Argyreia albiflora Staples & Traiperm, 2015

Staples, George W., Traiperm, Paweena & Chow, Janeny, 2015, Another New Thai Argyreia Species (Convolvulaceae), Phytotaxa 204 (3), pp. 223-229 : 227-228

Argyreia albiflora Staples & Traiperm , sp. nov. ( Fig. 1 , 2 , 3A )

Similar to A. wallichii in having a capitate inflorescence with white flowers, but differing from that species by a prostrate creeping habit, ovate, elliptic, oblong-elliptic, or broadly elliptic leaf shape, with an obtuse or rounded base, oblong or oblong-lanceolate bracts, and 3 outer sepals larger than 2 inner.

Type:— THAILAND. Chiang Mai, Om Koi district, along Hwy 1099 between Om Koi and Mae Tuen, 25 October 2010, Staples, Suksathan & Sangirotjanapat 1439 (holotype BKF!; isotypes A!, BK!, BKF!, E!, HNL!, K!, KKU!, KUN!, L!, P!, QBG!, SING!, US!). Flowers in spirit are stored in SING under no. 5177 .

Argyreia sp. , sensu Kerr (1954: 26).

Prostrate herbaceous creeper or twiner. Root enlarged, main tap root 23–65 cm long, thickened, woody, twisted irregularly, 4–13 mm diam., lateral roots fibrous. Trichomes simple, non-glandular; a mixed indumentum on stems, petioles, peduncles and leaf undersides of longer (1–1.2 mm), yellowish, ascending, hirsute hairs and shorter, whitish, erect, villous hairs. Stem wiry, sprawling on ground or tips twining, 15–75 cm long. Leaf petiole 1.0– 5.3 cm long, stout, hairy; blade ovate, elliptic, oblong-elliptic, or broadly elliptic (rarely oblanceolate-obovate), 4.1–9.5 × 1.0–6.0 cm, ± rugose, stiffly chartaceous to coriaceous, base usually obtuse to cuneate or rounded, margins entire to undulate, apex obtuse or acute, acuminate, mucronate, upper side glabrous or with few pilose-hirsute hairs on midvein, dark green, finely pitted with minute dots, underside ashy whitish hairy, especially dense on midrib and secondary veins; venation pinnate, deeply impressed on upper side, prominent below. Inflorescence axillary, erect-ascending, capitate, few-flowered; peduncle 4–15(–30) mm long, always shorter than subtending petiole, (sometimes none or ± hidden); bracts oblong or oblong-lanceolate, 15–20 × 4–7 mm, apex acute or obtuse, outside hairy like the leaves, inner side glabrous; pedicels terete, ca. 5 mm long, sericeous; bracteoles like bracts only smaller, less densely hairy. Flowers diurnal, erect-ascending, odourless. Sepals very unequal, outer 3 longer, oblong-acute, 13–14 × 5–6 mm, sericeous outside, glabrous inside, margins slightly undulate, the third sepal unequal-sided, inner sepals lanceolate-acute, 6–7 × 2–3 mm, sericeous outside, especially along the middle, glabrous inside, indumentum coarse and more dense along middle, finer and thinner at margins, inner margin of third sepal and the inner 2 sepals with scattered dark dots near base. Corolla tubular-funnelform, 4–5 cm long, pure white, thinly membranous, fugacious, base of tube cylindrical, ca. 6.5 mm long, flaring gradually above, limb reflexed, ruffled, sericeous-hirsute on midpetaline bands and upper tube outside, glabrous elsewhere, glabrous inside except at filament attachment. Stamens included, equal, white, filament base expanded, ca. 6.5 mm long, villous at insertion point, free portion filamentous, 2.6–2.7 cm long, glabrous; anthers linear-oblong, ca. 3.5 × 1.5 mm, base deeply lobed, lobes parallel; pollen globose, pantoporate, minutely spinulose. Pistil included, longer than stamens, white; nectary disc annular, undulate, ca. 2 mm diam., glabrous; ovary ovoid, glabrous, 2-celled; style ca. 35–40 mm long; stigmas 2-globose. Fruit not seen.

Phenology:—Flowers open during day time, odourless. Collected once in July and three times in October in flower; fruits not seen.

Ecology:—Prostrate or low-twining in disturbed pasture area along roadside; in grassy understory beneath mixed pine-deciduous-dipterocarp forest; often (always?) in shady situations, not in full sun. On heavy red clay soil.

Elevation:— 989–1300 m.

Conservation assessment:—VU (Vulnerable). According to the current Red List criteria (IUCN 2012: 20–22) we rate Argyreia albiflora as Vulnerable according to criteria D1: a population size estimated to be less than 1,000 mature individuals—we counted less than 20 mature individuals in the two sites directly observed, and criteria D2: the populations have a very restricted number of locations such that it is prone to the effects of human activities or stochastic events—the two sites we observed are in fragmented habitats subject to human disturbance (land clearing, livestock grazing, vegetable farming) and are located on steep slopes that would erode badly following heavy rainfall, a frequent occurrence during the hot wet season. Any further forest clearing at the second site observed would very likely eradicate the entire population there. These same human activities and stochastic processes prevail throughout northern Thailand and are very likely to occur at all known sites where A. albiflora has been collected. We believe a conservation status of Vulnerable is appropriate initially, and further field survey is needed to make additional observations.

Other observations:—The leaves are often chewed by caterpillars, so many plants have rather few intact leaves and a characteristic appearance of ragged, chewed leaves seems typical. There is an enlarged, semi-woody tap root extending deep into the soil, which suggests the plant may be deciduous during the dry season. And the stem and leaf undersides are often thickly coated with soil particles, which stick to them until drying and handling dislodges them.

Additional specimens examined:— THAILAND. Chiang Mai: Om Koi district, ca. 3–4 km outside Om Koi along Hwy 1099, towards Mae Tuen , mixed pine-dipterocarp forest, 25 October 2010, Staples et al. 1437 ( QBG) ; near village of Ban Mu Ser , on small dirt track leading off paved road into patch of forest among cabbage fields, 26 October 2010, Staples et al. 1446 ( A, BKF, K, L, QBG, SING) ; “ MêTûn ” in open grassy forest, ca. 1100 m elev., 5 July 1922, A. F. G. Kerr s.n. ( BM) ; Tak: Ban Muser, 12 October 1992, Herbarium trip 312 ( BCU), Herbarium trip s.n. ( BCU) .

Notes:—One additional specimen seen in BCU, Herbarium trip 319, from Monjong in Chiang Mai province, is morphologically similar to the specimens cited above, but the label reports the corolla is purple. Possibly this is a label error resulting from confusion with other species of Argyreia .

Figures

FIGURE 1. Argyreia albiflora: A. flowers in side view; B. flowers in front view; C, D. habitat, all from Staples et al., 1446 (photos G. Staples).

FIGURE 2. Argyreia albiflora: A. flowering stem; B. bracts; C. sepals, outer (left) to innermost (right); D. opened corolla with stamens; E. pistil; F. abaxial leaf surface; G. adaxial leaf surface (drawn by W. Nuchthongmuang from the type specimens G. Staples et al., 1439).

FIGURE 3. A–C Argyreia albiflora (G. Staples et al., 1439, 1446), A. Plant habit, inset a. close-up of flowers (photos G. Staples); B. upper epidermis from LM (photo P. Traiperm); C. upper epidermis from SEM (photo J. Chow). D–F Argyreia wallichii (G. Staples et al., 1529), D. Plant habit, inset d. close up of flowers (photos P. Traiperm); E. upper epidermis from LM (photo P. Traiperm); F. upper epidermis from SEM (photo J. Chow).