Justicia tanalensis S. Moore (1906: 220). (Figs. 1, 2, 3)

Type:— MADAGASCAR. Fianarantsoa, Amoron’i Mania, Ambositra, Tanala, Ambohimitombo Forest, 1350–1450 m, 27 November, 1894, Forsysth-Major 414 (lectotype designated here!: BM [BM000931344], Fig. 2, digital image!).

Terrestrial or lithophytic, prostrate, rhizomatous herbs, up to 70 cm long. Rhizome trailing with adventitious roots. Stems branched, with internodes 0.5–2.5 cm long, sparsely pubescent with short brown hairs. Petiole 1–2.2 mm long, sparsely pubescent with short brown trichomes; leaf blades dark green above, whitish-green or greyish-green below, lanceolate, 5–15 × 2–6 mm, base obtuse to rounded, margin entire, apex attenuate or sometimes mucronate apiculate, both surfaces sparsely pubescent with sparse hairs along main veins, more numerous along margins, hairs brown; cystoliths linear; lateral veins 3–4 pairs, brochidodromous, ascending. Inflorescences of axillary, spiciform cymes, 1.5–3.5 cm long, axes sparsely pubescent with short spreading translucid eglandular hairs. Bracts linear, ca. 0.3 mm long; bracteoles longer than bracts, linear or ensiform, often curved, ca. 0.5 mm long, both sparsely with short indumentum. Calyx divided into 4 subequal lobes, lobes linear-lanceolate, ca. 3 mm long, ornamented with black dots, sparsely pubescent. Corolla ca. 7 mm long, white, with purplish marking in throat; tube with basal conic portion ca. 4 mm long; limb 2-lipped, upper lip of two slightly rounded lobes ca. 3 mm long; lower lip divided into 3-lobes, lateral lobes rounded, median lobe slightly elliptic, ca. 2 mm long. Stamens included within corolla tube, inserted ca. 2 mm from base of corolla; filaments ca. 2 mm long; anthers ca. 0.5 mm long. Ovary dark brown, ca. 0.3 mm, glabrous; style brown, ca. 4.7 mm long, with very sparse short hairs; style ca. 4.2 mm long; stigma with one expanded, flattened small lobe. Capsule brown, 2-seeded, ca. 4 × 1.2 mm, sessile, surface glabrous, slightly verrucose; seed brown, rounded, ca. 0.2 mm diameter, surface slightly verrucose and glabrous.

Phenology:— Flowering from September to January.

Distribution and ecology:— The species is found at Antavolobe Iaroka forest, Moramanga in Alaotra-Mangoro region and in Ambohimitombo forest, Ambositra in Amoron’i Mania region, central highland of Madagascar (Fig. 4). This region is described by Moat and Smith (2007) as mid-elevation humid forest. It grows on mossy rock outcrops. There is a possibility that Justicia tanalensis occurs in further adjacent areas that have not yet been fully explored.

Conservation status:— Justicia tanalensis is known only from three collections from Antavolobe Iaroka and Ambohimitombo forests, occurring within two threat-defined locations in the central highland mid-elevation forests of Madagascar. But regarding the potential range of its distribution, the species may occur along the forest corridor between the two locations with an EOO; defined as the area contained within the shortest continuous imaginary boundary which can be drawn to encompass all the known, inferred or projected sites of present occurrence of a taxon, excluding cases of vagrancy (IUCN, 2014), of 5,894 km 2 and an AOO, defined as the area within its extent of occurrence, which is occupied by a taxon, excluding cases of vagrancy (IUCN), of 28 km 2 automatically calculated using the Kew’s GeoCat (http://geocat.kew.org/; Bachman et al. 2011) platform, estimated from the currently known localities. From its range, the major threat of this species is the habitat loss due to bushfire, illegal logging and slash and burn agriculture. Hence, this species should be assessed as Endangered under the criterion EN B2ab (I, II, III), following the categories and criteria of the IUCN (2014).

Additional specimens examined:— MADAGASCAR. Fianarantsoa: Ambositra, Tanala, Ambohimitombo Forest, 1350–1450 m, 19 January 1895, Forsyth-Major 414 (BM, K); Toamasina: Alaotra-Mangoro, Moramanga, Antavolobe Iaroka Forest, 19º01′32.49″S; 48º26′28.29″E, 1150 m, 24 September 2019, OLG 1501 (TAN, HIB); same locality, 12 November, 2019, SAJIT 3367 (TAN, HIB).

Lectotypification:— Justicia tanalensis was described by Moore (1906) based on the collection Forsyth-Major 414 collected from Ambohimitombo forest, Tanala, District of Ambositra, region of Amoron’i Mania, province of Fianarantsoa. In searching the online herbarium, two herbarium sheets were traced at herbaria BM and K respectively. On the sheet at BM, it includes two different specimens collected on 27 November 1894 (BM000931344) and 19 January 1895 (BM0009313690), which are separated by pencil lines (Fig. 2). The sheet at K consists of only one specimen collected on January 19, 1895 (K000378558, Fig. 3). According to Art. 8.2 Footnote 2 of the ICN, the collection Forsyth-Major 414 comprises two different gatherings collected at the same locality with same collection number but at different time. According to Art. 9.6, all of them are syntypes since the original author did not indicate any one as the holotype, and they may be the candidate of the lectotype. Among these specimens, the duplicate BM000931344 is selected to serve as the lectotype for the name J. tanalensis here, because it is the best one with the complete flower preserved and bears a label printed the phrase “type specimen” by the haberium manager even though it has not yet effectively published.

Systematic notes:— The recent molecular evidence indicates that the genus Justicia is paraphyletic whereas the genus in the New World is monophyletic (McDade et al. 2000; Kiel et al. 2017). Morphological and color traits of the flowers, as well as the shape, the size and the inflorescence type, are highly diverse (Kiel et al. 2017). According to the work of Rueangsawang et al. (2019), the genus is sister to subtribe Diclipterinae including Peristrophe Nees (1832: 112), which was transferred to Dicliptera Jussieu (1807: 267) by Darbyshire & Vollesen (2007), and Hypoestes Sol. ex Brown (1810: 474). Furthermore, J. tanalensis belongs to the sect. Rostellaria Anderson (1863: 38), one of the sixteen sections described by Graham in 1988, which is characterized by an inflorescence with a simple spike with two or a single flower per node, the axis eglandular, and the bracts are narrowly triangular, shorter than the calyx. As well, this section is sister to the sect. Harnieria (Solms 1867: 109) Bentham (1867: 1109) and sect. Monechma Hochstetter (1841: 374) from the Old World (Kiel et al. 2017). Morphologically, J. tanalensis is close to J. delicatula Scott Elliot (1891: 39) where the type was recorded in Fort-Dauphin (Taolagnaro), South East of Madagascar but with some differences from J. delicatula by the leaf shape being lanceolate, smaller, apex attenuate or sometimes mucronate apiculate, sparsely covered by cystoliths and sparsely pubescents, petiole 1–2.2 mm long. The inflorescence is 1.5–3.5 cm long, calyx is sparsely pubescent. J. delicatula is erect, with broader leaves, ovates, with presence of prominent raphids on both sides, larger nerves reddish-yellow, spikes 1.5–2.5 cm long; capsules 6 mm long, seeds ovoid, echinulate.