Dissochaeta Blume, Flora 14: 492. 1831

Kartonegoro, Abdulrokhman, Veldkamp, Jan Frits, Hovenkamp, Peter & Welzen, Peter van, 2018, A revision of Dissochaeta (Melastomataceae, Dissochaeteae), PhytoKeys 107, pp. 1-178 : 1

Dissochaeta Blume, Flora 14: 492. 1831 Map 1

Dissochaeta Blume, Flora 14: 492. 1831. Dissochaeta sect. Dissochaeta Blume, Flora 14: 493. 1831. Dissochaeta sect. Eudissochaeta Blume ex Endl., Gen. Pl. 1219. 1840, nom. inval. Dissochaeta sect. Diplostemones Cogn. in Boerl., Handl. Fl. Ned. Ind. 2: 533. 1890, nom. superfl. Type: Dissochaeta vacillans (Blume) Blume (lectotype, designated by Kartonegoro and Veldkamp 2010, pg. 128).

Dissochaeta Blume sect. Diplectria Blume, Flora 14: 501. 1831. Diplectria (Blume) Rchb., Deut. Bot. Herb.-Buch.: 174. 1841. Type: Diplectria cyanocarpa (Blume) Kuntze (lectotype, designated by Veldkamp et al. 1979, pg. 410) [= Dissochaeta divaricata (Willd.) G.Don].

Aplectrum Blume, Flora 14: 502. 1831 [non Torr. 1826], nom. inval. Type: Aplectrum viminale (Jack) Blume (lectotype, designated by Veldkamp et al. 1979, pg. 410) [= Dissochaeta viminalis (Jack) Clausing].

Dalenia Korth. in Temminck, Verh. Nat. Gesch. Ned. Bezitt., Bot.: 243. 1844. Dissochaeta sect. Dalenia (Korth.) Baill., Hist. Pl. 7: 51. 1877. Type: Dalenia pulchra Korth. [= Dissochaeta pulchra (Korth.) J.F.Maxwell].

Omphalopus Naudin, Ann. Sci. Nat., Bot. sér. 3, 15: 277. 1851. Dissochaeta sect. Omphalopus (Naudin) Baill., Hist. Pl. 7: 51. 1877. Type: Omphalopus fallax (Jack) Naudin (lectotype, designated by Bakhuizen van den Brink f. 1943, pg. 118) [= Dissochaeta fallax (Jack) Blume].

Anplectrum A.Gray, U. S. Expl. Exped., Phan. 1: 597. 1854. nom. nov. for Aplectrum Blume, non. Torr. 1826. Type: Anplectrum viminale (Jack) Triana (designated by Veldkamp et al. 1979, pg. 410) [= Dissochaeta viminalis (Jack) Clausing].

Backeria Bakh. f., Contr. Melastom.: 130. 1943, nom. superfl. Type: Backeria viminalis (Jack) Bakh. f. (lectotype, designated by Veldkamp et al. 1979, pg. 410) [= Dissochaeta viminalis (Jack) Clausing].

Neodissochaeta Bakh. f., Contr. Melastom.: 134. 1943, nom. superfl. Type: Neodissochaeta gracilis (Jack) Bakh. f. (lectotype, designated by Kartonegoro and Veldkamp 2010, pg. 128) [= Dissochaeta gracilis (Jack) Blume].

Melastoma auct. non Burm. ex L.: Jack, Trans. Linn. Soc. London 14: 3. 1823; Blume, Bijdr. Fl. Ned. Ind. 17: 1067. 1826. p.p., excl.type.

Description.

