Justicia tamilnadensis P.Raja & Soosairaj, sp. nov.

(Figs 1, 2; Table 1).

Justicia tamilnadensis P.Raja & Soosairaj, sp. nov. is morphologically closely allied to Justicia salsoloides T.Anderson. It differs by its herbaceous, slender, purplish-green, glabrous, and angled stem, elliptic-oblong, lanceolate, glabrous, sub-sessile leaves, corolla pubescent on throat within and sub-terete capsules.

TYPUS. — India. Tamil Nadu, Pudukkottai district, Poosathurai, (10°20’58”N, 78°47’22”E), c. 82 m, 11.X.2021, P. Raja & S. Soosairaj 4760 (holo-, RHT!; iso-, MH!).

DISTRIBUTION, HABITAT AND ECOLOGY. — Justicia tamilnadensis sp. nov. is presently known only from the type locality where less than 20 individuals have been observed in open places in Vellar river bed at elevations of 70-85 m and associated with Fimbristylis falcata (Vahl) Kunth, Platostoma menthoides (L.) A.J.Paton, Evolvulus alsinoides (L.) L., Dyschoriste madurensis (Burm.f.) Kuntze, Eragrostis viscosa (Retz.) Trin., Euphorbia corrigioloides Boiss., Leucas diffusa Benth., Curculigo orchioides Gaertn., Cyanotis cristata (L.) D.Don, Vachellia leucophloea (Roxb.) Maslin, Siegler. & Ebinger and Melanocenchris monoica (Rottler) C.E.C.Fisch.

PHENOLOGY. — Flowering and fruiting were observed from July to December.

ETYMOLOGY. — The specific epithet tamilnadensis refers to one of the south Indian states Tamil Nadu from where the specimens were collected.

CONSERVATION STATUS. — Justicia tamilnadensis sp. nov. was observed at only one location which is fragmented by transportation. The total population of this species is enumerated to be less than 20 individuals, and based on the field observation, the conservation status of the species has been evaluated accordingly. We have been surveying the entire Pudukkottai district and the surrounding regions since 2012. And from the entire study in the past decade, it was noted that the proposed species is found only in that specific location (Fig. 3). The geographic range for the Area of Occupancy (AOO) is c. 0.5 km ² and the distribution is limited to the type locality (IUCN 2022). Urbanization, transportation and expansion of the highly invasive Prosopis juliflora (Sw.) DC. threatens the population of this species. Hence, this species is classified in criterion B (AOO) under B2a and B2b and criterion D (number of mature individuals is less than 20) as well to meet the criteria for the Critically Endangered B2ab (ii,iii,v); D.

ADDITIONAL SPECIMEN EXAMINED. — India. Tamil Nadu, Pudukkottai district, Poosathurai, (10°20’58”N, 78°47’22”E), c. 80 m, 09.X.2022, P. Raja 4766 (RHT!).

DESCRIPTION

Prostrate herb, 200-300 mm long; rootstock woody with fleshy roots. Stem prostrate, angled, slender, glabrous, bearded at nodes. Leaves sub-sessile, 9-35 × 3-6 mm, subcoriaceous, elliptic to oblong, opposite, cuneate at base, margins entire on young leaves and occasionally margins undulate on mature leaves, obtusely acute at apex, mid nerve prominent, lateral nerves 3-4, obscure. Inflorescence sub-terminal and terminal spikes, 15-50 mm long, loosely arranged, peduncle 4-10 mm long. Bracts linear-lanceolate, 5-9 × 2-3 mm, base truncate, margin entire, apex acute, ciliate at base. Bracteoles 2, lanceolate, 10-12 × 1.5-2 mm, 3-nerved, nerves obscure, base truncate, margin entire, ciliate at base, acute at apex. Flowers 1 cm long; calyx lobes 5, equal in length, 5 × 1 mm, narrow, linear, cuneate at base, acute at apex, pubescent; corolla 1 cm long, pubescent without; corolla tube 5 mm long, pubescent in throat; bilabiate, upper two-lobed, lobes connate except tip, lower broadly 3-lobed, mid lobe broader than lateral lobes, 4 × 3 mm, purplish inside, lateral lobes 4 × 2 mm, white inside. Stamens 2, exserted; filaments 5 mm long, glabrous; anthers 2-celled, pubescent on upper anther cell, 3 mm long with 1 mm appendage on lower anther cell. Pistil 8 mm long, ovary 2 × 1.5 mm, ovules 4, style slender, 6 mm long, pubescent on basal half, stigma simple. Capsule 12-15 × 5 mm, sub-terete, white tomentose without, shortly mucronate at apex. Seeds 3-4, echinate.

TAXONOMIC COMMENTS

Justicia tamilnadensis sp. nov. and J. salsoloides are restricted in distribution (Carnatic regions of Indian Peninsula). In the field, the habit of J. tamilnadensis closely resembles to that of Lepidagathis cristata Willd. and it could be mistaken in the absence of inflorescences. The rootstock of J. tamilnadensis resembles that of the Justicia trinervia Vahl. There are about 5-7 fleshy roots per plant. Each root is about 100-160 mm long and 2-3 mm wide and deeply rooted to the barren or gravel soil up to 200 mm in depth. The tuberous root system enables the persistent stem to tolerate the dry season.