Impatiens lixianensis S. X. Yu, 2013

Yu, Sheng-Xiang, Lidén, Magnus, Han, Bao-Cai & Zhang, Xiao-Xia, 2013, Impatiens lixianensis, a new species of Balsaminaceae from Sichuan, China, Phytotaxa 115 (1), pp. 25-30 : 25-29

Impatiens lixianensis S. X. Yu , sp. nov. ( Fig. 1 , 2 A–F )

This species is closely related to I. apsotis in having small flowers, white to greenish-white petals, 2 lateral sepals, and 1– 2-flowered short raceme, but differs by its non-crested dorsal petals, short 2-lobed swollen spur, long-clawed lower petals, small scale-shaped upper petals, smaller lumina of the reticulum of pollen surface ornament and much more granulae in the lumina.

Type:— CHINA. Sichuan Province: Lixian county, Zhegushan Mountain , Shady places in forest, 31°51’28.4”N, 102°40’48.7”E, 2680–3000 m, 6 August 2006, S . X. Yu 3922 (holotype PE!, isotype IBK!) .

Annual herbs, 30–40 cm tall, glabrous. Stem succulent, erect, often branched above. Leaves alternate, aggregated towards the top of the stem; petiolate. Petiole 2–3(–4) cm long. Blades ovate or ovate-oblong, 5–7 cm long, 3–5 cm wide, base cuneate, margin crenate, apex acute, lateral veins 5–7 pairs. Racemes in upper axils, 1–2-flowered with the peduncle 2–3 cm long. Bracts inconspicuous, ovate-lanceolate, 1–2 mm long. Flowers small. Pedicels slender, 1.5–2 cm long. Lateral sepals 2, ovate-oblong, conchate, 3–5 mm long, 2–3 mm wide, apex mucronate; lower sepal infundibuliform, ca. 5 mm long, ca. 3 mm deep, abruptly constricted into a 2–3 mm long incurved spur, with swollen, bilobed apex. Petals white to greenish white; dorsal petal oblong, ca. 5 mm long, 5–6 mm wide, apex mucronate, dorsally with a narrow crest; lateral united petals 0.8– 1.2 cm long, upper petal of each pair obovate-orbicular, ca. 1 mm long, ca. 1 mm wide; lower petal of each pair subquadrate to subrhombic, with a long claw in the basal part, 0.8–1.2 cm long, 5–7 mm wide. Stamens 5; filaments 3–5 mm long, flat; anthers obtuse. Capsule ca. 2 cm long.

Palynology:—Pollen grains of Impatiens lixianensis are subcircular in polar view, ca. 9.4 (8.6–10.2) × 21.1 (19.3–22.0) × 24.3 (22.7–26.5) µm ( P [polar length] × E 1 [short equatorial length] × E 2 [long equatorial length]), tetracolpate, colpi long, thin, exine with reticulate ornamentation, dense granules in lumina ( Fig. 2 G–I ). Pollen grains of the related I. apsotis are also subcircular in polar view, ca. 12.2 (11.4–13.6) × 20.0 (19.3–21.6) × 21.1 (20.1–22.3) µm, tetracolpate, colpi long, thin, exine with reticulate ornamentation, a few granules in lumina ( Fig. 2 J–L ). The pollen of I. lixianensis therefore differs from that of I. apsotis in size, density of the granules in the lumina and size of the lumina. Moreover, the pollen grains of I. lixianensis are more flat than those of I. apsotis in equatorial view and are longer in polar view.

Phenology:—Flowering in July to August and fruiting in August to September.

Distribution and habitat:— Impatiens lixianensis grows sparsely in small populations, in shady places in deciduous broad-leaved forest, and is only known from the type locality at 2680–3520 m elevation ( Fig. 3 ).

Conservation status:— Impatiens lixianensis is assessed as Critically Endangered (CR) according to the IUCN Red List criteria ( IUCN 2010). There are only three small populations found in one valley of mountain Zhegushan from 2680 m to 3520 m. There are ca. 50 individuals recorded. Among the known populations, the one from the lowest elevation is the largest with about 30 individuals, and there were only ca. 10 individuals found in the middle and highest one, respectively. In addition, the habitat is disturbed heavily by grazing.

Discussion:—Although Impatiens lixianensis is closely related to I. apsotis , it can be easily distinguished by its white to greenish white flowers; very small upper petals of the lateral united petals which is about1/5 the size of the lower ones, short swollen spur with slightly bilobed apices. Impatiens lixianensis and the related species are compared with each other in table 1, on the basis of their reproductive and vegetative characters. Impatiens apsotis occurs in western Sichuan, eastern Xizang and with a few individuals extending to south-eastern Qinghai. Impatiens lixianensis is confined to the central part of Sichuan only ( Fig. 3 ). Although the above two species are partially sympatric, they can be readily distinguished by the gross morphology and palynological characters (table 1).

The character of long-clawed lower petals is the key trait of Impatiens lixianensis . The species also shares small white to greenish-white flowers with I. nubigena Smith (1914:190) but differs from it in having 2-lobed swollen spurs (vs. no spur). There are also some other Chinese species with white flowers, for example, I. wilsonii Hooker (1908: 244) , but they differ from I. lixianensis in having larger flowers and multi-flowered racemes, as well as the absence of a 2-lobed swollen spur. The lateral united petals of I. lixianensis are also distinctive. There is another species, Impatiens xanthocephala Smith (1920: 206) , which also has a long clawed lower petal, but the species differs from I. lixianensis in having completely reduced upper petals (vs. small scale-shaped upper petals). The differences are summarized in table 1.

Figures

FIGURE 1. Impatiens lixianensis: A. habit; B. flower, lateral view; C. flower, frontal view; D. lateral sepal; E. lower sepal; F. dorsal petal; G. lateral united petals; G 1. lower petal, G2. upper petal; H. androecium; I. capsular fruit. (Drawn by P. Liu from S. X. Yu 3922).

FIGURE 2. A–F: Flower morphology of Impatiens lixianensis. A. lower sepal; B. spur (part of lower sepal); C. lateral sepal; D. dorsal petal; E. lateral united petals; F. androecium. A–F, scale bar = 1 mm. G–I: Pollen micromorphology of I. lixianensis under SEM. G. polar view, scale bar = 5 µm. H. equatorial view, scale bar = 5 µm. I. partial view, scale bar = 2 µm. J–L: Pollen micromorphology of I. apsotis. J. polar view, scale bar = 5 µm. K. equatorial view, scale bar = 5 µm. L. partial view, scale bar = 2 µm (A–I from S. X. Yu 3922, PE; J–L from S. X. Yu 3872, PE).

FIGURE 3. Distribution of Impatiens lixianensis () and I. apsotis (●) in China.