Rhynchosia senna Gillies ex Hook. & Arn., Bot. Misc.

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 : 61-63

27. Rhynchosia senna Gillies ex Hook. & Arn., Bot. Misc. 3: 199–200. 1833.

Dolicholus senna (Gillies ex Hook. & Arn.) Kuntze., Revis. Gen. Pl. 3(3): 62. 1898., pro parte. Type: — ARGENTINA, Cordoba, Rio Quarto , on the pampas of Cordoba, s.d. (fl./fr.), J. Gillies s.n. (Lectotype, designated by Grear [1978]: K 000530052 [digital image!]; isolectotypes: E 00183077 [digital image!], E 00183078 [digital image!], E 00183079 [digital image!], K 000530049 [digital image!]). Iconography: Rodriguésia 70: 17. 2019. ( Fig. 14 K–L )

Rhynchosia texana Torr. & A. Gray, Fl. N. Amer. 1(4): 687. 1840. Type: UNITED STATES, Texas, s.d. (fl./fr.), Drummond s.n. (Lectotype, designated inadvertently [as holotype] by Grear [1978]: NY 00026915 [!]; isolectotypes: K 000900422 [digital image!], K 000900424 [digital image!], LE [not seen]).

Rhynchosia texana var. angustifolia A. Gray, Smithsonian Contr. Knowl. 3(5): 44. 1852. Dolicholus angustifolius (A. Gray) Kuntze , Revis. Gen. Pl. 3(3): 60. 1898. Dolicholus texensis (A. Gray) Vail, Bull. Torrey Bot. Club 26(3): 108. 1899. Dolicholus texensis var. angustifolius (A. Gray) Vail, Bull. Torrey Bot. Club 26(3): 108. 1899 . Rhynchosia senna var. angustifolia (A. Gray) Grear, Mem. New York Bot. Gard. 31(1): 67. 1978. Type: UNITED STATES, Texas, Comanche Spring , New Braunfels, July 1850 (fl.), F. J. Lindheimer 412 (Lectotype, designated by Grear [1978]: MO 277404 [digital image!]; isolectotypes: GH 00063793 [digital image!], K 000900417 [digital image!], MICH [not seen], NY [not seen], PH 00024230 [digital image!]) .

Rhynchosia angustifolia Engelm. ex A. Gray, Smithsonian Contr. Knowl. 3(5): 44. 1852. nom. nud.

Rhynchosia texana fo. cordobensis Griseb. , Pl. Lorentz. 74–75. 1874. Type: ARGENTINA, Cordoba , “em las cercanías de Córdoba”, 1870 (fl./fr.), P. G. Lorentz 360 (Lectotype, designated inadvertently [as holotype] by Grear [1978]: GOET [not seen]; isolectotype: SI 002529 [digital image!]).

Rhynchosia texana var. microphylla Hassl., Repert. Spec. Nov. Regni Veg. 16: 230. 1919. Type: PARAGUAY, Chaco , July 1906 (fl./fr.), K. Fiebrig 1323 (Lectotype, designated by Grear [1978]: G 00379285 [digital image!]; isolectotypes; F [not seen], K 000502983 [digital image!]).

Rhynchosia senna fo. minor Griseb., Pl. Lorentz. 74. 1874. Type: ARGENTINA, Cordoba, “Auf Weiden bei San Francisco”, 1871 (fl.), P. G. Lorentz 355 (Lectotype. designated here: GOET 042400 [digital image!]) .

Rhynchosia senna var. foliolis late ovatis Ball, J. Linn. Soc., Bot. 21: 216. 1884. Type: ARGENTINA, Buenos Aires, Bahia Blanca , 1881 (fl.), G. Claraz 189 (Holotype: K 000530054 [digital image!]).

Rhynchosia senna var. foliolis lanceolatis Ball, J. Linn. Soc., Bot. 21: 216. 1884. Type: ARGENTINA, Buenos Aires, Bahia Blanca , 1881 (fl.), G. Claraz 80 (Holotype: K 000530053 [digital image!]).

