Glechon villosissima 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 : 269-270

Glechon villosissima L.Luz & Bordignon , sp. nov. ( Figures 3 , 4 )

Type:— BRAZIL. Rio Grande do Sul: Jari, Estrada Passo da Maria Inácia, 381 m, 29°18’13.93”S 54°10’36.48”W, 27 January 2024, L. Luz & S. Bordignon 149 (holotype ICN!, isotypes RB!, MBM!).

Species most similar to Glechon spathulata due to comparable leaf size and shape, venation, and leaf margin but distinguished by the villous indumentum (vs. pubescent), presence of peduncles 0.8–1.0 mm (vs. sessile flowers), longer floral bracteoles (1.0–2.0 vs. 0.8–1.0 mm long), and calyx with unequal elongated lobes, 2.5–3.4 mm long (vs. subequal lobes 0.5–0.8 mm long), and dark castaneous mericarps covered with long white trichomes (vs. ochre and glabrous).

Herbs to subshrubs, slightly aromatic, 30−100 cm high; Stem erect, with few ramifications towards the apex, main stem thickened and woody at the base, 2.0−5.0 mm diam., older stems rounded at the base, younger stems quadrangular, villous with patent trichomes. Leaves simple, mostly congested near the apex or somewhat spreading along the branches, opposite to fasciculate, short petiolate; blade 0.6−1.6 × 0.6−1.5 cm, pale green with whitish aspect due to a dense covering of long trichomes, membranous, concolorous, obovate to ovate-spathulate, base attenuate, cuneate or truncate, apex acute to round, adaxial surface villous, venation prominent, abaxial surface villous, trichomes distinctly elongated along the midvein and secondary veins, palmately veined, venation prominent, margins slightly revolute with trichomes, crenate to serrate, entire towards the base, 2−4 teeth on each side, sometimes unequally distributed; petiole 2.5−5.0 mm long, villous. Flowers solitary in the axil of leaves, peduncle 0.8−1.0 mm; bracteoles inconspicuous linear, 1.0−2.0 mm long; calyx at anthesis 5.0− 5.5 mm long, tube 1.5−2.2 mm long, campanulate, externally villous, tube 13−15 nerved, internally glabrescent with a ring of white hairs at throat, lobes 2.5−3.4 mm long, unequal, two lipped (3/2), deltate with a long attenuate apex, apex straight to curved, calyx in fruit 3.8−4.5 mm long; corolla white to pale lilac, 8.0− 9.7 mm long, tube 3.0−3.5 × 1.4−2.3 mm, with a small hump at the base of the lower lip, externally villous; upper lobes falcate, white often with lilac blotch internally; lower lobes patent, white with lilac to purplish blotches and spots, usually darker in the mid lobe; stamens included; filaments white, glabrous; thecae divaricate, dark purple; gynoecium with style curved, stigma exserted, bifid, unequal lobes, lower lobe longer than upper lobe. Mericarps 4 (sometimes 2–3 for abortion), 0.9−1.0 × 0.4−0.5 mm, dark castaneous when mature, ovoid-oblong, rugulose, shiny, villous, with long sparse trichomes, with deep white abscission scars at the cuneate base, mucilaginous when wet.

Additional Specimens Examined (Paratypes): — BRAZIL. Rio Grande do Sul: Vacaria, no Aeródromo , 912 m, 28°25’38.66”S, 51°01’34.78”W, 16 December 1932, L. Rambo 3006 (ICN!) ; Tupanciretã, B. Vista da Serra , 464 m, 29°04’50.44”S, 53° 50’ 11.56” W, 27 January 1942, L. Rambo 9464 (ICN!) ; Itaara, Reserva Biológica do Ibicuí-Mirim- Barragem de Saturnino , 441 m, 29°32’59.24”S, 53°48’25.13”W, 06 July 1982, O. Bueno 3555 (HAS!) ; ibidem, 19 July 1988, O. Bueno 5448 (HAS!); ibidem, 09 November 1988, N. Silveira 5893 (HAS!); ibidem, 09 November 1988, M. Neves 1069 (HAS!); ibidem, 09 November 1988, M.L. Abruzzi 1647 (HAS!); ibidem, 03 October 1989, M.L. Abruzzi 1828 (HAS!); ibidem, 03 October 1989, N. Silveira 6878 (HAS!); ibidem, 05 July 1990, N. Silveira 7651 (HAS!); ibidem, 08 November 1990, O. Bueno 6033 (HAS!); Toropi, Boca da Picada , 330 m, 29°25’54.73”S, 54°13’59.93”W, 09 April 2000, A. Knob & S. Bordignon 7175 (UNILASALLE!) ; Quevedos , estrada depois da rótula com letreiro de Quevedos, 322 m, 29°19’24.60”S, 54°08’56.40”W, 27 January 2024, L. Luz & S. Bordignon 152 (ICN!) .

Etymology: —The specific epithet is derived from Latin, meaning “most villous” or “densely covered with hairs”, in reference to the plant’s indumentum, which is entirely covered by a dense layer of white trichomes.

Distribution and habitat: — Glechon villosissima is known from five municipalities, four are located in the center of Rio Grande do Sul state, in the Pampas grasslands with elevations around 300 m. There is only one record for the municipality of Vacaria, northeastern state region, in high altitude grasslands with elevations around 900 m ( Figure 1 ). We recently made field expeditions to this region in search of this taxon, but without success.

Preliminary conservation status: —The species can be assessed as endangered (EN) based on criteria and subcriteria B1ab(i+ii+iii) + B2ab(i+ii+iii) IUCN (2012), because of the restricted extent of occurrence (EOO = 8,512 km ²) and area of occupancy (AOO = 24 km ²) and declining habitat quality. The species inhabits dry grasslands adjacent to extensive monocultures of Glycine max (Linnaeus 725: 1753) Merril (1917: 274) (soy), which pose a significant threat due to habitat degradation. Observations indicate that the species is more frequently found in areas where soy monocultures begin to diminish. According to data from MapBiomas (2025), soy monocultures have expanded exponentially in the regions where Glechon villosissima occurs, further exacerbating the threat to its habitat ( Figure 3 ).

Notes: — Glechon villosissima is similar to G. spathulata Bentham (1834: 406) and can be distinguished by its indument, Glechon villosissima is densely covered with white villous trichomes that differ from the pubescent trichomes of G. spathulata . Glechon villosissima possesses peduncles (0.8–1.0 mm long), while G. spathulata has sessile flowers. Glechon villosissima floral bracteoles are longer (1.0–2.0 mm vs. 0.8–1.0 mm long). The calyx of G. villosissima is distinguished by unequal (vs. subequal in G. spathulata ), elongated lobes (2.6–3.4 mm vs. 0.5–0.8 mm long). Glechon villosissima grows parapatric with G. spathulata , nonetheless the latter also inhabits northeast Argentina (Misiones) and has a broader distribution in Rio Grande do Sul state extending its distribution to southern Santa Catarina state (speciesLink 2025, POWO 2025). The main features that distinguish Glechon villosissima and G. spathulata are listed in Table 2.

Figures

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

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.

FIGURE 4. Glechon villosissima L.Luz & Bordignon. A. Inflorescence with flowers in anthesis. B. Habit. C. Branch showing leaves and stem trichomes. D. Branch with flowers. E. Adaxial leaf surface. F. Abaxial leaf surface. G. Open calyx. H. Bracteoles. I. Calyx with bud. J. Mericarps (Photos: A to D by Sérgio Bordignon, E to J by Laura Luz). Scale bars: 1 mm (G to J).