Memecylon pachaimalayanum R. Rajesh, M.B. Viswan. & R. Silambarasan, 2021

Rajesh, R., Viswanathan, M. B. & Silambarasan, R., 2021, Memecylon pachaimalayanum (Melastomataceae) - a new species from the Eastern Ghats of Tamil Nadu in India, Phytotaxa 496 (1), pp. 69-76 : 69-74

Memecylon pachaimalayanum R. Rajesh, M.B. Viswan. & R. Silambarasan , sp. nov. ( Figs. 1 and 2 ).

Diagnosis:— Memecylon pachaimalayanum is closely related to M. bremeri , M. kollimalayanum and M. lushingtonii in the arrangement, shape and oblique nature of leaves, flowers and fruits and shape of the floral parts. Nevertheless, leaf blades are larger in M. pachaimalayanum (1.5–7.2 × 0.6–3.0 cm) and M. kollimalayanum (1.5–7.2 × 0.6–2.8 cm) but smaller in M. bremeri (2.0–3.6 × 0.9–1.8 cm) and M. lushingtonii (1.4–5.2 × 0.4–2.1 cm). Transverse veins of the leaves are in 7–9 pairs in M. pachaimalayanum , in 4–6 pairs in M. bremeri and 5 or 6 pairs each in M. kollimalayanum and M. lushingtonii . Foliar sclereids are dimorphic in M. pachaimalayanum (narrowly filiform, unbranched, often mixed with spheroidal ones), M. bremeri (terminal or diffuse, vermiform or columnar, infrequently aggregated to sclerocysts around the veins or vein endings) and M. kollimalayanum (terminal, vermiform, aggregated to sclerocysts around the veins or vein endings) but polymorphic in M. lushingtonii (osteo-sclereids and ophiuroid or astero-sclereids). Fascicles of flowers are ca. 1.5 cm wide in M. pachaimalayanum but smaller, ca. 1 cm wide in M. bremeri , ca. 0.8 cm wide in M. kollimalayanum and ca. 0.5 cm wide in M. lushingtonii . Pedicels of the flowers are whitish-cream to pale brown in M. pachaimalayanum but greenish-white in M. bremeri and M. lushingtonii and creamish-pink in M. kollimalayanum . Hypantho-calyx is verrucose in M. pachaimalayanum but smooth in M. bremeri , M. kollimalayanum and M. lushingtonii . The hypantho-calyx is whitish-cream, pale brown to pale red and ca. 1.3 × 2.0 mm in M. pachaimalayanum , pale cream to dark purple and ca. 0.25 × 1.2 mm in M. bremeri , creamish-pink, white-tinged and ca. 0.25 × 1.2 mm in M. kollimalayanum and creamish-pink and ca. 1 × 0.2 mm in M. lushingtonii . Petals are different in colour and at margin such as whitish pale blue and slightly fimbriate at base to erose towards apex and ca. 2 × 2 mm in M. pachaimalayanum , pale to dark blue with entire margin and ca. 0.4 × 0.2 mm in M. lushingtonii , creamish purple and irregularly erose margin and ca. 1.2 × 1.2 mm each in M. bremeri and M. kollimalayanum . Anthers are ca. 0.2 × 0.3 mm in M. pachaimalayanum but larger, ca. 0.3 × 0.2 mm in M. lushingtonii , ca. 0.4 × 0.2 mm in M. bremeri and ca. 0.45 × 0.3 mm in M. kollimalayanum . Connectives are ca. 1 × 0.4 mm long in M. pachaimalayanum but smaller, ca. 0.6 × 0.2 mm in M. lushingtonii , ca. 0.7 × 0.3 mm in M. bremeri and ca. 0.8 × 0.3 mm in M. kollimalayanum . Style is whitish to pale blue and ca. 8.0 × 0.3 mm in M. pachaimalayanum , pale blue and ca. 3.5 × 0.2 mm in M. lushingtonii , creamish white and ca. 4.2 × 0.25 mm in M. bremeri and purple and ca. 4.5 × 0.2 mm in M. kollimalayanum . Berries are dark blue in M. pachaimalayanum , blue in M. bremeri , creamish to whitish-blue to dark blue in M. kollimalayanum and yellow in M. lushingtonii . Seeds are ca. 8 mm wide in M. pachaimalayanum but smaller, ca. 3 mm wide in both M. bremeri and M. lushingtonii and ca. 4 mm wide in M. kollimalayanum .

