Elatostema agasthyanum Jeomol & Sunojk., 2020

Jeomol, K. K. & Sunojkumar, P., 2020, Elatostema agasthyanum (Urticaceae), a new lithophytic species from the southern Western Ghats, India, Phytotaxa 430 (1), pp. 33-40 : 34-35

Elatostema agasthyanum Jeomol & Sunojk. , sp. nov. ( Fig. 1 , 2 & 3 ).

Elatostema agasthyanum is morphologically similar to E. strigillosum , but differs in habit (erect or procumbent vs prostrate or suspending), stem surface (densely hispid vs densely strigillous); larger leaves (2.5–5.5 cm vs 0.9–2.5 cm), lamina apex (acute-acuminate vs acute), lamina surface (papillose hispid vs densely hirtellous), leaf texture (membranous vs charatceous); shape of stipules (ovate-lanceolate vs narrowly triangular), stipule length (c. 4 mm vs <1.8 mm); shape of pistillate inflorescence (sub-quadrate vs ellipticdiscoid), involucral bracts (widely ovate vs narrow elliptic), bracteoles (obovate-oblanceolate vs narrowly oblong-cymbiform) and achene ormanentation (9–10 ribs vs 8 ribs).

Type: — INDIA. Kerala, Thiruvananthapuram district: Agasthyamala hills, Attayar, 08°38.026’ N, 077°12.548’ E, 568 m, 15 May 2018, K. K. Jeomol, N. Krishna & K.M. Manudev 157972 (holotype CALI!, isotype MH!).

Perennial, lithophytic herbs, c. 15 cm long, monoecious. Roots at lower nodes. Stem clustered and erect or procumbent, branched; internodes short, terete, 0.5–1 cm long, 1–2.4 mm diam., densely hispid, not furfuraceous, green, brownishgreen at basal parts. Stipules 2, free, lateral, persistant on upper nodes, ovate-lanceolate, c. 4 × 1–1.5 mm, apex acute, membranous with few linear cystoliths, margins ciliolate, abaxially sparsely sericeous, adaxially glabrous, middle green, translucent towards margins. Leaves alternate, distichous, sessile; laminae membranous, asymmetrically obovate to oblanceolate, 2.5–5.5 × 1–1.5 cm, base oblique, broad side obtuse, narrow side cuneate, margins entire about halfway to the base with 3–4 serrations on broad side and 1–2 serrations on narrow side, apex acute-acuminate, adaxially papillose-hispid, abaxially hispid, green above, pale green below, with dense linear cystoliths; venation semitriplinerved, raised beneath, lateral nerves on broad side 3–5, on narrow side 2–3. Nanophylls absent. Inflorescence unisexual, axillary, solitary capitulum, crowded, short pedunculate, abaxial surface of bracts and bracteoles with linear cystoliths; flowers intermixed with bracteoles. Staminate capitulum c. 2.5 × 3 mm, bilobed, few flowered; peduncles c. 1 mm long, sparsely hispid, cream-green; receptacles c. 3.5 × 4.5 mm, ellipsoid-subquadrate; involucral bracts 6; outer bracts 2, widely ovate, c. 2 × 3.5 mm, enclosing each, confluent at base, slightly corniculate, apex truncate, abaxially sparsely hispid, adaxially glabrous, cream to green; inner bracts 4, 2 per lobe, oblong, c. 1.5 × 1 mm, apex truncate, margins ciliate, adaxially glabrous, translucent; bracteoles narrowly oblong, c. 1.5 × 0.5 mm, apex truncate, margins ciliate, adaxially glabrous, translucent. Staminate buds c. 3 × 1 mm wide, laterally compressed, imbricate; pedicels 1.5–2 mm long, glabrous, translucent; tepals 4, unequal, corniculate below apex, apex obtuse-round, glabrous with 1–3 hair at apex, translucent; pistillode small, triangular flap; stamens 4, basifixed, inflexed in bud; filaments distinct; anther 2-celled, arrow-shaped, white, dehiscing longitudinally. Pistillate capitulum c. 2 × 0.5–3 mm, divided into 2 secondary capitula, green; peduncles c. 0.65 mm, sparsely hispid; receptacles c. 1.5 × 2 mm, sub-quadrate; involucral bracts 6; outer bracts 2, widely ovate, c. 1.5 × 1.5 mm, confluent at base, slightly corniculate below apex, abaxially sparsely hispid, adaxially glabrous; inner bracts 4, elliptic-oblanceolate, c. 1 × 0.5 mm, apex acute, margins and apex long ciliate, adaxially glabrous, green; bracteoles numerous, longer than flowers, obovate-oblanceolate, 0.8–0.9 × 0.25–0.4 mm, apex acute, upper half densely long ciliate, adaxially glabrous, translucent. Pistillate flowers 0.9–1 mm long; pedicels 0.3–0.5 mm long, glabrous, translucent; tepals 3, triangular, c. 0.2 mm long, shorter than ovary; staminodes 3, inflexed, rudimentary, enlarged when fruiting, glabrous, translucent; ovary ellipsoid, c. 0.5 × 0.3 mm long, white, superior, erect; style absent; stigma penicillate. Achenes ellipsoid, c. 0.60 × 0.40 mm, length: width ratio 3:2, stipitate, longitudinally 9–10 ribbed, cream-yellow.

