Henckelia arunachalensis D.Borah, V.Sahani & Pertin, 2024

Sahani, Vinay Kumar, Pertin, Minom, Taram, Momang, Maity, Rohan & Borah, Dipankar, 2024, Henckelia arunachalensis (Gesneriaceae), a new species from Patkai Hills of Arunachal Pradesh, India, Phytotaxa 678 (1), pp. 71-76 : 72-74

Henckelia arunachalensis D.Borah, V.Sahani & Pertin sp. nov. ( Fig. 1 )

Type:― INDIA. Arunachal Pradesh: Changlang District, Near Miao, 506 m a.s.l., 10 March 2024, Vinay Kumar Sahani 0167 (holotype CAL!, isotype ASSAM!).

Diagnosis:― H. arunachalensis is closely allied to H. dibangensis (B.L.Burtt, S.K.Srivast. & Mehrotra) Middleton & Möller (2011: 775) ; however, it differs by having elliptic to obovate leaves with 9–13 pairs of lateral veins (vs ovate to ovate-elliptic with 5–8 pairs of lateral veins); 1–5 flowered cymes borne erect to perpendicular (vs cymes with 1–2 on a pendulous inflorescence), broadly ovate to ovate lanceolate, 1.5–2.8 cm long bracts, 1 per flower at the base of pedicels (vs linear, c. 6 mm long bract, at the middle of pedicel); campanulate, 4–5 cm long, leathery calyx, pale green and puberulous to pubescent outside, whitish-green and glabrous inside (vs light green, campanulate, 3–4.5 cm long, glabrous calyx); 6–9 cm long, purplish white corolla, with dark blue to purple stripes on lower lip lobes extending upto throat, two parallel yellow flanges on the floor of throat and two white flaps on roof of corolla tube, pubescent outside, glabrous to glandular pubescent inside (vs pale pink to pinkish white, glabrous corolla with 2 yellow lines on the floor of lower lip extending to the throat without any white flaps on roof of tube).

Description:― Herb, caulescent, erect, 30–40 cm high. Stem terete, green, puberulent to pubescent. Leaves opposite, decussate, sometimes slightly unequal, petiolate; petioles terete, sometimes slightly flattened on the surface facing stem, 3–4 cm long, puberulent; lamina elliptic to obovate, 11–25 × 3.5–10 cm, base cuneate to slightly attenuate, sometimes oblique, margin serrate–dentate, sometimes obscure towards base, apex acuminate, coriaceous, dark green above, pale green beneath, pubescent along the veins beneath; midvein prominent, raised and pubescent beneath; lateral veins 9–13 pairs. Cymes axillary, 1–5-flowered; peduncles 1–3 mm long, pubescent; bracts 1 per flower, present at the base of pedicels, broadly ovate to ovate lanceolate, 1.5–2.8 × 0.5–0.8 cm, apex acute to acuminate, margin serrate, sometimes obscure, green above, greenish white to pale green below with prominent brownish veins, glabrescent; pedicels terete, 2.5–4.0 cm long, pubescent. Calyx campanulate, 4–5 cm long, leathery, pale green outside, whitish-green inside, puberulous to pubescent outside, glabrous inside, 5-lobed; lobes unequal, free up to half of calyx or slightly more, narrow triangular, 1.8–2.6 × 0.3–0.6 cm, acute at apex; tube 1.8–2.0 cm long, ridged along the midveins of lobes. Corolla infundibuliform, 6–9 cm long, distinctly 2-lipped, lips divergent, purplish white with dark blue to purple stripes on lower lip lobes extending upto throat, two parallel yellow flanges on the floor of throat and two white flaps on roof of corolla tube, pubescent outside, glabrous to glandular pubescent inside; upper lip 2- lobed, lobes broadly ovate, 2–2.5 × 1–1.2 cm; lower lip 3-lobed, lobes sub equal, broadly ovate to rounded, 1.1–1.5 × 1.5–2cm; tube 4–6 cm long, white. Stamens 2, filaments 1.8–2.2 cm long, glabrous, inserted above c. 1.5 cm to corolla base, geniculate, geniculations yellow; anthers c. 3 mm long, adaxially fused, cream turning brown at maturity, bearded at back. Staminodes 3, lateral staminodes curved, 4–6 mm long with dilated base, antherodes c. 1 mm long, brown; central staminode curved c. 1 mm long. Disk annular, c. 1 mm high. Pistil 4–4.7 cm long; ovary 2.4–3 cm long, greenish-white, glabrous; style c. 2 mm long, white, dense pubescent, sometimes gland-tipped; stigma chiritoid, white, upper lip much reduced, hairy as style, lower lip 2-lobed, lobes broadly ovate to oblong, c. 3 × 1 mm, glabrous. Capsule not seen.

Flowering and Fruiting:― March–April.

Habitat and ecology:― Henckelia arunachalensis was found growing near a roadside ditch on a steep upper part of slope in association with Carex baccans Nees in Wight (1834: 122), Steudnera assamica Hooker (1893: 520) , Begonia sp. , Elatostemma sp. , Dicranopteris sp. , Rubus sp. , Colocasia sp. , grasses and mosses. It is only known from Miao, Arunachal Pradesh, India, where one population with 18 plants have been recorded.

Distribution:― Only known from India (Arunachal Pradesh).

Etymology:― The species is named after the state of Arunachal Pradesh.

Conservation status:― Henckelia arunachalensis is only known from the type locality, with a very low number of individuals. The ecoregion of this area is Eastern Himalayan tropical forests, which has large extents of intact forest in the vicinity, and extremely rugged terrain which is the preferred habitat for the species. Despite the lack of additional populations in the vicinity, considering the occurrence of several Henckelia species found outside their type localities in our recent studies, and the discovery of many Chinese species in northeastern India, it is possible that more populations might be found with further exploration. Therefore, even if species with a very low number of individuals are often assessed as Critically Endangered ( Wagensommer et al. 2014, 2017) or Endangered ( Ben Mahmoud et al. 2024), we currently prefer to categorize Henckelia arunachalensis as Data Deficient (DD) following the IUCN guidelines ( IUCN 2024).

Notes:― This new species is allied to H. dibangensis ( Burtt et al., 1989) , and a detailed diagnosis is provided above. H. dibangensis wa s so far known only from its type collection (S.K.Srivastava 16730), which was inadequate to ascertain details, however, a fresh collection of this species was made recently from its type locality (Bipankar Hajong pers. comm.). It also appears to be similar to H. urticifolia in floral appearance, however, can be differentiated from that by much larger obovate leaves (versus ovate to elliptic leaves); bracts 1 per flower, at the base of the pedicel (versus bracts 2 per flower, at the middle of pedicel); puberulous to pubescent calyx (versus pilose to hispid hairy); larger whitish-purple corolla with 2 white flaps on the roof of corolla tube (versus absence of any such structures). This newly described species is also characterized by having two white flaps on the roof of corolla tube, a character which is only found in H. khasiana Nampy & M.K. Akhil hitherto ( Nampy et al., 2021).

Figures

FIGURE 1. Henckelia arunachalensis sp. nov. (Gesneriaceae) from Arunachal Pradesh, India. (A) Habit, (B) Leaves, (C)–(D) Side view of flower, (E) Front view of flower, (F) Pedicel, with bracts, calyx and pistil with corolla removed, (G) Split corolla, (H) Split calyx, (I) Pistil. Photos by Vinay Kumar Sahani.