Syzygium contiguum Brambach, Byng & Culmsee, 2017

Brambach, Fabian, Byng, James W. & Culmsee, Heike, 2017, Five new species of Syzygium (Myrtaceae) from Sulawesi, Indonesia, PhytoKeys 81, pp. 47-78 : 56-61

2. Syzygium contiguum Brambach, Byng & Culmsee sp. nov. Figures 3 , 4 , 8

Myrtaceae " sp. 9" ( Culmsee and Pitopang 2009).

Diagnosis.

Syzygium contiguum is a species of treelets with slender, angular young branchlets and (sub-)sessile, chartaceous leaves with few (8-13), distinct secondary veins, two marginal veins, and conspicuous cordate bases; the basal lobes of opposed leaves often reach each other. The dense or lax paniculate inflorescences are terminal or arise from the upper leaf axils and bear small (5-6 × 3-4 mm in mature buds) pyriform flowers with numerous white stamens. The species is similar to Syzygium urdanetense (Elmer) Merrill (1951, 420) from the Philippines but differs from that species by angular (vs usually terete) young branchlets and inflorescence axes, by smaller (usually 9-14 × 3.5-5 vs 18-35 × 6-11cm), chartaceous (vs coriaceous) leaves with shorter (0-1.5 vs 3-5 mm) petioles and fewer secondary vein pairs (8-13 vs 17-35), and by gland-dotted (vs smooth) petals. It differs from Syzygium paucipunctatum (Koord. and Valeton) Merrill and Perry (1939, 169) from Sumatra, Java, and Borneo, in chartaceous (vs coriaceous), leaves with no or few gland dots (vs gland-dotted beneath) which dry dark reddish brown to very dusky red above and (dark) reddish brown beneath (vs. olive-green above and brownish beneath) and shorter (5-6 vs c. 9 mm long) mature flower buds. Floral formula B1 Bt2 K4* C4* A∞* Ĝ (2)┼ Vx~8.

Type.

INDONESIA. Central Sulawesi (Sulawesi Tengah), LLNP, Kab. Sigi, Kec. Kulawi, 2.4 km ENE of Toro, NW of Pono Valley, tree-inventory plot Pono , 1°29.7'S, 120°03.4'E, 1050 m, Jul 2006: Culmsee H 535 (flowers; holotype L[L.3962133]!, isotype CEB) .

Description.

Treelets, up to 10 m tall, diameter at breast height ≤ 11 cm. Bark and wood not known. Young branchlets 0.5-1 × 1-2 mm, slender, rectangular in cross section, sometimes narrowly winged, epidermis drying dark reddish brown, smooth; soon becoming terete with 4 ridges and eventually terete, bark pale or yellowish brown with flaking remnants of epidermis; with (1-) 2 (-4) pairs of ≤ 2 mm long, caducous cataphylls near the base of the current flush.

Leaves opposite, (sub-)sessile. Petioles 0-1.5 × 1-2 mm, absent or very short and stout, drying very dusky red. Blades (6.5-) 9-14 (-19) × (2.3-) 3.5-5 (-6.1) cm, ratio (1.9-) 2.5-3.2 (-3.6), narrowly elliptic or lanceolate, rarely oblanceolate, base distinctly cordate (or auriculate), basal lobes of opposed leaves often touching each other, apex (long-)acuminate or caudate, margin flat or sometimes minutely revolute; chartaceous, drying dull to satin, dark reddish brown to very dusky red above, (dark) reddish brown beneath; sometimes with scattered black gland dots. Midrib channelled above, prominent, rounded, and darker than the lamina beneath. Secondary vein pairs 8-12, (3-) 5-11 (-18) mm apart, slightly sunken or sometimes slightly prominent, rather inconspicuous above, very prominent and darker than the lamina beneath; some intersecondary veins usually present. Tertiary veins sub-parallel near the midrib to reticulate towards the margin, faint above, prominulous beneath. Inner intramarginal vein 3-7 mm from leaf margin, hardly looping; outer intramarginal vein 0.5-2 mm from leaf margin.

Inflorescences terminal and in the axils of 1-2 distal leaf-pairs, ± lax panicles, (2.5-) 3.5-7.5 (-11) cm long, peduncles 1-3.5 cm long, axes (sub-)angular, flattened. Bracts c. 0.5-2 (-7) mm long, lowermost foliaceous, caducous, others deltate, keeled, ± persistent; bracteoles 2 per flower, 0.5-1 mm long, similar to bracts.

