Tarenna flava Alston (1931: 150)

Nair, Maya Sukumaran, Prabhukumar, Konickal Mambetta, Pillai, Sunilkumar Trivikraman & Chhabra, Tarun, 2022, Revisiting The Taxonomy Of Tarenna Flava Alston (Rubiaceae: Ixoroideae), Phytotaxa 574 (3), pp. 251-258 : 252-256

Tarenna flava Alston (1931: 150) . ( Figures 1 & 2 )

Type (lectotype, designated here):— Ceylon (= Sri Lanka). Nuvara Eliya , 6000 ft, s.d., Gardner 337 K000031409 [digital image!]; isolectotype, BR532715 [digital image!] Figure 3 .

Heterotypic synonym: Stylocoryna webera A. Rich (1834: 248) var. montana Thwaites (1859: 158) .

Type (lectotype, designated here):— Ceylon (= Sri Lanka). s.d., Thwaites 158 K000031410 [digital image!]; isolectotypes, K000031411 [digital image!], BM014118049 [digital image!], P02273269 [digital image!], P03804015 [digital image!], P03804014 [digital image!], BR000000532748 [digital image!], BR000000552374 [digital image!]. Figure 4 .

Description: Erect shrub, 3–12 m tall. Stem branched, woody, angular, green, glabrous; internodes 1.2–3 cm long. Stipules interpetiolar, linear, 6.9–7 × 5.9–6 mm, base broad, margin entire, acute at apex, green, glabrous. Leaves porrect, petiolate; petioles 1–1.1 cm long, thick, green, glabrous; lamina leathery, elliptic, 7–11 × 3.5–6 cm, base attenuate, margins entire, apex acuminate, dark green, turns dark brown on drying, glabrous on both sides; midrib canaliculated on upper surface, secondary veins 8–11 pairs, glabrous. Inflorescence terminal, corymbose cymes; 24– 27 flowers, peduncle glabrous, 1.8–2 cm long, thick; bracts and bracteoles distinct; bracts lanceolate, 6–6.5 mm long, glabrous; bracteoles short, ca. 1mm long, scale like, glabrous. Pedicel terete, 1.8–2.1 mm long, shiny, glabrous. Flower hermaphrodite, pentamerous, homostylous, 14–17 mm long, white to yellowish-white, glabrous; flower bud green at apex, remains white and covered with waxy exudation. Calyx cup-shaped; lobes 5, lanceolate, 4–5 mm long, apex acute, margin entire, green, glabrous. Corolla infundibuliform, 10–12 mm long, white to yellowish-white, glabrous outside; corolla tube short, completely concealed in the calyx cup, throat and basal part of lobes are pubescent; lobes ovatelanceolate, 5–6 × 2.5–3 mm, prominently veined. Stamens 5, eipetalous, exerted; filaments inconspicuous, ca. 0.15 mm long, arising from the corolla tube hair ring, glabrous; anthers oblong, ca. 5 mm long, connective mucron curved outwardly with extended protrusion. Style short, stout, 3–4 mm long, glabrous; stigma club shaped with longitudinal grooves, 2.9–3.2 mm long, glabrous. Disc cylindrical, 0.2–0.3 mm long, glabrous; ovary 2-celled with many ovules in each cell, glabrous. Fruit berry, bilocular, globular, 0.6 × 0.6 cm, calyx persistent, dark green, glabrous always. Seeds 6–8, angular, black at maturity.

Phenology: Flowering October–April, Fruiting December–June.

Distribution and Ecology:— Restricted to Sri Lanka and south India (so far collected from Kerala and Tamil Nadu). In the protologue, Alston (1931) mentioned the distribution area as south India without any precise locality. Since then, no representative collections were made by any subsequent researchers from south India untill the collection by Matthew from Palni hills of Tamil Nadu (1999). Recently, Murugan (2020) discussed the distribution of Tarenna flava in Kerala based upon the voucher specimens deposited in TBGT herbarium from Agasthyamala hills of Thiruvananthpuram district collected by Mohanan in 1988. But an elaborated taxonomic description along with colour photographs still lacking for this taxon yet, to delineate the species from its close resemblance Tarenna asiatica . During the present study, we succeded to collect and record many more good populations in high altitude forests ranges of Elival hills of Muthikulam, Palakkad district of Kerala; Pettimudi, Idukki district of Kerala and different forest regions of Nilgiris in Tamil Nadu. During the field investigation it is also observed that, in Elival hills, the plants are grown in the patches of shola grass lands and grows upto a height of 3 m. But in Nilgiris, they are grown into a tree like habit in the evergreen forest’s patches and shola upto a height of 12 m. In Pettimudi they are growing as tall shrubs upto a height of 3m in the patches of evergreen forests.

