Henckelia bracteata (Gesneriaceae), from the S Western Ghats in India, is described as new to science and illustrated. It is compared with the similar H. humboldtiana from S India and Sri Lanka. Its conservation status is assessed according to IUCN categories and criteria. The name Didymocarpus humboldtianus, the basionym of H. humboldtiana, is lectotypified.
The genus Henckelia Spreng., which is easily distinguished from Didymocarpus Wall. by its perennial habit and plagiocarpic fruits that dehisce along the dorsal suture, was re-established by Weber & Burtt (1997). In their recent papers, Weber & al. (2011) and Middleton & al. (2013) restricted the concept of Henckelia to include only 56 species worldwide, distributed in Sri Lanka, S and NE India, Nepal, Bhutan, S China, N Vietnam, N Laos and N Thailand. However, the above list does not include two species described from S India, namely H. sivagiriensis (Rajakumar & al.) E. S. S. Kumar (Santhosh Kumar 2014), based on D. sivagiriensis Rajakumar & al. (Rajakumar & al. 2009), and H. pradeepiana Nampy & al. (Manudev & al. 2012). At present, 30 species are know to occur in India, of which 13 are endemic to the Western Ghats, including the new species described here.
During a recent scientific survey in the S Western Ghats, as a part of revisionary study of Gesneriaceae in India, the authors came across a few populations of Henckelia from Kurisumala in Kottayam district. The locality Kurisumala is a famous Catholic pilgrim centre and is part of the Vagamon hills, one of the tourist destinations in Kerala. These mist-laden hills are the abode of several endemic plants and are under threat from anthropogenic disturbances. Critical examination revealed this Henckelia as a distinct, hitherto undescribed species, which is described as new to science and illustrated here.
Holotype: India, S Western Ghats, Kerala, Kottayam district, Kurisumala, near to 10th Cross, 1100 m, 7 Aug 2014, A. P. Janeesha & Santhosh Nampy 134270 (CALI; isotypes: CAL, MH).
Diagnosis — Henckelia bracteata Janeesha & Nampy is similar to H. humboldtiana (Gardner) A. Weber & B. L. Burtt in the shape of its leaves, the presence of bracts, and in having scapes much longer than the leaves, but is readily distinguished by its cymes having a greater number of flowers (14–38), its large elliptic to obovate bracts, ovate calyx lobes, and the presence of eglandular trichomes at the junction of the anther lobes and filaments.
Description — Herbs perennial, with rootstocks, stemless, scapigerous, hairy. Roots adventitious, thin. Leaves 8–14, basal; petiole 2–9 cm long, pubescent, winged, wings 2–3 mm wide; leaf blade elliptic-ovate, 5.5-12.5 × 3-9 cm, thick, surfaces usually rugose, both surfaces tomentulose, but more so on younger leaves and on veins abaxially, becoming less so with age, base narrowly cuneate to attenuate, margin shallowly crenate, apex acute or obtuse to rounded; veins 5 on each side of midrib, much branched and conspicuous abaxially. Inflorescences axillary, densely cymose; cymes 1–11 per plant, 3–5(or 6) times divided, 14–38-flowered, pubescent; peduncle reddish brown, terete, 14–32 cm long, pubescent; bracts 2 at each branching point, elliptic to obovate, 10-21 × 5-8 mm, tomentose, margin crenate, apex obtuse to rounded; pedicels narrowly terete, 2–10 mm long, eglandular pubescent. Flowers zygomorphic, 10-20 × 4-9 mm. Calyx 5(or 6)-partite, very deeply divided or basally connate; lobes reddish brown, ovate, 3-4 × 1-2 mm, unequal, white tomentose, margin entire, apex slightly acute. Corolla campanulate, 5-lobed, villous outside, glabrous inside; tube lilac to pale lilac with a yellow patch in throat, 7-9 × 5.5-7.5 mm; lobes pale lilac to lilac, 5.2-7 × 7.4-8.3 mm, unequal, apex ovate to rounded. Stamens 2, adnate to base of corolla, included; filaments colourless toward base and green at apex, 4–6 mm long, glabrous or sparsely pubescent toward region of connective; anthers bithecate, coherent by adaxial surface, milky white, reniform, 1.5-1.8 × 0.8-0.9 mm, with eglandular trichomes at junction of anther lobes and filament. Staminodes (2 or)3; filaments hyaline, 2.5–3 mm long, glabrous; antherodes not seen. Ovary unilocular, green, ovoid to oblong, 5-7 × 1.25-1.5 mm, pubescent, placentation parietal; style green, terete, 2–2.5 mm long, glabrous; stigma 0.8-1.1 × 0.5-0.82 mm, papillate. Capsule reddish brown, cylindric, straight or slightly curved, stout, 18-30 × 1.6-2 mm, tomentulose with rudimentary stigma. Seeds numerous, elliptic, 0.4-0.6 × 0.2-0.25 mm, base truncate, apex slightly acute: testa dark brown to black, pitted.
