Chiloschista glabrisepala Vuong, Aver. & V.S. Dang, 2022

Pham, Phuoc Dien, Averyanov, Leonid V., Nguyen, Dinh Hiep, Maisak, Tatiana, Nguyen, Van Canh, Dang, Minh Quan, Truong, Ba Vuong & Dang, Van Son, 2022, A new species of Chiloschista (Orchidaceae, Aeridinae) from northern Vietnam, Phytotaxa 556 (1), pp. 94-98 : 95-97

Chiloschista glabrisepala Vuong, Aver. & V.S. Dang sp. nov. ( Fig. 1 )

Type: — VIETNAM. Son La Province, Thuan Chau District, forest around Pha Din Pass, cultivated in Da Lat city and flowering in 7 April 2022, Truong Ba Vuong & Nghiem Xuan Son BV 1443 (holotype VNM 00069956 , authentic photos LE01123096 https:// en.herbariumle.ru/?t=occ&id=134267) .

Description:—Herb leafless during flowering time, miniature, monopodial, with abbreviated stem 2–4 mm long, with many long, glabrous, flattened, green roots. Inflorescence green to brownish, up to 35 cm long, covered by short white hairs; peduncle ca. 8 cm with 7–8 distant brownish sterile bracts; rachis ca. 25 cm long, bears to 30 flowers; floral bracts narrowly triangular, acute, ca. 5 mm long. Pedicel and ovary ca. 4 mm long, densely white-haired. Flowers open acropetally, sepals and petals yellow with many large orange dots or blotches, lip almost white, with orange dots outside and many orange warty streaks on side lobes. Median sepal obovate, 6–7 mm long, 4.5–5 mm wide, rounded at apex, slightly concave to almost flat, glabrous on both surfaces, sparsely ciliate along the margin. Lateral sepals broadly obovate, slightly oblique, 4.5–5 mm long, ca. 4 mm wide, rounded or blunt at apex, entirely glabrous. Petals obscurely rectangular, 5.5–6 mm long, truncate, glabrous on both surfaces, ciliate along the margin. Lip 3-lobed, saccate; side lobes obscurely rhomboid, oblique, 2.5–3 mm long, 1.5–2 mm wide, erect, forward directed, apex obtuse, inner surface with many warty streaks; median lobe very small triangular, glabrous, ca. 0.5 mm long, slightly down curved; central callus shortly cylindrical, erect, white, ca. 1.3 mm long, 1 mm wide, slightly down curved; base of the lip saccate, broadly conoid; back-wall callus white, fleshy, erect, conoid, shortly stiff puberulent, bifid at apex, front wall with glabrous low longitudinal ridge. Column stout, ca. 2 mm long and wide; stigma transversely elliptic to almost circular, concave; column foot at straight angle to column and ovary, forward directed, slightly upcurved, ca. 4 mm long; anther cap with 2 filiform lateral setae, ca. 1.2 mm long; pollinarium with 2 pollinia, oblong stipe and rectangular viscidium. Fruit not seen.

Paratypes: — VIETNAM. Son La Province, Thuan Chau District, forest around Pha Din Pass, cultivated in Da Lat city and flowering in 7 April 2022, Truong Ba Vuong & Nghiem Xuan Son BV 1444 ( VNM00069957 ), BV 1445 ( VNM 00069958 ) .

Etymology:—The specific epithet is originated from the Latin ‘glabri-‘ (glabrous) and ‘sepala’ (sepals), in reference to the glabrous sepals.

Distribution: —NW Vietnam (Son La Province, Thuan Chau District). Presumed endemic, currently only known from the type location.

Habitat and phenology: —Miniature leafless (when flowering) branch epiphyte found in primary broad-leaved forests. Flowers in March–April.

Estimated conservation status: —Several samples of the new species were collected by local people near Pha Din Pass (Son La Province, Thuan Chau District) and offered for sale in local plant market. The data about environment, natural conditions of the species habitat and its rarity remain unclear. However, the uncontrolled collecting of plants for sale provides certain evidence that the lone known population could be severely depleted and the species may become extinct in the very near future. Being into consideration the species occurrence (EOO) and area of the species occupancy (AOO) surely is less than 100 and 10 km 2 respectively, the conservation status of the new species may be preliminarily estimated as critically endangered – EN following to formal IUCN (2019) criteria, CR A3(a,d), B1(a,bi,ii), B2(a,bi,ii), C1, C2(ai,ii).

Note: —The new species resembles Chiloschista himalaica and C. parishii (sensu Averyanov & Averyanova 2003 https://en.herbariumle.ru/?t=occ&s=chiloschista%20parishii&f=%5Ball%5D) in the shape and color scheme of the flower. However, it differs in having a central callus which is twice longer than the median lip lobe (vs. central callus shorter, or as long as median lip lobe).Vietnamese samples of C. parishii in understanding of Averyanov and Averyanova (2003: 20) have sepals with many stiff hairs outside, lip inside with hairy longitudinal callus, and central callus distinctly shorter than median lip lobe, that can be clearly seen on the following collections from Vietnam: LE01089230 https:// en.herbariumle.ru/?t=occ&id=72895), LE01089231 (https://en.herbariumle.ru/?t=occ&id=72896), LE01089212 (https://en.herbariumle.ru/?t=occ&id=72875), and LE01089211 (https://en.herbariumle.ru/?t=occ&id=72179).

The series of plants collected in Vietnam (https://en.herbariumle.ru?t=occ&s=chiloschista%20parishii&f=%5B all%5D) named here as C. parishii (in understanding of Averyanov & Averyanova 2003) somewhat differ from the type and may be represent a new, not yet described species. Further studies of C. parishii complex in Indochina are necessary to understand of its real nature.

Figures

FIGURE 1. Chiloschista glabrisepala. A. Flowering plant.B. Stem and roots of mature plant.C. Inflorescence.D.Portion of inflorescence. E. Flowers, frontal and side views. F. Median sepal, abaxial and adaxial side. G. Lateral sepal, abaxial and adaxial side. H. Petal, abaxial and adaxial side. I. Lip, frontal view. J. Lip, view from behind with exposed back wall calli. K. Lip, half side view. L. Lip, side view. M. Lip, sagittal section. N. Ovary and column with anther cap. O. Ovary and column without anther cap. P. Apex of column, frontal view. Q. Anther cap, frontal view and view from back. R. Pollinarium, frontal view and view from back. Photos by Ba Vuong Truong from specimen BV 1443, photos correction and plate design by Ba Vuong Truong, L. Averyanov, and T. Maisak.