Woody climbers, scrambling; bark greyish, tan to light brown, finely fissured. Branchlets terete or subangular; glabrous to tomentose or floccose with minute stellate or simple glandular or eglandular bristly hairs; sometimes with adventitious roots; nodes swollen with an interpetiolar annular line, ridge or crest, annular or pectinate. Leaves opposite; petioles terete, rarely flattened with a dorsal groove, glabrous to tomentose or with bristly hairs; blades membranous, subcoriaceous or rarely chartaceous with acrodromal venation, ovate to lanceolate, rarely suborbicular, base rounded to cordate, margins entire, rarely serrulate, apex acute to acuminate, midnerve with 1 or 2 pairs of lateral veins and 1 pair of intramarginal veins, secondary venation reticulate; nerves typically sunken adaxially, raised abaxially; adaxial side glabrous, rarely with scattered simple bristle hairs, abaxial side glabrous to densely brown tomentose or with dense bristle hairs. Inflorescences terminal, or rarely axillary, many-flowered, thyrses with 2 to 5 ramifications, decussate, ending with 3-flowered cymules; main axis quadrangular, indumentum similar to that of the branchlets; bracts and bracteoles distinct or minute, linear to ovate, glabrous to densely tomentose, mostly inconspicuous and early caducous; pedicels glabrous to tomentose, sometimes with bristle hairs, longer in central flower, shorter in lateral ones. Flowers 4-merous. Hypanthium campanulate, urceolate, tubular or cyathiform, glabrous to densely tomentose, with or without bristle hairs, often with 4 or 8 vertical ridges; calyx lobes truncate or with distinct rounded, triangular or lanceolate lobes, glabrous or with scattered bristle hairs to nearly densely tomentose; petals in bud conical or rounded, tubular or angular, tip rounded to acute or acuminate, contorted; mature petals ovate, obovate or suborbicular, reflexed or not, apex acute or obtuse, base thin, truncate to clawed, symmetric, glabrous, sometimes with appressed hairs at base and apex or margins puberulous. Stamens 4 or 8, heterantherous when 8, alternipetalous and oppositipetalous or 4 alternipetalous only, smooth or tessellate-reticulate, beaked or not, with terminal pore; filaments flattened, straight or curved sideways; anthers basifixed, sometimes medifixed; the alternipetalous ones thinner, when mature straight or curved and sickle-shaped, at base forming a pedoconnective, sometimes locule not developed and of being staminodal, basal crest membranous, triangular, sagittate, hastate or ligular, with or without paired filiform lateral appendages; the oppositipetalous ones thicker, when mature straight or curved with hooked or S-shaped, connective ridge with erose, bifid or spur-like appendages, basally with or without filiform appendages, sometimes reduced and staminodial less than ⅓ as long as the alternipetalous or absent. Ovary ⅓ to nearly as long as the hypanthium, apex glabrous to densely villous, sometimes with scattered bristle hairs, 4-locular; style straight or curved and hooked at the tip when mature; stigma minute, capitate; ovary concrescent with the hypanthium, with or without 4 or 8 longitudinal septa forming extra-ovarial chambers for the anthers, shallow to reaching to the base of the ovary. Fruits baccate, globose, ovoid to urceolate, dark blue or purple when mature, sometimes with four prominent erect or reflexed calyx remnants, glabrous to floccose; some with distinct vertical ridges. Seeds numerous, cuneate, smooth, flat-topped.

Distribution.

The genus has 54 species and two varieties which are distributed in South China to South–East Asia, mainly in the Malesian Region (Map 1 ). It is present in South China (Hainan; Chen and Renner 2007), Myanmar, Indochina (Cambodia, Laos and Vietnam), the Nicobar Islands, Thailand and throughout Malesia except for the eastern part of the Lesser Sunda Islands (Flores, Sumba and Timor). Borneo is the centre of its distribution with almost 50% of the species. Some species also have a restricted distribution.

Ecology.

The genus is found predominantly in secondary vegetation or more open places within the primary vegetation, such as tree fall gaps, river margins and roadsides ( Kadereit 2006) in evergreen forest, mixed dipterocarp forest, heath forest, hilly forest, swamp forest and montane forest. The plants climb several metres high and produce their flowering and fruiting branches over the tops of small trees and larger shrubs at the end of branches that are in the open.

Notes.

From its inception in 1831, several authors created infrageneric classifications ( Blume 1831a, 1831b, Endlicher 1840, Naudin 1851, Miquel 1855, Baillon 1877, Cogniaux 1890, 1891, Krasser 1893, Merrill 1917, Maxwell 1980b), which were based on floral characters that are highly variable. Therefore, we here refrain from using an infrageneric classification until a phylogenetic analysis shows the various clades that can be recognised morphologically.

Figures

Map 1. Distribution of Dissochaeta (grey).