Vaccinium exiguum M.N.Tamayo, R.Bustam. & P.W.Fritsch, 2021

Tamayo, Maverick N., Bustamante, Rene Alfred Anton & Fritsch, Peter W., 2021, Vaccinium exiguum (Ericaceae, Vaccinieae), a new species from the ultramafic summit of Mt. Victoria, Palawan Island, Philippines, PhytoKeys 179, pp. 145-154 : 145

Vaccinium exiguum M.N.Tamayo, R.Bustam. & P.W.Fritsch sp. nov.

Figs 1B , 2 , 3

Type.

Philippines, Palawan Island (= Palawan Province) , Municipality of Narra, Mt. Victoria , 9°21'56"N, 118°20'02"E, exposed ultramafic summit, ca. 1700 m elevation, 27 February 2021, PTI-8 with R. Bustamante (holotype: PNH!; isotypes: PPC!; BRIT!) .

Diagnosis.

Vaccinium exiguum closely resembles V. hamiguitanense , but is distinct by having shorter petioles (0.5-1.0 mm vs. 1.2-1.8 mm), shorter leaves (4.9-9.3 mm vs. 8.8-16.0 mm), longer calyx lobes (1.8-2.0 mm vs. 1.1-1.3 mm) that are glabrous (vs. merely ciliate) with serrate calyx lobe margins (vs. entire), a larger corolla (6.0-7.0 × 4.0-5.0 mm vs. 4.6-5.0 × ca. 2.6 mm) with deeper (vs. shallow) sulcations, and longer stamens (3.5-4.0 mm vs. 2.8-3.5 mm) with spurs oriented laterally (vs. slightly upcurved and oriented ± apically). The calyx lobes of V. exiguum are unique amongst Philippine species in that they are nearly as long as or longer than the hypanthium. Unlike V. hamiguitanense , V. exiguum has a corolla that appears distinctly star-shaped in cross section because of its deep sulcations.

Description.