Type:— INDIA. Tamil Nadu: Tiruchirappalli District, Pachaimalai hills, near Shri Perumal Temple , Punavarai , ± 850 m, 11°19’58.69”N, 78°33’17.27”E, 11 March 2016, R. Rajesh, M. B. Viswanathan & R. Silambarasan 1431 (Holotype MH!, isotypes! Herbarium, Department of Botany , Bharathidasan University, Tiruchirappalli) .

Trees, semi-evergreen, subcanopy, 3–5 m high; bark ashy grey mixed with brown and whitish patches; branches and branchlets subquadrangular; nodes annular; internodes abbreviated, 0.5–3.2 cm long. Leaves decussate-opposite, dark green with pale yellow above, yellowish green beneath when dry, yellow when become old, glabrous; petioles 2–4 mm long; blades elliptic, obliquely cuneate at base, entire at margin, retuse or obtusely retuse at apex, 1.5–7.2 × 0.6–3.0 cm; mid-nerve prominent, impressed, sulcate above; transverse veins obscurely conspicuous above, rarely visible beneath, 7–9 pairs. Foliar sclereids dimorphic, narrowly filiform, unbranched, often mixed with spheroidal ones. Flowers in axillary fascicles, either at leaf axils or leafless nodes, 5–15 pairs in each fascicle, either at one side or both sides, 4-merous, bisexual with an epigynous disc; fascicles each ca. 1.5 cm wide; flowers ca. 1.2 × 0.4 cm; pedicels terete, whitish cream pale brown, ca. 1.2 × 0.2 mm in flowering, ca. 2.8 × 0.3 mm in fruiting. Hypantho-calyx whitish cream pale brown to pale fleshy red, campanulate-cyathiform, verrucose, ca. 1.3 × 2.0 mm; margin 4-lobed; lobes deltoid or triangular, ca. 0.3 × 0.2 mm. Petals 4, imbricate in bud, whitish pale blue, orbicular, slightly fimbriate at base to erose towards apex, clawed at base, grooved within, ca. 2 × 2 mm; claw narrow, entire. Stamens 8, equal; filaments whitish pale blue, incurved in bud, straight, 4.0–5.0 × ca. 0.2 mm; anthers 2, pale brown, opening by slits, ca. 0.2 × 0.3 mm; connectives whitish pale blue, attached ventrally with anthers, nearly axe-shaped, obtuse-rounded at base with brown disc-shaped gland at dorsal middle surface, ca. 1.0 × 0.4 mm. Ovules 8, attached to central placenta; style whitish pale blue, ca. 8.0 × 0.3 mm. Berries subglobose, dark blue, crowned by persistent calyx at apex, 8–10 × 5–7 mm; calycinal crown 4-angular, ca. 1.6 × 4.3 mm; scars dentate, ca. 1.6 × 3.3 mm each; staminal filament and central style scars persistent; epigynous chamber shallow. Seed 1, 7–9 × 4–6 mm.

Habitat:— Southern tropical semi-evergreen forest (primary and secondary forest) with trees of Syzygium cumini ( Linnaeus 1753: 471) Skeels (1912: 248) , Memecylon talbotianum Brandis (1906: 336) , Vitex altissima Linnaeus filius (1782: 294), herbs of Barleria longiflora Linnaeus filius (1782: 290), Oplismenus compositus Beauvois (1812: 54) , Spermacoce articularis Linnaeus filius (1782: 119) and Stachytarpheta indica Vahl (1804: 206) .

Etymology:— The epithet “ pachaimalayanum ” refers to the type locality, the Pachaimalai Hills of Tiruchirappalli District in the Eastern Ghats of Tamil Nadu.

