Sonerila longipedunculata Resmi & Nampy

Resmi, Sekarathil & Nampy, Santhosh, 2021, Sonerila longipedunculata sp. nov., a new species of Melastomataceae from the southern Western Ghats, India, with additional notes and lectotypification of Sonerila travancorica, European Journal of Taxonomy 733, pp. 160-174 : 161-163

Sonerila longipedunculata Resmi & Nampy sp. nov.

urn:lsid:ipni.org:names:77214918-1 Figs 1–3 , 4A 1–G1

Diagnosis

Morphologically similar to S. travancorica in having caulescent habit, densely pubescent, long petiolate leaves, densely glandular-pubescent hypanthium and abaxially glandular-hairy petals, but differs by its tuberous root stock (vs non-tuberous in S. travancorica ), fleshy stems with whitish or claret coloured bristles (vs woody stems with long, dense white hairs), 2–4-cm-long internodes (vs 2.5–6.5-cm-long internodes), 5–9-cm-long petioles with dense bristles (vs 2–7-cm-long petioles with long, dense hairs), ovate to cordate lamina with serrate margins (vs ovate to elliptic lamina with serrulate margins), 10–16-cm-long, angular peduncles (vs 3–6-cm-long, terete peduncles), 3-ribbed hypanthium (vs 6-ribbed hypanthium), ovate-elliptic petals with acute to mucronate apex (vs ovate to broadly ovate petals with mucronate or emarginate apex), acute anthers (vs acuminate to rostrate anthers) and 3-ribbed capsules (vs 6-ribbed capsules).

Etymology

The epithet ‘ longipedunculata ʼ refers to the characteristically long peduncle of the inflorescence of the new species.

Material examined

Type

INDIA • Kerala, Wayanad district, Banasura hills , Kattukunnu ; ca 1000 m a.s.l.; growing under wet rocks in grassy slopes; 13 Aug. 2017; Resmi S. & Santhosh Nampy 151222 ; holotype: CALI!; isotype: MH!.

Additional material

INDIA • Kerala, Wayanad district, Banasura hills , Kattukunnu ; ca 1000 m a.s.l.; on humus-covered soil and rock crevices; 8 Oct. 2017; Resmi S., Dani Francis & Aswathy Ganga 151239 ; CALI !.

Description

Erect or procumbent perennial herbs, 10–30 cm tall. Root stocks tuberous; tubers globose, 1–1.5 cm in diameter, white to pale green, covered by tufts of roots. Stems sub-terete with shallow grooves arising from axils of each pair of leaves, 3–5 mm thick, fleshy, claret coloured, with 2 or 3 branches occasionally developing from distal nodes; internodes 2–4 cm long; nodes densely glandular- or eglandular-hairy. Leaves simple, decussate; petioles adaxially grooved or canaliculated, 5–9 × 0.1–0.2 cm, claret coloured with dense glandular or eglandular bristles; laminae ovate, basal ones cordate to broadly ovate, 3–6 × 3–6 cm, dark green adaxially, claret coloured abaxially, cordate or sub-rounded at base with nonoverlapping or overlapping margins (basal ones), obtuse or rounded at apex, serrate at margins with each tooth ending in terminal eglandular trichome, bullate when mature, with eglandular bristles densely on adaxial surface and on midrib and lateral veins abaxially; veins pinnate, 1–2 pairs from base and 2–3 pairs from above, less branched, impressed adaxially, conspicuous abaxially. Cymes scorpioid of 6–14 flowers in two rows, terminal, unbranched; peduncles angular, 10–16 × 0.15–0.2 cm, longer than petiole, densely glandular-pubescent; bracts caducous. Flowers 1–1.6 × 1–1.5 cm; pedicels terete, 4–5 × 1–2 mm, longer in fruit, claret coloured, densely glandular-pubescent. Hypanthium campanulate, 5–6 × 2–3 mm, 3-lobed, 3-ribbed, claret coloured with greenish tinge distally, densely glandular-pubescent; lobes triangular, 1–2 × 1–2 mm, acute at apex. Petals 3, ovate to elliptic, 7–8 × 4–5 mm, pale pink with darker midrib, obtuse to rounded at base, acute to mucronate at apex, glabrous adaxially, with glandular trichomes on midrib abaxially. Stamens 3, alternate to petals; filaments 4–5 mm long, pale pink, glabrous, dilated and twisted downwards; anthers sagittate to deeply cordate at base, acute at apex, 4–5 mm long, yellow, dehiscing through apical pores. Ovary inferior, 2–2.5 × 2–3 mm; style filiform, 8–9 mm long, pale pink, dark towards apex, longer than stamen; stigma capitate, pink, rugose, glabrous. Capsules urceolate, 5–9 × 3–3.5 mm, claret coloured or green with claret tinge, 3-ribbed, with sparse bristly trichomes. Seeds many, obovoid, 0.5–0.6 mm long, pale brown; raphe prominent, excurrent; testa densely tuberculate throughout.

