Henckelia peduncularis (Burtt 1965: 265) Middleton & Möller (2011: 776)

Maity, Rohan, Chowlu, Krishna & Dash, Sudhansu Sekhar, 2024, The current status of Henckelia peduncularis (Gesneriaceae): Taxonomy, typification, distribution and IUCN Red List assessment, Phytotaxa 644 (1), pp. 27-34 : 28-30

Henckelia peduncularis (Burtt 1965: 265) Middleton & Möller (2011: 776) [ Fig. 1 ]

≡ Chirita peduncularis Burtt (1965: 265) .

Lectotype (designated here):— MYANMAR. Valley of Nam Tamai : 27°15'[“45'”] N, 97°55' E, 900–1200 m, 12 September 1926, Kingdon-Ward 7240 (K, barcode K000858402, digital image!) [ Fig. 2 ] . Isolectotypes: K, barcode K000858403, digital image!; E, barcode E00096835, digital image! PE, barcode 00030717, digital image!.

Henckelia dasii Taram, Borah, Singh & Tag (2021: 364) syn. nov.

Holotype:— INDIA. Arunachal Pradesh, Lower Subansiri district, Ziro Valley , 27°29'04.7" N, 93°49'47.5" E, 1950 m, 22 August 2018, M. Taram 31878 (ASSAM, barcode ASSAM0000000931!) [ Fig. 3 ] . Isotypes: ARUN, barcode ARUN000010462!, CAL, barcode CAL0000033963!

Description:— Perennial herbs, caulescent, erect, sometimes with decumbent base, 30–150 cm tall; stem unbranched, terete, striated, green, pubescent to glabrescent; leaves opposite decussate, subequal to unequal; petiole terete, up to 6.5 cm cm long, pubescent–glabrescent; lamina ovate-elliptic, 8–25 × 4–11 cm, base rounded or slightly oblique, margins crenate-dentate, apex acute, adaxially dark green, puberulent, abaxially light green, pubescent along veins; venation pinnately reticulate with subopposite lateral veins 8–14 pairs; inflorescences axillary, 2(–5)-flowered cymes; peduncles 1–4 cm long, light green, pubescent–pilose; pedicels 0.3–1.2 cm long, enclosed within the bracts, light green, puberulent–pilose; bracts 2, free, opposite, green, suborbicular–broadly ovate, 0.6–2.5 × 0.6–2.5 cm, concealing the flower buds, margins serrate, apex acute, pubescent–glabrescent, veins prominent; calyx urceolate, 1.7–2.3 × 0.8–1.2 cm, cream-white, puberulent outside, glabrous inside, 5-lobed; tube fused up to more than ¾ of the calyx length, 1.4–1.7 cm long; lobes ovate-triangular, 0.2–0.6 cm long, margins entire, apex acute; corolla 2-lipped, 4–5 cm long; tube infundibuliform, basally bulged to widened towards apex with constricted in middle, 3–4 cm long, white with light pinkish tinge and with two yellow flanges from centre of the tube to the lower lip, glabrous on both sides; lips divergent; upper lip 2-lobed; lobes equal, suborbicular, 0.6–1.1 × 0.7–1.2 cm, margins entire, apex rounded; lower lip 3-lobed; lobes subequal, broadly ovate–suborbicular, 0.6–1.3 × 0.5–0.8 cm, margins entire, apex obtuse–rounded; stamens 2, inserted 1.8–2 cm above from the corolla base; filaments 0.6–1 cm long, white, glabrous, geniculate; anthers 0.1–0.2 × 0.2–0.3 cm, cohering face to face, dark purple, glabrous; staminodes 2, inserted 1.6–1.8 cm above from the corolla base, filaments 0.5–0.7 cm long, curved, glabrous; antherodes c. 0.1 cm across, white, glabrous; ovary 1.4–1.6 cm long, pale cream-white, glabrescent–glabrous; style 1.2–1.3 cm long, white, glabrescent–glabrous; stigma flabellate, 0.2–0.3 cm long, cream-white–cream-yellow; disc annular, 0.1–0.2 cm long, pale white–creamy; capsules linear, 7–13.5 × 0.2–0.3 cm, dark purple–maroon, glabrous.

Phenology:— July to September (flowering); August to October (fruiting).

Habitat:— This species is a scipohyte and grows in colonies in subtropical forests in between 900 – 2000 m.

Distribution:— INDIA: Arunachal Pradesh, MYANMAR: Kachin state [ Fig. 4 ].

Additional specimen examined:— MYANMAR. Valley of Nam Tamai: 27°45' N, 97°50' E, 6000 ft., 07 August 1937, Kingdon-Ward 12935.

