Vaccinium cebuense Salares & Pelser, 2018

Salares, Val B., Obico, Jasper John A., Ormerod, Paul, Barcelona, Julie F. & Pelser, Pieter B., 2018, Taxonomic novelties from Cebu: a new species of Vaccinium (Ericaceae) and a new record of Phaius (Orchidaceae) for the Philippines, Phytotaxa 360 (3), pp. 255-262 : 257-260

Vaccinium cebuense Salares & Pelser , sp. nov. ( Figs. 1 & 2 )

Type:— PHILIPPINES. Cebu: Cebu Province, Municipality Alcoy, Barangay Nug-as , 775 m a.s.l., 14 December 2016, Obico 801 (holotype PNH!; isotype CHR!) .

Diagnosis: — Vaccinium cebuense is unique among the known species of Vaccinium in having the combination of adaxially grooved petioles, distinct marginal glands along the entire length of the leaf blade, and large recurved dorsal anther spurs.

Description: —Tree, up to 6 m tall. Bark dark brown to dark grey, peeling in strips and flakes, inner bark reddish brown. Young branches 2–4 mm diam., subangular and slightly compressed, striate, densely puberulent with simple up to 0.25 mm long white or reddish trichomes but very early glabrescent, youngest parts reddish to pink, becoming light green and tinged red on sun-facing side. Mature branches 2–4 mm diam., terete, glabrous, grey or reddish brown. Leaves distichous, densely puberulent with simple up to 0.25 mm long white or reddish trichomes but very early glabrescent, in erect reddish pink flushes when young. Petioles (2–) 5–12 mm long, adaxially grooved, pink turning reddish. Lamina (26–)28–59(–61) × (8–)10–25(–27) mm on branches of mature plants, 71–81 × 38–45 mm on branches of young plants or young shoots emerging from resprouting mature plants, narrowly elliptic to elliptic; base acute to obtuse to rounded; margin entire but with distinct marginal glands along the entire length of leaf; apex for 15–20 mm prominently caudate-acuminate, ultimate apex rounded; primary and secondary veins slightly prominent on abaxial side, secondary veins 4–7 on each side, with first 2 or 3 pairs more prominent and originating near base, tertiary venation laxly reticulate; subcoriaceous to coriaceous, light to dark green when mature. Racemes terminal and subterminal, 10–14-flowered; bracts (perules) subtending inflorescences early caducous (not observed); rachis 60–70 × 0.7–1.5 mm, pale green, glabrous; bracteoles absent. Flowers subsecund, all facing down, slightly fragrant. Pedicels 5–10 (in fruit up to 15) × 0.5–0.8 mm, swollen at base, articulate distally with the flower, glabrous. Calyx cupuliform, glabrous; tube 1.7–2.2 × 2.6–3 mm, green; lobes 5 (or 6), 1–1.5 mm long, triangular, occasionally with an apical gland, apex acute, greenish-white. Corolla urceolate, greenish white or white; tube c. 5.5–6.1 × 4.9–5.5 mm, externally glabrous, internally pubescent in basal half; lobes 5 (or 6), c. 1 mm long, recurved, glabrous. Stamens 10(– 12), considerably shorter than the corolla; filaments c. 2 mm long, filiform, pubescent at base; anther cells echinulate, c. 1 mm long, broadly oblong, base obtuse; dorsal spurs c. 0.5 mm long, recurved; tubules c. 1.1–1.3 × 0.4 mm, cylindric, slightly curved, opening by terminal pores without teeth, eglandular. Disk pubescent, greenish white. Style c. 6 mm long, glabrous. Stigma slightly exerted from corolla. Immature berry globose, pseudo-10-locular, c. 4 mm diam., calyx tube fused to ovary.

Paratypes:— PHILIPPINES. Cebu: Cebu Province, Municipality Alcoy, Barangay Nug-as, 758–780 m a.s.l., Barcelona et. al. 4490 (CEBU), 6 January 2018 ; Barcelona et al. 4491 (CEBU), 6 January 2018, Barcelona et al. 4492 (CEBU), 7 January 2018 ; Municipality Balamban, Barangay Sunog , 884 m, 11 January 2018, Obico 924 (CEBU) .

Phenology: —Flowering plants were observed in May, June, and December. Fruiting plants were recorded in July and January.

Distribution, habitat, and conservation: — Vaccinium cebuense is currently only known from an elevation of 600–700 m a.s.l. in two of the very few remaining forests on Cebu Island. It was first discovered in southern Cebu in Barangay (Brgy.) Nug-as (Alcoy) and later collected from the CCPL in Brgy. Sunog (Balamban), which is located ca. 100 km north of Alcoy.

Nug-as forest is one of the largest remaining forests in Cebu and appears to be the least disturbed. It is composed of fragmented naturally regenerating forest in an area with former exotic tree plantations and farms ( Paguntalan & Jakosalem 2008). Most of the forest is secondary growth on a limestone substrate, with closed canopy forest mostly confined to gullies. Nug-as forest is actively managed by a resident people’s organization, the Kapunungan sa mga Mag-uuma sa Yutang Lasangan sa Bululakaw (KMYLB), under the Community-based Forest Management Agreement (CBFMA) with the Department of Environment and Natural Resources (DENR; Paguntalan & Jakosalem 2008). The 19 individuals of V. cebuense that were found in Nug-as were all growing along a 100–200 m stretch of the main road through Brgy. Nug-as. Neither we nor the KMYLB forest wardens have observed this species in other parts of Nug-as forest. This small population of V. cebuense is currently at risk of extirpation, because most of the individuals grow immediately next to a road for which plans for widening are currently being developed.

