Zingiber ventricosum L.Bai, Škorničk., N.H.Xia & Y.S.Ye, 2016

Bai, Lin, Leong-Škorničková, Jana, Xia, Nian-He & Ye, Yu-Shi, 2016, Taxonomic studies on Zingiber (Zingiberaceae) in China III: Z. ventricosum, a new species from Yunnan, and notes on three closely related species, Phytotaxa 261 (2), pp. 101-120 : 102-107

Zingiber ventricosum L.Bai, Škorničk., N.H.Xia & Y.S.Ye , sp. nov. ( Figs. 1–3 , 4A )

Similar to Zingiber oligophyllum K.Schum. , Z. thorelii Gagnep. and Z. xishuangbannaense S.Q.Tong in having much-reduced ligules, usually elongated petioles, similar general flowers shape, and glabrous ovaries, but differs from all three species by having longer and erect peduncles and bracts which are convex and prominently inflated at their bases (giving the inflorescence somewhat bullate appearance) and acuminate and wide-spreading apices. Additionally it differs from Z. xishuangbannaense , the only other species among the above three with tightly arranged bracts, by tough, fibrous, well-elongated and creeping rhizomes.

Type:— CHINA. Yunnan Province: Xishuangbanna, Jinghong City , Puwen Zhen , Puwen Forest Farm , near the Puwen River , elev. ca. 780 m, 101°23′E, 22°33′N, 26 August 2014, L.Bai 14082601 (holotype IBSC!; isotypes E!, KUN!, SING!, US!) .

Perennial rhizomatous herb 0.8–1.2 m tall. Rhizomes tough, fibrous, well-elongated and creeping, to 30 cm long, internodes ca. 2.2 cm long, 1–2 cm in diam., light brown externally, white to cream-white internally; root tubers ovoid or fusiform, formed in the middle of the roots, ca. 3 × 1.2 cm, pale brown externally, cream-white internally. Leafy shoots 3–8 per plant, forming loose clumps, ca. 10 cm apart, erect to slightly spreading, each shoot comprising 8–15 well developed leaves at flowering, usually spaced evenly along the pseudostem; leaf sheaths pale green, usually red tinged towards the base, sparsely white pubescent; ligules reduced, 1–2 mm long, weakly bilobed, membranaceous, yellowish green, sometimes with slight reddish tinge, slightly pubescent, apices rounded, semi-hyaline; petiole 5–35 mm long, often comprising a pulvinus and the narrowed base of lamina (rarely in some individuals petiole consisting of pulvinus only); pulvinus ca. 5 mm long, glabrous to slightly pubescent; lamina narrowly-obovate, rarely ovate on basal leaves, 23–27 × 4.5–8 cm, length:width ratio 4.2–6.6, prominently plicate, adaxially green to yellowish green, sparsely pubescent, abaxially pale green, densely pubescent (appressed), base attenuate (rarely auriculate), margins of the basal part of laminas always slightly undulate, apex acuminate. Inflorescences 2–3 per plant, radical, remote from the pseudostem; peduncle erect, 12–25(–45) cm long, 0.6 cm in diam., glabrous; sheathing bracts ovate to narrowly ovate, tightly embracing the peduncle, 2–5.5 cm long (shortest at basal ones, progressively longer distally), ca. 2 cm wide when flattened, basal ones pink-red, upper ones green, with prominent ridges abaxially, glabrous; spike long-ovoid, 7–15 × 3–4 cm, comprising 30–50 densely imbricated bracts, each subtending single flower (uppermost 2–8 bracts usually sterile and somewhat smaller); fertile bracts oblong to ovate, ca. 3.5 × 1.7 cm, bright green, sometimes red tinged towards the margin, glabrous, basal part prominently convex and inflated, ca. 3.5 cm wide when flattened, apex acuminate and wide-spreading, lateral margin usually prominently crisped; bracteoles narrowly oblong, ca. 2.5 cm long, ca. 0.9 cm wide when flattened, cream-yellow to green, slightly purple-red tinged at apex, glabrous externally and internally, apex emarginate. Flowers ca. 6 cm long, much exserted beyond the bracts; calyx tubular, membranaceous, ca. 10 mm long, with unilateral incision to 5 mm deep, cream-yellow, glabrous externally and internally, apex truncate; floral tube ca. 3 cm long, cylindrical at base (ca. 3 mm in diam.) to weakly funnel shaped at apex (ca. 4 mm in diam.), cream-white, glabrous externally and internally; dorsal corolla lobe narrowly ovate, ca. 30 × 10 mm, yellow with dense red tinge, glabrous externally and internally, apex mucronate; lateral corolla lobes narrowly triangular-ovate, ca. 28 × 6 mm, yellow with dense red tinge, much deflexed, glabrous externally and internally; labellum narrowly oblong, basal part slightly broadened, 31–36 × 7–9 mm, thin and yellow on the margin, thicker and pale yellow in the middle, glabrous, apex rounded or obtuse, margins conspicuously revolute; lateral staminodes narrowly ovate, 19–21 × 4–5 mm, connate to labellum in their basal 1/2 to 3/5, yellow, slightly paler at base, glabrous, apices acute. Stamen ca. 24 mm long (ca. 29 mm long with anther crest stretched); filament ca. 2 mm long, 2.5 mm wide, cream yellow, glabrous; anther ca. 12 mm long (excluding anther crest), connective tissue yellow, glabrous; anther thecae 12 mm long, dehiscing throughout entire length, pollen light yellow; anther crest beak shaped, ca. 15 mm long when stretched, yellow, apex entire. Style filiform, white, glabrous; stigma extending to the tip of anther crest, slightly thicker than the style, 1–2 mm long, funnel-shaped, white, ostiole ciliate. Ovary cylindrical, trilocular, ca. 5.5–8 × 4–4.5 mm, cream-white, glabrous; Epigynous glands two, narrowly conical, 9–10.5 mm long, 0.3 mm in diam. at base, pale yellow, apex sharp. Immature fruits long-ovoid to fusiform, bluntly trigonous septifragal capsule, ca. 26 × 12 mm, greenish with pink-red tinge externally, light green internally, placenta pink, presumably opening by three valves upon maturity; seeds obovoid, ca. 6 × 4.5 mm, pink (immature), striate, aril sac-like with irregularly edged apex, white, nearly fully embedding the seeds.

