Introduction
Sumatra is one of the largest islands in Indonesia and one of the richest in biodiversity (Whitten, Reference Whitten1999), although it is also among the least known. Land conversion, the development of industries, illegal logging and forest fires have caused severe pressure on the biodiversity of Sumatran habitats. Syzygium species are key components of Southeast Asian lowland forests, where they provide nectar, pollen and fruit as food for a wide range of insects, birds and mammals (Parnell et al., Reference Parnell, Craven, Biffin, Hodkinson and Parnell2007). These species are also of economic importance for their flowers, fruit, timber, tannins and medicinal properties (Heywood et al., Reference Heywood, Brummitt, Culham and Seberg2007).
In the past, Sumatra was rich in Syzygium, but recent conversion of land from forest to transmigration areas, rice fields and plantations has caused significant biodiversity decline. Furthermore, logging and fire have accelerated the loss of diversity of Syzygium. If this not addressed, Sumatra may suffer a grave loss of endemic plant diversity. Unless they are described very soon, many species of Syzygium may become extinct before they are known. Information on Syzygium in Sumatra must be updated to improve our understanding of what still exists on this island.
The names Syzygium angustovatum Widodo, S. longipetiolatum Widodo and S. tassellum Widodo (Widodo, Reference Widodo2011) were not validly published, because they did not include diagnoses or descriptions in Latin, as required by article 36.1 of the International Code of Botanical Nomenclature in effect at that time (McNeill et al., Reference McNeill, Barrie, Burdet, Demoulin, Hawksworth, Marhold, Nicolson, Prado, Silva, Skog, Wiersema and Turland2006). These names are validly published here.
Since 1 January 2012, it has been permissible to use either Latin or English diagnoses or descriptions (McNeill et al., Reference McNeill, Barrie, Buck, Demoulin, Greuter, Hawksworth, Herendeen, Knapp, Marhold, Prado, Prud'homme van Reine, Smith, Wiersema and Turland2012; article 39.2). Here, we give diagnoses and complete descriptions in English.
This article is based on examination of more than 7000 specimens kept at ANDA, BIOT, BO, K, L and PUNS (Herbarium Fakultas Biologi Unsoed Purwokerto), including specimens from Sumatra and surrounding islands and countries, namely Australia, Borneo, Burma, Indochina, Java, the Moluccas, New Guinea, Peninsular Malaysia, the Philippines, Sri Lanka and Thailand.
For each species, the conservation status is proposed, following IUCN guidelines (IUCN, 2015).
Species Descriptions
1. Syzygium abatakum Widodo, sp. nov.
Close to Syzygium pyrifolium (Blume) DC. but the leaves are elliptic to oblong, 10–20 × 5–8 cm (not 6–10 × 3–4 cm). – Type: Indonesia, North Sumatra, Sibolangit Bandar Baru, 750 m, J.A. Lörzing 6391 (holo BO, iso L). Fig. 1.
Syzygium abatakum. A, Leafy twig and inflorescence. B, Leaf venation. C, Flower bud. D, Flower, longitudinal section. E, Petals. Drawn by Subari.
Tree 10 m tall, 10 cm dbh. Twigs terete-compressed, bark smooth. Leaves opposite, elliptic to oblong, 10–20 × 5–8 cm; upper surface olivaceous brown when dry, smooth and glossy, lower surface brownish; base cuneate, apex shortly acuminate; midrib yellowish to dark brown; major lateral veins straight, 15–25 pairs, 0.5–1.5 cm apart, minor lateral veins 1; oil dots between 2 major lateral veins c.80 per cm2; intramarginal veins 2, 3–4 mm from margin; petiole > 15 mm long with longitudinal stripes, grooved above. Inflorescence terminal, a simple panicle-corymb, > 60 flowers per inflorescence; peduncle terete or slightly angled, 3 mm thick. Flowers shortly pedicellate or sessile, pseudostipe 2–3 mm, hypanthial cup 3–4 mm, funnel-shaped. Sepals persistent, straight, 4, free, semicircular, 1–2 mm long. Petals white, 4, free, semicircular, 2–3 mm long. Outer stamens 7–10 mm long, 25–50 filaments, anther 0.7 mm long. Style c.0.8 cm long. Fruits unknown.
