Chiloschista eckhardii Vuong, Aver., V.C.Nguyen, Wojtas & Q.T.Truong, 2024

Dang, Minh Quan, Averyanov, Leonid V., Maisak, Tatiana V., Wook, Um Sung, Canh, Nguyen Van, Phan, Xuan Thuy, Truong, Quang Tam, Wojtas, K. Philip & Truong, Ba Vuong, 2024, Chiloschista eckhardii (Orchidaceae, Aeridinae), a new miniature leafless orchid from northern Vietnam, Phytotaxa 664 (2), pp. 139-145 : 140-142

Chiloschista eckhardii Vuong, Aver., V.C.Nguyen, Wojtas & Q.T.Truong , sp. nov.

( Figure 1 )

Type:— VIETNAM. Ha Giang Province, Dong Van District, 21 March 2023, elev. around 1300 m, Truong Ba Vuong, Nguyen Van Canh, Phan Xuan Thuy & Um Sung Wook, BV 1704 (Holotype, VNM 00067722).

Paratypes:— VIETNAM. Ha Giang Province, Dong Van District , 9 May 2024, Truong Ba Vuong, Nguyen Van Canh & Um Sung Wook, BV 1898 ( VNM) ; ibidem, 18 November 2020, Truong Ba Vuong & Ngo Quang Dang, BV 1027 ( VNM) ; ibidem 10 May 2020, Truong Ba Vuong & Ngo Quang Dang, BV 746 ( VNM) .

Diagnosis:— Chiloschista eckhardii in its morphology is most similar to C. parishii and C. glabrisepala , but it clearly differs by having a lip callus that is densely hairy in the middle (versus the lip disc and lip callus being entirely hairy in C. parishii , and the lip callus being hairy only at the apex in C. glabrisepala ). Chiloschista eckhardii is also similar to C. quangdangii but can be distinguished by its disc callus, which is slightly shorter than the median lobe (versus the disc callus being much shorter than median lobe), triangular-ovate side lobes (vs. rhomboid or oblongelliptic side lobes), and large back-wall callus (vs. an insignificant back-wall callus). In addition, Chiloschista eckhardii may be misidentified as C. yunnanensis , but it can be distinguished by its tepals, which are sparsely puberulent on the outer surface and margin (vs. a puberulent surface and ciliate margin), and by its spur-like lip (vs a broadly saccate lip). A detailed morphological comparison is presented in Table 1.

Description:— Herb leafless, miniature, monopodial, with abbreviated stem ca. 3 mm long and many long, glabrous, flattened, green roots. Inflorescence green, covered by short stiff white hairs; peduncle 2.5 cm long with 3 to 4 distant bracts; rachis 2.5–8.7 cm long, with 5–9 flowers; floral bracts brown, glabrous, ovate, ca. 2.3 mm long, acute, shortly mucronate; pedicel and ovary green, 2–2.5 mm, with densely white stiff hairs. Flowers open acropetally, ca. 1.6 cm across, tepals yellow with red-brown dots, lip white or light yellow, with many red marks on side lobes, column foot broadly trapezoidal, ca. 5 mm long and ca. 4 mm wide, with many brown blotches. Dorsal sepal elliptic, obovate to broadly obovate, 6–8 mm long, 3–7 mm wide, apex rounded, abaxially with minute stiff hairs. Lateral sepals obovate, broadly obovate, 6–8 mm long, 4–6 mm wide, apex rounded, abaxially with stiff hairs. Petals oblong, abaxially with minute stiff hairs, 6–8 mm long, 3–3.5 mm wide, apex truncate. Lip attached to the apex of column foot, 3 lobed, spur ovoid ca. 2 mm in diam.; median lobe fleshy, obscurely rectangular, ca. 1 mm long and wide, rounded, bifid; side lobes erect, not embracing column, directed forward, 5–7 mm long, 2–3 mm wide, rounded at apex, adaxially with many warty streaks; central callus Y-shaped, covered with stiff and clavate hairs, apex bilobed, downcurved, shorter than median lobe, glabrous; spur backwall fleshy, covered by minute hairs; front wall callus densely hairy along median keel. Column stout, column foot ovate-oblong, slightly incurved, ca. 4 mm long; stigma obscurely rectangular; anther cap obscurely cubic, ca. 1 mm long and wide, with 2 filiform setae from each side of anther cap, ca. 1.5 mm long; pollinarium with 2 almost globose notched pollinia, arrow-shaped stipe broadening distally, slightly contracted at the middle, and rectangular viscidium. Fruit not seen.

