Rhynchosia arenicola Hassl., Bull. Herb. Boissier

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 : 11

1. Rhynchosia arenicola Hassl., Bull. Herb. Boissier , sér. 2 7: 167. 1907. Type:— PARAGUAY, Department Caaguazú, Yhu, October 1905 (fl.), Hassler 9565 (Lectotype, designated inadvertently [as holotype] by Grear [1978]: G [not seen]; isolectotypes: BM 000538505 [digital image!], K 00048404 [digital image!], NY 00026940 [!], P 00708585 [digital image!]). Iconography: Rodriguésia 70: 5. 2019. ( Fig. 2 A–C )

Rhynchosia arenicola var. major Hassl., Bull. Herb. Boissier , sér. 2 7: 167. 1907. Type: Paraguay, Department Caaguazú, Yhu , Hassler 9564 (Holotype: G [not seen]).

Subshrub erect to prostrate, stems branched, glabrescent to pilose, indumentum white to light yellow, with yellow vesicular glands and bulbous-based trichomes. Stipules 2–5 × 0.5–1.5 mm, free, persistent, lanceolate to triangular, externally pubescent with yellow vesicular glands and bulbous-based trichomes. Leaves trifoliolate; petiole 1.5–3.1 cm long; leaf rachis 0.4–1 cm long; stipels absent; leaflets 1.1–3.6 × 1.1–2.3 cm, narrowly elliptical to elliptical, lanceolate, rounded, or ovate, surface not bullate, retuse, obtuse, or rounded at apex, obtuse or rounded at base, margin entire, pilose, with yellow vesicular glands on both surfaces. Inflorescences axillary, corymbiform to congested racemose, 1.2–2 cm long, bearing 4–10 flowers, not exceeding the length of the subtending leaf; bracts caducous; pedicel 1–2 mm long. Flowers 7–11 mm long excluding the pedicel; calyx 7.5–12 mm long, pilose to pubescent with yellow vesicular glands and bulbous-based trichomes, lobes linear to lanceolate, all of them equaling or exceeding the corolla in length; standard petal 6–9 × 3–4 mm, obovate, rounded at apex, glabrous, lacking vesicular glands and bulbous-based trichomes, claw 1–2 mm long, auricle ca. 0.5 mm long; wing petals 6–8.5 × 1–1.5 mm, oblong, claw 1.5–2 mm long, auricle ca. 0.5 mm long; keel petals 6.2–9 × 2–2.5 mm, falcate, claw 2–2.5 mm long; stamens 6.7–9 mm long; ovary 2–4 mm long, pilose, with yellow vesicular glands. Fruits 1.3–1.6 × 0.5–0.6 cm, brownish, without constrictions between the seeds, oblong to elliptical, pilose with sparse yellow vesicular glands but lacking bulbous-based trichomes. Seeds 3–3.8 × 2.5–3.2 mm, orbicular, unicolored, brown.

Nomenclatural and taxonomic notes: — Rhynchosia arenicola var. major was based on a Hassler collection (Hassler 9564) gathered from the same locality and on the same date as the type of the typical variety. According to the protologue, they are differentiated by the size of the leaflets, which are a little larger in R. arenicola var. major , and by the length of the inflorescences, which are a bit more elongate in R. arenicola var. major . Grear (1978) found that no consistent distinctions exist between the two varieties when he studied additional material. We were unable to study the lectotype of the typical variety housed in G, the curator having informed us that some material of the genus was sent on loan and not returned.

Rhynchosia arenicola is characterized by the calyx lobes exceeding the corolla in length ( Fig. 2A ) and prostrate stems ( Fig. 2B ). It is similar to Rhynchosia mineira due to its corymbiform inflorescence not exceeding the length of the subtending leaf ( Fig. 2C ) and well-developed calyx lobes. However, in R. arenicola the stipules are 2–5 mm long and lanceolate to triangular (vs. 5–10 mm long and ovate in R. mineira ) and the stems glabrescent to pilose (vs. densely pubescent).

Reproductive phenology: —Flowering in February, March, October and November; fruiting in February, March, August and November.

Distribution and habitat: —This species is distributed in Brazil, Argentina and Paraguay ( Fig. 3 ). It occurs in campos rupestres (rocky fields), “campos limpos” (open grassland), recently burnt grassland, open areas, and along roadsides.

Conservation status: —Least Concern (LC). Rhynchosia arenicola has an EOO of 352,739 km 2 (GeoCAT, accessed in May 2022). There are many records of R. arenicola from Brazil and Argentina, and the species was recently collected in Botucatu, São Paulo, Brazil (L. M. P. A. Bezerra et al. 140, BOTU).

Selected Specimens Examined:— ARGENTINA. Corrientes: Concepción, 6 km E de Santa Rosa, estancia Millán , 27 March 1975 (fl./fr), M. M. Arbo et al. 846 ( MBM) . Mburucuyá, Parque Nacional Mburucuyá, Potrero Maizal , 17 October 2006 (fl.), M. M. Arbo et al. 9263 ( ICN) . Misiones: Candelaria, Santa Ana, 10 November 1945 (fl./fr.), Montes 1469 ( NY) ; San Ignacio , November 1896 (fl.), N. Alboff s.n. ( NY) ; ibid., alrededores de la casa de Horacio Quiroga, 5 November 1993 (fl.), A. Krapovickas & C. L. Cristóbal 44603 ( NY) ; ibid., Teyú Cuaré, camiño al paraje Payal , 20 February 1996 (fl.), O. Morrone et al. 1047 ( NY) ; ibid. 23 November 1995 (fl./fr.), E. R. Guaglianone et al. 3037 ( NY) . BRAZIL. Minas Gerais: s.loc., November 1833 (fl./fr.), Riedel 1571 (US) . Paraná: Jaguariaiva, Joaquim Murtinho , 09 October 1958 (fl.), G. Hatschbach 5094 ( MBM) ; Rio Samambaia , 13 November 1974 (fl./fr.), G. Hatschbach 35460 ( MBM) ; Palmeira, Rio do Salto , 10 November 1951 (fl./fr.), G. Hatschbach 2577 ( MBM) ; Ponta Grossa, Parque Estadual de Vila Velha , 19 March 2012 (fl.), J. M. Silva et al. 8285 ( MBM) . São Paulo: Botucatu, a margem da rodovia João Melão, que liga São Manuel a Avaré , no km 296, 22º54’ lat. S., 48º44’19” long W., 20 November 1986 (fl./fr.), L. R. Hernandes et al. 1712 ( UEC / SP); ibid., Borda do horto florestal de Botucatu, 06 August 2020 (fr.), T. C. Monteiro, I. C. Castro & A. P. Fortuna-Perez 286 ( BOTU) ; ibid., 06 February 2020 (fr.), T. C. Monteiro 466 ( BOTU) ; ibid., 23 June 2021 (fr.), L. M. P. A. Bezerra et al. 140 ( BOTU) ; s.loc., 06 October 1986 (fl.), L. R. Hernades Bicudo et al. 1552 ( BOTU) . PARAGUAY. Itapúa: “ruderalis circa Ecclesiam antiquam Trinidad ”, 15 November 1978 (fl.), Bernardi 18662 ( NY) .

Figures

FIGURE 2. Rhynchosia species. A–C. R. arenicola. D, E. R. balansae. F. R. claussenii. G–J. R. corylifolia. (A–C, G–J by T.C. Monteiro); (D, E by R. Ripley) and (F. by C. Martins).

FIGURE 3. Geographical distribution of Rhynchosia arenicola, R. balansae, R. burkartii and R. caagazuensis in South America.