Impatiens wawuensis B. Ding & S. X. Yu, 2016

Ding, Bo, Gadagkar, Sudhindra R., Wang, Jia-Cai, Zhang, Mei, Guo, Hui & Yu, Sheng-Xiang, 2016, Impatiens wawuensis (Balsaminaceae): a new species from Sichuan, China, Phytotaxa 273 (4), pp. 293-298 : 294-297

Impatiens wawuensis B. Ding & S. X. Yu , sp. nov. ( Figs. 1–3 )

Diagnosis: Similar to I. oxyanthera Hooker & Joseph Dalton (1908: 254) with the inflorescence comprising two pink flowers with a reddish vein, but differing from this species by smaller leaves and flowers, lower sepals with shorter and a slightly incurved spur, the lower petal of the lateral united petals with an elongate linear auricle inserted into the spur, and a fusiform capsule that is sparsely verrucous.

Type:— CHINA. Sichuan Province: Hongya County, Wawu Township, Baisha River , Wawu Mountain Provincial Nature Reserve , 29°26′34.4″N, 102°54′37.8″E, ca. 2350 m a.s.l., 24 September 2015, B. Ding 201509062 (holotype PE! , isotype KUN! , IBK! ).

Description: — Herbs, annual, 15–30 cm tall, Stems erect or creeper, slender, branched. Leaves alternate, petiolate or subsessile on upper stem; petiole 0.5–1 cm; leaf blades ovate-oblong, 2–4 × 1–1.5 cm, membranaceous, abaxially puberulent, with 2 stipitate glands at base, base cuneate, margin crenate, apex acuminate. Inflorescences axillary, 2-flowered, peduncle 1.5–2.5 cm long, puberulent, pedicels 0.5–1cm long, bracteate above base, bracts persistent, lanceolate, 2–3 mm. Flowers pink, 0.5–1 cm long; lateral sepals 2, ovate, ca. 3 × 2 mm, entire, apex acuminate, mucronulate. Lower sepal navicular, ca. 0.5 cm long, spur narrowed into a slightly incurved spur; spur stout, obtuse; mouth oblique, tip acute; dorsal petal orbicular, ca. 5 × 5 mm, base retuse, apex rostellate, abaxial midvein puberulent; lateral united petals not clawed, with fuchsia striations, ca. 0.5 cm long, 2-lobed; upper lateral united petals orbicular; lower lateral united petals dolabriform, auricle linear, elongate, inserted into spur. Stamens 5, filaments linear, anther small, apex obtuse. Ovary 4–5 mm long, erect, apex acuminate, glabrous. Capsule erect, fusiform, 1–1.5 cm long, 5- angled, sparsely verruculose along ribs.

Palynology— Pollen grains subellipsoid in polar view, 4-colpate, P×E = (17.7–19.5) 18.4 × (27.9–29.3) 28.7 μm, broadly ellipsoid in equatorial view; sexine ornamentation reticulate, bottom of ridge with irregular granules, lumina sparsely granulated ( Fig. 3A–C ).

Seed micromorphology— Seeds ellipsoid, 2.5 (2.3–2.7) × 1.5 (1.4–1.8) mm, local epidermal cells digitiform ( Fig. 3D ), digitiform cells channeled ( Fig. 3F ), most epidermal cells irregularly alveolate ( Fig. 3E ).

Etymology— The species epithet wawuensis refers to the locality of the type specimen: Wawu Shan Provincial Nature Reserve, Sichuan, China.

Phenology— Flowering and fruiting from August to November.

Ecology and distribution— Impatiens wawuensis occurs in forest understories, along canals, shaded moist places, and roadsides at ca. 2300–2400 m a.s.l. It grows together with I. imbecilla Hooker & Joseph Dalton (1910: 2917) , I. undulata Chen & Yi Lin [g] & Lu & Ying-ching (1990: 23–25) and I. tortisepala Hooker & Joseph Dalton (1910: 270) , and with species of various other genera such as Berberis Linnaeus & Carl von (1753: 330), Cardamine Linnaeus & Carl von (1753: 654), Cyperus Linnaeus & Carl von (1753: 44), and Ribes Linnaeus & Carl von (1753: 200), and with Chimonobambusa szechuanensis Keng & Pai Chieh (1948: 15) , Picea brachytyla Pritzel & Ernst Georg (1900: 216–217) , Pilea notata Wright & Charles Henry (1899: 476) , Philadelphus calvescens Hwang & Shu Mei (1991: 11) , Rubus setchuenensis Bureau & Louis Édouard & Franchet & Adrien (1891: 46) , Salvia tricuspis Franchet & Adrien René (1891: 150) , Sorbaria arborea Schneider & Camillo Karl (1905: 490) , Stranvaesia davidiana Decaisne & Joseph (1874: 179) , Tetracentron sinense Oliver & Daniel (1889: 1892) , and Tsuga chinensis Pritzel & George August (1901: 217). Impatiens wawuensis is currently known from only two small populations in the Wawu Mountain Provincial Nature Reserve.

Conservation status— Only two populations, with a total of about 400 individuals, were found in a small area (<4 km 2) in Wawu Mountain Provincial Nature Reserve. We classify the conservation status of Impatiens wawuensis as Vulnerable (VU D2), based on current information and following the International Union for Conservation of Nature and Natural Resources guidelines ( IUCN 2011). Although the area is under protection as a national nature reserve, habitat disturbance brought about by human activities such as grazing, trampling and forest clearance (e.g., firebreaks) may have a negative impact on the species.

Paratypes — CHINA. Sichuan: Wawu Mountain Provincial Nature Reserve , 29°26′35.2″N, 102°54′38.0″E, elev. ca. 2300 m, 25 September 2015, B. Ding 201509064 ( PE!) .

Similar species— Impatiens wawuensis is superficially similar to I. oxyanthera in its inflorescence comprising two pink flowers with a reddish vein. However, it differs from this species by the following characters: flower much shorter: 0.5–1 cm vs. 2–2.5 cm; spur slightly incurved vs. incurved; lower petal of the lateral united petals with elongate linear auricle inserted into the spur vs. linear auricle absent; capsule fusiform vs. linear; capsule ribs verruculose vs. smooth.

Figures

FIGURE 1. Impatiens wawuensis B. Ding & S. X. Yu. A. Flowering plant; B. Enlarged basal portion of leaf; C. Flower (lateral view); D. Flower (front view); E. Flower (dorsal view); F. Lateral sepal; G. Dorsal petal; H. Lower sepal; I. Lateral united petals; J. Ovary surrounded by stamens; K. Immature capsule; L. Mature capsule.

FIGURE 3. SEM micrographs of pollen grains and seeds of Impatiens wawuensis B. Ding & S. X. Yu.A–C. SEM images of pollen grains. A, B. Whole view; C. Exine sculpture; D–F. SEM images of seeds; D. Whole view; E–F. Partial view.