Sonerila lundinii Resmi & Nampy, 2022

Sonerila lundinii Resmi & Nampy View in CoL , sp. nov. FigS. 1–3 View Fig View Fig View Fig

Sonerila lundinii is morphologically close to S. pedunculosa sharing a prostrate or creeping habit rooting at nodes, but is distinguished by its densely villous stem ( vs. glabrous in S. pedunculosa ), finely serrulate laminae ( vs. crenate or finely serrate), 2–4 cm long peduncles ( vs. 3–7 cm), broadly ovate, pale rose petals ( vs. ovate, dark pink), lanceolate acuminate anthers ( vs. narrowly ovate, obtuse to acute), and campanulate, 3-ribbed capsules ( vs. obconic, 6-ribbed).

Type: INDIA, Kerala, Thiruvananthapuram district, Agasthyamala Biosphere Reserve, Chemunji , way to hill top, 1200 m, 05.01.2018, S . Resmi , M. P . Krishnapriya & S . Nampy 151257 (holo CALI!; iso MH!) .

Annual, caulescent, prostrate or creeping herbs. Root stock thick; roots arising from all nodes, 5–8 cm long. Stems terete, 0.2–0.3 cm thick, green or vinaceous, repeatedly branched from a common node and ramify in all directions, densely covered with eglandular trichomes; branches 5–15 cm long; internodes 1–2.5 cm long, short towards apex. Leaves decussate, whorled towards apex forming a rosette in young stage; petioles adaxially grooved or canaliculated, 0.5– 3 cm long, green, densely covered with eglandular trichomes; laminae ovate to broadly ovate, 2–5 × 1.7–3 cm, dark green or with a purple tinge adaxially, equal and rounded or sub-cordate at base with nonoverlapping margins, finely serrulate at margins with each tooth ending in a terminal eglandular trichome, acute to obtuse at apex, membraneous, densely villous adaxially with eglandular trichomes, but only on veins abaxially; veins pinnate, 1–2 pairs from the base and 1–2 pairs from midrib above, less branched, impressed adaxially, conspicuous abaxially. Cymes scorpioid, unbranched, 3–7-flowered, terminal; peduncles sub-terete to quadrangular, 2–4 × 0.10–0.15 cm, green or green with a vinaceous or claret tinge; bracts sometimes present. Flowers 1–1.5 × 1–1.5 cm; pedicels sub-angular, 1–3 × 1–2 mm, longer in fruit, vinaceous or claret, sparsely covered by gland-tipped trichomes. Hypanthia campanulate, 5–7 × 2–2.5 mm, 3-lobed, 3-ribbed, green with a vinaceous or claret tinge, sparsely covered by gland tipped trichomes; lobes triangular, 1–1.5 × 1–1.5 mm, acute at apex. Petals 3, broadly ovate, 6–9 × 4–5 mm, pale rose with a darker midrib, rounded at base, mucronate at apex, glabrous adaxially, with gland-tipped trichomes on midrib abaxially. Stamens 3; filaments 4–6 mm long, pale pink, glabrous; anthers lanceolate, 4–6 mm long, acuminate at apex. Ovary 2–3 × 2–3 mm; style 8–9 mm long, pale pink, dark towards apex, equal to the stamen; stigma capitate, pink, rugose, glabrous. Capsules campanulate, 5–7 × 3–3.5 mm, green with a vinaceous or claret tinge, 3-ribbed, sparsely covered with gland-tipped trichomes, less so with age. Seeds numerous, obovoid, 0.5–0.6 × 0.2–0.3 mm, pale brown; raphe prominent, excurrent or remaining out into a lateral appendage; testa densely pusticulate throughout, tuberculate at dorsal angle; tubercles pyramidal, covered all over by small pusticles.

Flowering & fruiting: Flowering from December to January and fruiting from January to March.

Habitat: Sonerila lundinii occurs in shady habitats with a relatively thick mossy substratum. It grows along the edges of evergreen forests, at elevations between 750–1200 m above sea level, in association with S. tinnevelliensis C.E.C.Fisch. , S. brunonis Wight & Arn. ( Melastomataceae ), Cyanotis villosa (Spreng.) Schult. & Schult.f. ( Commelinaceae ), Henckelia repens (Bedd.) A.Weber & B.L.Burtt ( Gesneriaceae ), Justicia betonica L. ( Acanthaceae ) and some mosses.

Distribution: Endemic to southern Western Ghats, India ( Fig. 4 View Fig ).

Etymology: The epithet ‘lundinii’ honours the late Roger Lundin for his valuable contribution to the taxonomy of the genus Sonerila .

