Sagina nilagirica Athira & Maya, 2024

Athira, Subramanian, Kanakambika, Govindan, Smitha, Manikandan, Remya, Sivakumaran, Muhsina, Abdul Azeez & Maya, Chandrasekharan Nair, 2024, Sagina nilagirica (Sagineae, Caryophyllaceae), a new species from Nilgiri Biosphere Reserve (Western Ghats, India), Phytotaxa 676 (1), pp. 75-84 : 77-83

Sagina nilagirica Athira & Maya sp. nov. ( Figs. 1–2 ).

Type:— INDIA, Tamil Nadu, Nilgiris district, Doddabetta hills, 11˚ 24’ 01” N, 76˚44’ 10” E, 2615 m a.s.l., 21 December 2020, Subramanian Athira 60 (holotype: MH!, isotypes: CALI!, GVCH!).

Diagnosis:— Sagina nilagirica is morphologically similar to S. procumbens from which differs in the habit (annual vs. perennial), the absence of persistent central rosette of leaves (vs. persistent central rosette of leaves), non-succulent leaves (vs. succulent), upright fruiting pedicel (vs. recurved), lanceolate and glandular pubescent sepal (vs. broadly ovate and glabrous), trigonal bilobed petal (vs. obovate and entire), capsule valves equal to the length of sepal (vs. longer than sepal), reniform, non-grooved seeds with elongate, cog-wheel like epidermal cells (vs. obliquely triangular, grooved, smooth with uniform compressed cog-wheel pattern) ( Table 1; Figs. 3–4 ).

Description:—Annuals, 30–40 mm tall, ascending to decumbent with deciduous central laxly rosette of basal leaves, upper part of the plant body glandular pubescent. Stem laxly branched, spreading or sub-erect, green, glabrous. Stipules absent. Leaves simple, sessile, 3.5–5 × 0.3–0.5 mm, basal leaves in rosette when young; cauline leaves non-succulent, opposite, linear, base truncate, margin entire, apex cuspidate, rarely minute hairs at sheathy base. Inflorescence terminal or axillary. Pedicels 2–7 mm long, erect, with glandular hairs for half the length from base of the flower. Sepals 4(–5), 1.7–2.5 × 0.1–0.7 mm, lanceolate, hooded, margin scarious, obtuse at apex, greenish, glandular pubescent towards base, free from the capsule valve. Petals 4(–5), 0.3–0.4 × c. 0.1 mm, triangular, limb bilobed for half the length with triangular ovate lobes, minutely clawed, base cuneate, white-transparent, inconspicuous, glabrous. Stamens 4, filaments glabrous, 0.7–0.9 mm long; anthers globose, c. 0.1 mm, dorsifixed, light yellow; pollen grains 15–16 µm, spheroidal, poly pantoporate, pores 20–30, surface with unevenly arranged close echinae, inter-echinular distance short, perforations rare. Ovary 0.6–0.7 × 0.5–1.1 mm, ovoid, unilocular, greenish-yellow, glabrous; ovules many, transparent; style 4, 0.2–0.3 mm long, papillose throughout; stigma not distinct. Capsule 4-valved, ovoid, 2.0– 2.5 × 1.0– 1.5 mm, glabrous; valves lanceolate, dehiscing to the base, equal to the length of sepals, yellowish-white. Seeds 0.2–0.3 × 0.1–0.2 mm, reniform, smooth, non-grooved with elongate, cog-wheel like epidermal cells, interdigitating teeth acute or rarely obtuse, brownish-black.

Etymology:—The taxon is named after the type locality, Nilgiri hills, Tamil Nadu, where the rocky crevices of Doddabetta peak form the habitat of this new species.

Distribution and ecology:—The new species was first observed from the type locality (Doddabetta hill, Nilgiris district, Tamil Nadu) where it grows in rocky crevices and open areas at an elevation of 2000–2600 m a.s.l. ( Fig. 5 ). The species is known from only two locations (each with 20–30 individuals).

