Ixora alejandroi Banag & Tandang, 2015

Banag, Cecilia I., Tandang, Danilo, Meve, Ulrich & Liede-Schumann, Sigrid, 2015, Two new species of Ixora (Ixoroideae, Rubiaceae) endemic to the Philippines, Phytotaxa 202 (2), pp. 155-160 : 156-158

Ixora alejandroi Banag & Tandang sp. nov. ( Fig.1 )

Ixora alejandroi differs from other species of the genus by its elongated cyme with congested secondary axes, reddish-brown corolla and stigmatic lobes shortly cleft in the middle, round at tip.

Type:— PHILIPPINES. Luzon: Palawan: Mt. St. Paul, Sabang, 10°9’43.9914”N, 118°54’30.9954”E, 400 m, 31 May 2012, G.J.D. Alejandro, A. Arriola & A. Wong 12439 (Holotype PNH 254886, isotypes USTH, K, US).

Shrub, 0.5–3 m tall; young internodes brown, older internodes grayish brown; vegetative parts glabrous; reproductive parts puberulent. Stipules narrowly triangular, 2–3 mm long, awn 6–7 mm long. Leaves with petioles 1.5–2 cm long; blades elliptic to lanceolate, 18.2–27.5 × 4–9.8 cm, coriaceous, drying brown or dark brown above, paler brown below; apex acuminate; base cuneate to round; secondary veins 9–19 on each side. Inflorescences terminal, elongated cymes with congested secondary axes, 3.5–6 × 0.5–1 cm, pendulous, non-articulate throughout; leaf-like bracts subtending the inflorescence1(–2) pairs, subsessile, blades narrowly elliptic to lanceolate, 1.5–2 × 0.6–1 cm, base cuneate to round; peduncles 10–18 cm long, reddish brown; central first order axis 1–2 cm long, lateral first order axes ≤ 0.5 cm long; first order bracts with stipular parts absent and the foliar parts narrowly triangular, up to 3 mm long; higher order bracts with stipular parts absent and foliar parts narrowly triangular to filiform, 1–2 mm long; ultimate flower triad with pedicellate flowers; pedicels 1.9–2.1 mm long (3.6–5 mm long in fruiting stage), pedicel of the central flower as long as or usually somewhat shorter than the pedicels of the lateral ones, bracteoles present on most pedicels, subopposite at the base of the ovary or more often just underneath it on the pedicels, triangular, apices acute, 0.5–1 mm long, reaching the base of the ovary. Hypanthium, calyx and corolla reddish brown, filaments, anthers, style and stigma yellow. Flower buds obtuse or round at apex. Hypanthium 1.2–2.3 mm long. Calyx tube ca. 0.5 mm long; lobes widely triangular, 1.4–1.8 mm long, their bases not overlapping Corolla tube 10–20 mm long; lobes 4, 4–4.4 × 3–3.5 mm, elliptic, obtuse at apex. Stamens inserted at corolla mouth, filaments 0.5–0.8 mm long; anthers 3–4 mm long. Style exserted 1–2 mm beyond the corolla mouth; stigmatic lobes 1.2–2 mm long, shortly cleft in the middle, round at tip. Fruits subglobose, 4.4–5.9 × 4.6–6.4 mm, green when young, pinkish when ripe, with persistent calyx; fruit wall ca. ≤ 1 mm thick; seeds 2.4–3.5 × 1.5–2.5 mm.

Distribution and Habitat:— Ixora alejandroi is endemic in Palawan and thrives in limestone forest, at 400–600 m elevation.

Etymology: —The specific epithet is dedicated to Dr. Grecebio Jonathan D. Alejandro, University of Santo Tomas, Manila, who has made significant contributions to the knowledge of Philippine Rubiaceae .

Phenology: —Flowering specimens were collected in April–May and September; fruiting specimens were collected in January and May.

Conservation Status: —IUCN Red List Category (2014): Endangered (EN; B2a; B2b (i–v); D). B2: total area of occupancy less than 500 km 2; B2a: less than five locations known; b (i–v): continuing habitat decline inferred; D: less than 250 mature individuals. Tourism is identified as a major threat for the suitable habitat of I. alejandroi due to the increasing environmental effects of uncontrolled access of visitors in the mountain and number of tourist activities at the Puerto Princesa Subterranean River National Park, a well-known tourist attraction in Palawan also located in the St. Paul Mountain Range. Other threats to the habitat of I. alejandroi include activities such as forest clearing and agriculture of the local inhabitants. The rarity of the species is suspected by the authors based on the number of mature individuals after careful exploration of the area and several field surveys conducted in Palawan.

Discussion: — Ixora alejandroi has short, round stigmatic lobes, a rare feature for Ixora as most species of the genus has elongate branches recurved at maturity. Short, round stigmatic lobes have been recorded only for two species from India, I. katchalensis Husain & Paul (1984: 153) with lobes 2–3 mm long, and I. brachiata Roxburgh (1820: 381) with lobes 4–8 mm long ( Mouly 2008). Ixora alejandroi is most similar to I. tenelliflora , a non–endemic species also found in Palawan, because of the pendulous inflorescences with clusters of flowers along the central axis but differing from it by the stigmatic lobes, shortly cleft in the middle and round at tip (vs. stigmatic lobes elongate), the length of the central first order axis 1–2 cm long (vs. 9–12 cm long), lateral order axes ≤ 0.5 cm long (vs. 3–5 cm long) and first order bracts with stipular parts absent (vs. stipular parts fused to an ovate blade with central awn). Florally, I. tenelliflora is easily distinguishable from I. alejandroi by its white corolla, much longer corolla tube and long, narrowly elliptic corolla lobes.

Additional specimens examined (paratypes): — PHILIPPINES. Luzon: Palawan: Mt. Cleopatra’s Needle , Puerto Princesa, 20 January 1998, G.C.G Argent, Q. Cronk, M. Mendum, D.J. Middleton, P. Wilkie, R. Fuentes & R.V. Chavez 5387 (K, L, SAN) & 25396 (L) ; Mt. St. Paul, Sabang , May 2012, D. Tandang MH1707 (PNH) .

Figures

FIGURE 1. Ixora alejandroi. A. Flowering branch. B. Inflorescence. C. Stigma. D. Open flower. E. Flower bud. F. Stipules. G. Cross section of fruit. H. Dried fruit. Drawn from G.J.D. Alejandro, A. Arriola & A. Wong 12439 (A, F–H) and D. Tandang MH1707 (B–E) by Arianne Zacarias (A, C, F–H) and Nemesio B. Diego, Jr. (B, D–E).