Gastrochilus sessanicus A.N.Rao, J. Orchid Soc.

Gastrochilus sessanicus A.N.Rao, J. Orchid Soc. View in CoL India 11: 1. 1997. Type: INDIA , Arunachal Pradesh, West Kameng district, Sessa, 1100 m, 20.11.1996, A.N. Rao 29273 (holo. OHT!). Gastrochilus pumilus D.P.Ye & H.Jiang, Wild Orchid Yunnan 476. 2010, nom. inval. Gastrochilus minimus J.W.Li, D.P.Ye & X.H.Jin , Plant Diversity , https://doi.org/10.1016/j.pld.2021.01.009 (2021, published online: corrected proof version; final version in press), nom. inval. (as of 26.9.2021).

Epiphytic herbs; up to 4 cm high. Stems 1–3 cm long. Leaves 3–6, elliptic-lanceolate to ovate-lanceolate, 1.5–4 × 0.4–0.8 cm, closely arranged on short stem, acute to acuminate, sometimes with three setae at apex, sessile, green, sometimes tinted purple adaxially. Inflorescences sub-umbellate, 1 or 2, extra-axillary, 0.5–1.8 cm long, 2–8-flowered. Floral bracts ovate-lanceolate to triangular, 0.09– 0.3 × 0.09–0.2 cm, acute, slightly incurved, beaked at apex. Flowers small, 0.7–1.0 cm across, with green to yellowish-green sepals; petals dotted with purple-red or with reddish stripes; labellum yellowish-green to pale whitish-yellow with purple-red central cushion adaxially, dotted with purple-red mostly near rim of the sac. Pedicelled ovary 0.3 – 0.5 cm long. Sepals subsimilar, ellipticoblong or spatulate, 0.32 – 0.35 × 0.12 – 0.17 cm, concave, often keeled externally along mid-vein, rounded to obtuse-acute at apex. Petals ellipticoblong to oblanceolate, 0.25–0.28 × 0.14–0.15 cm, keeled externally along mid-vein, sometimes slightly erose at upper margins, subacute to rounded at apex. Labellum attached with base of column; hypochile saccate, subconical, 0.2 – 0.3 cm long, abaxially with keel, obtuse, entire at apex; epichile triangular to flabellate, 0.2 – 0.25 × 0.4 – 0.5 cm,

densely hairy to hirsute on upper surface, along Li et al. (2021, final version in press) have margins, with elliptic cushion on upper surface, keel estimated the suitable habitat of this species in or broad conical swelling sub-terminally on lower China to be less than 500 ha. (= 5 km 2),

surface, slightly reflexed at apex. Column 0.12 – 0.15 harbouring around 200 mature individuals and

cm long, broader at base; rostellum bilobed. Anther considered its threat status as

0.1–0.15 cm long; pollinia 2, globular, porate; stipe ‘Critically Endangered’ [CR B1ab(iii)

filiform, 0.06–0.1 cm long; viscidium oblong, 0.03– +2ab(iii)] based on single location and

0.06 cm long; fruits not observed. decline in quality of habitat. Globally, the species is known to exist at only two

Flowering & fruiting: Flowering From July– distinct sites, in China and India ,

September in China; October–November in constituting an Area of Occupancy (AOO) of

India ; fruiting not observed.

8 sq. km 2 ( Fig. 2 View Fig ). According to A.N. Rao

Habitat: Growing on moss covered slender branches (pers. comm., 12.9.2021) the type locality (Sessa, India ) had less than half a dozen

of small trees in wet evergreen subtropical mixed, mature individuals only in 1996 and after

coniferous broad-leaved forests at 1100 m elevation. that, he could not observe any individual. The

Distribution: China and India . two localities in India and China are separated by

a

distance of nearly 900 km and

Etymology: The specific epithet was coined after hence, the possibility of gene flow between

the type locality (Sessa) of the species. them is highly unlikely. This implies that the

Specimens examined: CHINA: Yunnan species can be considered ‘ Severely province, Simao district, Yixiang township , N Fragmented’ at present. However, it is a

22.79̊, E 100.97 ̊, 1287 m, 13.09.2020, D. P. fact that not much area in between the two

Ye 1922 (HITBC, photo; specimen cited as localities is properly explored, particularly in holotype of G. minimus ). INDIA : Arunachal Myanmar, and it is possible that the species

Pradesh, West Kameng district, Sessa, 16.09.1996 can be found in more localities in future. The

(not in fl.), A.N. Rao 29420 (OHT). extent and quality of habitat are on the decline due to developmental work,

Conservation status: Gastrochilus sessanicus was broadening of roads, tourism and other

until now considered endemic to India . anthropogenic activities even at Sessa in India

However, it was found to be present in China and its surrounding area. Hence, the species

under different names ( G. pumilus , nom. inval. and can be assessed as ‘Critically

G. minimus , nom. inval.), which have now been Endangered’ [CR B2ab(iii)] at present treated under G. sessanicus . following IUCN guidelines ( IUCN 2019).

Note: The colour, size, density and intensity of blotches on perianth and colour of the perianth as a whole are variable ( Seidenfaden, 1988) in several species of Gastrochilus . The minute differences in size of some floral parts between plants/ subpopulations fall under range of variation only due to climatic/altitudinal factors.