Syzygium parvipomum Fernando & Mansibang

Fernando, E. S., Quimado, M. O. & Mansibang, J. A., 2024, Two New Species Of Syzygium (Myrtaceae) From Ultramafic Soils In Northeastern Mindanao, Philippines, With Notes On Three Other Rare Species, Edinburgh Journal of Botany 81 (2027), pp. 1-19 : 7-11

Syzygium parvipomum Fernando & Mansibang , sp. nov. [subg. Perikion ]

Compared with all Philippine Syzygium subg. Perikion with axillary-ramiflorous inflorescence, S. parvipomum is most similar to S. iwahigense (Elmer) Merr. in its oblanceolate-obovate lamina shape, revolute margins, and rigid coriaceous texture but differs by its quadrangular twigs (vs terete), smaller lamina 3.2–4.5 × 0.8–1.3 cm (vs

6 × 3 cm), adaxially punctate leaf surface (vs adaxially epunctulate), fewer secondary veins (7–)8–9 pairs (vs 10–15), and fewer flowered inflorescence 1–3(–4) flowers (vs 5–12(–15)). – Type: Philippines, Mindanao Island, Surigao del Norte Prov., Claver , in forests on ultramafic soils, on steep slope, c. 320 m elevation, 6 vi 2019 (fl), E. S. Fernando 4765 (holotype PNH; isotypes LBC, SING). Figures 3, 4 .

Small glabrous tree 4–6 m tall; stem 10–15 cm in diameter, trunk and branches tending to be upright, erect. Twigs quadrangular, seldom laterally flattened. Leaves opposite, young leaves purple when fresh. Petiole 1.3–2.0(–2.2) mm long. Lamina oblanceolate, rigidly coriaceous, base attenuate, apex bluntly obtuse to rounded, margins revolute, entire, sparsely punctate adaxially, epunctulate abaxially, 3.2–4.5 × 0.8–1.3 cm; secondary veins (7–)8–9 pairs, thin, 3.0–4.0(–4.8) mm apart, intramarginal vein thin, 0.6–1.0 mm from the margin; pale olive brown when dry. Inflorescence (pseudoterminal–) axillary, solitary (–simple cyme), 1–3(–4) flowers, sessile (or 12 mm long when present, slender, quadrangular). Flower buds clavate. Hypanthium claviform, white, with dense fibre bundles, 12 × 2.7–3.3 mm, rim subtruncate in outline, obscurely 4-lobed, rounded, 0.5–0.6 × 0.7–0.8 mm, pseudo-pedicel slender, 1.7–4.1 mm. Corolla pseudo-calyptrate, white, 4-merous, irregular rounded. Stamens many, filaments slender, white, 2.8–4.7 mm, anthers basifixed, oblong, parallel, yellowish brown (yellow when fresh), c.0.3 × 0.2 mm. Style 1, 6–8 mm long. Ovary bilocular, axile placentation; ovules c.6 per locule. Fruits solitary on axils (or rarely in very short axis, 12 mm long), broadly obovoid, 11–12 × 10.0– 11.5 mm, surface smooth, ripening dull, waxy red when fresh, brown when dry; pericarp fleshy, with longitudinally striated fibres covering the testa.

Seedling germination hypogeal, cotyledons remain inside the testa, unexposed; epicotyl angular, with alternate cataphylls preceding the eophylls; first two eophylls opposite, narrowly elliptic, 1.2–3.4 × 1.5–2.0 mm.

Distribution. Endemic to the Philippines. This species is, thus far, known only from Surigao del Norte Province on Mindanao Island, Philippines.

Habitat and ecology. This species occurs on steep ultramafic hill slopes at 320 m elevation. Associated species include two Myrtaceae , namely the common Leptospermum amboinense Blume and saplings of Xanthostemon verdugonianus Náves ex Fern. -Vill., Gymnostoma rumphianum (Miq.) L.A.S.Johnson ( Casuarinaceae ), Norrisia malaccensis Gardner ( Loganiaceae ) and Scaevola micrantha C.Presl ( Goodeniaceae ).

Etymology. The epithet parvipomum (Latin: parvi, ‘small’; pomum, ‘apple’) refers to the similarity of the ripe fruits to small, red apples.

Notes. Floral characters suggest that this species belongs to Syzygium subg. Perikion sensu Hatt et al. (2023) with a claviform hypanthium and the presence of fibre bundles in the hypanthium wall. The results of a thorough review of Philippine Syzygium (see methodology) suggest that there are c.12 species (including S. parvipomum ) that belong to subg. Perikion , of which seven have consistent terminal inflorescence. Meanwhile, representatives of the subgenus with axillary to ramiflorous inflorescence are unique to only five of species in the Philippines so far. An identification key for the Philippine representatives of this group is presented below.

Proposed IUCN conservation category. Only two adjacent populations, each consisting of fewer than 15 mature individuals of Syzygium parvipomum , have been observed in the type locality. A continuing decline in the number of mature individuals in each population is probable, as all populations are within an area subject to surface mining. Following the IUCN Red List Categories and Criteria ( IUCN, 2012) and Guidelines for Using the IUCN Red List Categories and Criteria ( IUCN Standards and Petitions Subcommittee, 2022), we preliminarily assess Syzygium parvipomum as Critically Endangered [CR C+C2a(i)].

Additional specimens examined (paratypes). PHILIPPINES. Mindanao Island: Surigao del Norte Prov., Claver , in forests on ultramafic soils, on steep slope, c. 370 m elevation, 22 vi 2023 (fr., + spirit), E. S. Fernando 5407 ( CAHP, LBC, PNH, PUH) ; ibid. (+ spirit), E. S. Fernando 5408 ( K, LBC, PNH, PUH, SING) ; ibid., (seedling, + spirit), E. S. Fernando 5408 A ( LBC) .

Key to Philippine Syzygium subg. Perikion With aXillarY to ramiflorouS infloreSCenCeS

1a. Leaf apex bluntly acute to shortly acuminate, lamina elliptic to oblong, texture chartaceous to coriaceous (never rigid) ____________________________________________ 2

1b. Leaf apex obtuse to rounded, lamina oblanceolate to obovate, texture rigidly coriaceous ________________________________________________________________________ 4

2a. Inflorescence subumbellate, flowers many (4–)5–10(–12), inflorescence axes conspicuous (geographically widespread) ______ S. claviflorum (Roxb.) Wall. ex Steud. 2b. Inflorescence mostly solitary (rarely in 3’s) and flowers sessile (–subsessile) _______ 3

3a. Leaves 6–10 × 2.5–4 cm, hypanthium 15–17 mm long (Samar and Leyte Islands)

S. subsessiliflorum (Merr.) Merr. 3b. Leaves 2–4 × 1–2 cm, hypanthium c. 8 mm long (young fruits) (Luzon: Rizal Prov.)

S. rizalense (Merr.) Merr.

4a. Twigs terete, leaf surface adaxially epunctulate, inflorescence with more flowers (5–12(–15)) (Palawan Island) ___________________________ S. iwahigense (Elmer) Merr.

4b. Twigs quadrangular, leaf surface adaxially punctate, inflorescence with fewer flowers (1–3(–4)) (Mindanao: Surigao del Norte Prov.) __ S. parvipomum Fernando & Mansibang