Flowers ≤ 40 per inflorescence, within the panicles in monads or triads, 4-merous, anthopodium absent, c. 15 mm in diameter at anthesis, mature buds 5-6 × 3-4 mm. Hypanthium 4-5 × 3-5.5 mm, obconical to infundibuliform, gland-dotted or ± smooth, hypanthium rim 2 mm long. Calyx lobes 0.5-1 × 1-2.5 mm, deltate first, becoming broadly rounded and eventually splitting irregularly at anthesis. Petals 3-6 × 3-6 mm, pseudocalyptrate, orbicular, gland-dotted. Stamens c. 80-100, filaments 6-10 mm long, white, anthers c. 0.5 mm long, ellipsoid. Ovary bilocular, locules subtended by spongy tissue, ovules c. 8 per locule, spreading. Style 6-8 mm long, pointed.

Fruits 2-seeded, 1.1-1.3 × 1.8-1.9 cm, globose to oblate, drying smooth, pericarp c. 2 mm thick, hypanthium rim c. 5 mm in diameter.

Seeds 9-10 × 12-13 mm, half-moon shaped.

Etymology.

The specific epithet refers to the leaf bases of opposing leaves which, due to their cordate shape and the short petioles, often approach or touch each other.

Phenology.

In Central Sulawesi a slight dry season usually lasts from May to September or October. Flowering was observed during the wet and dry seasons: in July 2016, January/February 2007, July 2007 in Pono and in April 1975 on Mt Nokilalaki.

Distribution and habitat.

According to our present knowledge, the species is endemic to the province of Central Sulawesi. It has been recorded from only three localities in and around LLNP at 1000-1150 m elevation (Figure 4 ). Most of the specimens were collected in our (FB and HC) inventory plot in Pono Valley near the western border of LLNP.

In the Pono inventory plot, the species was found in undisturbed submontane rainforest on flat terraces with Sideralic Cambisols ( IUSS Working Group WRB 2014) developed from metamorphic rocks. The forest at Pono was dominated by Fagaceae , Lauraceae , Sapotaceae , Moraceae , and Rubiaceae species (families with top five FIV) and contained seven other species of Syzygium : S. acuminatissimum (Blume) de Candolle (1828, 261), S. balgooyi , S. galanthum , S. lineatum (DC.) Merrill and Perry (1938a, 109), S. phaeostictum Merrill and Perry (1942, 270), and two undetermined species ( Brambach et al. in press). See Culmsee and Pitopang (2009) for more information on the floristics of the Pono valley plot. The collection locality of Widjaja EAW 3502 in the almost entirely deforested Napu valley suggests remnant riparian forest as habitat.

Conservation status.

Syzygium contiguum has a limited geographical distribution (estimated EOO 557 km²) and seems to be restricted to submontane forest within a narrow elevational belt. We assume that the estimated AOO of 12 km² is unrealistically low, due to limited collection activities in Central Sulawesi. However, only the collection locality of Meijer 9572 seems to be covered by intact forest habitat. The other two localities are small forest fragments (Widjaja EAW 3502) and forest with recent deforestation activities in close proximity (Pono inventory plots, detected using the Global Forest Change website, Hansen et al. 2013), possibly related to the establishment of cocoa plantations (Aiyen Tjoa, Tadulako University, personal communication, June 2015). Given the apparent narrow geographical and elevational distribution and the recommendation to use a precautionary attitude in conservation assessments (IUCN Standards and Petitions Subcommittee 2014) we propose a preliminary extinction risk assessment of “Endangered” (EN B1ab(i,ii,iii)).

Notes.

Syzygium urdanetense (as Eugenia urdanetensis , Elmer 1914, 2356), the species most similar to S. contiguum , was originally described from Mt Masay (previously Mt Urdaneta) on the southern Philippine island of Mindanao and is widespread throughout the Philippines ( Merrill 1951, Pelser et al. 2011). The species is variable in vegetative characters such as leaf size, leaf base (usually rounded and only the very base cordate, but sometimes distinctly cordate) and branchlet shape (usually terete, but rarely subangular). In addition to the characters mentioned in the diagnosis, there are differences in the tertiary venation, the veins being ± ladder-like and perpendicular to the midrib in S. urdanetense whereas in S. contiguum they are ± parallel to the secondary veins near the midrib and become reticulate towards the leaf margin (Figure 8f ). While with the available material, S. contiguum can be clearly distinguished from S. urdanetense on morphological grounds, we do not discard the possibility that future collections, especially from the northern peninsula of Sulawesi, will uncover populations with intermediate characters. If so, S. contiguum may eventually have to be sunk into an expanded S. urdanetense . In light of the almost complete lack of taxonomic resolution for Syzygium in Sulawesi, we nevertheless consider it advisable to propose S. contiguum as a distinct species.

