Diphylax Hooker (1889

Averyanov, Leonid V., Nguyen, Van Canh, Le, Tuan Anh, Vuong, Truong Ba, Nuraliev, Maxim S., Maisak, Tatiana V., Yudova, Daria A., Nguyen, Cuong Huu & Nong, Duy Van, 2024, New orchids in the flora of Vietnam IX (Orchidaceae: Orchidoideae, tribes Cranichideae and Orchideae), Phytotaxa 664 (4), pp. 229-248 : 231-234

Diphylax Hooker (1889 : t. 1865)

≡ Platanthera subgen. Platanthera sect. Diphylax (Hook.f.) Efimov (2016: 29) .

Diphylax urceolata (C.B.Clarke) Hooker (1889 : t. 1865), Jain & Mehrotra (1984: 52), Deva & Naithani (1986: 119, Fig. 55), Chen & Tsi (1998: 38), Bose et al. (1999: 220, drawing), Hynniewta et al. (2000: 159, fig. 48), Pearce & Cribb (2002: 139), Chen et al. (2009a: 186, photo, 2009b: 118, Fig. 165 (10, 11)), Raskoti (2009: 111), Xu et al. (2010: 91).

( Fig. 2 & 3 )

≡ Habenaria urceolata Clarke (1889: 73 , t. 30), Hooker (1890: 165), King & Pantling (1898: 316, pl. 415), Banerji (1996: 25).

≡ Platanthera urceolata (C.B.Clarke) Bateman (2009: 439) , Rokaya et al. (2013: 544), Jalal & Jayanthi (2015: 48), Efimov (2016: 29, fig. 3C, 60A), Zhou et al. (2016: 116), Lidén & Bharali (2019: 173), Aung et al. (2020: 99), Ormerod et al. (2021: 208) , Prasad (2023: 44).

Type: — INDIA . Nagaland: Naga Hills, Jakpho , 9000 ft. [2743 m], 25 October 1885, C. B. Clarke 41272 (lectotype, designated by Efimov (2016: 133): K K000247409 (duplicate 41272c) photo! https://data.kew.org/records/occurrences/b9209d5c-c90c-4a8a-b8f0- fe481aef2437 ; isolectotypes: BM 000034631 (duplicate 41272b) photo! https://data.nhm.ac.uk/object/5e2f826e-ea96-46be-9f5aae821a548a7f, CAL CAL0000000732 (duplicate 41272a) photo!). Citation of protologue: —“Jakpho, alt. 9000 feet [n. 41272]” .

Habitat and phenology in Vietnam: —Evergreen broad-leaved forests on granite at elevation of about 2500 m a.s.l., very rare. Flowers in August–September.

Distribution: — Vietnam (Lao Cai Province: Bat Xat District). Nepal, Bhutan, NE India, SW China (Tibet, Sichuan, Yunnan), N Myanmar.

Conservation status in Vietnam: — Diphylax urceolata is known in the country from a single location in the northern part of Lao Cai Province (Bat Xat District), without any records about the habitat of this population. In accordance with the scarcity of available data, we estimate the national conservation status of the species as Data Deficient (DD). Its conservation status outside Vietnam has never been evaluated.

Notes: — Efimov (2016) stated that two collections are mentioned in the protologue of Habenaria urceolata ( Clarke 1889) , Clarke 41272 and Clarke 10244. This statement was probably based on the treatment by Pearce & Cribb (2002), who indicated these two gatherings as “ syntypes ”. However, the protologue actually cites a single gathering, Clarke 41272, without indication of a place of its deposition. Thus, Efimov’s choice between the two gatherings has no nomenclatural significance, but his treatment still provides a valid designation of a particular specimen among the duplicates of Clarke 41272 as a lectotype. In addition, Efimov (2016) erroneously indicated the duplicate 41272b to be housed at K, and this error was reproduced by Prasad (2023); this duplicate is confirmed here to be kept at BM.