Distribution
Endemic in Sumatra.
Habitat and ecology
100–930 m altitude.
Proposed IUCN conservation assessment
Although this species is known from several areas in Sumatra, it occurs in lowland forest that has been extensively cleared and there are no recent collections. It is likely that a significant reduction has occurred, but in the absence of more precise information about its current distribution, it is difficult to quantify. An assessment of Near Threatened would be conservative.
Specimens examined. Indonesia. Aceh: Simeulue Island, Tapak Defayan, 9 iv 1920, Achmad 1783 (BO, L). North Sumatra: Sibolangit Bandar Baru, 9 x 1925, J.A. Lörzing 14090 (BO, L); loc. cit., J.A. Lörzing 4256 (BO, L); loc. cit., 24 iv 1919, J.A. Lörzing 6391 (BO, L); Tapanuli North Nias 2 m, 19 vii 1928, Choeroeddin s.n. (BO, L). West Sumatra: Sijunjung Muara, Baharoedin 26 (bb 9066) (BO); Suliki, 3 viii 1922, Rasad 6 (BO); Ophir, Watu Pauk, 15 iii 1924, St. Maharadja 11 (BO); West Coast and Agam, 23 vii 1923, Datoek Bungsu 7 (BO, L). South Sumatra: Lematang Ulu, P.M. Lambach 1916 (BO, L); Rewas, Grashoff 1135 (BO, L).
Vernacular names
Kalek jambu (Minangkabau), kilat jambu.
Syzygium abatakum resembles S. pyrifolium, but the upper leaf surface is shiny and olivaceous brown, and the lower part is brown when dry; the leaf base is cuneate and the leaf apex is acuminate. Furthermore, Syzygium abatakum is calyptrate-petalled whereas S. pyrifolium is free-petalled.
2. Syzygium angustovatum Widodo & Chikmawati, sp. nov.
Close to Syzygium confusum (Blume) Bakh.f. but differs in its leaf shape, which is very narrowly ovate (not oblong-lanceolate), and its petiole is not swollen. – Type: Indonesia, Riau Islands, Batam Island, 649 HB (holo BO, accession number BO 1283228). Fig. 2.
Syzygium angustovatum. A, Leafy twig and inflorescence. B, Leaf venation. C, Inflorescence. D, Flower. E, Flower, longitudinal section. Drawn by Anne and Subari.
Syzygium angustovatum Widodo, Syzygium Sumatra: 59 (2011) (nom. inval., no Latin description).
Tree to 8 m tall. All parts glabrous. Twigs terete and slightly compressed near the nodes. Leaves opposite, very narrowly ovate, somewhat lanceolate to linear, 20–44 × 3–5 cm, tapered gradually from below the middle to apex; upper surface blackish brown, lower surface reddish brown when dry; base broadly obtuse or rounded, apex long acute; midrib rounded below, reddish brown when dry; major lateral veins very faint on both the upper and lower surfaces, c.30 pairs, 1–2 cm apart, at an angle of 60–70° to midrib, oil dots a few per cm2; intramarginal veins faint, 1–2 mm from margin; petiole slender, 10–13 mm long, scaly, peeling off, black when dry. Inflorescence to 5 cm long, terminal, with up to 21 flowers; peduncle terete and 4-angled, drying dark brown. Flowers with short ultimate inflorescence axis, pseudostipe c.7 mm long, hypanthial cup c.10 mm long, trumpet-shaped to turbinate. Sepals 4, free, 3.5 × c.4 mm. Petals semicircular, free, c.5.5 × 5.5 mm, with a few gland dots. Outer stamens 15 mm long. Style c.20 mm long. Ovary 2-locular. Fruits campanulate, 10 mm long (immature).
Distribution
Endemic in Sumatra. Known from the type specimen only.
Habitat and ecology
Lowland forest.
Proposed IUCN conservation assessment
This species is known only from the type locality, which is in an area that has been heavily developed as a free trade zone. Its total distribution and population size are unknown. Further surveys are required to establish whether it still occurs in its type locality or on surrounding islands. Until more information is available, it should be assessed as Data Deficient.