Phenology — The new species flowers and fruits from July to October.
Distribution and ecology — Henckelia bracteata is endemic to the S Western Ghats, currently known only from the type locality, Kurisumala in Kottayam district (Fig. 3). The species grows in wet humus in granite rock crevices at altitudes of c. 1100 m. It is found in association with species of grasses (Poaceae), Mitracarpus Zucc. (Rubiaceae), Selaginella P. Beauv. (Selaginellaceae), several mosses, and Porella L. (Porellaceae).
Conservation status — Henckelia bracteata is currently known only from three populations in an unprotected area, separated by a distance of only 30–50 m. A total of only 42 mature individuals was found in the area. Therefore the species may be assessed as Critically Endangered CR B lab(iii)+2ab(iii); D (IUCN 2012), considering the future possibility of further ecological disturbances.
Etymology — The specific epithet “bracteata” refers to the very prominent bracts of the new species.
Remarks — Henckelia bracteata is robust and dull green, with the peduncle, pedicel, calyx and capsules generally reddish brown. Although the margin of the leaf blade is crenate, the crenation is shallow when compared to the similar H. humboldtiana, which is distributed in S India and Sri Lanka. The corolla is pale lilac with a yellow blotch at the throat in its natural habitat, but in cultivation in the
greenhouse at the University of Calicut (60 m in altitude), the corolla colour is dark lilac or violet. The morphological differences between H. bracteata and H. humboldtiana are illustrated in Fig. 4 and summarized in Table 1.
Additional specimens seen (paratypes) — India: Kerala: S Western Ghats, Kottayam district, Kurisumala, 17 Aug 2013, K. M. Manudev & A. P. Janeesha 134206 & 134209 (CALI); ibid., way to 6th cross, 7 Aug 2014, A. P. Janeesha & A. P. Roshan 134268 (CALI); ibid., near to 6th cross, 7 Aug 2014, A. P. Janeesha & A. P. Roshan 134269 (CALI).
Comparison of Henckelia bracteata and H. humboldtiana.
Lectotypification of Didymocarpus humboldtianus
Didymocarpus humboldtianus Gardner in Calcutta J. Nat. Hist. 6: 477. 1846 [“humboldtiana”] ≡ Roettlera humboldtiana (Gardner) Kuntze, Revis. Gen. Pl. 2: 476. 1891 ≡Henckelia humboldtiana (Gardner) A. Weber & B. L. Burtt in Beitr. Biol. Pflanzen 70: 346. 1998. — Lectotype (designated here): Sri Lanka [“Ceylon”], Rambodde, Gardner 600 (K000858189; isolectotype: K000858188).
Henckelia humboldtiana was first described as Didymocarpus humboldtianus (Gardner 1846), from Ceylon (i.e. Sri Lanka), with the citation: “Hab. — On moist shady rocks above Rambodde; at an elevation of from 4000–5000 feet above the sea.” As per the protologue, the species is characterized by an ovate-elliptic leaf blade with tomentose hairs, subcordate base, crenate margin and obtuse apex, longer scapes that divide three times, with oblong bracts and linear calyx lobes. Weber & Burtt (1997) transferred this species to Henckelia along with many other species of Didymocarpus. While searching for Gardner's materials in different herbaria it was found that there are two sheets at K, both apparently part of a single gathering, Gardner 600. One sheet (K000858188) bears a small label annotated “600 | Gardn | Ceylon” and four plants in flower, one of them also with a young fruit. The other sheet (K000858189) bears a larger label annotated “600. | Didymocarpus Humboldtiana [sic!], Gardn. | Rambodde, Ceylon” and three plants in flower, one of them also with several well-developed fruits. The latter sheet is the better specimen and is therefore selected here as the lectotype (Fig. 5).
We thank Dr K. M. Jayaram, Head of the Department of Botany, University of Calicut, for facilities; the curators of K for the virtual images of type specimens and the herbaria BLAT, BSI, CAL, CALI, DEV, FRC, JCB, KFRI, MH, RHT and TBGT for permitting us to consult specimens; Mr K. M. Manudev and Mr A. P. Roshan for assisting collections; and Dr Michael Moeller (E) and an anonymous reviewer for their comments on an earlier draft of this paper. One of us (A.P.J.) thanks the University Grants Commission, New Delhi, for Fellowship.
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