Vaccinium burburan M.N.Tamayo & P.W.Fritsch, 2022

Tamayo, Maverick N. & Fritsch, Peter W., 2022, Two new endemic species of blueberry (Vaccinium L., Ericaceae) from Luzon and Mindanao islands, Philippines, Phytotaxa 564 (2), pp. 139-148 : 140-143

Vaccinium burburan M.N.Tamayo & P.W.Fritsch , sp. nov. ( Figs. 1–2 ).

Type:— PHILIPPINES. Luzon Island, Ifugao Province, Municipality of Banaue, Mt. Semegar , along the ridge, 1704 m elevation, 28 March 1994, PPI [Philippine Plant Inventory] 12790 (holotype BRIT BRIT26917 !, isotype L L3786386 !) .

Paratypes:— PHILIPPINES. Luzon Island, Mountain Province, Mt. Polis , 2042 m elevation, March 1948, Celestino 7974 ( L L2625604 !, A02006792 !) ; Luzon Island, Ifugao and Bontoc Provinces , May 1923, Zschokke & Laraya 29412 ( UC UC 237454!) ; Luzon Island, Banaue , Ifugao, 16 May 1967, Mendoza 97474 ( L L2625603 !) .

Diagnosis:— Vaccinium burburan resembles V. tenuipes Merrill (1908: 375) , but differs by having shorter petioles (1.0–2.0 mm vs. 2.0–3.0 mm), pubescent adaxial leaf surface (vs. glabrous), a cordate leaf blade base (vs. rounded), shorter pedicels (5.0–6.0 mm vs. 10–20 mm), shorter corollas (5.0–6.0 mm vs. ca. 10 mm) with exterior apical pubescence (vs. glabrous), and pubescent filaments throughout (vs. pubescent only at base).

Description:—Habit shrub or vine, epiphytic, evergreen, multi-branched. Branchlets brown, lanate when young, sparsely pubescent at maturity, with a combination of simple and stipitate-glandular trichomes, 0.3–3.0 mm long, rounded in cross section, 1.5–5.0 mm wide, lenticellate; perennating buds triangular, obtuse, 1.0– 1.3 mm long; bud scales non-overlapping, hirsute. Leaves persistent on older branchlets, spirally and evenly arranged, condensed, overlapping, internodes 2–10 mm long; petiole brown, in cross section abaxially and adaxially rounded, 1.0–2.0 × 0.8–1.0 mm, pubescent; leaf blade elliptic to cordate, with larger blades on each branchlet 2.2–4.0 × 2.0– 2.5 cm, coriaceous, both surfaces reddish when young turning dull green abaxially and dark green adaxially, without punctae, pubescent on both surfaces, partially glabrescent adaxially when mature, hirsute, trichomes simple, abaxial surface generally more pubescent than adaxial surface; midvein raised abaxially and adaxially, secondary veins 2 to 4 on each side of midvein with first pair arising from base and remainder along midvein, arc-ascending, abaxially raised, adaxially faintly evident or obscure, tertiary veins faintly evident or obscure, base cordate, margin entire, thinly revolute, apex acuminate, marginal glands slightly raised, ca. 1.0 mm from leaf base, one pair per leaf, 0.3–0.4 mm wide. Inflorescences pseudo-terminal or terminal, racemose, developing beyond confines of perennating bud, 1 per axil, 1.5–2.5 cm long at anthesis, 4- or 5-flowered; peduncle and rachis brown, terete, pubescent, trichomes same as on branchlets; bracts semi-persistent, reddish brown, non-foliaceous, ovate to elliptic, planar or occasionally cucullate, 1.0–1.5 × 0.5–0.8 mm, subcoriaceous, glabrous abaxially, pubescent adaxially, margin entire, occasionally with 1 or 2 glands near base. Pedicel ascending to slightly erect, 5.0–6.0 × 0.5–0.7 mm at anthesis, terete, pubescent; bracteoles borne at base of pedicel, linear or lanceolate, ca. 0.2 mm long, pubescent. Flowers articulated at junction with pedicel, 5.0–7.0 mm long. Hypanthium dark brown, triangular-obtuse, 1.0–1.2 × 0.8–1.0 mm, pubescent, trichomes same as on branchlets; calyx limb ca. 1.5 mm long; calyx lobes 5 or 6, narrowly triangular, 1.0– 1.2 mm long, pubescent, trichomes same as on branchlets, margin entire, apex acuminate, without sessile terminal gland. Corolla narrowly conical-urceolate, tapering at middle toward apex, dark brown, 5.0–6.0 × 2.0– 2.5 mm, glabrous outside except for apical portion including corolla lobes, inside glabrous; corolla lobes 5 or 6, pubescent, 0.5–0.7 × 0.3–0.4 mm, apex acute to obtuse. Stamens 8 to 10, monomorphic, distinct, 3.7–4.5 mm long; filaments brown, straight, dilated at base, 2.8–3.1 mm long, white-lanate especially toward base, trichomes 0.4–0.5 mm long; anthers 1.0– 1.4 mm long, cells 0.6–0.9 mm long, obscurely echinulate, tubules parallel, broadly cylindrical, opening by oblique ventrally oriented apical pores, 0.4–0.5 mm long, pore apex shallowly crested, spurs absent. Ovary 5- or 6-locular but appearing pseudo-10- to 12-locular with false partitions extending ca. 0.8 mm from inner wall; ovules in two columns per locule. Disk annular, bulky, conspicuously larger than hypanthium, 0.7–1.0 × 1.5–2.0 mm, puberulent, margin obscurely ridged. Style not seen. Fruit dark brown, globose, non-ridged, 3.0–3.5 × 2.5–3.0 mm, pubescent, trichomes same as on branchlets; calyx lobes persistent, slightly recurved, disk bulged, annular, ca. 1.0 × ca. 2.0 mm; fruiting pedicels ca. 5 mm long.

