Clematis uruboensis Lourteig 1956

Clematis uruboensis Lourteig (1956: 51) emend. Piovesani (Figure 3.) Holotype: BOLIVIA. Santa Cruz: [Andrés Ibáñez], Cercado, Bosque del Urubó, 450 m, 14 Apr 1928, pist. fl., Steinbach 7991 (LIL barcode LIL000456 image!; isotypes: A barcode 00055215 image!, F barcode V0067993F image!, G barcode G00440686 image!, GH barcode 00055216 image!, K barcode K000220138 image!, MO 964185 image!, NY barcode 00353274 image!, S S-R-1131 image!). Woody climbers, height unknown, dioecious with occasional perfect flowers present in staminate inflorescences (pleogamy). Stems striate, sericeous. Leaves trifoliolate or imparipinnate with 3 or 5 leaflets, petioles canaliculate, 50–130 × 2–3.5 mm, sericeous, leaf rachis canaliculate, 20–70 × 1–2 mm, sericeous, petiolules canaliculate, 4.5–35 × 1–1.7 mm, sericeous, leaflet blades broadly ovate or rhombic, occasionally trilobed, 20–90(–115) × 10–60(–115) mm, chartaceous or papery, apex straight and apiculate, base cuneate or concave, margin serrate with 1–7 pairs of teeth, incised 1/5 to 1/3 towards the midvein, abaxial and adaxial surfaces sericeous, denser indumentum on the abaxial, primary veins 3 or 5, prominent on the abaxial surface, flat on the adaxial, secondary veins inconspicuous and sparse. Inflorescences dichasia or thyrsoids with 2 branches, flowers 3–7, primary branch 50–90 × 2–3 mm with up to 2 nodes, tomentose, secondary branch 15–20 × 1.2–1.5 mm with a single node, tomentose, primary bracts similar to the leaflet blades, 10–50 × 2.5–30 mm, sericeous, bracteoles elliptic or obovate, 9–20 × 2.5–10 mm, sericeous. Staminate flowers arranged in compressed cymes within the inflorescence, pedicels 12–25 × 1–1.5 mm, tomentose, buds obconic, 8–10 × 7.5–8.5 mm, sepals 4, elliptic, 10–15 × 4.5–6.5 mm, abaxial and adaxial surfaces densely sericeous, stamens 52–79, filaments 5.5–8 mm long, anthers 1.4–1.8 mm long, pistillodes not observed. Pistillate flowers solitary or arranged in cymes within the inflorescence, pedicels 30–60 × 1–1.5 mm, tomentose, buds ellipsoid, 10–14 × 6–9 mm, sepals 4, oblong, 10–21 × 4–6 mm, adaxial surface sparsely sericeous, glabrous on the basal half, abaxial sericeous, carpels 34–82, 11–17 mm long in anthesis, reaching up to 100 mm at fruit maturity, staminodes 8–11 mm long. Achenes ellipsoid or ovoid, 2.5–3 × 1.5–2 mm, pubescent. Distribution and habitat: —The species is found in the Santa Cruz department of Bolivia, and in the Brazilian states of Mato Grosso and Mato Grosso do Sul (Figure 4). The biogeographical context corresponds to the Rondônia province (Morrone 2022), characterized by lowland seasonally dry forests. In Brazil, the dominant vegetation type is the Pantanal, whereas in Bolivia, the region represents an ecotone between the Chaco and the Amazon rainforest, known as the Chiquitanía. The species occurs at the edges of secondary and riparian forests, at elevations ranging from 110 to 900 m. Flowering and fruiting periods: —It can be found flowering from April to May and fruiting from April to August. Preliminary extinction risk assessment: —We assessed the species as Vulnerable (VU) according to the IUCN (2024) categories and criteria B2ac(i,ii). The Extent of Occurrence (EOO) is estimated at 198,300 km ², while the Area of Occupancy (AOO) was calculated to be 1,200 km ². The species is known from ten localities, spanning both Bolivia and Brazil. The main threat to the species is habitat fragmentation due to land conversion for soybean monocultures and large-scale wildfires, leading to extreme fluctuations in its extent of occurrence and area of occupancy. Since 2020, large-scale fires have been reported in the Pantanal, driven by a combination of climate change and the expansion of agribusiness. In 2024, an area of 627,000 hectares was burned, surpassing 143% of the fires of 2020 (UFRJ 2024). Similarly, in Bolivia, large fires have devastated millions of hectares of forest since 2019, especially in the Chiquitanía region (FAN 2019). Although this type of vegetation is adapted to drought and periodic fires, the increased frequency and intensity of these events may promote an ecological shift towards a dominance of fire-tolerant species in the communities (Hartung et al. 2021). Notes: —The species can be distinguished by having the largest flowers among related species, with pedicels measuring 1–1.5 mm in width, 52–79 stamens, and carpels 11–17 mm long in anthesis (Figure 3). It is similar to Clematis serrana Piovesani et al. (2024: 150) in having inflorescences with up to 20 flowers and leaflet blades with similarly shaped and numbered teeth. Vegetatively it also resembles C. haenkeana, a widespread species in western South America, due to its imparipinnate leaves with broadly ovate and toothed leaflets. However, it differs from both species by possessing larger flowers and approximately twice the number of carpels and stamens. Specimens examined: — BOLIVIA. Santa Cruz: Buena Vista, 450 m, April 1915, pist, fl., J, Steibach 1269 (LIL image!). Concepción, 16°15’00.0”S 62°05’00.0”W, 28 April 1977, stam. fl., A. Krapovickas & A. Schinini 31909 (CTES!). Gral. Saavedra, Estación Experimental, 17°13’00.0”S 63°12’00.0”W, 19 April 1977, stam. fl., A. Krapovickas & A. Schinini 31496 (CTES!). San Ignacio, 27 km S de San Ignacio, camino a San Miguel, 16°36’00.0”S 61°00’00.0”W, 07 May 1977, fr., A. Krapovickas & A. Schinini 32363 (CTES!). Santa Cruz de la Sierra, El Pari, 440 m, 14 April 1946, pist. fl., J. Peredo s.n. (LIL 161732 image!). Santa Cruz de la Sierra, Jardín Botánico de Santa Cruz, 375 m, 17°46’00.0”S 63°04’00.0”W, 15 May 1991, fr., M. Nee 40443 (CTES!). BRAZIL. Mato Grosso: Barão do Melgaço, RPPN SESC Pantanal, 16 April 2022, stam. fl., S.R. Zaniolo et al. 239 (HUEM image!, UPCB!), 17 April 2002, pist. fl., S.R. Zaniolo et al. 247 (UPCB!). Cáceres, Gleba Facão, 5 May 1995, stam. fl., G. Hatschbach et al. 62325 (RB image!). Mato Grosso do Sul: Corumbá, Estrada do Tamarindeiro, 110 m, 19°06’00.0”S 57°47’00.0”W, 23 May 1987, fr., A. Pott et al. 2731 (CTES!, RB!). Corumbá, Morro Santa Cruz, Mineração Corumbaense, 900 m, 07 April 1998, fr., G.A. Damasceno-Junior et al. 1193 (COR image!). Corumbá, Passo da Lontra (Base de Pesquisa da UFMS), 19 August 1999, fr., R.D. Delmão 49 (COR image!). Ladário, Fazenda Vale do Paraíso, Morro Santa Cruz, 200 m, 19°10’31.3”S 57°34’51.5”W, 29 May 2001, fr., G.A. Damasceno-Junior 2418 (COR image!).