The discovery of a single individual of V. cebuense (Obico 924, CEBU!) in CCPL suggests that this species might be more widespread in Cebu. Therefore , until more is known about the distribution and population numbers and sizes of this species, we consider its conservation status to be Data Deficient ( DD; IUCN 2017 ) .

Notes: — Sleumer (1967) accommodated the Philippine species of Vaccinium in two sections, V. sect. Oarianthe and V. sect. Bracteata Nakai in Nakai & Koidzumi (1927: 241). Vaccinium cebuense is best placed in sect. Bracteata, which is characterized by having relatively short calyx lobes, well developed and often many-flowered racemes, and anthers that open by short introrse slits or terminal pores ( Sleumer 1967, Co et al. 2002).

Vaccinium cebuense can be distinguished from most other Malesian Vaccinium species by its marginal laminar glands. These are commonly observed in Vaccinium but are usually limited to either only a pair or two, or are distributed only on the proximal half of the leaf ( Sleumer 1967). This new species, however, has marginal glands that are distributed from the base to the apex of the leaves. Some other Malesian taxa also display this character (e.g., V. vidalii Merrill & Rolfe in Merrill (1909: 374), V. cumingianum Vidal (1886: 167) ssp. igorotorum Copeland (1930: 586)) , but only V. jagori Warburg (1905: 174) exhibits this in combination with an entire leaf margin. Vaccinium jagori can readily be differentiated from V. cebuense by, amongst other characters, its generally shorter petioles (2–4 vs. 2–12 mm), usually shorter pedicels (4–5 vs. 5–10 mm when flowering), red instead of greenish white or white flowers and the lack of dorsal anther spurs.

Dorsal anther spurs are reported for 35 species of Vaccinium in the Malesian region that are included in Sleumer (1967), and for five of the 13 Malesian species that have since been described ( Ng 1976, Argent 1982, 2011, Takeuchi 2008). The orientation of anther spurs is rarely reported, but they are usually erect. This is in sharp contrast with the wide spreading to downwardly curved spurs of V. cebuense , a most unusual feature of this new species. Of the 40 Malesian species with anther spurs, only three have spurs of about the same length (c. 0.5 mm) as V. cebuense , namely V. besagiense Smith (1916: 4) , V. palawanense Merrill (1909: 373) , and V. vidalii ( Sleumer 1967) . Of these three species, only V. vidalii has marginal glands along the entire length of the leaf margin, but it differs from V. cebuense in having much smaller leaves, a faintly crenulate leaf margin (vs. entire), racemes with fewer flowers ((3–)4–8 vs. 10–14), a semi-globose (vs. cupuliform) calyx, and an entirely glabrous corolla (vs. internally pubescent in the basal half). Vaccinium besagiense has oblong-obovate leaves with a rounded retuse apex (vs. narrowly elliptic to elliptic with prominently caudate-acuminate non-retuse apex), an obconical calyx, a corolla that is 4–5 × 3 vs. 5.5–6.1 × 4.9–5.5 mm, and anther tubules with gland-tipped hairs (vs. glabrous), amongst many other differences between the two species ( Sleumer 1967). Also V. palawanense can easily be distinguished from V. cebuense . Although the dimensions of the floral parts are similar and both species have a corolla with a glabrous outer surface but pubescent lower half of the inner surface, V. palawanense has a narrower corolla (6–7(–8) x ca. 2.5 vs. 5.5–6.1 x 4.9–5.5 mm) that is white to red (vs. greenish-white or white), and a pubescent (vs. glabrous) style. None of these three species has the distinct adaxially grooved petioles of V. cebuense .

The leaves of V. caudatum Warburg (1905: 173) are similar to those of V. cebuense in size and shape, but they only have one pair of basal marginal glands. Vaccinium caudatum also has slender anther tubules but these terminate in irregular teeth, often tipped by a small gland, unlike the rounded and consistently eglandular pores of the new species. Several other flower characters are also substantially different. For example, the corolla of V. caudatum is narrower (5 by 2.5 mm) than that of V. cebuense and is internally glabrous, the anthers usually lack dorsal spurs, and the stamens are slightly exerted from the corolla at anthesis (vs. considerably inserted within the corolla).

It became evident during this study that the taxonomic delimitation of Philippine Vaccinium species requires further and more in-depth study. Little is known about their intraspecific morphological variation due to a lack of sufficient specimens available for study. This makes it especially difficult to determine if some species (e.g., V. caudatum and V. benguetense Vidal 1886: 168 ) are truly distinct or if they represent the extremes of a morphological gradient.

Figures

FIGURE 1. A–I. Vaccinium cebuense. A. Flowering branches. B. Inflorescences in axillary and terminal racemes. C. Flowers. D. Longitudinal section of flower. E. Young infructescence. F. Young fruit. G. Branch with leaves. H. Margin of young leaf apex showing marginal glands. I. Marginal glands at leaf base.A–D: Obico 801. E–G: Barcelona et al. 4490. H, I: Barcelona et al. 4491. Photographs by P.B. Pelser & J.F. Barcelona; additional photos are available from the PhytoImages website (Nickrent et al. 2006 onwards).

FIGURE 2. A, B. Vaccinium cebuense. A. Stem showing peeling bark. B. Obico 801. Photographs by V.B. Salares.