Distribution and Habitat: —This new species is endemic to Luzon Island, Northern Philippines. It can be found within the montane forests of the central Cordillera Mountain Range in Ifugao and Mountain Provinces.

Etymology: —The new species is notably hairy on the stem, leaves, and inflorescences. We have therefore used “ burburan ,” derived from the Iloco (Ilokano) language meaning hairy, for the specific epithet. Iloco (Ilokano) is the most frequently spoken regional language in the north and central parts of Luzon Island.

Phenology: —Flowering and fruiting from March to May.

Proposed Conservation Status: — Vaccinium burburan is restricted to montane forests of the central Cordillera Mountain Range. It has a very narrow distribution that is confined only to the high-elevation area. Based on the available data of its distribution (EOO 48.986 km 2), we recommend that this species be categorized as critically endangered [CR:B1(i,iv)] ( IUCN Standards and Petitions Committee 2022).

Discussion: —We consider Vaccinium burburan to be a member of Vaccinium sect. Bracteata Nakai in Nakai and Koidzumi (1927: 234) sensu Sleumer ( Sleumer 1966 –1967), as based on its multi-flowered racemose inflorescences, caducous bracts, absence of a membranaceous wing at the sinuses of the ampullaceous corolla, and anthers that open by short terminal pores or introrse slits ( Sleumer 1966 –1967; Co et al. 2002; Salares et al. 2018).

