Himalaya; Bhutan; Nepal.[1]

A. octandra var. chinensis is found from Southeast Zhōngguó/China (including Hainan) to northern Vietnam.[3]

A. octandra var. malesiana is found from parts of Malesia to southwestern Thailand.[4] Countries and regions in which it is native include: Philippines; Indonesia (Sulawesi, Kalimantan, Sumatera, Jawa); Malaysia (Sabah, Sarawak, Peninsular Malaysia); Thailand (southwest). It is noted that it has been recorded in error in New Guinea and Queensland.[4]

The native distribution of the autonym variety A. octandra var. octandra is from Southeast Asia to South Central Zhōngguó/China and the Himalaya.[5] Countries and regions in which it occurs are: Thailand; Cambodia; Vietnam; Zhōngguó/China (Guangdong, Guangxi, Hainan); Laos; Myanmar; India (Nicobar Islands, Andaman Islands, Assam, and other areas); Bangladesh; East and West Himalaya region; Nepal.

A. octandra var. yunnanensis is native to an area of Southeast Asia to Yunnan (Zhōngguó/China).[6] Countries and regions in which it grows are: Thailand; Cambodia; Myanmar; Laos; and Yunnan (Zhōngguó/China).

The species grows in a variety of habitats: primary, secondary, subtropical, evergreen, and (mixed) deciduous forests, savannah, belukar (low forest/scrub, perhaps anthropogenic), moist to rather dry.[8] It favours shaded understorey or (partly) open places (though see below in Hong Kong). The tree tends to be a gallery species, favouring hills, (steep) slopes, forest edges, road sides, plains, thickets and alongside watercourses. It is found in a wide range of soils: from sandy to sandstone, granitic sand, limestone, clay, rocky to rocky loam, on granite or sandstone bedrocks. Grows at altitudes from 40m to 1500m. The plant generally flowers and fruits throughout the year.

In the Na Haeo Forest Reserve (Na Haeo District, Loei Province, northeastern Thailand), A. octandra var. yunnanensis is locally dominant in the bamboo-deciduous forest, alongside Cananga brandisiana, Croton persimilis, Gardenia sootepensis, Lagerstroemia sp., Colona flagrocarpa and Pterocarpus macrocarpus.[17] In the medium layer of the forest (some 6-9m tall), the varieties octandra and yunnanensis are common, along with Quercus kerrii, Memecylon scutellatum, Harrisonia perforata and a dense bamboo understory. The bamboo cover is so high that in order to increase woody tree species richness and diversity, that control measures on the bamboo may be advisable.

There is a project of reforestation in the Doi Tung mountainous area of northern Thailand. Two varieties of A. octandra grow in the area.[18] Both are deciduous trees in habit at this place, flower in January and February and fruit in May and June. The octandra variety grows in both evergreen with bamboo forest and disturbed areas (including roadsides); it grows on soils derived from granite and limestone bedrocks; is found between 1200 and 1375m altitutude; and has leaves from May until December. The yunnanensis variety grows in evergreen forest; in soils derived from granite bedrock; at elevations of 1100 to 1450m; and has leaves from April to December.

On the islands of the Mekong river in Kratié and Steung Treng Provinces, northern Cambodia, the variety yunnanensis is moderarately common in dipterous deciduous forest, and also occurs in degraded areas and secondary growth communities. The tree is deciduous in this area, grows on sediments derived from metamorphic sandstone bedrock, at about 25 to 30m.a.s.l.[16]

In India it is commonly found in primary forests and grasslands, growing on sandy, clay or rocky soil, at up to 1200 m altitude.

Mizoram University (India) is embedded in a regenerating tropical wet evergreen and semi-evergreen forest. The dominant trees of this forest are Schima wallichii, Aporosa octandra, Castanopsis tribuloides, and Syzgium praecox.[19]

The now regenerating forests of Hong Kong were heavily degraded in the 19th and early 20th centuries with the most impact occurring during World War II (here 1941-5).[20] A. octandra is not only one of the light demanding early pioneers in the rainforest, but is also an indicator species, alongside Garcinia oblongifolia of early pioneer communities that tend to disappear as more mature vegetation communities take over. This causes the pioneer communities to have higher diversity than more established vegetation.

The variety octandra grows in montane sparse forests or scrub in Zhōngguó/China.[13]

The whitefly species Cockerelliella setosus, of Little Andaman Island (India), infests A. octandra.[21]

Hanuman langurs (Semnopithecus entellus) in subtropical forest of Nepal eat the young leafy parts and inflorescences, but not the fruits, thus playing no part in the plants dispersal.[8]

Three insect species have been recorded forming galls on the leaves or twigs of the species: Dolcrothrips tryboni, Acerocecidium sp., and Eriophyes aporosae.[8]

The species is rated as at Least Concern by the IUCN Redlist.[1] This is because the tree has a very wide distribution with a large population and that it is not at the moment and foreseeable future experiencing any major threats. However, the populations are severely fragmented, there is a continuing decline of mature individuals, and there is a continuing decline in the area, extent and quality of habitat, pretty much business as usual for human impacts on the natural world.

The tree/shrub provides fodder for domesticated animals, timber for house construction (particularly house-posts), wood for fuel. The bark yields a red dye, while a decoction of the leaves is used to dye clothes black in northeast India. The fruits are edible. The bark is chewed as a kind of betel[8] In India, the wood (called kokra or coco wood) is used, it is described as durable, (very) hard and close-grained. It is used in construction, and for house-posts, rafter, rice pounder and furniture.

The Karbi people in Karbi Anglong district (Assam, India) use the twigs and leaves of what they call tamsir as a mordant when using black minerals to dye yarn black.[23] The leaves are additionally used to prevent the yarn making contact with the dyeing vessel, which is held to make the yarn brittle. This latter use also occurs when dyeing with the lac insect Kerria lacca, to make pink yarn. Yarn dyed black contributes to the red, white and black striped fabric usually worn by elderly women, and is used in ritual to appease gods in case of sudden illness.

There are many recorded uses of the species in traditional medicine in Asia, including in old Ayurvedic medical practices.[25][24] In Cambodia the bark is a component of a folk-remedy to relieve tooth-ache, while the roots are used in another folk-medicine mixture to be used "against women diseases after delivery".[22] In Mizoram it is recorded as treating many ailments.

A. octandra var. malesiana has rather hard wood that is used for planks in houses, and for beams or furniture.[8]

• Balakrishnan & Chakrabarty, 2007, The family Euphorbiaceae in India: A synopsis of its profile, taxonomy and bibliography, Bishen Singh Mahendra Pal Singh, Dehra Dun[2]
• Chakrabarty & Balakrishnan, 2018 Indo-Burmese Phyllanthaceae: A Taxonomic Revision, Bishen Singh Mahendra Pal Singh, Dehra Dun
• Chayamarit & Van Welzen, 2005, Euphorbiaceae (Genera A-F): Flora of Thailand 8(1), The Forest Herbarium, National Park, Wildlife and Plant Conservation Department, Bangkok
• Govaerts, 1995 World Checklist of Seed Plants, MIM, Deurne [does not accept var. yunnanensis, cites as Aporusa villosa]
• Govaerts & others, 2000, World Checklist and Bibliography of Euphorbiaceae (and Pandaceae), The Board of Trustees of the Royal Botanic Gardens, Kew [does not accept var. yunnanensis, cites as Aporusa villosa.]
• Leti and others, 2013, Flore photographique du Cambodge, Éditions Privat, Toulouse
• Pandey, 2009, Floristic diversity of Ferrargunj forest area in South Andaman, Journal of Economic and Taxonomic Botany 33:747-68