Syzygium angustovatum also resembles S. korthalsii Widodo but differs in its twig, which is terete and slightly compressed below the nodes, not 4-angled or 4-winged. Syzygium angustovatum is characterised by its hypanthial cup, which is trumpet-shaped.
3. Syzygium bengkulense Widodo, sp. nov.
Very like Syzygium jambos (L.) Alston but the leaves are lanceolate to very narrowly ovate (not elliptic-lanceolate), the dried leaf colour dirty dark brown and yellowish to orangish brown (not olive green to yellowish). – Type: Indonesia, Sumatra, Bengkulu, Kepahiang, 700 m, 29 viii 1973, Eddy D Kosih 112 (holo BO; iso L, K). Fig. 3.
Syzygium bengkulense. A, Leafy twig and inflorescence. B, Leaf venation. C, Flower buds. D, Petal from Eddy D Kosih 112 (BO). Drawn by Subari.
Small tree. Twigs terete, smooth, bark yellowish brown, peeling irregularly or sometimes slightly scaly. Leaves opposite, thickly coriaceous, lanceolate to very narrowly ovate, 15–27 × 3–5.5 cm; upper surface dirty dark brown, lower surface yellowish to orangish brown when dry; base cuneate, apex acute; midrib narrowly channelled on the upper surface, rounded and impressed, raised on the lower surface; major lateral veins very faint, 9–15 pairs, 1.5–2 cm apart, curved then straightening to follow margin; minor lateral veins also very faint, at an angle of 45–60° to midrib; intramarginal veins 2, the outer c.1 mm from margin, the inner 3–4 mm from margin; petiole 6–10 mm long, not swollen, longitudinally striped. Inflorescence a terminal panicle, 2–3 × c.3 cm, flowers lax, up to 27 per inflorescence, peduncle 4-angled. Flowers with pedicel 3–4 mm long, bluntly 4-angled; pseudostipe 4-angled, up to 4 mm long; hypanthial cup none or 1 mm long. Sepals 4 persistent, free, two kinds, the longer narrower ones outside the wider ones; calyx shape semicircular and/or triangular, 3–5 × 4–6 mm wide. Petals 4 free, light red. Mature stamens and style not seen. Fruits white.
Distribution
Endemic in Sumatra. Known from the type specimen only.
Habitat and ecology
Slopes in forest, 700 m altitude.
Proposed IUCN conservation assessment
This species is known only from the type locality, which is in an area that has been subject to significant deforestation. However, without further surveys, there is insufficient information about its distribution and population size. Therefore it is assessed as Data Deficient.
Syzygium bengkulense is very like S. jambos, but the leaves are lanceolate to very narrowly ovate (not elliptic-lanceolate), the dried leaf colour is dirty dark brown and yellowish to orangish brown (not olive green to yellowish), the inflorescence position is terminal (not terminal and axillary) and the petals are light red (not white).
4. Syzygium comosum Widodo, sp. nov.
Like Syzygium jambos (L.) Alston but the leaves are narrower and shorter, and it is a rheophytic shrub. – Type: Indonesia, Sumatra, West Sumatra, Payakumbuh-Pakanbaru, Lubu Bangku 15 vii 1956, M. Jacobs 4605 (holo BO; iso L, 2 sheets). Fig. 4.
Syzygium comosum. A, Leafy twig and fruit. B, Leaf venation. C, Winged twig and leaf arrangement. D, Hypanthial cup. E, Hypanthial cup, longitudinal section. F, Fruit, longitudinal section. G, Seed. Drawn by Wahyu and Subari.
Syzygium tassellum Widodo, Syzygium Sumatra: 40 (2011) (nom. inval., no Latin description).
