Discospermum philippinensis Arriola & Alejandro, 2015

Arriola, Axel H. & Alejandro, Grecebio Jonathan D., 2015, A new species of Discospermum (Coffeeae, Rubiaceae) from Luzon, Philippines including its conservation status, Phytotaxa 206 (1), pp. 43-46 : 44

Discospermum philippinensis Arriola & Alejandro , sp. nov. ( Fig. 1 )

Type:— PHILIPPINES. Luzon, Quezon Province: Municipality of Tayabas, Mount Banahaw , 623 m, 11 February 2010, Arriola T016 ( Holotype PNH 254951 ; isotype PNH 254952 , USTH 012604 )

Discospermum philippinensis is similar to D. whitfordii ( Elmer 1906: 4) S.J. Ali & Robbrecht (1991: 301) by having a persistent calyx and a prominent disk below the apex of the fruit, from which it can be distinguished by the leaf blades 5.5–15.5 × 3.5–6.5 cm, acute to attenuate leaf apex (vs. 4.5–10.0 × 2.0–4.5, caudate, in D. whitfordii ), smaller faintly ribbed fruit with thin mesocarp (vs. non-ribbed, with thick mesocarp), and 4–6 seeds per locule (vs. 5–12 seeds per locule).

Tree, 5–7 m tall; branches terete, glabrous. Stipules sheath 1.0–2.0 mm long, glabrous on both sides, interpetiolar awn 0.4–0.7 mm long. Petioles 0.5–1.5 × 0.3–0.5 cm, glabrous; leaf blades elliptic, 5.5–15.5 × 3.5–6.5 cm, base cuneate, apex acute to attenuate, coriaceous, glabrous throughout; secondary veins 4–6(–8) on each side of the midrib, domatia absent. Inflorescences axillary, 3-flowered; peduncle 0.8–1.4 mm long, glabrous. Bracteoles free, alternate, 0.2–0.4 mm long to nearly inconspicuous, apex triangular. Pedicels 0.6–1.5 mm long, glabrous. Flowers 4–merous, hermaphroditic. Calyx tube infundibuliform, 0.8–1 × 0.5–0.8 mm, glabrous; lobes triangular, 0.2–0.4 mm, sparsely ciliated; colleters present. Corolla hypocrateriform; tube 0.8–1.5 × 0.5–1.5 mm, glabrous on both sides; lobes 4, ovate, 5–6.5 × 0.6–1 mm, glabrous outside, densely pilose at mouth. Anthers 4, 3–4 mm long, medifixed. Style 1–2.3 mm long, stigmatic branches lanceolate, 0.8 × 1.2 mm. Ovary bilocular, ovules 4–6 per locule, attached in a well-developed, axile placenta. Fruits ellipsoid, 1.3–1.8 cm in diameter, orange to red, turning purplish-black at maturity, glabrous, faintly ribbed; calyx persistent with a prominent crescent disk below the apex; mesocarp thin, 1.5–2.0 mm thick, sclerified; fruit stalk 0.8–1.2 mm long, glabrous. Seeds embedded in a well-developed placenta, 4–6 per cell, 3–5 × 2.5–4.5(–5) mm, lenticular, exotestal cells elongated with thickenings along the radial wall; embryo radicle pointed away from the septum.

Phenology:— Flowering from March to June, fruiting from July to December

Habitat:— Secondary forest.

Etymology:— Survey of numerous specimens of Discospermum from India and Malesia revealed that the new species is endemic to the Philippines, thus the specific epithet.

Conservation status:— Observation of various undetermined herbarium sheets from K, P and PNH revealed that there is no previous collection that matches our D. philippinensis . Moreover, after several botanical explorations in various parts of the Philippines by our group, no additional collections of D. philippinensis were made. Currently, the small population of D. philippinensis is restricted to its type locality, with less than 50 mature individuals observed. Therefore, with the present available data we assessed the conservation status of D. philippinensis as critically endangered (CR-D) based on the guidelines of the IUCN Red List (2001).

Discussion:— In the survey made by Ali and Robbrecht (1991) and our observation of several herbarium sheets of Discospermum from various herbaria, the presence of both persistent calyx and a prominent disk below the apex of the fruit separates Discospermum philippinensis from the rest of the currently recognized Indian and Malesian species of the genus. On the other hand, the combination of characters mentioned in the diagnosis supports the similarity of D. philippinensis and D. whitfordii . Meticulous observation and examination of D. philippinensis shows that it differs from the latter by having larger leaf blades, acute to attenuate leaf apex, smaller faintly ribbed fruit with thin mesocarp and a 4–6 seeds per locule. Table 1 shows the morphological differences of the two Philippine Discospermum .

Figures

FIGURE 1. Discospermum philippinensis. A. Flowering branch. B. Inflorescences. C. Flower. D. Infructiscences. E. Fruit longitudinal section. F. Fruit cross section.A–B & D–F drawn from the holotype by N. Diego, C drawn by A. Arriola.

Tables

TABLE 1. Morphological differences between Discospermum philippinensis and D. whitfordii. D. philippinensis D. whitfordii

		D. philippinensis	D. whitfordii
Leaf
	Leaf blade dimensions (cm)	5.5–15.5 × 3.5–6.5	4.5–10.0 × 2.0–4.5
	Leaf apex	Acute to attenuate	Caudate
Fruit
	External features	Faintly ribbed	Not ribbed
	Diameter (cm)	1.3–1.8	2.0–2.7
	Mesocarp thickness (mm)	1.5–2.0	3.5–5.0
Seeds
	Number per cell	4–6	5–12
	Size (mm)	3–5 × 2.5–4.5(–5)	5–6.5 × 5–6.5(–7)