Glechon rupestris L.Luz & Bordignon, 2025

Luz, Laura, Bordignon, Sérgio Augusto De Loreto & Thode, Verônica, 2025, Novelties in Glechon (Lamiaceae): Two new species endemic to Rio Grande do Sul (Brazil), Phytotaxa 697 (3), pp. 265-273 : 267

Glechon rupestris L.Luz & Bordignon , sp. nov. ( Figures 1–3 )

Type:— BRAZIL. Rio Grande do Sul: Pinheiro Machado, Torrinhas, 235 m, 31°13’31.33”S, 53°29’55.36”W, 19 November 2023, L. Luz & S. Bordignon 125 (holotype ICN!, isotypes RB!, MBM!).

Species most similar to Glechon thymoides due to comparable leaf size, shape, venation and indumentum, but distinguished by the antrorse stem indumentum (vs. retrorse), longer floral bracteoles 3.7–4.0 mm long (vs. 0.3–0.4 mm long) and calyx with unequal elongated lobes 4.2–4.7 mm long (vs. subequal lobes 0.5–1.0 mm long).

Herbs to subshrubs, aromatic, 20−50 cm high; Stem erect to decumbent, with few ramifications towards the apex, main stem thin and only woody at the base, 1.5−2.3 mm diam., older stems rounded at the base, younger stems quadrangular, pubescent with antrorse trichomes. Leaves simple, spreading along the branches, opposite, petiolate; blade 1.0−1.3 × 0.4−0.7 cm, vivid green, membranous, concolorous, ovate to oblanceolate, base attenuate, apex acute to round, adaxial surface pubescent with appressed trichomes, venation almost invisible, abaxial surface pubescent with appressed trichomes slightly longer than in adaxial surface, camptodromous venation, primary and secondary veins plane although visible, margins serrate, entire towards the base, 1−2 teeth on each side of leaf, sometimes unequally distributed; petiole 1.6−5.4 mm long, pubescent with appressed trichomes. Flowers solitary in the axil of leaves, peduncle 0.5−0.6 mm long; bracteoles leaflike with mid vein, lanceolate, 3.7−4.0 mm long; calyx at anthesis 5.6−6.6 mm long, tube 1.6−2.2 mm long, campanulate, externally pubescent, tube 10−13-nerved, internally glabrescent with a ring of white hairs at throat, lobes 4.2−4.7 mm long, subequal, lanceolate, calyx in fruit 3.7−4.8 mm long; corolla white to pale yellowish, 9.0− 9.4 mm long, tube 5.0−6.0 × 2.8−3.2 mm, externally pubescent, upper lobes falcate, white to yellowish, sometimes vinaceous, lower lobes patent, white to yellowish, sometimes vinaceous, with lilac to purplish spots in the mid lobe; stamens included, filaments white, glabrous, thecae divergent, dark purple; gynoecium with style curved, stigma exserted, bifid, unequal lobes, lower lobe longer than upper lobe. Mericarps 4 (sometimes 2–3 for abortion), 0.8−0.9 × 0.3−0.4 mm, dark castaneous when mature, ovoid-oblong, rugulose, shiny, with short thin white trichomes, with deep white abscission scars at the cuneate base, mucilaginous when wet.

Additional Specimens Examined (Paratypes): — BRAZIL. Rio Grande do Sul: Pinheiro Machado, Torrinhas , 236 m, 31°13’31.00”S, 53°29’56.00”W, 6 September 2019, S. Bordignon 5889 (UNILASALLE!) ; ibidem, 236 m, 31°13’31.00”S, 53°29’56.00”W, 11 October 2019, S. Bordignon et al. 5987 (UNILASALLE!); ibidem, 233 m, 31°13’31.40”S, 53°29’53.50”W, 31 October 2020, S. Bordignon 6191 (ICN!); ibidem, 235 m, 31°13’28.78”S, 53°29’36.17”W, 19 November 2023, L. Luz & S. Bordignon 126 (ICN!).

Etymology: —The specific epithet was chosen in reference to the species habitat, which only occurs in a rocky outcrop of the region campos rupestres.

Distribution and habitat: — Glechon rupestris is only known from one location, where it grows along a rocky outcrop. The area is located within the Pampa grasslands in southern Rio Grande do Sul state at elevations between 200 and 235 m ( Figures 1–3 ).

Preliminary conservation status: —The species can be assessed as critically endangered (CR) based on criteria and sub-criteria B1ab(i, ii, iii) + B2ab(i, ii, iii) of IUCN (2012). This classification is based on its highly restricted distribution, including extent of occurrence (EOO = 0.006 Km²), area of occupancy (AOO = 4 Km²), and a very limited number of known locations. The species is restricted to rocky outcrops and hillside habitats and has been documented exclusively in the district of Torrinhas, located in the municipality of Pinheiro Machado ( Figure 3 ). This region is isolated and falls outside any legally protected areas (MapBiomas 2025), leaving the species at significant threat. The absence of conservation measures increases the risk of extinction, as it remains exposed to potential extreme climatic events or environmental degradation.

Notes: — Glechon rupestris is similar to G. thymoides Sprengel (1827: 222) and can be distinguished by stem indumentum, antrorse in Glechon rupestris and retrorse in G. thymoides . Glechon rupestris possesses long lanceolate floral bracteoles 3.7–4.0 mm long, whereas these are linear and inconspicuous in G. thymoides (0.3–0.4 mm long). The calyx of Glechon rupestris is distinguished by the unequal and elongated lobes (4.2–4.7 mm long), compared to the short subequal lobes of G. thymoides (0.5–0.8 mm long). Glechon rupestris grows parapatric with G. thymoides , nonetheless the latter also inhabits northeast Argentina (Misiones) and Uruguay (Cerro Largo) and has a broader distribution in Rio Grande do Sul state extending its distribution to Santa Catarina and Paraná states (speciesLink 2025, POWO 2025). Glechon rupestris and G. thymoides are mainly distinguished by the features listed in Table 1.

Figures

FIGURE 1. Distribution map for Glechon rupestris L.Luz & Bordignon and Glechon villosissima L.Luz & Bordignon.

FIGURE 2. Glechon rupestris L.Luz & Bordignon. A. Inflorescence with flowers in anthesis. B. Habit. C. Branch showing leaves and calyx. D. Branch with flowers. E. Adaxial leaf surface. F. Abaxial leaf surface. G. Antrorse stem indument. H. Flower. I. Bracteoles. J. Mericarps. (Photos: A to D by Sérgio Bordignon, E to J by Laura Luz). Scale bars: 1 mm (G to J).

FIGURE 3. Habitats of Glechon rupestris L.Luz & Bordignon and Glechon villosissima L.Luz & Bordignon. A, B. Rocky outcrops where G. rupestris occurs. C. Dry grasslands where G. villosissima occurs. D. Native grasslands (left) where Glechon villosissima occurs and soy monocultures (right), highlighting the contrast and the threat of soy expansion to the native biodiversity. A–D. Photos by Laura Luz.