Cephalanthera yintiaolingensis F.Chen, C.Xiong & X.H.Jin, 2023

Chen, Feng, Xiong, Chi, Zheng, Chang-Bing, Jin, Xiao-Hua & He, Hai, 2023, Cephalanthera yintiaolingensis (Orchidaceae, Epidendroidee, Neottieae), a new mycoheterotrophic orchid from Northeast Chongqing, China, Phytotaxa 626 (2), pp. 119-125 : 120-123

Cephalanthera yintiaolingensis F.Chen, C.Xiong & X.H.Jin , sp. nov. ( Figs. 1 & 2 ).

Diagnosis: — Cephalanthera yintiaolingensis resembles Cephalanthera exigua Seidenf. in the mycoheterotrophic habit, but differs from it by having conical spur at the base of the lip, flabellate middle lobe with five to seven lamellae and acuminate apex ( Table 1 ). Cephalanthera yintiaolingensis is also close to C. subaphylla Miyabe & Kudô by sharing flower with spur at the base of the lip, but differs from it by having its mycoheterotrophic with wholly achlorophyllous leaves, flabellate middle lobe, sepals and petals obtuse at apex( Table 1 ).

Type: — CHINA. Chongqing: Wuxi County, Yintiaoling National Nature Reserve, Sheliangzi , 109°54′29″E, 31°28′44″N, elev. ca. 1660 m, under moist broadleaf forest, in flowering, 7 May 2022, Feng Chen & Su Wang YTL22-314 (Holotype CQNM 0025462 !; isotypes CQNM 0025463 !, PE!) .

Description: —Mycoheterotrophic terrestrial herb, 8–20 cm tall. Rhizome creeping, ca. 3 mm in diameter. Roots fasciculate, 1–5 cm long and 3–6 mm in diameter, with brown hairs. Stem slender, more or less flexuous, whitish, glabrous, covered by 3–5 sheaths; distally 2–3 sheaths densely spaced and the distally others well spaced, 1–3 cm long, tubular below, slightly spreading apex above, and the distally sheath with longer apex. Inflorescence 4–7 cm long, 3–5(–6)-flowered; lowest bract elliptic-lanceolate, 10–12 × 4–8 mm, veins 10–12; upper bracts triangular lanceolate, 1–3 mm long, shorter than pedicel and ovary; pedicel and ovary not well differentiated, whitish, 1.1–1.5 cm long, slightly ridged. Flowers white, 7–8 mm long, suberect, outwardly oblique at anthesis; dorsal sepal elliptic, obtuse at apex, 14–16 × 4–6 mm, 3-veined; lateral sepals ovate-lanceolate, falcate, obtuse at apex, 10–12 × 6–7 mm, 3(–4)- veined; petals obovate-lanceolate, slightly falcate, 13–14 × ca. 4 mm, 3(–4)-veined, apex broadly obtuse; lip suberect, 8–10 × ca. 9 mm, three lobed; lateral lobes triangular-lanceolate, ca. 5 × 3.5 mm; middle lobe flabellate, ca. 8 × 6 mm, three median fleshy-thickened and longitudinal lamellae with several lateral lamellae converged at apex; spur 3–5 mm long, directedly protruding on the base of lateral sepals. Column semi-terete, slightly curved, ca. 8 × 1.5 mm; stigma circular on the top of the column; anther erect, ellipse, hinged with column by a short stalk; pollinia 2, each divided into 2 halves, ca. 2.5 mm, white, naked, farinaceous; staminodes 2, ligulate, obtuse at apex; rostellum absent. Capsules unseen.

Ecology and Distribution: — Cephalanthera yintiaolingensis grows in the moist broadleaf mixed forest dominated by Quercus oxyodon Miq. ( Fagaceae ), Q. engleriana Seem. ( Fagaceae ), Q. myrsinifolia Blume ( Fagaceae ) and Acer sterculiaceum subsp. franchetii (Pax) A.E.Murray ( Sapindaceae ). A vine, Sinofranchetia chinensis (Franch.) Hemsl. ( Lardizabalaceae ), is obvious in this forest. And the identified herbaceous species among others around the vicinity include Chrysosplenium macrophyllum Oliv. ( Saxifragaceae ), Oxalis griffithii Edgew. & Hook.f. ( Oxalidaceae ), Paris bashanensis F.T.Wang & Tang ( Melanthiaceae ), and Primula tsiangii W.W.Sm. ( Primulaceae ). A few individuals of another species of Cephalanthera , the white flowered C. erecta (Thunb.) Blume , was also found under this forest. Cephalanthera yintiaolingensis is only known from the type locality, where is also bordering West Hubei and Southeast Shaanxi in South Central China.

Phenology: —Flowering in May, but fruiting immature during our investigation.

Etymology: —The specific epithet refers to Yintiaoling Nature Reserve, where the type specimens of this new species was collected. Concerning to its only presently known from the type locality, the Chinese name of this orchid, Yīn Tiáo Lǐng Tóu Ruǐ Lán (Dzȇ岭ẍṽ兰), is also suggested.