Phenology:— Flowering: March–May; Fruiting: April–July.

Distribution:— Memecylon pachaimalayanum is restrictedly distributed to the Pachaimalai Hills of Tiruchirappalli District in the Eastern Ghats of Tamil Nadu ( Fig. 3 ). Memecylon lushingtonii is distributed in the Eastern Ghats (Kadapa District in Andhra Pradesh) and Western Ghats (Biligirirangan and Mahadeshwara Hills in Chamrajnagara District in Karnataka, Conoor in the Nilgiris District and Osahatti in Coimbatore District of Tamil Nadu). Memecylon bremeri and M. kollimalayanum are restrictedly distributed in the Kolli Hills of Namakkal District in the Eastern Ghats of Tamil Nadu.

Conservation Status:— IUCN Red List Category ( IUCN Standards and Petitions Committee 2019) of Critically Endangered is assigned on the basis of two the sub-categories (B) geographic range and (C) small population size and decline. Under (B), it qualifies to both (B1) extent of occurrence (EOO): 4.21 km 2 and (B2) area of occupancy (AOO): 0.102 km 2. Under (C), it qualifies by the number of mature individuals: 300 and number of populations: 4 ( Fig. 3 ). Conversion of forest lands for agricultural purposes by regular annual man-made firing is a major threat factor, because of which this tree species exists as thickets in primary forests and patches/isolated individuals in the secondary forests. Assignment of threat category will help to conserve this tree species by the Tamil Nadu Forest Department.

Paratypes:— INDIA. Tamil Nadu: Tiruchirappalli District, Pachaimalai hills, near Shri Perumal Temple , Punavarai , ± 850 m, 11°19’58.69”N, 78°33’17.27”E, 29 May 2016, R. Rajesh, M. B. Viswanathan & R. Silambarasan 1443 (Herbarium, Department of Botany , Bharathidasan University, Tiruchirappalli!) .

Notes:— The distinguishing characters among M. bremeri , M. kollimalayanum , M. lushingtonii and M. pachaimalayanum are given in Table 1. Foliar sclereids have been reported in M. lushingtonii by Subramanyam & Ananda Rao (1949) and M. bremeri and M. kollimalayanum by Viswanathan (2001).

Type Specimens examined: — Memecylon kollimalayanum : INDIA. Tamil Nadu: Salem District , Kollihills, Karavallicombai R. F ., ± 1200 m, 11°8’N, 78°20’E, 2 April 1994, M. B . Viswanathan 2 ( MH!). Memecylon bremeri : INDIA. Tamil Nadu: Salem District , Kollihills, Karavallicombai R. F ., ± 1200 m, 11°8’N, 78°20’E, 2 April 1994, M. B . Viswanathan 3 ( MH!). Memecylon lushingtonii : INDIA. Andhra Pradesh: Kadapa District, Horsleykonda , ± 1219 m, July 1884, J. S . Gamble 15110 ( K!); Tamil Nadu: Coimbatore District , Osahatti, A. W . Lushington s.n. ( K000859151 , K!) .

Figures

FIGURE 1. Memecylon pachaimalayanum—a. Twig, b. Flower, c. Hypantho-calyx, d. Petal, e. Hypantho-calyx, style and stamen, f. Stamen, g. Fruit. (All drawn from R. Rajesh, M.B. Viswanathan & R. Silambarasan 1431 by R. Suresh).

FIGURE 2. Memecylon pachaimalayanum—a. Tree, b. Twig, c. Floral buds in axillary fascicle, d. Axillary fascicles in full blossom, e. Immature fruits, f. Mature fruit, g.A portion of cleared leaf, showing narrowly filiform, unbranched, often mixed with spheroidal sclereids. Photographs: C. Rajasekar and R. Rajesh.

FIGURE 3. a. Distribution of four Memecylon species in Peninsular India, b. Distribution of four populations of Memecylon pachaimalayanum in the Pachaimalai hills. Images: R. Jegankumar, R. Silambarasan and P. Sakthidhasan.