Impatiens xanthinoides G. W. Hu, 2015

Cai, Xiu-Zhen, Hu, Guang-Wan & Cong, Yi-Yan, 2015, Impatiens xanthinoides (Balsaminaceae), a new species from Yunnan, China, Phytotaxa 227 (3), pp. 261-267 : 262-266

Impatiens xanthinoides G. W. Hu , sp. nov. (See Figure 1 and Figure 2 )

Diagnosis: —The new species differs from Impatiens xanthina by having the lower sepal obconic with red striae, dorsal petal glabrous, and the lateral united petals stipitate with fan-shaped, apex acute lower lobes.

Type: — CHINA. Yunnan: Tongbiguan Township , Yingjiang County, on the rocks mixed with mosses along streams, 939 m, 97°34.893′ E, 24°37.749′ N, 25 October 2011, G. W. Hu HGW-00893 (holotype, HIB!; isotypes, PE!, HIB!, HNNU!) .

Herb annual, small, 4–15 (–25) cm tall. Stem erect, fleshy, lower part often naked, simple or rarely branched from middle, pale green, yellow-green when dry, with numerous fibrous roots, glabrous. Leaves alternate, often crowded toward apex of stem, subsessile in upper part, 1–1.8 cm long, petiolate in lower part of stem; stipule absent; lamina membranous, 3–10 × 1–2.5 cm, lanceolate or elliptic-lanceolate, green above, with scabrid puberulent, pale green beneath, glabrous, lateral veins 4–7 pairs, curved, midvein conspicuously raised abaxially, base cuneate or attenuate, margin coarsely crenate-denticulate, setose between marginal teeth, apex acute or obtuse-acute. Inflorescences in upper leaf axils, 1- or 2-flowered; peduncles slender, 0.5–1.8 cm long, sparsely pubescent; pedicels 0.8–1.5 cm long, elongate in fruit, sparsely pubescent; bracts very small, lanceolate, situated at the base of the pedicel, persistent, pale green, glabrous. Flowers golden-yellow, small, 18–23 mm long. Lateral sepals 2, pale yellow, lanceolate or narrowly ovate, ca. 5 × 3 mm, apex acuminate, glabrous. Lower sepal obconic, glabrous, limb navicular, mouth ca. 8 mm wide, anterior acute, base abruptly narrowed into an incurved spur 15–23 mm. Dorsal petal galeiform, widely ovate, 5.5– 6.2 × 3.8–4.1 mm, base broadly cuneate, apex obtuse-rounded, abaxial midvein slightly thickened, glabrous. Lateral united petals stipitate, red striae nearly at base, 12–15 mm long, 2-lobed, upper lobes small, elliptic, ca. 2 mm wide, apex obtuse-rounded; lower lobes fan-shaped, ca. 8 × 6 mm, apex acute, abaxial auricle slightly inflexed. Stamens 5, ca. 2 mm long, filaments linear, upper part dilated; anthers ovoid, joined into a ring surrounding the ovary apex, apex obtuse. Ovary superior, 5-carpellate, placentation axile, fusiform, ca. 3 mm long, erect, apex acute; style 1. Capsule fusiform, 5-angled, ca. 12 × 4.5 mm, apex acute, rostellate, 5-valved, fleshy. Seeds numerous, yellowish brown.

Distribution: —The new species is only known in the type locality, Tongbiguan Township, elevation 939 m, Yingjiang County, western Yunnan, China.

Ecology & Habitat: — Impatiens xanthinoides grows on the rocks mixed with mosses along streams at elevation of 900–1000 m. The vegetation in this area is tropical mountain rainforest.

Phenology: —Flowering and fruiting from August to November.

Etymology: —The epithetic xanthinoides refers to its morphological similarity of the new species to Impatiens xanthina .

IUCN Red List Category: — Impatiens xanthinoides is only found from Tongbiguan Township, Yingjiang County, western Yunnan, China. It only distributes in a protected area in Tongbiguan Natural Reserve less than 100 km 2. During the second investigation, we found fewer mature individuals in the population than we found at the first time. According to the IUCN Red List Categories and Criteria ( IUCN 2010), we categorize I. xanthinoides as Critically Endangered (CR B1a; B1b(ii)) because of its limited distribution range and the decline of its mature individuals.