Phenology:—September to February.

Conservation status:—Both the locations are tourist spots and hence there is risk of human interference. We prefer to avoid IUCN assessment, since Sagina nilagirica could occur in further sites of Western Ghats. Consequently, we considered the category DD (Data Deficient) of IUCN (2012).

Taxonomic key to the Indian species of Sagina :— A diagnostic key follows:

1a. Flowers tetramerous; sepals not appressed to capsule valves during dehiscence ..............................................................................2

1b. Flowers pentamerous; sepals appressed to capsule valves during dehiscence...................................................................................5

2a. Petals absent; anthers red...................................................................................................................................................... S. apetala

2b. Petals present; anthers yellow ............................................................................................................................................................3

3a. Sepals shorter than petals; pistil tricarpellary syncarpous with 3 styles .................................................................................. S. purii

3b. Sepals longer than petals; pistil tetracarpellary syncarpous with 4 styles..........................................................................................4

4a. Fruiting pedicel recurved during capsular development; petals obovate, entire; seeds obliquely triangular............... S. procumbens

4b. Fruiting pedicel upright during capsular development; petals trigonal, bilobed; seeds reniform-globose ...................... S. nilagirica

5a. Stem glabrous, seeds grooved and smooth...................................................................................................................... S. saginoides

5b. Stem glandular pubescent, seeds non- grooved and tuberculate ........................................................................................ S. japonica

Taxonomic notes:—The new species also shows morphological similarities with Sagin apetala by its filiform habit, tetramerous flowers, and upright and pubescent pedicel; however, it differs in lax and erect branching pattern (vs. usually dense and caespitose), leaves with mostly glabrous or minute hairy leaf sheath (vs. long ciliate leaf sheath), lanceolate sepals (vs. ovate-elliptical), trigonal and bilobed petals (vs. absent), reniform and non-grooved seeds (vs. obliquely triangular, grooved), smooth surface covered by elongate, cog-wheel like epidermal cells with acute or rarely obtuse interdigitating teeth, forming shallow ridges (vs. tuberculate with mammillate papillae, ridges absent).

Further, Sagina nilagirica shows some affinities with S. purii in its filiform habit, lanceolate and non-succulent leaves, straight pedicel, ovoid capsule and non-grooved seeds but differs in having lanceolate sepal (vs. ovate-oblong), trigonal and bilobed petal (vs. ovate-oblong, entire) and reniform seed with cog-wheel surface (vs. reniform-pyramidal with warty surface).

Additional specimens examined:— INDIA, Tamil Nadu, Nilgiris district, Rose Garden, Ooty , 11˚ 24’ 20” N, 76˚42’ 32” E, 2285 m, 30 December 2022, Athira & Smitha 190 ( GVCH!) ; Dodabetta peak, 11˚ 24’ 01” N, 76˚44’ 10” E, 2615 m, 31 December 2022, Athira & Smitha 193 ( GVCH!) .

Figures

FIGURE 1. Sagina nilagirica. A. Habitat; B. Habit; C. Leaf; D. Inflorescence; E. Single flower; F. L.S. of Flower; G. Sepal; H. Petal; I. Stamen; J. Gynoecium; K. C.S. of ovary; L. Flower with capsule; M. Capsule; N. Seed (Photos:Athira S).

FIGURE 2. Sagina nilagirica. A. Habit; B. Leaf; C. Inflorescence; D. Sepal; E. Petal; F. Stamen; G. Gynoecium; H. Single flower with capsule; I. Capsule; J. Seed (illustration by Athira S. based on Subramanian Athira 60).

FIGURE 3. Scanning Electron Microscopic images of seed and seed surface. A.&B. Sagina nilagirica; C. & D. S. procumbens; E. & F. S. japonica.

FIGURE 4. Scanning Electron Microscopic images of pollen grain and pollen surface.A.&B. Sagina nilagirica; C. & D. S. procumbens; E. & F. S. japonica.

FIGURE 5. A–D. Habitats of Sagina nilagirica.