Plectranthus sahyadricus Smitha & Sunojk., 2018

Smitha, Kokkaraniyil & Sunojkumar, Purayidathkandy, 2018, Plectranthus sahyadricus (Lamiaceae): a new species from Western Ghats, India, Phytotaxa 345 (2), pp. 165-169 : 166

Plectranthus sahyadricus Smitha & Sunojk. , sp. nov. ( Fig. 1 )

Plectranthus sahyadricus is similar to P. beddomei Raizada (1958: 503) , but differs in the presence of ring of hairs at young nodes (vs. ring of hairs absent); leaves base rounded to cordate, 6–13 × 3–11 cm (vs. base rounded to cuneate, 14–26 × 11–25 cm); inflorescence up to 20 cm long, green, cymes 1–4 cm long, 5–10-flowered (vs. up to 40 cm long, purple, cymes 4–8 cm long, 10–20-flowered); flower 8–10 mm long, off-white, anterior lip ovate, not fully opened, form an inverted dome over mouth (vs. 18–22 mm long, purple, anterior lip fully opened and boat shaped); calyx 2.5–3.5 × 2–3 mm at anthesis, 4–5 × 3–4 mm in fruit, green (vs. 3–4 × 2–3 mm at anthesis, 4–8 × 3–5 mm in fruit, dark purple); fruiting calyx tube almost straight, 1–2 mm long (vs. fruiting calyx tube recurved, 1.5–3 mm long); corolla tube 5–7 mm long, long white hairs inside (vs. 10–13 mm long, inside glabrous); disc 0.5 mm long, smaller than ovary (vs. 1 mm long, larger and exceeding ovary)

TYPE:— INDIA. Kerala: Idukki district, Munnar, Lockhart Gap view point, elev. 1600 m, 21 September 2015, Smitha & Sunojkumar 135456 (holotype CALI!, isotypes CALI!).

Erect annual herbs, up to 60 cm tall. Stem fleshy, light green with purple spots, branches quadrangular, winged, glabrous, internodes 2–4 cm, a ring of hairs at young nodes. Leaves membraneous, cordate, 6–13 × 3–11 cm, apex acuminate, base rounded to cordate, margin mainly crenate, sometimes doubly crenate, 13–30-pairs of tooth, upper surface glabrous, lower surface slightly pubescent along veins, 6–8-nerved, venation eucamptodromous; petioles fleshy, ridged, 5–9 cm long, light purple, upper side slightly pubescent. Inflorescence terminal, up to 20 cm long, without basal branches, light green colored, axis fleshy, pubescent with simple hairs; floral nodes 1–2 cm apart, cymes 1–4 cm long, pedunculate, producing lax lateral cincinnal, 5–10-flowered, peduncle 2–4 cm long; bracts caducous, cordate, 4–5 × 2.5–3 mm, apex acuminate, margin ciliate, pubescent along margins; bracteole absent; flower 8–10 mm long, off-white; pedicels slender, 2 mm long at anthesis, 3 mm in fruit, pubescent. Calyx green, campanulate, 2.5–3.5 × 2–3 mm at anthesis, enlarges up to 4–5 × 3–4 mm in fruit, tube 1–2 mm long, 10-nerved, inside glabrous, pubescent with sessile glands outside; posterior lip broad, ovate, decurrent to tube, apex acute-rounded, margin ciliate, ca. 2 × 2 mm at anthesis, ca. 3 × 2 mm in fruit, inside glabrous, pubescent with sessile glands outside; teeth of the anterior lip lanceolate, margin ciliate, lateral teeth smaller than median teeth, 2 mm long at anthesis, 2.5 mm in fruit, median teeth 2.5 mm long at anthesis, 3 mm in fruit, pubescent with sessile glands outside. Corolla off-white, 7–9 mm long, 4 mm in diameter, pubescent; tube 5–7 mm long, sigmoid below the middle, gradually dilated towards base, widely expanded at throat, long white hairs inside; posterior lip 4 lobed, lobes rounded at apex, pubescent, median lobes (1 × 1 mm) larger than lateral lobes (0.5 × 0.5 mm); anterior lip ovate, not fully opened, form an inverted dome over mouth to partially close opening, ca. 3 × 2 mm, concave, long hairs along inner margin, pubescent with sessile glands outside. Stamens free, anterior pair attached at the mouth of corolla tube, posterior pair attached just below anterior but not united, filament of posterior pair 1.5 mm long, anterior pair 2 mm long, included in anterior lip; anthers bilobed, dorsifixed, ca. 1 mm long, yellowish, dehisces longitudinally. Disc anterior side enlarged, white, 0.5 mm long, smaller than ovary; ovary 1 mm high; style sigmoid, ca. 5 mm long, glabrous; stigma bifid with equal branches.

Phenology:—Flowering and fruiting from September to January.

Etymology:—The species is named after the type locality, Western Ghats which is also known as ‘Sahyadri’ in regional Malayalam language (It was collected from Lockhart Gap view point of Idukki district).

Distribution, habitat and ecology:— Plectranthus sahyadricus is known only from Lockhart gap view pont, Munnar, Idukki district, southern Western Ghats. The plants grow on wet rocky surfaces and sides amidst mosses, at an elevation of ± 1600 m.

Additional specimens examined (paratypes):— INDIA. Kerala: Idukki district, Munnar, Lockhart Gap view point, elev. 1600 m, 13 August 2017, Smitha & Sunojkumar 135477 (CALI!)

Conservation status:— P. sahyadricus was collected from Lockhart Gap view point, Munnar in southern Western Ghats. In the present collection, very few mature plants (less than 30) are noticed at a height of 1600 m. near a tourist place. This species was found in a single location and this area is prone to severe grazing and other disruptive people activities like tourism and widening of roads. Thus the habitat is under severe threat. The extent of occurrence for P. sahyadricus was less than 100 km 2. Therefore, we suggest that P. sahyadricus should be evaluated as critically endangered, CR [B1a, b (ii, iii) + D] according to the IUCN (2012) categories and criteria.

Discussion:—After critical examination with live specimens of similar species, we found that Plectranthus sahyadricus is morphologically very similar to P. beddomei in its stem and leaf structure, but differs in ring of hairs at young nodes, smaller leaves, rounded to cordate leaf base, length of cyme, fewer number of flowers per cyme, structure of the fruiting calyx tube, corolla with anterior lip not fully opened, form an inverted dome over mouth, presence of hairs in the corolla tube and size of the disc. The new species also shows similarity with Plectranthus anamudianus Smitha & Sunojkumar (2016: 51) , in its inflorescence architecture but differs mainly by its habit, nature of stem, size and shape of leaves and floral characters like structure of the bract, flower and calyx. The most important diagnostic characters and comparisons between P. sahyadricus , P. beddomei and P. anamudianus are given in Table 1.

Figures

FIGURE 1. Plectranthus sahyadricus. A. Habit; B. Flower; C. Corolla; D. Corolla tube opened; E. Flowering calyx; F. Calyx opened; G. Bract; H. Corolla upper lip; I Corolla lower lip; J. Stamen; K. Ovary; L. Fruiting calyx.