Rhynchosia senna var. azuaensis Grear, Mem. New York Bot. Gard. 31(1): 73–75. 1978. Rhynchosia azuaensis (Grear) B.L. Turner, Lundellia 14: 27. 2011. Type: Ecuador, Azuay, Valley of the Rio Paute , between Paute and Cuenca, March 1954, W. H. Champ 2325 (Holotype: NY [not seen]; isotypes: F 0059821F [digital image!], US 00004823 [digital image!]).

Subshrub prostrate to twining, stems branched, pilose to pubescent, white, lacking vesicular glands and bulbous-based trichomes. Stipules 2–4 × 0.5–1 mm, free, persistent, narrowly lanceolate to lanceolate, externally pubescent with yellow vesicular glands, but lacking bulbous-based trichomes. Leaves trifoliolate; petiole 0.5–2.8 cm long; leaf rachis 0.5–1.5 cm long; stipels caducous; leaflets 0.9–2.3 × 0.4–1.5 cm, lanceolate or ovate, surface not bullate, cuneate to acuminate at apex, rounded at base, margin entire, pilose, with yellow vesicular glands on both surfaces. Inflorescences axillary, fasciculate, 0.3–1.8 cm long, bearing 1–5 flowers, not exceeding the length of the subtending leaf; bracts caducous; pedicels 7–11 mm long. Flowers 7–9 mm long excluding the pedicel; calyx 5–7 mm long, pubescent, with yellow vesicular glands, but lacking bulbous-based trichomes, lobes lanceolate, not exceeding the corolla in length; standard petal 6–8 × 3–4 mm, obovate to oblong, emarginate or rounded at apex, pilose to pubescent, with yellow vesicular glands, but lacking bulbous-based trichomes, claw 1–1.5 mm long, auricle ca. 0.5 mm long; wing petals 6–7 × 0.5–1 mm, oblong, claw ca. 1–2 mm long, auricle ca. 0.5 mm long; keel petals 6–7.5 × 1–2.5 mm, falcate, claw 1–2 mm long; stamens 4–9 mm long; ovary 2.5–3.2 mm long, pubescent, with yellow vesicular glands. Fruits 1.8–2.6 × 0.5–0.8 cm, brownish, without constrictions between the seeds, falcate, puberulous, with yellow vesicular glands, but lacking bulbous-based trichomes. Seeds 2.8–3.8 × 3–4 mm, suborbicular, unicolored, brownish to black.

Nomenclatural and taxonomic notes: — Hooker & Arnott (1833) described Rhynchosia senna . Grear (1978) synonymized R. texana under R. senna var. angustifolia and published a new variety: R. senna var. azuaensis . Johnston (1984) stated that the correct name for R. senna var. angustifolia should be R. senna var. texana . Turner (2011) studied the R. senna “complex” and accepted the typical variety as a distinct species and treated R. senna var. texana as a biological species with a bicentric distribution reinstating the name R. texana . He also elevated R. senna var. azuaensis , a taxon known by only a single collection from Azuay, Ecuador, to a specific rank. Ståhl et al. (2016) in the Flora of Ecuador discussed the similarity between these taxa and preferred a broader circumscription of R. senna , placing all the above-named taxa into synonymy. In view of the overllaping variation between the taxa, here we follow Ståhl et al. (2016). Torrey and Gray (1838) described R. texana based on the collection Drummond s.n. from Texas, but they did not designate a specific specimen as a type. As there are four duplicates of the Drummond collection, housed in different herbaria, Grear’s (1978) citation of the specimen at NY as the holotype constitutes an inadvertent lectotypification (see Turland et al. 2018, Art. 9.10, Ex. 11; Prado et al. 2020).

In the protologue of R. texana fo. cordobensis Grisebach (1874) cited the collection locality as “ Cordoba ” but did not give any other information. When Grear (1978) subsequently cited the collection Lorentz 122 as the holotype of the taxon he inadvertently lecotypified it.

Grisebach (1874) mentioned in the protologue of R. senna fo. minor a collection from “in pascuis pr. S. Francisco”. Grear (1978) cited as holotype a specimen at GOET but stated that he had “not seen” the specimen. The curator at GOET informed us that there is no collection that matches the locality cited by Grisebach. We designate here the collection Lorentz 355 deposited in GOET from “Auf Weiden bei San Francisco” as the lectotype of R. senna fo. minor.