In the keys to Philippine Vaccinium [ Merrill 1908; Copeland 1930 (the artificial key in the treatment)] and Malesian Vaccinium sect. Bracteata ( Sleumer 1966 –1967), V. burburan keys to V. tenuipes . Vaccinium tenuipes is also present in Luzon Island and is typically found as an epiphyte in high-elevation forests (1800–2800 m elevation) (Tamayo pers. obs.). In addition to the characters mentioned in the diagnosis, V. burburan can be distinguished from V. tenuipes by its fewer-flowered (4 or 5 vs. 5 to 10) and shorter [1.5–2.5 cm vs. (2–) 3–5 cm] inflorescences. In the key to the Bornean species of Vaccinium ( Argent 2019) , the species best keys to Vaccinium beamanianum Wilbur & Luteyn (2008: 219 , non Vaccinium cordifolium Stapf 1894: 189 ). However, the new species is distinct by having non-leafy bracts (vs. leafy), shorter pedicels (5.0–6.0 mm vs. 8.0– 12 mm), shorter and narrower corollas (5.0–6.0 × 2.0– 2.5 mm vs. 12–15 × 5.0–6.0 mm) that are narrowly conical-urceolate (vs. tubular urceolate), apically pubescent corollas (vs. glabrous), shorter filaments (2.8–3.1 mm vs. 6.0–7.0 mm), and an absence of dorsal spurs (vs. presence). Moreover, the leaves of V. burburan are pubescent (vs. glabrous except basally in V. beamanianum ). The new species also bears stipitate-glandular trichomes on its stem and inflorescence, a character not present in V. beamanianum .

Vaccinium burburan has long been presumed to be a phenotypic variant of V. tenuipes . In his treatment of the Philippine Vaccinium, Copeland (1930) cited the specimen Zschokke & Laraya 29412 (UC UC237454!) as V. tenuipes ; however, he also suspected that this variant might soon result in the description of a new infraspecific taxon or even species once more material had been studied. His decision to consider the specimens as conspecific under a broad V. tenuipes circumscription may also be due to the absence of flowers in any of the specimens previously available.

The paratype Celestino 7974 (L L2625604!) was annotated as Vaccinium polisense Merr. & Quisumb. , a name that apparently was never published. This specimen clearly represents V. burburan as exhibited by its spirally arranged and condensed leaves that are pubescent on both surfaces, cordate leaf blade base, and the presence of stipitate glands on the stem and inflorescence. The reason that this name was not published might be because the specimen is sterile, preventing a complete description for the species or leaving some doubt as to its distinctness.The isotype (L L3786386!) was annotated by Dr. George Argent as “ Vaccinium sp. ” We presume that this specimen was not confidently identified because the specimen is sterile, thus precluding confident identification.

Vaccinium burburan is only one of two species in the Philippines that possesses a cordate leaf blade base, the other being V. oscarlopezianum Co (2002: 373) ( Co et al. 2002). However, V. burburan is distinct from V. oscarlopezianum by the presence of stipitate-glandular trichomes (vs. absence), smaller leaf blades (2.2–4.0 × 2.0– 2.5 cm vs. 4.0–8.0 × 2.0– 4.2 cm), shorter inflorescences (1.5–2.5 cm vs. 8.0– 15 cm), non-foliaceous bracts (vs. foliaceous), apically pubescent corollas (vs. non-apically pubescent), and shorter stamens (3.7–4.5 mm vs. 5.0–7.0 mm). Moreover, the widespread Vaccinium myrtoides ( Blume 1826: 861) Miquel (1859: 1062) on occasion may exhibit a cordate leaf blade base. However, V. burburan can be distinguished from this species by the presence of stipitate-glandular trichomes on its branches, leaves, and hypanthium (vs. absence), and a narrowly conical corolla (vs. urceolate) that is apically pubescent (vs. glabrous).

Figures

FIGURE 1. Vaccinium burburan. A. Flowering branch. B. Stem indumentum. C. Flower. D. Flower (corolla removed) exposing the disk. E. Ventral view of stamen. F. Dorsal view of stamen. G. Fruit. Illustration by Maverick N. Tamayo.

FIGURE 2. Holotype of Vaccinium burburan M.N.Tamayo & P.W.Fritsch (BRIT BRIT26917). Image courtesy of the Botanical Research Institute of Texas.