Rhynchosia hauthalii (Kuntze) Grear, Mem.

Bezerra, Luísa Maria De Paula Alves, Cândido, Elisa Silva, Vargas, Wanderleia De, Torke, Benjamin Marland, Lewis, Gwilym Peter & Perez, Ana Paula Fortuna, 2024, Taxonomic revision of Rhynchosia Lour. (Leguminosae, Papilionoideae, Phaseoleae) in South America, Phytotaxa 643 (1), pp. 1-67 : 32-33

12. Rhynchosia hauthalii (Kuntze) Grear, Mem. New York Bot. Gard. 20(3): 89. 1970.

Basionym: — Dolicholus hauthalii Kuntze, Revis. Gen. Pl. 3(3): 60. 1898. Type : PARAGUAY, “Sude Paraguay ”, November 1892 (fl./fr.), O. Kuntze s.n. (Neotype, designated inadvertently [as holotype] by Grear [1978]: NY 00026946 [!]). Iconography: Rodriguésia 70: 9. 2019 .

Eriosema rotundifolium Micheli, Mém. Soc. Phys. Genève 28(7): 35. 1883. Type : PARAGUAY, “Cerro Peron, prope Paraguari in pratis”, November 1876, Balansa 1538 (Lectotype, designated inadvertently [as holotype] by Grear [1978]: G [not seen]; isolectotypes: F 940492 [digital image!], K000502984 [digital image!], P 02748615, 02748616 [digital image!]).

Rhynchosia uruguaya Arechav. Anales Mus. Hist. Nat. Montevideo 3: 395. 1901. Type : URUGUAY, Tacuarembó, January 1901 (fl./fr.), Arechavaleta 1151 (Holotype: MVM [digita image!]).

Eriosema rotundifolium var. macrophyllum Chodat & Hassl. Bull. Herb. Boissier , sér. 2. 4(9): 905. 1904. Type : PARAGUAY, ‘in glareosis pr. Valenzuela ”, January 1900 (fl.) Hassler 6946 (Lectotype, first-step designated by Grear [1978]; second-step designated here: G 00400123 [digital image!]; isolectotypes: G 00400124, 00400125 [digital image!]; NY 00007876 [!]; UC 940780 [digital image!]).

Subshrub prostrate, stems not branched, pilose, indumentum light yellow, lacking vesicular glands and bulbous-based trichomes. Stipules 3–6.8 × 1–2 mm, free, persistent, lanceolate, externally pilose with sparse bulbous-based trichomes and yellow vesicular glands. Leaves trifoliolate; petiole 0,9– 2.5 cm long; leaf rachis 0.9–2 cm long; stipels persistent; leaflets 2.6–6.1 x 2.2–5.8 cm, obovate to rounded, surface not bullate, mucronate, or rounded at apex, rounded at base, margin entire, pilose, with yellow vesicular glands on both surfaces. Inflorescences axillary, racemose, 7.1–18 cm long, many-flowered, exceeding the length of the subtending leaf; bracts caducous; pedicel 1.5–2.5 mm long. Flowers 8–11 mm long excluding the pedicel; calyx 4–8.1 mm long, pubescent with yellow vesicular glands and bulbous-based trichomes, lobes lanceolate, not exceeding the corolla in length; standard petal 7–10 × 5.3–6 mm, obovate, rounded at apex, pilose to glabrescent, with sparse vesicular glands and bulbous-based trichomes, claw ca. 2 mm long, auricle ca. 0.5 mm long; wing petals 9–10 × 1–2 mm, oblong, claw 2–2.5 mm long, auricle 0.5–1 mm long; keel petals 8.5–10 × 2–3 mm, falcate, claw 2–3 mm long; stamens 8.2–11 mm long; ovary 3.3–4 mm long, pubescent, with yellow vesicular glands. Fruits 1.8–2.2 × 0.5–0.6 cm, greenish to brown, without constrictions between the seeds, oblong in outline, pubescent to hirsute, with yellow to brown vesicular glands and bulbous-based trichomes. Seeds 2.5–4 × 2.5–3.5 mm, suborbicular, unicolored, brown to black.

Nomenclatural and taxonomic notes: — Grear (1978) cited a Kuntze gathering from “Sude Paraguay ” as the holotype. Because Kuntze had studied this specimen from NY (NY 00026946), Grear (1978) inadvertently designated it as the neotype of D. hauthalii (see Turland et al., 2018, Art. 9.10).

Eriosema rotundifolium var. macrophyllum was described based on the collections Hassler 5496 and 6946. Grear’s (1978) citation of the Hassler 6946 specimen at G as the holotype constitutes an inadvertent lectotypification (see Turland et al., 2018, Art. 9.10, Ex. 11; Prado et al., 2020). Since there are two duplicate specimens of Hassler 6946 at G, Grear’s (1978) citation of the specimen G as the “ holotype ” constitutes the first step in the lectotypification of the name (see Turland et al. 2018, Art. 9.17). Thus, we designate here the specimen with barcode number G 00400123 as the second-step lectotype of Eriosema rotundifolium var. macrophyllum since it has the diagnostic characteristics most preserved.

Rhynchosia hauthalii is characterized by having prostrate stems, obovate to rounded leaflets, and racemose axillary inflorescences. It morphologically resembles R. lateritia , since they both have prostrate stems and a well-developed axillary racemose inflorescence (up to 18 cm in R. hauthalii and 21 cm in R. lateritia ). However, they are easily differentiated by their calyces (4–8.1 mm long and not exceeding the corolla in length in R. hauthalii vs. 9–10 mm long and exceeding the corolla in length in R. lateritia ).

Reproductive phenology: —Flowering in January, March to May and October to December. Fruiting in January, March to May, November and December.

Distribution and habitat: — Rhynchosia hauthalli occurs in Brazil, Paraguay and Argentina ( Fig. 9 ). Miotto (1988) recorded this species for Uruguay, but that apparent occurrence has not been confirmed in this work. The species is found in pampean environments, pastures, along roadsides, at forest edges, in grasslands, and on sandy soils.

Conservation status: — Least Concern ( LC). Based on an EOO of 286,657 km 2 (GeoCAT, accessed in May 2022), R. hauthalii is classified as LC following IUCN Red List criteria ( IUCN 2022). It is common in herbaria (especially those from southern Brazil), and is often found in conservation areas such as the Parque Nacional de Itapuã , Rio Grande do Sul, Brazil .

Selected Specimens Examined:— ARGENTINA. Corrientes: Dep. Empedrado, 13 November 1954 (fl./fr.), A. Burkart 2982 (P); ibid., Estancia “Las Tres Marias”, 13 November 1954 (fl./fr.), T. M. Pedersen 2982 ( NY) . BRAZIL.

Figures

FIGURE 9. Geographical distribution of Rhynchosia hauthalii, R. lateritia, R. leucophylla and R. lineata in South America.