Habit shrubs, terrestrial, evergreen, 0.3-1.5 m tall, densely branched. Branchlets when young with finely translucent erect, straight trichomes ca. 0.2 mm long, at maturity brown, slightly compressed and often ridged, 0.5-1.5 mm wide, not lenticellate, outer surface brownish; perennating buds compressed-ovoid, 0.5-0.8 mm long, with several obscurely overlapping scales. Leaves persistent on older branchlets, densely crowded, spirally and evenly arranged; petiole green with a tinge of red, 0.5-1.0 × 0.4-0.8 mm, nearly as long as wide, with translucent, erect, straight trichomes ca. 0.1 mm long, in cross section abaxially rounded, adaxially nearly flat; leaf blade elliptic or oblong, larger leaves on each branchlet 4.9-9.3 × 3.0-6.0 mm, coriaceous, both surfaces greenish red when young, glabrous, except occasionally puberulent at base, smooth, abaxial surface without punctae, green and glossy, light brown in sicco, adaxial surface green and nitid, dark brown in sicco, base cuneate, margin with 4 or 5 impressed ± evenly distributed crenations per side with occasional minute translucent lanceolate glands on crenations, thinly recurved, apex obtuse to rounded, the very tip with a gland, marginal glands 3 or 4 per side, scattered along length of margin, ca. 0.1 mm diameter, midvein slightly raised abaxially, flattened adaxially or nearly so, secondary veins 2 to 4 on each side of midvein with first pair arising from base and remainder along midvein, arc-ascending, slightly raised or obscure abaxially, obscure adaxially, tertiary veins faintly evident or obscure. Inflorescences pseudo-terminal or terminal, racemose, ca. 1.5 cm long at anthesis, developing beyond confines of perennating bud, densely flowered, 3 to 8 per axil, (3 to)5 or 6-flowered; rachis green, puberulent, slightly ridged with translucent trichomes ca. 0.1 mm long; bracts subtending pedicels, foliaceous, greenish, brown in sicco, ovate to elliptic, planar or occasionally cucullate, 3.0-8.0 × 4.0-7.5 mm, coriaceous, glabrous, margin crenulate or serrulate with 4 or 5 (or 6) impressed crenations per side, with minute translucent lanceolate glands on crenations, apex obtuse or rounded. Flowers articulated at junction with pedicel, 6.0-7.0 mm long. Pedicel nodding, 2.0-5.0 × 0.8-0.9 mm at anthesis, white-puberulent; bracteoles persistent, 2, borne at base of pedicel, margin with minute translucent lanceolate glands on crenations, linear-lanceolate to oblong or nearly so, 1.0-1.2 × 0.3-0.5 mm long, glabrous, margin serrate, apex sharply acute. Hypanthium green, glossy, cupuliform, 1.4-1.8 × 0.9-1.0 mm, glabrous; calyx limb 0.7-1.0 mm long, glabrous; calyx lobes broadly triangular, 1.8-2.0 mm long, glabrous both sides, margin serrate, with minute translucent lanceolate glands on crenations, apex acute, without sessile and terminal gland. Corolla in bud closed, broadly urceolate and strongly 5- to 7-ribbed (sulcations) along the petal midveins, pale green, at anthesis strongly 5- to 7- ribbed, white with tinge of pale red or pink near and on lobes, 6.0-7.0 × 4.0-5.0 mm, glabrous inside and outside; corolla lobes 5 to 7, ca. 1.0 × 1.0 mm, apex acute or obtuse. Stamens 8 to 10, monomorphic, free from each other, 3.5-4.0 mm long; filaments straight, 1.9-2.0 mm long, white-pubescent mainly at base, trichomes ca. 0.1 mm long (shorter distally); anthers 1.5-2.1 mm long, cells 1.2-1.3 mm long, echinulate, tubules parallel, broadly cylindrical, 0.8-1.0 mm long, slightly narrower than cells, opening by oblique ventrally oriented apical pores, pore apex rounded, spurs present, minute, borne ± midway along anther, laterally oriented, 0.15-0.20 mm long. Ovary 5 or 6 (or 7)-locular, but appearing pseudo-10- to 12- (to 14-) locular with false partitions extending 0.20-0.25 mm from inner wall; ovules in two columns per locule, each column separated by false partitions; disk circular with prominent ridges on margin, ca. 2.0 mm in diameter, glabrous; style not exserted from corolla, 4.0-5.0 mm long, glabrous. Fruit not observed.

Etymology.

The epithet " Vaccinium exiguum " refers to the overall small stature and leaf morphology of the new species.

Distribution and habitat.

Vaccinium exiguum is currently known from a single individual from a single location at the exposed ultramafic forest summit of Mt. Victoria, Palawan Island, Philippines at ca. 1700 m elevation.

Conservation status.

Only a single flowering plant was documented from a single location at the summit of Mt. Victoria, Palawan. Other summits within the mountain range are similar to the type locality in elevation, but these have yet to be explored. As such, we propose the conservation threat status Data Deficient (DD) ( IUCN Standards and Petitions Committee 2019) due to the scarcity of data with which to confidently assess the species against the IUCN guidelines.

Many species are endemic to Mt. Victoria ( Robinson et al. 2009, 2016). Though harboring high biodiversity, Mt. Victoria is unfortunately not legislated as a protected area (PA). Mining activities within the area are considered a significant threat that poses the risk of habitat and forest degradation. Thus, the lack of legal protection is the greatest threat to this species and to the biodiversity of the area.

Phenology.

The new species was observed flowering during the month of February.

Figures

Figure 1. Vaccinium exiguum A ultramafic summit of Mt. Victoria B flowering branchlets in situ. Photo A by Alastair Robinson. Photo B by Rene Alfred Anton Bustamante.

Figure 2. Vaccinium exiguum A flowering branchlet B leaf, abaxial view C lateral view of flower showing ribbed corolla D distal portion of pedicel, as well as hypanthium, calyx lobes and style E stamen in oblique-lateral view showing spurs F stamen in ventral view G cross section of ovary showing seven locules. Illustrated by Maverick N. Tamayo.

Figure 3. Translucent glands of Vaccinium exiguum A leaf margin B calyx lobe C bract. Photos by Maverick N. Tamayo.