Vaccinium fallax M.N.Tamayo & P.W.Fritsch

Tamayo, Maverick N., Amoroso, Victor B., Coritico, Fulgent P., Penneys, Darin S., Callado, John Rey C., Horner, John D. & Fritsch, Peter W., 2024, Three new species of Vaccinium L. (Ericaceae) from Mindanao Island, Philippines, Phytotaxa 647 (1), pp. 19-33 : 20-22

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

Type:— PHILIPPINES.Mindanao Island, Province of Davao del Sur, Davao City, Mt.Apo Natural Park, Mt.Apo summit area, 6.986306°N, 125.271944°E, 2907 m elevation, 2 May 2014, D.S. Penneys 2352 (holotype CAS 490395 !, isotypes BRIT BRIT423194 !, US 04131958 !) .

Paratypes:— PHILIPPINES. Mindanao Island, Province of North Cotabato, Ilomavis , Mt. Apo , 2900 m elevation, found near the summit, 16 March 1992, PPI (Philippine Plant Inventory) 9720 ( BRIT BRIT26866 !) ; ibid. Kidapawan, Mt. Apo, 7.0175ºN, 125.05ºE, 3000 m elevation, found along the trail to the peak of Mt. Apo , March–April 1991, PPI (Philippine Plant Inventory) 2521 ( BRIT BRIT26920 !) ; ibid. Province of Davao del Sur, Municipality of Santa Cruz, Barangay Sibulan , Sitio Colan , Mt. Apo boulders, 6.98423°N, 125.28214°E, 2329 m elevation, growing on volcanic and rhyolite boulder and bedrock in open, full sun, on southeast facing slope, 5 August 2022, PLSPH 3735 (Plants and Lichens of the Southern Philippines Survey ) ( BRIT!, CMUH!, PNH!) .

Diagnosis:— Vaccinium fallax most closely resembles V. myrtoides ( Blume 1826: 861) Miquel (1859: 1062) but can be distinguished by having smaller leaves [0.7–2.0 × 0.25–1.0 cm vs. 1.3–2.0 (–2.5) × (0.6–) 0.7–1.3 (–1.8) cm], caducous bracts (vs. partly persistent), shorter pedicels [0.5–0.7 cm vs. 0.5–1(– 1.4 cm)], a broadly obconical hypanthium (vs. cupuliform), broadly triangular calyx lobes (vs. triangular), and a deep pink (vs. pale pink) and broadly urceolate corolla (vs. narrowly cylindric-urceolate).

Description:—Habit shrubs, terrestrial, evergreen, 0.7–1.5 m tall, densely branched. Young branchlets reddish brown in vivo, light to dark brown in sicco, puberulent, with simple erect trichomes 0.1–0.2 mm long. Mature branchlets dark brown in vivo, obscurely ridged, glabrous, lenticellate, 4.0–6.0 mm wide; perennating buds acute-triangular, 0.6–0.7 mm long, with several obscurely overlapping scales, scale apices acute, margin entire with occasional simple erect trichomes ca. 0.1 mm long. Leaves persistent on older branchlets, densely crowded, spirally and evenly arranged; petiole reddish green, pubescent, with trichomes same as branchlets, with glands near leaf blade, in cross section abaxially rounded, adaxially nearly flat, 1.2–1.8 × 0.8–1.5 mm; leaf blade elliptic, larger leaves on each branchlet 0.7– 2.0 × 0.25–1.0 cm, coriaceous, abaxial surface without punctae, pale green, adaxial surface leathery green, base obtuse to slightly rounded, margin entire, thinly revolute, with 2 to 3 pairs of impressed ± evenly distributed glands per side, with first gland ca. 1 mm from leaf blade base and ca. 0.3 mm diameter, leaf blade apex acute, midvein strongly raised abaxially, flattened or slightly sunken adaxially, secondary veins 2 to 4 on each side of midvein with first pair arising from base and remainder along midvein, arc-ascending, raised abaxially, obscure or non-evident adaxially, tertiary veins faintly evident or obscure. Inflorescences pseudo-terminal or terminal, racemose, developing beyond confines of perennating bud, 1 per leaf axil, sub-densely 8- or 10-flowered, 1.5–2.0 cm long; peduncle and rachis reddish green in vivo, reddish brown in sicco, slightly ridged, glabrous, peduncle ca. 4 mm long, rachis ca. 5 long mm; bracts dark brown in sicco, caducous, non-foliaceous, broadly elliptic, planar or occasionally cucullate, coriaceous, glabrous, 5.0–9.0 × 2.0– 3.5 mm, margin entire, ± minutely ciliolate, apex acute. Flowers with an articulation between the pedicel and hypanthium, 6.0–7.0 mm long. Pedicel red in vivo, nodding, glabrous, 5.0–7.0 × 0.5–0.6 mm at anthesis; bracteoles 2, subulate, early caducous, 1.0– 1.5 mm long, borne at 3.0–5.0 mm from base or occasionally at base of pedicel. Hypanthium red in vivo, reddish brown in sicco, broadly obconical, 1.5–1.7 × 1.5–2.0 mm; calyx limb 1.5–2.0 mm long; calyx lobes 5 or 6, broadly triangular, glabrous on both sides, 1.2–1.5 mm long, margin entire, apex acute with a few simple hairs and a ± sessile terminal gland. Corolla deep pink or red, broadly urceolate, glabrous on both sides, 4.5–5.0 × 2.5–3.5 mm; lobes 5 or 6, broadly triangular, ca. 0.8–1.0 × 1.0– 1.2 mm, apex acute or obtuse. Stamens 10 or 12, monomorphic, free from each other, 3.0– 3.2 mm long; filaments straight or slightly curved, 1.8–2.0 mm long, white-pubescent, trichomes ca. 0.3 mm long, borne mainly at base with a few scattered distally; anthers 1.2–1.5 mm long, opening by short introrse slits or terminal pores, slightly shorter than filaments, cells oblong, minutely echinulate, 0.6–0.8 mm long, tubules parallel, broadly cylindric, 0.7–0.9 mm long, slightly broader than cells, opening by oblique ventrally-oriented apical pores, pore apex rounded or oblong, spurs absent. Ovary 5- or 6-locular but appearing pseudo-10- to 12-locular with incomplete partitions extending 0.15–0.2 mm from inner wall; ovules in two columns per locule; disk non-bulky, nearly flat to slightly annular with obscure ridges on margin, with simple erect hairs ca. 0.1 mm long, ca. 1.5 mm in diameter; style not exserted from corolla, glabrous, 3.5–4.0 mm long, stigma truncate. Fruit deep purple at maturity, pyriform, subglobose, or globose, shiny, 5.0–6.0 × 5.0–7.0 mm.