Rhynchosia senna is characterized mainly by its prostrate stems, leaflet size and falcate fruits ( Fig. 14 K–L ). It is morphologically similar to R. diversifolia by its fasciculate inflorescences. The characters that distinguish the two species are listed in the taxonomic notes of R. diversifolia .

Reproductive phenology: —Flowering from January to March, and in June, August and from October to December; fruiting from January to May, and in July, August, November and December.

Distribution and habitat: — Rhynchosia senna occurs in Argentina, Brazil, southern Ecuador and Uruguay ( Fig. 15 ) and also in Mexico and the southern United States. It grows in rocky and shrubby fields, along roadsides, in clay soils.

Conservation status: —Least Concern (LC). Rhynchosia senna is assessed as LC following IUCN Red List criteria ( Groom 2012; IUCN 2022). The species has a wide distribution in central South America and Mexico.

Selected Specimens Examined:— ARGENTINA. Buenos Aires: Part. Torquinst, 10 km SE de Saldungaray por Ruta Prov. 72 hacia Dique Paso de Piedras , Arroyo Sauce Corto, s.d. (fr.), G. Seijo 1348 ( MBM) ; Sierra de la Ventana , February 1914 (fr.), A. C. Scala s.n. ( SP) . Catamarca: Andalgalá , November 1916 (fr.), P. Jörgensen 1434 ( SP) . Chaco: Laguna Blanca , 28 December 1944 (fl./fr.), Aguilar 108 ( NY) . Córdoba: Dep. Capital, Alrededores de la ciudad de Córdoba, cerca del caminho a Alta Gracia , 26 November 1949 (fl./fr.), A. T. Hunziker 8110 ( MBM) ; Ischilín , 24 October 1971 (fl.), T. M. Pedersen 9966 ( MBM) ; Punilla, Ruta provincial 14, 3 km NE de Copina, 12 December 1999 (fl./fr.), G. Seijo 2032 ( NY, SP) ; Valle Hermoso , 17 December 2009 (fl.), J. J. Cantero 5998 ( UEC) . Corrientes: Curuzú Cuatiá , RP-25, by the bridge on the A Pelado, 23 November 1990 (fl./fr.), T. M. Pedersen 15627 ( MBM, NY) . Entre Rios: Diamante , suburbios, 27 January 1981 (fl.), N. Troncoso & N. Bacigalupo 3011 ( SP) ; Fedaración, Cantera Chaviyú , 24 November 1976 (fl./fr.), N. Troncoso et al. 1365 ( SP) ; Gualeguaychú, aerodromo Gualeguaychú , 17 April 1965 (fr.), A. Burkart et al. 25738 ( RB) . La Pampa: Sierra de Lihuel Calel , 6 November 1972 (fl.), L. A. Mroginski & A. Fernandez 22616 ( MBM) . Salta: Metán , 24 January 2002 (fl./fr.), G. Seijo et al. 2819 ( MBM) . San Luis: Chacabuco, La coma, 16 February 1944 (fl.), Varela 552 ( NY) . Tucuman: Capital, Parque 9 de Julio, 08 November 1923 (fr.), Schreiter 4071 ( NY) ; Tafi del Vale , nos campos arredores, 03 November 1960 (fl./fr.), D. Andrade Lima 60-3583 ( IPA, MBM) . BOLIVIA. La Paz: Murillo, La Paz – La Florida ca. 17 kms., Rio Abajo , Huajchilla , 11 May 1986 (fr.), St. G. Beck et al. 12478 ( NY) . Tarija: Cercado, cerca Conception , 19 February 1986 (fr.), E. Bastión 782 ( NY) . BRAZIL. Rio Grande do Sul: Alegrete, próximo a Hoemania , 18 February 1962 (fl.), V. S. Fagundes 2678 ( BLA) ; Alto Alegre—Pedro Osório , 06 