Flowering phenology: Plants in flower were observed in late November, and in March to May.

Etymology:—The species is named after the late Dr. Eckhard von Raab-Straube, an enthusiastic botanist from the Botanic Garden Berlin.

Distribution:—The species has so far been reported only from the type locality in Ha Giang Province.

Habitat and ecology:—Branch epiphyte, in evergreen, broad-leaved forest at elevation about 1300 m a.s.l.

Other Specimens studied:— China. Yunnan, Szemao, 1500 m, A. Henry 11792A (AMES00106704, https:// data.huh.harvard.edu/databases/specimen_search.php?mode=details&id=38025) (AMES!- Isotype of Chiloschista yunnanensis Schltr. , image seen); ibidem, A. Henry 11792A (E01313787, https://data.rbge.org.uk/search/herbarium/?cfg=fulldetails.cfg&barcode=E01313787) (E!- Isotype of C. yunnanensis , image seen); ibidem, A. Henry 11792A (NY 4341314, https://sweetgum.nybg.org/science/vh/specimen-details/?irn=4341314) (NY!, - Isotype of C. yunnanensis , image seen); Yunnan, Mengtsz, A. Henry 11129 (K001599317) (K!, C. yunnanensis , image seen), duplicate of a single flower as spirit sample at C (C!, C. yunnanensis , images seen). MYANMAR. Moulmein, C.S.P.Parish 55 / Reichenbach Herb. Orchid. 26237 (W0017162, https://w.jacq.org/W0017162) (W!- holotype of Chiloschista parishii Seidenf. ); icon, Reichenbach Herb. Orchid. 11583 (W0017165, https://w.jacq.org/W0017165) (W!- isotype of C. parishii ).

Note:—The newly discovered plant belongs to a group of species with flowers that have yellow sepals and petals spotted with orange-brown or red-brown dots, which led to the new species being overlooked and misidentified as Chiloschista parishii . However, the newly described species differs from morphologically similar Chiloschista parishii , C. glabrisepala , C. quangdangii and C. yunnanensis in many features, as detailed in Table 1. The comparison of the floral morphology among C. eckhardii , C. glabrisepala , and C. quangdangii is shown in Figure 2 .

The morphological details of Chiloschista parishii were compiled from Gyeltshen et al. (2019 & 2020) and Dalström & Kolanowska (2020). The morphological details of C. yunnanensis based on of Schlechter’s protologue ( Schlechter 1919), Chen & Wood (2009), and the specimens A.Henry 11792A (AMES 00106704, E 01313787, NY 4341314), and A. Henry 11129 (K 001599317 and C).

Figures

FIGURE 1. Chiloschista eckhardii Vuong, Aver., V.C.Nguyen, Wojtas & Q.T.Truong. A. Flowering plant. B. Portion of rachis with open flowers. C. Floral bract, abaxial side. D. Flower, front view. E. Median sepal, abaxial and adaxial side. F. Lateral sepals, abaxial and adaxial side. G. Petal, abaxial and adaxial side. H. Ovary, column, column foot, and lip, side view. I. Lip, view from different sides. J. Apex of median lobe and apex of lip callus. K. Lip, tangential section. L. Ovary, column, and column foot, side view. M. Column and column foot, front view. N. Column apex with stigma. O. Anther cap, views from different sides. P. Pollinaria, front and view from rear. Photos by Ba Vuong Truong from the type specimens BV 1704. Photo-correction and design by Ba Vuong Truong and L. Averyanov.

FIGURE 2. Morphological comparison of Chiloschista eckhardii (A), C. glabrisepala (B), and C. quangdangii (C).