Distribution and Habitat:— This species is restricted to Mt. Apo Natural Park (MANP). It grows in exposed areas at and near the summit among sulfur vents, rhyolite boulders, and on a recently burned area on the northern slope of the mountain. The latter suggests that it is a pioneer species in fire-disturbed areas at the locality.

Etymology:— The epithet “fallax ” is Latin meaning deceptive. This is in reference to its close morphological resemblance to Vaccinium myrtoides .

Phenology:— Flowering and fruiting from March to August.

Proposed Conservation Status:— Vaccinium fallax has only been found at or near the summit of Mt.Apo, covering a small area (both AOO and EOO covering <10 km 2). MANP is a protected area (PA) and an Association of Southeast Asian Nations (ASEAN) Heritage Park; thus, a considerable level of protection is afforded to the species. However, increased tourism activities and anthropogenic wildfires are potential threats to the population. As such, we here assess its conservation status as Critically Endangered [CR: B1ab (i, ii, iii) + B2ab (i, ii, iii)] following IUCN guidelines ( IUCN Standards and Petitions Committee 2022).

Discussion:— In the keys to the Malesian species of Vaccinium sect. Bracteata sensu Sleumer (1966 –1967), and the artificial key to Philippine Vaccinium ( Copeland 1930) , V. fallax keys to V. myrtoides . Vaccinium fallax resembles V. myrtoides , especially in MANP where these two species occur sympatrically, often growing side-by-side. Vaccinium fallax can be readily distinguished from V. myrtoides by its deep pink corolla (vs. white to pale pink); red pedicels, hypanthium, calyx limb, and calyx lobes (vs. green with a tinge of red); and abaxially non-evident lateral veins (vs. evident). Moreover, the calyx limbs are longer, and the calyx lobes are broader compared to those of V. myrtoides ( Figure 1D ).

In the key to Bornean Vaccinium ( Argent 2019) , V. fallax keys to V. phillippsiae Argent (2019: 99) . The new species is distinct from V. phillippsiae by having smaller leaf blades (0.7–2.0 × 0.25–1.0 cm vs. 2.5–4.0 × 1.3–2.0 cm), glabrous pedicels (vs. pubescent), a glabrous hypanthium (vs. pubescent), an absence of sessile glands on the margin of the calyx lobes (vs. presence), a shorter corolla (4.5–5.0 mm vs. 8.0–10.0), and an absence of anther spurs (vs. presence). An updated key, superseding that of Tamayo et al. (2023), of the small-leaved Philippine species of Vaccinium (i.e., species with leaf blades <2 cm long) is provided here to accommodate V. fallax .

Figures

FIGURE 1. Vaccinium fallax. A. Summit area of Mt. Apo showing a vent spewing sulfur fumes. B & C. Flowering branchlet in vivo. D. Flowering branchlet showing pedicel, hypanthium, and calyx lobes. Photos B–D from PLSPH 3735; photos by P.W. Fritsch.

FIGURE 2. Vaccinium fallax. A. Flowering branchlet. B. Lateral view of flower showing pedicel, hypanthium, calyx, and corolla. C. Ventral view of stamen. D. Lateral view of stamen. Illustration by M.N. Tamayo.