Orinoquia brasiliensis T. S. Cout. & L. O. Alvarado. A. Habit. B. Detail 2025, sp. nov.

Orinoquia brasiliensis T.S. Cout. & L.O. Alvarado, sp. nov. (Figures 1, 2). Diagnosis: Orinoquia brasiliensis is similar to O. yanomamica by sharing hirsute branches, ovate leaf blades, long-peduncled inflorescences and corona with 15 segments, but differs especially by the branches with long simple trichomes only (vs. long and short trichomes), pedicels 1.5–2 cm long (vs. 3–3.5 cm long), sepals 11–13.5 mm long (vs. 6–6.6 mm long), ovate corolla lobes (vs. ovate-oblong), corona with apically 1-lobed staminal segments (vs. 2-lobed) and reniform pollinia (vs. obovoid). Type:— BRAZIL. Mato Grosso: Porto Estrela, Estação Ecológica da Serra das Araras, região Norte da Serra, 15°28’12,7’’ S, 57°06’4,9’’ W, 13 March 2024, fl. and fr., M.V. Rondon-Anjos & I.M. Melquíades 280 holotype: UFMT (48320)!; isotypes: HURB, RB, SPF, UFP). Description:—Liana, latex white, abundant. Branches cylindrical, hirsute along the entire length, long simple trichomes, 7–8 mm long, evenly distributed, erect, yellow to ferrugineous. Leaves opposite; petioles 10–11 cm long, hirsute, trichomes similar to the branches, flattened dorsi-ventrally; interpetiolar and intrapetiolar colleters absent; leaf blades membranaceous, 16.5–17.5 × 10.7–12.5 cm, ovate, base cordate, lobes 1.3–2.2 cm long, margins entire, flat, densely long-ciliate, trichomes simple, 3–4 mm long, apex cuspidate, cusp 1–1.1 cm long, hirsute on both surfaces, trichomes simple, 2–3 mm long; venation brochidodromous, 5–7 pairs of secondary veins; colleters absent. Inflorescence an axillary umbel, one per node, 7–10 flowers; peduncles 7.5–8 cm long, pendulous, indumentum similar to that of the branches; bracteoles grouped at the base of the flowers, 13–15 × 3–4 mm, lanceolate, hirsute, trichomes simple, apex long-acuminate; pedicels 1.5–2.0 cm long, hirsute. Calyx light brown to reddish brown, connate at the base for ca. 4–5 mm, lobes 11–13.5 × 3.5–4 mm, lanceolate to ovate, sparsely hirsute abaxially, eglandular trichomes simple ca. 7 mm long, and glandular trichomes ca. 1 mm long, both yellow, apex long-acuminate; colleters absent. Corolla vinaceous, nervate-reticulate, 53–60 mm diam., rotate to subcampanulate, connate at the base for ca. 8 mm, tube ca. 2 mm long, lobes 17–21 × 13–16 mm, ovate, patent, adaxial surface glabrous, villous only near the base, surrounding the corona, trichomes simple, hyaline, abaxial surface sparsely pilose, trichomes simple ca. 1 mm long, apex acute, with inconspicuous emargination. Gynostegial corona a disc or shallowly cup-shaped with 15 segments: staminal corona (Cs) formed by 10 vinaceous segments grouped in 5 pairs, each pair ca. 4.3 mm long, basally dilated and apically 1-lobed, lobes ca. 0.3 mm long, crenulate; interstaminal corona (Ci) formed by 5 segments, vinaceousgrayish, ca. 4.2–4.5 × 0.4 mm, oblong and sulcate longitudinally, apex curved and narrowed. Gynostegium sessile; anthers yellow, 1.5 × 3 mm, wings 0.8 mm long; pollinarium with horizontal pollinia, pollinia ca. 1.3 × 1.3 mm, reniform, caudicles ca. 0.2 mm long, retinaculum brown, 0.6 × 0.2 mm, fusiform-obovoid, 2-dentate at the base. Stylehead pentagonal, 4–4.5 mm diam. Follicle ca. 10 × 3.5 cm, fusiform, with long filiform projections, wingless, densely hirsute, trichomes simple, projections 15–18 mm long, soft, hirsute, trichomes simple; seeds not observed. Etymology: —The specific epithet refers to Brazil, where the new species is endemic. Distribution, habitat and phenology: — Orinoquia brasiliensis is known only from the Estação Ecológica da Serra das Araras, in the municipality of Porto Estrela, state of Mato Grosso, Brazil (Figure 3). This conservation unit has an area of 28,700 ha, in the Cerrado domain, but with influence of the Pantanal and Amazon Forest domains, forming a vegetation mosaic with high plant diversity (BRASIL 2016). Relief and elevation of the region differs from that the adjacent regions, as it is part of the geomorphological unit Serrana Province, with Köppen’s Aw climate (Köppen 1998), hot, humid and rainy in summer and dry in winter (BRASIL 2016). The new species was collected on the edge of semi-deciduous seasonal forest, with flowers and fruits in March. Conservation status: — Orinoquia brasiliensis is known only from the one population at the type locality. This makes it impossible to calculate the Area of Occupancy (AOO) and Extension of Occurrence (EOO), which are essential for a correct analysis of the conservation status. Therefore, we prefer to assess this species as Data Deficient (DD) according to IUCN (2022), until new collection efforts are carried out to search for new populations of the species. However, although it is found in the Cerrado, the only population of Orinoquia brasiliensis occurs inside a protected area, the Estação Ecológica da Serra das Araras. Discussion: — Orinoquia differs from all Gonolobinae from South America by corona with 15 segments (vs. 5 or 10, distinct or fused) (Table 1). Orinoquia brasiliensis is here proposed as the second known species of the previously monotypic genus Orinoquia, which had only O. yanomamica. The two species share the vegetative and floral attributes of the genus (Morillo 2015), highlighting the morphology of the gynostegial corona (Figures 1–2) composed of 15 segments, with 10 segments in pairs and opposite to the anthers (staminal corona—Cs), and 5 segments alternate to the anthers (interstaminal corona—Ci). Orinoquia brasilisensis differs from O. yanomamica by the branches bearing only long simple trichomes (vs. long and short trichomes), petioles 10–11 cm long (vs. 5–7 cm long), 7–10 flowers per inflorescences (vs. 3–5), pedicels 1.5–2 cm long (3–3.5 cm), bracteoles 13–15 mm long (8–11 mm), calyx lobes 11–13.5 mm long (vs. 6–6.5 mm), corolla lobes ovate and 13–16 mm wide (vs. ovate-oblong and 12 mm). Regarding the areas where both Orinoquia species are distributed, there are important differences (Figure 3). Orinoquia brasiliensis is endemic to the Brazilian savannah, with a marked dry and rainy season, as well as rainfall of less than 1500 mm per year (Schmidt et al. 2009, BRASIL 2016); while O. yanomamica is restricted to the Venezuelan Amazon rainforest in the headwaters of the Orinoco River, at 150–400 m altitude, with a rainfall of 2500 to 5000 mm (León 2005). Additionally, the distribution of both species has numerous physical barriers such as the Amazon biome and the Amazon River (Schmidt et al. 2009). The two species grow in contrasting environmental conditions, supporting the explanatory hypothesis that differences in environmental requirements are necessary. The new species represents a new taxon for Gonolobinae from the state of Mato Grosso. We provide an identification key for species of the subtribe in this Brazilian state.