Two fruiting specimens collected at low elevations (200-300 m) on Sulawesi’s Southeast Peninsula, Prawiroatmodjo & Maskuri 1231 [L.2517450] and 1957 [L.2517547], are morphologically similar to S. contiguum as defined above except for the leaf tips which are not long-acuminate. In the absence of flowering material, and because of the different habitat and distribution, we prefer not to include them here at present, but future additional collections may prove otherwise.

We choose Culmsee 535 as type specimen because it contains flowers in all stages of maturity although unfortunately, it was collected with only two duplicates (in CEB and L). Nevertheless, the more widely distributed paratypes collected by HC at the type locality all belong to the same population as the type.

Additional specimens examined

(Paratypes). INDONESIA. Central Sulawesi (Sulawesi Tengah), LLNP: Kab. Poso, Kec. Nokilalaki, N slopes of Mt Nokilalaki. (" Celebes, central part, area of Mt. Nokilalaki, Loro Kalimata Reserve "), 1°13'S, 120°08'E, ± 1000 m, 24 Apr 1975: Meijer 9572 (flowers; L [L.2535817]!, US [US-2995269] photo!).

Kab. Poso, Kec. Lore Peore, Road to Napu from camp Dongi-dongi, 1°31.2'S, 120°22.4'E, 1127 m, 26 Dec 1988: Widjaja EA EAW 3502 (fruits; BO [BO-1917489]! [BO-1917490]!, K!, L).

Kab. Sigi, Kec. Kulawi, 2.4 km ENE of Toro, NW of Pono Valley, tree-inventory plot Pono , 1°29.7'S, 120°03.4'E, 1050 m, Jul 2006: Culmsee H 284 (flowers; GOET [GOET020010]!) .

Kab. Sigi, Kec. Kulawi, 2.4 km ENE of Toro, NW of Pono Valley, tree-inventory plot “Pono”, 1°29.7'S, 120°03.4'E, 1050 m, Jan 2007: Culmsee H y410 (flower buds; BO [BO-1938450]! [BO-1938451]!, CEB, GOET [GOET020012]!, K [K000993488]!, L!); ibid. loco, Jul 2007: Culmsee H r463 (flower buds; BO [BO-1938464]!, CEB, GOET [GOET020011]!, K [K000993489]!, L!!) & y503 (flower buds; CEB, GOET [GOET020013]!) & y514 (flower buds; BO [BO-1938452]!, CEB) & y581 (flower buds; CEB, L!) & y582 (flower buds; CEB, K [K000993490]!) & y592 (flower buds; BO [BO-1938453]! [BO-1938454]!, CEB) & y595 (flower buds; CEB, GOET [GOET020014]!, L!).

Figures

Figure 3. Syzygium contiguum: a leafy twig with flowers in different developmental stages b flower bud with gland-dotted petals and shallow calyx lobes c flower bud, longitudinal section. All from holotype Culmsee 535.

Figure 4. Distribution map of four species of Syzygium in Central Sulawesi: Syzygium contiguum (orange diamonds), S. devogelii (yellow dots), S. eymae (light blue square), and S. galanthum (green triangles). Lore Lindu National Park is indicated by a black line. Map created with QGIS (QGIS Development Team 2016) using the digital elevation model of Jarvis et al. (2008).

Figure 8. Leaves of all new species described. Variation of Syzygium balgooyi (a-e), S. contiguum (f), S. devogelii (g), S. eymae (h), and S. galanthum (i). a Brambach et al. 0283 b Brambach et al. 0681 c Brambach et al. 1333 d de Vogel 5413 [L. 2517563] e Culmsee r 2162 f Culmsee r 463 g Brambach et al. 0818 h Eyma 3624 [L. 2535689] i Brambach et al. 0533. Scale bar: 10 cm, valid for all leaves.