Phenology

Sonerila longipedunculata sp. nov. was collected with flowers and fruits from September to October.

Distribution and habitat

The new taxon is presently known only from a small area in the Kattukunnu of Banasura hills within the South Wayanad forest division ( Fig. 1 ), where it has been growing under wet rocks on grassy slopes at an elevation of ca 1000 m. Although no detailed ecological studies have been undertaken, S. longipedunculata sp. nov. appears to be restricted to shaded rocky outcrops and is likely to occur in areas where a specific combination of light intensity and moisture prevails, such as vertical, mosscovered rocks or rock crevices, as is the case for many species of Sonerila . It is found in association with S. raghaviana Ratheesh, Sunil, Nandakumar & Shaju , species of grass ( Poaceae Barnhart ), Mitracarpus Zucc. ( Rubiaceae Juss. ), Selaginella P.Beauv. ( Selaginellaceae Willk. ) and several mosses.

Provisional conservation status

Sonerila longipedunculata sp. nov. is known from a single population in the type locality with about 60 mature individuals. The Area of Occupancy (AOO) is less than 10 km 2. No anthropogenic threat was detected as the area falls under a protected forest. However, this area is prone to landslides due to heavy rain, which has occurred in previous years. The habitat has been affected by climate-induced draught after the unexpected floods in 2018 and 2019. We suggest the status of S. longipedunculata sp. nov. as Critically Endangered (CR) B1ab(ii) + B2ab(ii) according to IUCN (2019) criteria.

Notes

The new species is remarkable by the presence of a tuberous root stock ( Fig. 2 C–E), a feature seen in some of the South Indian caulescent species of Sonerila that is apparently absent in Sri Lankan species ( Lundin 1983), but also reported in species from the Malay Peninsula, Vietnam and Cambodia ( Ridley 1912; Pham 2003; Cho et al. 2015; Van Dang et al. 2016). These tubers, with the arrival of the monsoon, produce new stem and tufts of roots. The species of Sonerila from India are mostly pedunculate (with terete or angular peduncles) and rarely sub-sessile. The longer peduncles (10–16 cm) and petioles (5–9 cm) further distinguish the new species, and these traits are not described in any other caulescent herbaceous species, other than the suffrutescent or woody species of Indian Sonerila . Sonerila longipedunculata sp. nov. has fleshy and simple stems, which occasionally branch at distal nodes and become procumbent with roots arising from many points along the stem basally, when grown in the greenhouse. Sonerila longipedunculata sp. nov. is also similar to S. raghaviana Ratheesh, Sunil, Nandakumar & Shaju described by Narayanan et al. (2014) in the hair pattern and floral features, but differs from it by the plants being caulescent (vs acaulescent/ scapigerous). A comparison of diagnostic characters between S. longipedunculata sp. nov. and S. travancorica is provided in Table 1 .

Figures

Fig. 1. Map showing the distribution of Sonerila longipedunculata Resmi & Nampy sp. nov. and S. travancorica Bedd.; prepared by Resmi S. using QGIS ver. 3.12.2 (QGIS 2020).

Fig. 2. Sonerila longipedunculata Resmi & Nampy sp. nov. A–B. Plants in natural habitat, see also S. raghaviana Ratheesh et al. nearby (white arrow). C. Habit. D–E. Base of stem showing tuberous root stock. F–G. Leaves, adaxial and abaxial views. H. Leaves, abaxial and adaxial views showing venation. I–J. Plants under cultivation. Photographs by Resmi S. based on Resmi S. & Santhosh Nampy 151222 (CALI).

Fig. 3. Sonerila longipedunculata Resmi & Nampy sp. nov. A. Habit. B. Plant with three inflorescences emerging from the distal node. C. Inflorescence. D–E. A portion of the inflorescence showing buds, flowers with glandular trichomes on peduncle, hypanthium and the abaxial surface of petals. F. Single flower. G. Hypanthium. H. Petals, adaxial view. I. Petals, abaxial view. J. Hypanthium with stamens and pistil. K. Stamens. L. Pistil. M. Capsule. N. Dehisced capsule. O. Seeds. Photographs by Resmi S. based on Resmi S. & Santhosh Nampy 151222 (CALI).

Fig. 4. Comparison between Sonerila longipedunculata Resmi & Nampy sp. nov. (A1–G1) and S. travancorica Bedd. (A2–G2). A. Habit. B. Root stock. C. Flowers. D. Leaves, adaxial and abaxial views. E. Hypanthium with stamens and pistil. F. Stamens. G. Capsule. A1–G1 based on Resmi & Santhosh Nampy 151222; A2–G2 based on Resmi S. & Santhosh Nampy 151284 (CALI).