Conservation assessment: —A total of ca. 50 individuals of Cephalanthera yintiaolingensis were discovered in broadleaf mixed forest at Yintiaoling Nature Reserve. They were subdivided into two subpopulations. The habitat of Cephalanthera yintiaolingensis is within the core zone of this nature reserve. We temporarily assessed its conservation status as Data Deficient (DD) based on Categories and Criteria of IUCN (2023).

Status of similar taxa regarding trophic modes:—It is notable that the most morphological similar species of Cephalanthera yintiaolingensis ( Table 1 ) had been treated to be an infraspecific abnormality of a generally considered autotrophic species, Cephalanthera erecta (Thunb. in Murray 1784: 816) Blume (1859: 188), as either C. erecta var. subaphylla (Miyabe & Kudô) Ohwi (1953: 69) or C. erecta f. subaphylla (Miyabe & Kudô) M. Hiroe (1971: 63) . But its independent species status was unequivocally supported by more recent studies of both molecular evidence ( Shin et al. 2019) and alloenzyme analysis ( Chung et al. 2019). Although it was not sure while could be inferred from its original description and latter literature (e.g., Suetsugu 2017) that C. subaphylla is most probably a mixotrophic species, and it was latter considered to be strongly (but not fully) mycoheterotrophic ( Sakamoto et al. 2016), and further investigation also revealed that it is associated with the same fungi family as the more autotrophic species C. erecta . Moreover, floral peloric and vegetative albino were generally observed in Cephalanthera ( Hayakawa et al. 2016, Suetsugu 2017), which lead to description of C. subaphylla f. conformis H.Hayak. in Hayakawa et al. (2016: 200) and C. subaphylla f. leucophylla Suetsugu (2017: 200) . Although it is tentatively placed the two forms (with undifferentiated lip in the former and being achlorophyllous in the latter) both as conspecific to C. erecta ( POWO 2023) , further analysis is necessary.

Another mycoheterotrophic species, Cephalanthera exigua Seidenf. (1975: 71) , is also comparably similar to this new species in its saprophytic habit and white colored and expanding tepals. It was firstly reported only in Laos, and it was later discovered also distributed in Thailand (Pedersen et al. 2019) and Vietnam ( Nuraliev et al. 2014). The most distinguishable difference lies in its absence of spur. In addition, habitat of these two species is different. Cephalanthera exigua grows in the tropical forest (Pedersen et al. 2019), Cephalanthera yintiaolingensis grows in subtropical broadleaf forest in Northeast Chongqing, southern Central China. However, further phylogenetic studies by incorporated more representative samples will clarify the interspecific relationships of this group of orchids with more diversified trophic modes and replete with pelorias.

Figures

FIGURE 1. Cephalanthera yintiaolingensis. A) Habitat; B) Habit; C) front view of a flower; D) anatomy of a flower; E) side view of lip and column; F) dorsal view of colume; G) side view of column; H) ventral view of column. A, B and C photographed by Feng Chen, others photographed by Chi Xiong.

FIGURE 2. Holotype of Cephalanthera yintiaolingensis (CQNM 0025462), photographed by Long Wang.

Tables

TABLE 1. Morphological comparison of Cephalanthera yintiaolingensis, C.exigua, and C. subaphylla. Owing to the unavailable physical material, characters of C.exigua were referred to Seidenfaden (1975), Pedersen et al. (2009), and Nuraliev et al. (2014), and those of C. subaphylla were referring to Miyabe & Kudô (1932), Hayakawa et al. (2016), and Shin et al. (2019).

	C. yintiaolingensis	C. exigua	C. subaphylla
Nutrition mode	Mycoheterotrophic	Mycoheterotrophic	Mixotrophic
Roots	Obviously fleshy	Slightly fleshy	Slightly fleshy
Leaves	Achlorophyllous and sheath-like	Achlorophyllous and sheath-like	With 1–2 leaves bearing blade ca. 3
	without obvious blade	without obvious blade	cm long
Lower bracts	Shorter or same length as pedicel and	Shorter or same length as pedicel and	Obviously longer than pedicel and
	ovary	ovary	ovary
Sepals	Obtuse at apex	Acuminate at apex	More or less emarginate at apex
Lateral petals	Obtuse at apex	Obtuse at apex	More or less acute at apex
Lip	Spur conical, acuminate at apex;	Without spur; lateral lobes falcate;	Spur conical, obtuse at apex; lateral
	lateral lobes falcate; middle lobe	middle lobe reniform with cuspidate	lobes ovate-triangle; middle lobe
	flabellate with acuminate apex; lip	apex; lip with three lamellae	transversely reniform with obtuse
	with five to seven lamellae		apex; lip with three lamellae
Fertile stamen	Anther hinged at the top of column	Anther hinged at the top of column	Anther sited directly on the top of
	with a short stalk	with a short stalk	column
Distribution	Central West China	Laos, Thailand and Vietnam	Japan and Korea