Etymology:—The specific epithet refers to the main character of the bracts that are ventricose (swollen) at the base.

Distribution and provisional IUCN conservation assessment:— Zingiber ventricosum is currently known only from its type locality and nearby areas where the plants cover an estimated Extent of Occurrence (EOO) of about 24 km 2. No material of this species was encountered during an extensive examination of herbarium specimens at BK, BKF, CMU, CDBI, EMA, GXMG, GXMI, HITBC, IBK, IBSC, KUN, PE, SYS, SING or high resolution specimen images from AAU, BM, C, E, G, HAST, K, KFRI, L, P, TAI, TAIF, US, W, WU. Individuals occurring near farmland were observed to be threatened by agricultural practices. Based on the latest IUCN criteria ( IUCN 2012; IUCN Standards and Petitions Subcommittee 2014) we propose this species be globally treated as Critically Endangered (CR), B1ab (iii, v).

Ecology and phenology:— Zingiber ventricosum occurs in open grassy areas or beneath shrubs along banks of rivers. The climate of the type locality is typical southern subtropical, comprising a wet season that commences in mid- April and finishes at the end of October. Flowering commences in late August and extends until mid-October. Fruits appear from mid-October.

Additional specimens examined (paratypes):— CHINA. Yunnan Province: Xishuangbanna, Jinghong City, Puwen Zhen , near the Puwen River , 12 September 2012, L.Bai 12091203 ( IBSC!) ; ibidem, 17 October 2014, L. Bai 14101701 ( IBSC!) .

Notes:—As already mentioned in the introduction, Z. ventricosum is most closely related to Z. oligophyllum , Z. thorelii and Z. xishuangbannaense . The main distinguishing features of the new species are outlined in the diagnosis and the key to the four species of the informal “ Z. oligophyllum complex”, and the detailed comparison is given in Table 1.