December 1991 (fr.), L. A. Z. Machado 1589 ( SMDB) . Bagé , 20 November 1993 (fr.), N. R. Bastos 361 ( PACA) ; ibid., 24 km da cidade, estrada Bagé / Serrilhada , 08 December 1990 (fl./fr.), L. A. Z. Machado 714 ( SMDB) ; ibid., rumo a Dom Pedrito - BR 293, perto da ponte, 11 November 1995 (fl.), S. T. S. Miotto 1979 ( FLOR) ; Bossoroca , 12 January 1991 (fl.), L. A. Z. Machado et al. 845 ( SMDB) ; Caçapava do Sul, 13 December 1982 (fl./fr.), D. B. Falkenberg 15 ( FLOR) ; ibid., 14 December 1982 (fl.), D. B. Falkenberg s.n. ( FLOR) ; ibid., 250 m de altitude, 21 January 1994 (fl./fr.), D. B. Falkenberg et al. 6464 ( FLOR) ; ibid., 18, 5 km S de Caçapava do Sul (RS 357), 11 November 2006 (fl./fr.), L. P. Queiroz 12394 ( INPA) ; ibid., em campo úmido, 6 December 1993 (fr.), N. R. Bastos 386 ( PACA) ; ibid., Irapuá, Cerro da Vigia , January 1987 (fr.), L. A. Z. Machado 29 ( SMDB) ; ibid., Vila Progresso , 04 November 1989 (fr.), L. A. Z. Machado 359 ( SMDB) ; Campanha , January 1972 (fl./fr.), Pott 128 ( BLA) ; Ibaré, rumo a Bagé , 30 March 1991 (fl./fr.), Machado et al. 1427 ( SMDB) ; Lavras do Sul, 23 July 1993 (fl.), N. Bastos s.n. ( PACA) ; ibid., 07 December 1993 (fr.), N. R. Bastos 421 ( PACA) ; Quaraí, Rio Garopa para Quaraí , 14 January 1941 (fl./fr.), B. Rambo s.n. ( PACA) ; Rio Pardo para Pantano Grande , August 1933 (fl./fr.), Barreto 32 ( BLA) ; Santana do Livramento , November 1916 (fl./fr.), E. F. Xavier s.n. ( BLA) ; Santiago, Capão do Cipó, Assentamento Santa Rita , 09 March 1989 (fl./fr.), L. A. Z. Machado 184 ( SMDB) ; ibid., 12 January 1991 (fl./fr.), Machado et al. 820 ( SMDB) ; São Sepé, Colônia do Santa Barbara , 23 February 1989 (fl./fr.), L. A. Z. Machado s.n. ( SMDB) ; Tupanciretã, Espinilho Grande , 11 January 1991 (fl.), L. A. Z. Machado et al. 800 ( SMDB) . ECUADOR. Azuay: Valley of the Rio Paute, between Paute and Cuenca , 26 March 1954 (fl.), W. H. Champ 2325 (F, US) . MEXICO. Querétaro: Querétaro, Camino a Los Cues , 28 June 1982 (fl.), F. Ramos & M. Souza 1813 ( MBM) . PARAGUAY. Boquerón: Col. Menno, 5 km al W de Cascabel , (km 160 del FFCC), 10 December 1992 (fl./fr.), A. Krapovickas & C. L. Cristobal 4303 ( NY) . UNITED STATES. Texas: Comanche Spring; New Braunfels , July 1850 (fl.), F. J. Lindheimer 784 ( US) . URUGUAY. Artigas: Loc. 3 km del desvio a T. Gomensoro, 10 December 1995 (fl./fr.), V. S. Neffa et al. 226 ( NY) . Salto: Salto, Cuchilla de Areranguá, along ROU-31, between km 160 from Salto and Los Orientales , 24 January 1965 (fl./fr.), T. M. Pedersen 16233 ( MBM) .

Figures

FIGURE 14. Rhynchosia species. A–C. R. phaseoloides. D. R. platyphylla. E–H. R. reticulata. I–J. R. schomburgkii. K–L. R. senna. (A, E–H, L by L. M. P.A. Bezerra), (B, C, K by T. C. Monteiro), (D by C. Martins) and (I–J by A. P. Fortuna-Perez).

FIGURE 15. Geographical distribution of Rhynchosia reticulata, R. rojasii, R. schomburgkii and R. senna in South America.