Rheophytic shrub, 1–3 m tall, < 5 cm dbh. All parts glabrous. Old twigs terete, young ones 4-angled. Bark smooth, not peeling, greyish. Leaves 3-verticillate or whorled, distally crowded and clustered, narrowly lanceolate, 7–14 × 0.5–1.6 cm, usually dark brown above and brown beneath when dry; base cuneate, apex acute, tip very narrowly rounded; midrib narrowly furrowed on the upper surface, slender and raised below, yellowish or reddish brown when dry; major lateral veins 13–15 pairs, 1–1.5 cm apart, faint on both surfaces, straight and curved, at an angle of c.45° to the midrib, oil dots none or a few between the two major lateral veins; intramarginal vein 1, straight, faint, 1–2 mm from margin; petiole slender, not swollen, 3–5 mm long, drying blackish. Inflorescences terminal and axillary, simple or solitary, to 5 cm long; peduncle and branches terete. Flowers with ultimate inflorescence axis c.3 mm long; pseudostipe c.3 mm long; hypanthial cup c.10 mm long. Sepals c.5 × c.7 mm. Petals not seen. Stamens not seen. Style c.20 mm long. Fruits globose, c.2 cm diameter, drying dull dark purple or blackish.
Distribution
Endemic in Sumatra.
Habitat and ecology
Near streams, 400–800 m altitude.
Proposed IUCN conservation assessment
There is insufficient information about the distribution and population size of this species to determine its conservation status. Therefore it is assessed as Data Deficient; further fieldwork is required to determine if it is still extant in its known localities and if it occurs in the surrounding areas.
Specimens examined. Indonesia. West Sumatra: from Payakumbuh 28 km towards Pekanbaru and Lubu Bangku; Padang above Teluk Kabung Mt Sunger Raja Agam, 15 vii 1956, Jacobs 4605 (BO, L); 7 vi 1953, van Borssum Waalkes 1607 (BO).
Syzygium comosum is very like S. jambos, but the leaves are narrower and shorter and it is a rheophytic shrub. It is also like Syzygium salictoides (Ridl.) I.M.Turner and S. vrieseanum (Miq.) Amshoff, but it differs from the former in its fruits, which are much larger, and from the latter in its habit, which is a shrub and the leaf upper surface drying dark brown not yellowish grey. The epithet comosum describes the leaves, which are crowded near the ends of the twigs, like tassels.
5. Syzygium ketambense Widodo, sp. nov.
Similar to Syzygium blumei (Steud.) Merr. & L.M.Perry, from which it differs in having elliptic-oblong leaves; cuneate (not subcordate) leaf bases; longer, more slender, not subsessile, black petioles and thicker, longer peduncles. – Type: Indonesia, Sumatra, Aceh, Ketambe Research Station, 700 m, 11 iii 1982, Kramadibrata 332 (holo BO). Fig. 5.
Syzygium ketambense. A, Leafy twig. B, Leaf venation. C, Inflorescence. D, Flower buds. E, Petals. A–E from K. Kramadibrata 332. Drawn by Anne.
Tree. Twigs terete, bark peeling off, pale yellow. Leaves opposite, elliptic-oblong, 8.5–13.5 × 2.8–4.5 cm, yellowish olive when dry; base cuneate, apex shortly acuminate; midrib flat above, narrowly furrowed; major lateral veins 8–9 pairs, 1–1.5 cm apart, direction at an angle of 60–70° to midrib, straight and curved; minor lateral veins 1–2; oil dots between 2 major lateral veins numerous; intramarginal veins 2, 2–3 mm from margin; petiole 5–8 mm long, drying black. Inflorescences to 13 × c.8 cm; terminal and axillary panicles, with 9–21 lax flowers each; peduncle terete or slightly 4-angled, thick. Flowers ultimate inflorescence axis to 2.6 cm long; pseudostipe 4–5 mm; hypanthial cup c.8 mm, funnel-shaped. Sepals persistent, 4, free, semicircular, 2.5–7 × 7–10 mm, oil dots > 80 per cm2, margin hyaline. Petals 4, free, semicircular, 5–10 × 5–7 mm, oil dots > 100 per petal, greenish white. Stamens > 100, c.1.2 cm long, anther c.1 mm long. Style c.1.5 cm long. Ovary 2-locular. Fruits unknown.
Distribution
Endemic in Sumatra. Known from the type specimen only.
Habitat and ecology
Mountainous land.
Proposed IUCN conservation assessment
This should be either Data Deficient, because it is known only from a single specimen and there is no other information about its distribution or population size, or Least Concern, because there are no identified threats, and it grows in a relatively well-preserved area.