Etymology:—It is believed that sage Agasthya was in penance in the southern most range of the Western Ghats, which was later named as Agasthyamala hills. The species being originally collected from here is given the specific epithet ‘ agasthyanum ’.

Habitat and ecology:— Elatostema agasthyanum grows well on the banks of river Attayar, which is an upper tributary of Karamana river originating from Agasthyamala hills ( Fig. 4). The Agasthyamala Biosphere Reserve is located in the southern end of the Western Ghats. It spans 3,500 km 2 within the Thiruvananthapuram and Kollam districts of Kerala and in the Tirunelveli and Kanniyakumari districts of Tamil Nadu. The plant is lithophytic, growing on rocks along the streams. It is found growing in association with mosses and E. heyneanum ( Weddell 1856: 287) Hallier f. (1896: 316) .

Distribution:— India (Kerala and Tamil Nadu).

Phenology:—Flowering and fruiting from January to May.

Additional specimen examined (Paratype):— INDIA. Kerala, Thiruvanthapuram District: Agasthyamala hills (cultivated at Calicut University Botanical Garden), 22 January 2019, K.K. Jeomol 157985. Tamil Nadu, Tirunelveli District: Agasthyamala hills, 1 April 2019, K.K. Jeomol 157992 (CALI!).

Taxonomic notes:—Even though, infrageneric classification of Tseng et al. (2019) is congruent with Schröter and Winkler (1935, 1936), the four clades recognized are maintained without assigning any taxonomic rank. Moreover, the phylogenetic analysis of Tseng et al. (2019) does not support Wang’s (1980a, b, 2014) sectional treatment of Elatostema . Hence, the exact systematic placement of E. agasthyanum cannot be ascertained and further studies are required to confirm the infrageneric placement of the new taxon within Elatostema .

Conservation status:—Data Deficient ( IUCN 2017).

Figures

FIGURE 1. A. Habitat of Elatostema agasthyanum; B. Stem with staminate inflorescence; C. Stem with pistillate inflorescence; D. Stem showing hispid hairs; E. Leaf adaxial surface; F. Leaf abaxial surface (A: photographed by Manudev K.M.; D–F photographed by Jeomol K.K.).

FIGURE 2. Elatostema agasthyanum. A. Habit; B. Stem; C. Leaf; D. Stipule; E–G. Staminate inflorescence (lateral, adaxial, abaxial view); H–J. Pistillate inflorescence (lateral, adaxial, abaxial view); K–L. Staminate bract; M–N. Staminate bracteole; O–P. Pistillate bract; Q–R. Pistillate bracteole; S. Staminate bud; T. Staminate flower; U. Pistillate flower; V. Achene. (A: photographed by Manudev K.M.; B–V: photographed by Jeomol K.K.).

FIGURE 3. Elatostema agasthyanum. A. Habit; B. Lamina enlarged showing cystoliths; C. Stipule; D–E. Staminate inflorescence (lateral, abaxial view); F. Staminate bract; G. Staminate bracteoles; H–I. Pistillate inflorescence (lateral, abaxial view); J. Pistillate bract; K. Pistillate bracteole; L. Staminate bud; M. Staminate flower; N. Pistillate bud; O. Pistillate flower; P. Achene (Illustrated by Jeomol K.K.).