Thismia aurantiaca Hareesh & M.Sabu, 2018

Hareesh, V. S., Alappatt, J. P. & Sabu, M., 2018, Thismia aurantiaca sp. nov. (section Rodwaya, Thismiaceae): First record of the family from Andaman and Nicobar Islands, India with a new species, Blumea 63 (2), pp. 135-139 : 135-138

Thismia aurantiaca Hareesh & M.Sabu , sp. nov. — Fig. 1 , 2 ; Map 1

This species is similar to T. rodwayi but differs from the latter in having outer perianth lobes 5 times larger than inner perianth lobes (vs sub-equal), broadly triangular recurved outer perianth lobes (vs spathulate, up-curved) and inner perianth lobes with minute 0.5 mm long, erect mitre (vs well developed more than 1 mm long, bent and inter locking mitre). — Type: M. Sabu & V. S. Hareesh 152774 (holo CALI;iso CAL, PBL), India , Andaman Islands , South Andaman, Mount Harriet National Park, elevation ± 320 m, 7 Aug. 2017 .

Etymology. The name ‘ aurantiaca ’ denotes the orange coloured flower of the plant.

Terrestrial, mycoheterotrophic erect herbs up to 9 cm tall. Roots clustered, prostrate, unbranched, pale yellow, vermiform, 5–15 by 0.5–1 mm, tapering towards apex. Stem erect, 15–25 by 1.75–2.5 mm at the base, c. 3.0 mm wide near the apex; unbranched, pale yellow to off white, somewhat translucent. Leaves alternate, 3–5, 4–5 by 1.5–2 mm, lanceolate, acute at apex, entire, translucent, white. Involucral bract 6–9 by 2–3 mm, narrowly triangular, acute at apex, glabrous, white. Flowers solitary, actinomorphic, 1.5–2.5 cm long, 6.5–7.5 mm wide, orange. Pedicel 2–2.5 by c. 2.5 mm, terete, white; tepals fused to form a perianth tube with a whorl of 3 inner and 3 outer free apical perianth lobes. Hypanthium 10–15 by 5–10 mm obovoid, narrower towards base (c. 5 mm diam), wider above (c. 10 mm diam), white tinged with 12 depressed orange ribs of which 6 alternate ribs run from the base of the tube to the mouth of the annulus on the upper part of the perianth tube. Annulus c. 1 mm high, erect, forming a broad aperture, fleshy, orange. Perianth, 6 tepals in 2 whorls of 3 each, attached to the hypanthium top, orange. Outer tepals alternating with involucral bracts, c. 3 by c. 3.5 mm, broadly triangular, entire, apex acuminate to round- ed, orange. Inner tepals at the same radii with involucral bracts, distally arching inward and apically broadly fused (inseparable without tearing) to form a thick convex-topped mitre c. 0.5 mm high. Lobes 15–17 by 14–16 mm, broadly spathulate, bases 3, orange, smooth, erect, thick, attached to annulus, basally 4.5–5 mm wide, broadened towards mitre. Inner surface of mitre slightly concave, glabrous. Stamens 6, 5.8–6.3 by 2 mm, quadrangular, attached on the top of the hypanthium, free from annulus; filaments fused with hypanthium and laterally fused with stamens, forming a staminal tube, suspended above the stigma; anthers c. 1 by 0.5 mm, mounted on fused connectives, thecae free, opening with longitudinal slits facing the inner wall of the perianth tube, covered with sparse glandular trichomes especially along the longitudinal slit, white. Ovary inferior, 2.5–3 by 3.5–4 mm, obconical, unilocular, outer wall longitudinally verrucose; style cylindrical, c. 0.5 by 1 mm; stigmas 3, 1.25 by c. 1.5 mm long, fused together and forming a dome-like struc- ture, papillose, off white. Fruit 5–6.5 by 6–6.5, cup-shaped, verrucate, pale orange in colour. Seeds not seen.

Habitat & Ecology — So far, we could observe three popula- tions with around 18 individuals each in the evergreen forest patches of Mount Harriet National Park, South Andaman. The plants are growing in a damp habitat in the understory of evergreen forest in association with Amomum andamanicum V.P.Thomas, Dan & M.Sabu ( Zingiberaceae ), Dipterocarpus sp. and Hopea sp. ( Dipterocarpaceae ), Phrynium sp. ( Marantaceae ), Malaxis sp. ( Orchidaceae ).

Conservation assessment — Due to the known limited area of occurrence of T. aurantiaca , the new species is to be classified as Critically Endangered based on IUCN Red-list criteria CR B2ab(i,ii,iii,iv,v) and C2a(i,ii)b ( IUCN 2017).

Figures

Map 1 Distribution map of Thismia aurantiaca Hareesh & M.Sabu.

Fig. 1 Thismia aurantiaca Hareesh & M.Sabu. a–b. Plant in habitat; c–e. habit (M. Sabu & V.S. Hareesh 152774). — Scale bar = 2 cm. — Photos by M. Sabu & V.S. Hareesh.

Fig. 2 Thismia aurantiaca Hareesh & M.Sabu floral parts. a. Habit showing split-opened flower with stamens; b–c. mitre; d. hypanthium side view; e. hypan- thium front view; f–i. outer tepals; f–g. adaxial view; h–i. abaxial view; j–k. ovary with stigma (M. Sabu & V.S. Hareesh 152774). — Scale bars: a = 1 cm; b–c = 5 mm; d–e = 3 mm; f–k = 1 mm. — Photos by M. Sabu & V.S. Hareesh.