Specimens examined: INDIA, Kerala, Thiruvananthapuram district, Chemunji , 21.03.1996, E. S . Santhosh Kumar 25412 ( TBGT); Ibid. , 23.12.2020, M. K . Akhil, T. P . Krishnaraj, S . Resmi & S . Nampy 164469 ( CALI); Koviltherimala , 750 m, 09.10.2009, K. P . Deepthikumari & A. G . Pandurangan 60599 (in vegetative state); Ibid . , 18.10.2010, K. P . Deepthikumari & Usha 67987 ( TBGT) .

Conservation status: The new species is currently known only from Chemunji and Koviltherimala in the Agasthyamala Biosphere Reserve. We were able to observe one population of approximately 90 mature individuals in the Chemunji hills. The habitat is severely affected by controlled burning activities by the Forest Department. It is likely that there may be more populations in similar habitats and these areas will be negatively impacted by further disturbances in the future due to local human activities involving the harvesting of wood, honey and forage grasses. The lack of collections from additional locations precludes the accurate estimation of the Extent of Occurrence ( EOO), but the Area of Occupancy ( AOO) is c. 8 km 2. This species is thus assessed here as Critically Endangered ( CR), B 2ab (ii,iii,v); D according to IUCN Red List Categories and Criteria ( IUCN, 2012; IUCN Standards and Petitions Committee, 2022).

Notes: Sonerila lundinii appears to be closely related to S. pedunculosa in its creeping habit. Nevertheless, it differs by characteristics of the stem, leaf margins, and the morphology of petals, anthers and capsules. According to Thwaites (1864), S. pedunculosa is a distinct, creeping plant, rooting at nodes with rounded or ovate, obtuse, crenate leaves, sparsely hairy adaxially and, nearly so, abaxially. It is also characterised by elongated, few-flowered cymes, cordate-acute anthers, and 6-ribbed capsules. Trimen (1894) and Lundin (1983) added that these plants have glabrous stems with long internodes, which was evident in Lundin’s ( l.c.) illustration (based on Fagerlind 1229 in S). Clarke (1879), Cogniaux (1891) and Trimen (1894) recorded the extended distribution of S. pedunculosa in Travancore and Quilon by citing specimen Wight 1111. However, Stapf (1892), Willis (1911), Bremer (1987) and Lundin (1983) followed Triana’s treatment and considered this taxon only to occur in Southwest Sri Lanka ( Ceylon).

According to Yoganarasimhan et al. (1976), Wight 1111 should be identified as S. rheedei sensu Wight & Arn. and not S. pedunculosa as stated by Clarke (1879). We studied Wight 1111 at K [ K 001325401] and confirm its identity as S. rheedei . Yoganarasimhan et al. ( l.c.) cited a collection ( Yoganarasimhan 1331) from Charmadi Ghats, Chikamaglur district, Karnataka as S. pedunculosa and according to Giri and Nayar (1986), this should also be identified as S. rheedei . We tried to locate specimen Yoganarasimhan 1331 at K, CAL, and PDA, but to no avail.

Several recent authors also wrongly recorded S. pedunculosa from the Western Ghats ( Sharma et al., 1984; Mohanan & Henry, 1994; Saldanha, 1996; Nayar et al., 2006 Sasidharan, 2004; Manickam et al., 2008; Nayar et al., 2014). Manickam et al. ( l.c.) mentioned its distribution in Tamil Nadu, but we confirmed that the voucher specimen deposited at XCH are Sonerila travancorica Bedd. , not S. pedunculosa . Additionally, we noticed that some recent collections from Chemunji and Koviltherimala in TBGT were also identified as S. pedunculosa . According to Murthy and Nair (2016), S. pedunculosa reported from India by various authors is actually S. rheedei Wight & Arn. This misidentification created ambiguity in the identity and distribution of S. pedunculosa rather than clarifying the confusion. Detailed herbarium studies showed that Thwaites specimens of S. pedunculosa available at different herbaria ( BM, CAL, HUH [ HUH 00073221], BR [ BR 000000522366, BR 000000522398], K [ K 001325399], [ K 001325400], G [ G 00319944], P [ P 04888228, P 05282776, P 05282775] and PDA [ PDA 00002846]) are very distinct from S. lundinii . Further, no collection of this species from other parts of tropical Asia could be located in other Indian and foreign herbaria consulted by us. This study sheds light on the erroneous identification of specimens recorded from Chemunji and nearby areas as reported in local floras, and confirmed the endemism of S. pedunculosa in Sri Lanka.

286 Sonerila lundinii , a new species of Melastomataceae from India