Syzygium ketambense is most similar to S. blumei and S. astronioides (C.B.Rob.) Merr. It differs from the former in having elliptic-oblong leaves; cuneate, not subcordate, leaf bases; longer, more slender, not subsessile, black petioles; and thicker, longer peduncles. It differs from the latter in having the leaves drying yellowish not dark brown, much larger flowers, and free petals. The specific characters of Syzygium ketambense are the large panicle up to 13 cm long, with large hypanthium up to 1 cm diameter, long ultimate inflorescence axis up to 2.5 cm long and midrib with oil dots.
6. Syzygium longipetiolatum Widodo, sp. nov.
Similar to Syzygium tahanense (Ridl.) I.M.Turner but a medium-sized tree up to 26 m tall and 26 cm diameter, not a shrub, and much longer petioles. – Type: Indonesia, Sumatra, South Sumatra, Banyuasin, 15 m, Boschproefstation n 1.29T 1P.32 (holo BO).
Syzygium longipetiolatum Widodo, Syzygium Sumatra: 80 (2011), fig. 39 (nom. inval., no Latin description).
Tree to 26 m tall, 26 cm dbh. All parts glabrous. Twigs usually terete. Leaves opposite, obovate, ovate, or elliptic, 4–10 × 5–8 cm, brownish yellow when dry; base obtuse, apex obtuse with short acumen; midrib impressed above, raised below, drying dark brown; major lateral veins faint, straight and curved, 6–8 pairs, 1–1.5 cm apart, at an angle of 55–65° to midrib; minor lateral veins 2–3 between major laterals; oil dots between 2 major lateral veins a few per cm2; intramarginal veins 2, 1–2 mm from margin; petiole 15–20 mm long, slender, black when dry. Inflorescences terminal and axillary fascicles, to 6 cm long, very dense, > 60 flowers per inflorescence, peduncle terete. Flowers with ultimate inflorescence axis or pedicel sessile to 3 mm long; pseudostipe to 10 mm long; hypanthial cup 12–17 mm long, funnel-shaped. Sepals 4, free, semicircular and semitriangular, 2–3 × c.5 mm. Petals 4, free, semicircular, 3–4 × c.6 mm. Stamens > 100, 6–10 mm long, anther 1 mm long. Style c.12 mm long. Ovary 2-locular. Fruits globose, 10–15 mm diameter.
Distribution
Endemic in Sumatra, North and South Sumatra provinces.
Habitat and ecology
Lowland forest, 0–75 m altitude.
Proposed IUCN conservation assessment
Although this species is known from several areas in Sumatra, it occurs in lowland forest that has been extensively cleared and there are no recent collections. It is likely that a significant reduction has occurred, but in the absence of more precise information about its current distribution, it is difficult to quantify. An assessment of Near Threatened would be conservative.
Specimens examined. Indonesia. North Sumatra: Maware Duwe, Sibolangit Iwaan T3 P 542 (BO); Bb T 798 (BO, L); Endert 217 (BO), E.iP 914 (BO), 915 (BO), 129E (BO), iP 798 (BO, L); Thorenaar 29 T2 P32 (BO, L); Iwaan 1298 Zip 798 (BO); South Sumatra: Palembang Lematang Ilir, Banyuasin, Kebunkelon Dorst 29 (BO, L). T2 P.32 (BO, L); Teijsmann 3786 A (BO, L); Bünnemeijer 6 (BO, L).
Vernacular name
Kelat rawang.
Syzygium longipetiolatum is similar to S. tahanense, but it is a medium-sized tree up to 26 m tall and 26 cm diameter, not a shrub. It has longer petioles, up to 2 cm long and drying black not reddish brown. It also differs in its pseudostipe size, which is up to 10 mm long, not 1 mm long.
Acknowledgements
We should like to thank Prof. Dr Eko B. Walujo (BO), and the keepers of ANDA, BIOT, K and L for permission to examine their collections and for the use of their facilities. Prof. Mien A. Rifai (BO), the late Lyn Craven (CANB), Prof. John Parnell (TCD), Dr Jan Frits Veldkamp (L), Prof. Peter Ashton (K) and Dr Eve Lucas (K) are thanked for advice, references and helpful discussion. Subari, Wahyu and Anne are also thanked for drawing the figures. The Directorate General of Higher Education of the Republic of Indonesia is acknowledged for providing scholarships via IPB.