Taxonomic Affinity:— Tarenna flava differs from T. asiatica by its porrect leaves (vs. non porrect), glabrous petiole (vs. puberulous), 24–27 flowers per inflorescence (vs. 50–65), glabrous pedicel and calyx (vs. puberulous), presence of waxy exudation on the young flower bud (vs. without waxy exudation), completely concealed corolla tube in the calyx cup (vs. partially protruded out), anther connective extened and protruding out (vs. very short protrusion), fruit with persistant calyx (vs. calyx deciduous at maturity), 6–8 seeds per fruit (vs. 4–5). More delineation attributes are provided in Table 1 .

Specimens examined:— INDIA. Kerala: Palakkad district, Elival hills, Muthikulam, 1845 m, 10°56’12” N, 76°38’26” E, 22 November 2013, K. M. Prabhukumar 7667 (CMPR); 11 November 2016, K. M. Prabhukumar & P. M. Binu Prakash 9898 (CMPR). Idukki district, Thekkadi, 1650 m, 25 February 2021, Maya S. Nair 5031 (SD College Herbarium); Munnar, Pettimudi outpost, 1852 m, 27 February 2022, Maya S. Nair 11143 (KUBH); Thekkadi to Devikulam, 1500 m, 16 June 1976, A. J. G. H. Kostermans 26129 (L). Thiruvananthapuram district, way to Agastyarkudam, 900 m, 05 March 1980, M. Mohanan 66036 (MH); Pongalapara, 1500 m, 07 February 1988, N. Mohanan 9510 (CALI & TBGT). Tamil Nadu: Near Border semi evergreen forest, close to 43/ 5 mile marker, 19 October 1974, D. D. Tirvengadum & A. J. G. H. Kostermans, 718/118 (L); Palni Hills, 1700–2100 m, s.d., K. M. Matthew 52511 (RHT).

SRI LANKA. Nuwara Eliya , 1850 m, 17 June 1969, C . F . Beusekom & R . J Beusekom 1398 ( US) ; Pidurutalagala , Nuwara Eliya District, Central Province, 1990 m, 22 September 1974, D. D. Tirvengadum & Shelton Waas 546 ( K) .

Lectotypification of the names Tarenna flava and Stylocoryna webera var. montana

Alston (1931) proposed the name Tarenna flava based on the Gardner’s collection from Nuvara Eliya , Sri Lanka (Ceylon), and he also mentioned “ Also in S. India ”. It appears that, Alston may also be seen the specimens from south India while describing the novelty. But our efforts to trace out any specimen from south India before 1931 in any of the repositories either in India or abroad are in vain. During the study, we have traced out the multiple sheets of Gardner’s homogenous collection from K ( K000031409 ) and BR ( BR 532715 ) herbaria. Of which, the specimen kept in K, with barcode K000031409 is well preserved and perfectly fit with the protologue (having fruits with persistent calyx), which is designated here as lectotype .

During the study, it is also noticed that, the name Stylocoryna webera A. Rich var. montana Thwaites is presently considered as a synonym of T. asiatica ( POWO 2022) . But the persistent calyx on fruits clearly distinct the former from the latter. Hence the former should be considered as a synonym under the name T. flava . Thwaites proposed the var. montana in 1859 based on collection (collection number 158, Ceylon Plants Number 1649) from Sri Lanka. In the protologue, Thwaites mentioned that, the proposed variety is very abundantly distributed in the Islands and other more elevated localities than var. webera . During the present study, we have traced out the multiple sheets of this homogenous collection from Kew (K000031410, K000031411), The Natural History Museum (BM014118049), Meise Botanic Garden Herbaria (BR000000532748, BR000000552374) and Paris (P02273269, P03804015, P03804014) herbaria respectively. Of which K000031410 is perfectly matching with the protologue with well preserved reproductive parts (flower buds and fruits) is considered to be the best choice and designated here as the lectotype.

Figures

FIGURE 1. Tarenna flava. A. Habit (Tree from); B. Habit (Shrubby); C. Single flower (Inset); D. Inflorescence; E. Infructescence.

FIGURE 2. Tarenna flava. A. Flowering twig; B. Stipule (inset); C. Inflorescence; D. Flower; E. Calyx; F & G. Corolla with stamens; H. Gynoecium with calyx; I. Gynoecium; J. C.S. of Ovary; K. Fruit; L. L.S. of Fruit.

FIGURE 3. Digital image of the lectotype designated for the name Tarenna flava. ©copyright of the Board of Trustees of the Royal Botanic Gardens, Kew.

FIGURE 4. Digital image of the lectotype designated for the name Stylocoryna webera var. montana. © copyright of the Board of Trustees of the Royal Botanic Gardens, Kew.