Notes on Typification of Chirita peduncularis :— Burtt (1965) described Chirita peduncularis based on specimens of a single collection made by Kingdon-Ward from Valley of Nam Tamai [at present in Kachin state] of upper Burma [ Myanmar] in 1926. In the protologue of C. peduncularis, Burtt mentioned type of this particular name to be deposited in K. Upon consultation, two specimens of C. peduncularis were found in K exactly matching with the protologue; however, both marked as holotype. According to the rules of Shenzhen Code (Turaland et al. 2018), vide Art. 9.1 and 9.6 any of the specimens deposited in Kew (K), cannot be treated as holotype but syntypes. Hence, a lectotype (K000858402) is chosen for the name C. peduncularis from the specimens deposited in K in accordance to the Shenzhen Code (Turland et al. 2018) vide Art. 7.11, 9.3, 9.11 and 9.12.

Distributional notes:— This species was hitherto believed to be a steno-endemic Burmese element. However, after its first collection in 1926, it was only once again collected from Myanmar in 1937 from its type locality by Kingdon-Ward. The present article reports its severely fragmented disjunct nature of distribution in Eastern Himalaya and Upper Burmese region.At present, the known distributions of this species are as follows: 1. around Hakhe Tari area near Ziro Valley, Lower Subansiri District ( Taram et al., 2021), 2. in Pakke-Kessang district (present communication) of Eastern Himalayan state, Arunachal Pradesh, in India; and 3. in valley of Nam Tamai, Putao District, Kachin State in Myanmar.

IUCN Red List Assessment:— Henckelia peduncularis shows a very restricted distribution at present, with only three (3) known localities worldwide: India (Arunachal Pradesh: Lower Subansiri and Pakke-Kessang districts) and Myanmar (Kachin State). The populations of this poorly known species in India and Myanmar are very far away and intersected by geographical barriers resulting in less likely propagule immigration or gene flow among the populations. A thorough survey was also done to locate other known past and present localities of this species from available literatures, herbarium specimens deposited in different herbaria worldwide and online database portals such as GBIF (https://www.gbif.org), iNaturalist (https://www.inaturalist.org), JSTOR (https://www.jstor.org); but in vain. Known distribution localities were plotted using web tool GeoCat (available at https://geocat.kew.org). Extent of Occurrence (EOO) and Area of Occupancy (AOO) were analyzed by using the same online platform BETA version ( Bachman et al. 2011). The Extent of Occurrence is calculated to be 8,104.251 km 2 and AOO is 12 km 2 (AOO based on grid size of 2× 2 km 2) during the present study. The AOO and the numbers of known locations (3) meet the threshold of Endangered category under Criteria B (B2a) of IUCN as per guidelines ( IUCN 2022). However, the known populations show ‘severely fragmented’ disjunct nature of distribution. After discovery, there are no reports of occurrence observed from Myanmar and on the other hand, Indian population also show (i) continuous decline of habitat quality due to continuous anthropogenic activities, expansion of agricultural fields, jhum cultivation, road cutting near both Hakhe Tari (nearby area of type locality of H. dasii ) and Pakke-Kessang area ; (ii) extreme fluctuation in the number of mature individuals has also been noticed during the poresent study. Taram et al. (2021) reported about 300 mature individuals were recorded in 2018 from type locality of H. dasii and assessed this taxon as “Vulrenable” only based upon numbers of mature individuals, under Criteria D of IUCN guidelines. However, Taram et al. (2021) did not consider Criteria D 2 according to which this taxon would have faced serious threat in near future as its AOO was less than 20 km 2 at that time and number of known locations of its population was only 1, the type locality. Upon visiting the same place in 2022, authors were unable to trace any populations; however, near Pakke-Kessang, one population was located with about 40–50 mature and very few young individuals. In view of above circumstances, it is observed that within only 4 years of first collection of H. peduncularis in India, the population of this taxon is rapidly decreasing with very restricted numbers of known localities within its distributional range. At present scenario the threat perception of the species is assessed as Critically Endangered under Criteria C [CR CC1C2a(i+ii)b] of IUCN guidelines (2022).

Figures

FIGURE 1. Henckelia peduncularis (B.L.Burtt) D.J.Middleton & Mich.Möller: A. Habitat and Habit, B. Inflorescence, C. Flower, D. Bracts, E. Calyx split open, F. Corolla split open, G. Stamens and staminodes, H. Pistil (Photo courtesy: K. Chowlu).

FIGURE 2. Lectotype of Chirita peduncularis B.L.Burtt [≡ Henckelia peduncularis (B.L.Burtt) D.J.Middleton & Mich.Möller] © The Board of Trustees, Royal Botanic Gardens, Kew.

FIGURE 3. Holotype of Henckelia dasii Taram, D.Borah, R.Kr.Singh & Tag. © Director, Botanical Survey of India, Kolkata.

FIGURE 4. Distributional map of Henckelia peduncularis.