Diphylax urceolata is reported here as a new record for the flora of Vietnam, representing the first record of the genus Diphylax in the country. The discovery of this highland species in Vietnam notably expands its known distribution area by more than 600 km in the southeast direction from the nearest locations of this species in northern Myanmar and western Yunnan (listed by Efimov 2016).

The flower structure of D. urceolata (which is a type species of the genus Diphylax ) makes this species, along with the several others placed traditionally in this genus or listed under Platanthera sect. Diphylax (see Ormerod 2013, Efimov 2016), morphologically distinct from all the other genera of the subtribe Orchidinae , including Platanthera Richard (1817: 20) s.str. Diphylax is characterized by two unique features. The first feature is the lip divided into a proximal part (hypochile), which is rather thin, cymbiform, or even tubular due to the involute margins, and a distal part (epichile) in the form of a thick, solid body with a rough or obscurely grooved adaxial surface (in the rest of Orchidinae , the lip is never distinctly divided into hypochile and epichile). The second feature is the filiform erect auricles (staminodes) placed at each side of the column that are as long as or a little longer than the anther (in the rest of Orchidinae , the auricles are semiglobular, ovoid or absent). These characters are well documented for the species of Diphylax (e.g. Clarke 1889, Pearce & Cribb 2002, Chen et al. 2009b, Efimov 2016). Thus, the morphological evidence, to our opinion, disagrees with the proposed merging of Diphylax with Platanthera ( Bateman 2009, Efimov 2016), but rather supports recognition of Diphylax at the generic rank.

Simultaneously with the specimen of D. urceolata cited below, a gathering Nguyen Van Canh et al. AL2440a (LE LE01254640 https://en.herbariumle.ru/?t=occ&id=218341) was collected, which somewhat resembles Platanthera anatina Ormerod (2013: 27 , see also Efimov 2016: 135) in the plant habit. Platanthera anatina apparently belongs to the genus Diphylax , but a corresponding nomenclatural combination is not available for this species. Moreover, P. anatina does not show any sufficient differences from D. urceolata in floral morphology, and these two species are believed to differ from each other mainly in characteristics of the vegetative organs ( Efimov 2016). Consequently, we argue that P. anatina is possibly conspecific with D. urceolata . We therefore currently maintain the species identity of the specimen Nguyen Van Canh et al. AL2440a as uncertain. At the same time, the Vietnamese specimen of D. urceolata (cited below) differs from the typical D. urceolata in having a very short, indistinct connective extension (vs. extension prominent, apiculate or acuminate) and a large, rather fleshy, bilobulate rostellum, scarious along the margin (vs. rostellum entire, very small and indistinct). Taking into consideration these morphological differences, we suppose that the Vietnamese specimen represents a separate variety well isolated geographically.

Studied specimen:— VIETNAM. Lao Cai Province: Bat Xat District, evergreen forest at elevation of about 2500 m a.s.l., living plants collected in October 2023 by Nguyen Van Canh, cultivated in private garden of Nguyen Van Canh, herbarium specimen made on 3 November 2023, Nguyen Van Canh, L. Averyanov, T. Maisak, AL2440 (LE LE01254626 https://en.herbariumle.ru/?t=occ&id=217577, drawing LE LE01124835 https://en.herbariumle.ru/?t=occ&id=220669, photos LE LE01124840 https://en.herbariumle.ru/?t=occ&id=221927).

Figures

FIGURE 2. Diphylax urceolata. A, B. Flowering plants. C. Inflorescence. Photos by Nguyen Hai Trieu in situ; specimen Nguyen Van Canh, L. Averyanov, T. Maisak, AL2440. Photo correction and design by L. Averyanov.

FIGURE 3. Diphylax urceolata. A. Flowering plant. B. Inflorescence. C. Flower, front and half-side views. D. Flattened flower, front view (lip removed). E. Lip, view from above. F. Lip, side view. G. Lip, sagittal section. H. Column, front view. I. Column with stelidia artificially bent outside, front view. J. Pollinarium, front and side views. K. Floral bract and ovary, side view. Drawn from the specimen Nguyen Van Canh, L. Averyanov, T. Maisak, AL2440 by L. Averyanov.