Habenaria adamantina Cruz-Lustre & J. A. N. Bat. 2026, sp. nov.

Habenaria adamantina Cruz-Lustre & J. A. N. Bat. sp. nov. Figs 1, 3, 4, 5 Type BRAZIL – Minas Gerais • Grão Mogol, Parque Estadual de Grão Mogol, Trilha do Barão, depois da Serra do Pagão; 16°32’41”S, 42°53’26”W; 972 m; 22 Dec. 2018; fl.; Cruz-Lustre G. & Gomes M. 407; holotype: BHCB [BHCB 197504]; isotypes: CEN, RB. Diagnosis Habenaria adamantina is morphologically similar to Habenaria australis J. A. N. Bat., A. A. Vale & Menini in its small auricles, but it can be distinguished by the patent lateral sepals (vs deflexed in H. australis) and by the insertion of the anterior petal segment at the base of the posterior segment (vs 3.0– 3.5 mm above in H. australis). It is also similar to Habenaria egleriana, Habenaria sobraliana J. A. N. Bat., A. A. Vale & Menini, and H. sprucei in that the anterior segment of the petals and the lateral segments of the lip are shorter than the posterior segment of the petals and median segment of the lip, respectively. However, it differs in that the auricles are arranged below the rostellum arms and the anther canals. Description Geophytic herb, caulescent, sympodial. Roots and tuber not examined. Stems erect, 13–31 cm long, including the inflorescence, 1.0– 1.6 mm wide. Leaves 3–4 (– 5), spirally alternate, evenly distributed along the stem, blades 20.0–44.0 × 2.5–7.0 mm, sheath-like, reducing in size towards the apex of the stem, linear or lanceolate, membranaceous, base sheathing, sheath closed, apex acute, margin entire. Inflorescence (rachis) (0 –) 0.5–8.5 cm long, spiral, lax; floral bracts ovate or broadly elliptical, 9.9–14.0 × 5.2–6.6 mm, apex caudate, shorter than the pedicellate ovary. Flowers (1 –) 2–3 (– 7), green, resupinate, ascending, glabrous; pedicellate ovary 17.0–27.0 mm long, 1.4–3.3 times longer than the floral bracts; ovary slightly curved, 15.0–19.0 mm long; pedicel 3.0–5.0 mm long. Sepals light green, margins whitish, translucent, slightly smooth; dorsal sepal 6.1–6.7 × 5.4–6.0 mm, concave, widely ovate or orbicular when flattened, apex truncate or mucronulate; lateral sepals 7.2–8.9 × 3.0– 3.4 mm, concave, obliquely ovate or obliquely lanceo-ovate, apex acute, mucronulate, patent, apex somewhat curved upward. Petals bipartite, light green; posterior segment 5.8–7.2 × 1.8–2.4 mm, falcate, adherent to the dorsal sepal, apex acute; anterior segment 4.0–6.1 × 0.3–0.5 mm, filiform, inserted at the base of the posterior segment, apex curved backwards, 0.6–0.9 times the length of the posterior segment. Labellum tripartite, light green; undivided basal part short, 0.2–1.0 mm long; lateral segments 6.7–7.8 × 0.4–0.6 mm, filiform, 0.7–0.8 times the length of the median segment, perpendicular to the medium segment, apex slightly curved backwards; median segment 8.6–10.0 × 1.3–1.8 mm, linear, apex acute or obtuse, apex slightly curved frontwards; spur 15.0–19.0 × 1.9–2.2 mm, slightly clavate, apex often covered by the bract, shorter than the pedicellate ovary, greenish-yellow. Gynostemium 2.5–2.9 mm high, erect; connective green, apex emarginated; lateral appendages (auricles) 1.6 × 0.9 mm, fleshy, verrucose, translucent, apex rounded, positioned below the rostellum arms and the anther canals. Anther bilocular, loculi parallel or slightly convergent, 2.2–2.4 mm high, translucent; canals 1.4–1.7 mm long, parallel, projected forward; pollinarium 3.6–4.1 mm long, separate, pollinia 1.3–1.5 × 0.7–0.9 mm; caudicles 2.1–2.4 mm long, filiform, translucent; viscidium 0.4–0.5 × 0.2–0.4 mm, subglobose, translucent to greyish, 1.6–1.9 mm apart from each other. Stigmatophores (stigma lobes) 2.6 mm long, closely parallel, light green, receptive surface 1.6 × 1.2–1.3 mm each, straight, turned frontwards, reclined almost 45 º in relation to the base, more or less in the same plane as the anther loculi, apex rounded or truncate, inner margin around the spur entrance slightly thickened. Rostellum 2.6–2.7 mm long, light green; midlobe 1.3 mm high, triangular, fleshy, erect, held between the anther loculi, green, apex rounded; side-lobes 1.8 mm long, parallel. Capsules not examined; seeds not examined. Distribution To date, H. adamantina is known from only two localities in Grão Mogol State Park, in Grão Mogol municipality, northern EMR, Minas Gerais state (Fig. 4). Given the rarity of endemism among Neotropical species of the genus (Batista et al. 2023), it is likely that the new species occurs in other localities, such as other nearby mountains or regions of the EMR. Habitat and ecology Habenaria adamantina is found in grassland vegetation surrounded by rocky fields (campo rupestre; see Fig. 5 for an example of the habitat), which are mainly quartzite outcrops, at an elevation of 900–1,200 m a. s. l. (for a detailed characterisation of the environment, see Pirani et al. 2003). It grows in slightly moist, white, sandy soils on the banks of small streams or small puddles of rainwater. It can also grow on the organic matter that accumulates on the