Similar species: —Morphologically, Impatiens xanthinoides is similar to I. xanthina in having a lanceolate or elliptic-lanceolate lamina with crenate-denticulate margin, 1–2-flowered peduncles, golden-yellow flowers, lateral sepals 2, stamen 5 with obtuse apex and 5-carpellate ovary. However, it differs from the latter in dorsal petal which is galeiform, glabrous without flecks at base (vs. suborbicular, abaxially puberulent, purple- or red-tinged at base in I. xanthina ), the lateral united petals which are stipitate with red striae nearly at base, upper lobes are elliptic, lower lobes are fan-shaped with acute apex and having abaxial auricle (vs. nearly sessile, abaxial auricle absent, upper lobes are orbicular with purple- or red-tinged flecks at base; lower lobes are dolabriform or ovate-dolabriform with obtuse apex in I. xanthina ). Apart from I. xanthina , the new species also resembles I. fugongensis K. M. Liu & Y. Y. Cong (2008: 161) , but it can be easily distinguished by the shape of lamina, persistent bracts (vs. caduceus in I. fugongensis ), a obconic, glabrous lower sepal (vs. cornuted, outside hair in I. fugongensis ), and the stipitate lateral united petals (vs. sessile, abaxial auricle absent, upper lobes narrowly elliptic, without flecks at base; lower lobes dolabriform-triangular, apically retuse in I. fugongensis ). More detailed morphological comparisons of these three species are presented in Table 1.

Palynology: —Pollen grains of Impatiens xanthinoides are subellipsoid in polar view, 25.4–27.8 × 18.3–19.5 (P [polar length] × E [equatorial length]) μm, 4-colpate, with long and thin colpi, exine with irregular reticulate ornamentation, and sparse granules in lumina can be seen at high magnification ( Figure 3 : A, B). While pollen grains of I. xanthina are long-elliptic in polar view, 26.9–28.5 × 18.0–19.1 μm, also 4-colpate, with long colpi, exine with reticulate ornamentation and dense granules in lumina. The pollen characters show that I. xanthinoides obviously differs from I. xanthina in shape and granule characters in lumina of the reticulate ornamentation ( Cai et al. 2007).

Seed micromorphology: —Seeds are ovate-elliptic, 0.93–1.43 × 0.62–0.88 mm, ratio of L/W (length/width) 1.50– 1.63 ( Figure 3 : C); some of the epidermal cells of Impatiens xanthinoides are significantly to form cristate protrusions which are spirally thickened, and fine cuticular granules densely cover the nonprotrusive epidermal cells ( Figure 3 : D–F). While in I. xanthina , seeds are ovate, some of the epidermal cells of the seedcoat protrude significantly to form cristate protrusions which are spirally thickened; in I. fugongensis , seeds are elliptic, and some of the epidermal cells of the seedcoat protrude significantly to form squamalate projections that are oblong and have conspicuous pits ( Cong et al. 2008).

Additional specimens examined: —The same location as the holotype, 22 August 2007, G. W. Hu 24498 (HIB!).

Figures

FIGURE 1. Illustration of Impatiens xanthinoides G. W. Hu. —A. Habit. —B. Flower, anterior view. —C. Lateral sepals. —D. Dorsal petal. —E. Lateral united petals. —F. Lower sepal. —G. Fruit. —H. Seeds. Drawn by JING TIAN based on the holotype.

FIGURE 2. A–H. Impatiens xanthinoides sp. nov. —A. Habitat. —B. Flowering habit. —C. Whole plant. —D. Inflorescences. —E. Flowers in front view, showing the shape of lower lobes of lateral united petals. —F. Flowers in lateral view. —G. Flowers in front view, showing abaxial auricle slightly inflexed of lateral united petals. —H.Young fruits. Photographed by GUANG WAN HU from Yingjiang, Yunnan. I–K. I. xanthina. —I. Flowering habit. —J. Flower in back view. —K. Flower in front view. Photographed by BEN-XI LIU from Gongshan, Yunnan.

FIGURE 3. Scanning electron microscope (SEM) photos of Impatiens xanthinoides sp. nov. A–B. Pollen grains. —A. Equatorial view, showing the shape of pollen grain. —B. Exine ornamentation. —C–F. Seed. —C. Entire view, showing the shape of the seed. —D. Testa surface. —E. Cristate protrusions. —F. Partial view, showing the fine cuticular granules. (Voucher specimen: HGW-00893).