The sectional placement of Z. ventricosum is not straightforward, partly due to ambiguous characters used in the old, but still accepted, infrageneric classification of Zingiber . This classification ( Bentham & Hooker 1883) uses inflorescence characters to define four sections within the genus (inflorescences apical on the leafy shoots: Z. sect. Dymczewiczia Bentham (1883: 646) ; inflorescences breaking through the leaf sheaths: Z. sect. Pleuranthesis Bentham (1883: 646); inflorescences radical, peduncles long and erect: Z. sect. Zingiber ; inflorescences radical, peduncles short or elongate and procumbent: Z. sect. Cryptanthium; for more details see Bai et al. 2015 a). The new species, Z. ventricosum , has radical inflorescences comprising long, erect peduncles and long-ovoid spikes comprising 30–50 closely arranged bracts and on the basis of these characters should be referred to Z. sect. Zingiber . However, two of its presumed close relatives (based on the similarity of vegetative and floral parts), Z. oligophyllum and Z. thorelii , have radical inflorescences with procumbent peduncles and loosely arranged bracts, and were referred to Z. sect. Cryptanthium by Schumann (1904) and Gagnepain (1907). These disparities highlight the inadequacies of the existing infra-generic classification within Zingiber and indicate the need for a further assessment of the sectional placement of Z. ventricosum , as will now be discussed.

Theilade et al. (1993) and Triboun (2006) noted that the inflorescence characters traditionally used since Bentham and Hooker (1883) to classify Zingiber are not always reliable. Examples include Z. newmanii Theilade (1999: 407) (with procumbent peduncle, but referred to Z. sect. Zingiber by Theilade 1999); Z. junceum Gagnepain (1906: 149) and Z. gramineum Blume (1827: 45) (inflorescences radical but sometimes also arising from the top of leafy shoots, fide Theilade et al. 1993), Z. kangleipakense (inflorescences borne directly from the rhizomes but sometimes protruding from the leafy shoots, fide Kishor & Leong-Škorničková 2013).

Notwithstanding the above, so far all species of Z. sect. Cryptanthium have ellipsoidal pollen with spiro-striate sculpturing, while members of the other three sections have spheroidal pollen with cerebroid or reticulate sculpturing ( Theilade et al. 1993, Bai et al. 2015a). The only phylogenetic study that has examined the infrageneric classification of Zingiber so far is that of Theerakulpisut et al. (2012). Although the results of this study did not fully support recognition of the four traditional sections, they did show that species with ellipsoidal pollen were aggregated on a single clade, and that these species are currently assigned to Z. sect. Cryptanthium. This clade was sister to a clade containing species from the other three sections and all these species possess spheroidal pollen. We therefore consider ellipsoidal pollen with a spiro-striate sculpturing a robust character for assigning species to Z. sect. Cryptanthium. Our observation reveals that pollen of Z. ventricosum , Z. oligophyllum and Z. xishuangbannaense all have ellipsoidal pollen with spiro-striate sculpturing and therefore should be placed to Z. sect. Cryptanthium.

The revision of the three relatives of Z. ventricosum from the informal “ Z. oligophyllum complex” is provided below. The species are ordered chronologically.

Figures

FIGURE 1. Zingiber ventricosum L.Bai, Škorničk., N.H.Xia & Y.S.Ye. A. Plant habit. B. Ligules. C. Rhizomes. D. Fruit, seeds and aril (immature). A–C are based on the type collection L.Bai 14082601, D is based on L.Bai 14101701 from the type locality. Photos: Lin Bai.

FIGURE 2. Zingiber ventricosum L.Bai, Škorničk., N.H.Xia & Y.S.Ye. A. Inflorescence. B. Flower (front view). C. Flower (side view). D. Single flower (side view, bracteole removed). E. Dissection (from left): bract, bracteole, calyx, dorsal corolla lobe, two lateral corolla lobes, labellum with lateral staminodes basally connate, apical part of floral tube with stamen and style, ovary with two epigynous glands. Based on the type collection L.Bai 14082601. Photos: Lin Bai.

FIGURE 3. Zingiber ventricosum L.Bai, Škorničk., N.H.Xia & Y.S.Ye. A. Rhizome. B. Leafy shoot. C. Ligule. D Inflorescence (spike with only the uppermost part of the peduncle). E. Single flower (side view, bracteole removed). F. Flower (front view). G. Bract. H. Bracteole. I. Calyx. J. Dorsal corolla lobe. K. Two lateral corolla lobes. L. Labellum with lateral staminodes basally connate. M.Apical part of floral tube with the stamen. N. Ovary with two epigynous glands. Based on the type collection L.Bai 14082601. Drawn by Mr. Dinghan Cui.

FIGURE 4. Type specimens of the four species in “Zingiber oligophyllum” complex. A. Z. ventricosum (holotype, L.Bai 14082601, IBSC). B. Z. oligophyllum (lectotype, A.Henry 1605, K). C. Z. thorelii (lectotype, C.Thorel 2363, P) D. Z. xishuangbannaense (lectotype, S.Q.Tong 24808, HITBC).