rocks in these environments. The areas in which the plants have been found remain moist only during the rainy season and are not usually burned during the dry season. The two collection sites are located at the edge of trails and are fully exposed to sun. The species grows between Cyperaceae, Poaceae, and Velloziaceae, and close to small shrubs. On the Barão Trail, the species forms a compact population composed of numerous closely growing individuals. On the Tropa Trail, the species is scarce, with individuals occurring in isolation. In fact, only five individuals were observed in 2018, with none observed in 2017 (Cruz-Lustre pers. comm.). Habenaria guilleminii Rchb. f. and Habenaria pseudoglaucophylla J. A. N. Bat., R. C. Mota & N. Abreu were observed growing close to the H. adamantina population on the Barão Trail, under similar ecological conditions. Phenology Flowering occurs in December and January, during the rainy season. Etymology The specific epithet is derived from the Latin “ adamas ”, meaning “ diamond ”, and refers to the abundance of these crystals in the Grão Mogol region, which was a major diamond mining area in the late 18 th and early 19 th centuries (Karfunkel et al. 1994; Chaves et al. 2006). Preliminary IUCN conservation assessment The new species is currently known from five collections from two sites within the Parque Estadual de Grão Mogol (Grão Mogol State Park): the Trilha da Tropa and the Trilha do Barão. As the populations are located within an integral protection unit, there are no expected significant impacts from activities such as mining, agriculture, or livestock farming. However, the main trails in the park cross both populations at these sites, making them susceptible to visitor trampling and possible soil erosion, particularly in steeper areas, such as the Barão Trail. Based on the available records, the species’ estimated EOO is 16.9 km ² and its AOO is 16 km ². According to the IUCN Red List Categories and Criteria and their associated guidelines (IUCN 2012, 2016), the reduced EOO and AOO, the small number of individuals in each population, coupled with the fact that the species is only present in two locations, could result in an assessment as Endangered: EN B 1 ab (iii) + 2 ab (iii); C 2 a (i). Notes Since H. nuda was first published by Lindley (1835), around 12 morphologically similar species have been described and included in a species complex (Batista et al. 2011 a, 2011 b). The vegetative and floral morphology of H. adamantina fit the pattern of this species complex. However, unlike most species in the complex, the anterior petal segment and lateral lip segments of H. adamantina are shorter than the posterior petal and median lip segments, respectively (see the key). In this respect, H. adamantina resembles H. egleriana, H. sobraliana, and H. sprucei, also from the complex, but differs in that its flowers are slightly smaller (e. g. dorsal sepal 6.1–6.7 × 5.4–6.0 mm vs 8–12 (– 17) × 8–9 mm, 9–13 mm × 5.5–7 (– 9) mm, and 6.5–8 × 4.5–6 mm, respectively), and in the position of the auricles, which are located below the rostellum arms and the anther canals (vs at the same level in the other three species). It is also restricted to the north of the EMR in the state of Minas Gerais (vs restricted to central Brazil, the Serra Gaúcha in the state of Rio Grande do Sul, and northern Brazil and northern South America, respectively) (Batista et al. 2008, 2012). Another unusual characteristic of H. adamantina in the complex is its small auricles. These are also found in H. australis, but in that species they are at the same level as the rostellum arms and anther canals, whereas in H. adamantina they are below these. The new species also differs from H. australis in having slightly smaller flowers (e. g. dorsal sepal 6.1–6.7 mm long vs 6.4–9.6 mm in H. australis), patent lateral sepals (vs deflexed), and the anterior segment of the petals inserted at the base of the posterior segment (vs 3.0– 3.5 mm above the base of the posterior segment), the less clavate spur (vs clavate), and the rounded to acute apex of the rostellum midlobe (vs obtuse). The geographical distributions of H. adamantina and H. australis also differ; the latter is restricted to the Serra Gaúcha region of the state of Rio Grande do Sul (Batista et al. 2012). Another species of the H. nuda complex, Habenaria fluminensis Hoehne, occasionally has a petal with an anterior segment shorter than the posterior segment. However, the two species are quite distinct and can be easily differentiated by floral size (e. g. dorsal sepal 6.1–6.7 mm long in H. adamantina vs 10–13 mm in H. fluminensis), among several other characteristics. Two additional specimens from Grão Mogol State Park (Bocayuva & Rocha 282 – RB and Meneguzzo 495 – RB, UB) appear to match our proposed morphological circumscription of H. adamantina, suggesting that the species may have been collected in the park during previous expeditions. The habitat, locality, flowering time, habit, ge