Rhynchosia sousae Fortunato, 2014

Fortunato, Renée H. & Robbiati, Federico O., 2014, Rhynchosia sousae (Leguminosae, Papilionoideae), a new species from eastern Mexico, Phytotaxa 178 (2), pp. 146-150 : 147-149

Rhynchosia sousae Fortunato , sp. nov. ( Fig. 1. A–N )

Differs from Rhynchosia amabilis in having large flowers to 11–15 mm long., short calyx lower lobe to 2.5 mm long., elliptic-oblong to subnavicular, yellowish to yellow-whitish, and large fruits to (2.2) 2.7–3 x 0.9–1.2 cm, position of and smaller fruit beak, red seed and large hilum to 3.5–4 mm long.

Type:— MEXICO. Veracruz: San Andrés, Cerro del Vigía , selva alta perennifolia, 200 m, 18° 35’ N, 95° 05’W, 21 October 1974, Calzada 1597 (holotype MEXU!, isotype MEXU!, BAB!) .

Suffrutescent to woody climbing vine; stems one to several from woody rootstock, simple or few branched, glanddotted, sericeous to tomentulose, hairs silvery. Stipules 2–4.5 x 1–1.25 mm, ovate-acuminate, caducous; petioles 1.8–8 cm long. Leaves 3–foliolate; leaflets 3.5–13.5 x 2.5–11.6 cm, ovate-rhombic to rhombic or deltoid, acute to acuminate, concolorous to discolorous in dry specimens, chartaceous to thin-coriaceous, upper surface puberulous to glabrate, lower surface gland-dotted and sparsely sericeous to tomentulose; stipels 0.75–2.25 mm long, filiform, usually lacking (caducous); rachis 0.9–3.5 cm long; petiolule 3–6(–6.25) mm long. Inflorescence pseudoracemose, axillary, 2.5–14 cm long, multiflorous, simple, equalling or not surpassing the caulinar leaves; peduncle 0.5–1cm long. Flowers 11–15 cm long, lax; bracts 4–5 x 1–1.25 mm, lanceolate to ovate-acuminate, caducous; pedicels 1.5–2 mm long; calyx 4.5–6.5 mm long, not exceeding the corolla, gland-dotted and pubescent, 5-lobed, lobes lanceolate, subequal, the two laterals subequalling the tube in length, vexillary sinus 1–1.2 mm long, lower lobe (carinal) 2.25–2.5 mm long; corolla greenish-yellow to yellow, some with purple to brown veins; standard 10–15 x 6–9 mm, obovate to elliptic, obtuse to emarginate, gland-dotted and puberulous, claw 2–2.25 mm long; wings 9–11 x 1.25–1.5 mm, obtuse, claw 2.25–2.75 mm long, gland-dotted and puberulous at apex; carinal petals (keel) 11.5–14 x 3–3.5 mm, falcate, glabrous to glabrescent and sparsely gland-dotted at the apex, claw 3.5–4 mm long; androecium and gynoecium 10–14 mm, ovary ± 3 mm, sericeous and gland-dotted, gynophore ± 1 mm, nectary appendices 0.75–1 mm long, short and ± fleshy. Fruits (2.2–)2.7–3 x 0.9–1.2 cm, elliptic-oblong to subnavicular, inflated and constricted, constriction 0.8–1 mm, densely villous and gland-dotted, yellowish to yellow-whitish, sometimes mixed with viscid-hirsute glandular pubescence (multicellular hairs)*, beak in the suture of the upper side (persistent style-base) 1–1.5(–2) mm long, ascending. Seeds 8–9 x 5.5–6.25 mm, subreniform to ovoid, red, radicular lobe to 0.5 mm long; hilum 3.5–4 mm long, oblong to oblong-elliptic, funicle attached to distal end, strophiole lobes lanceolate to linear.

Geographic distribution and Ecology: — Rhynchosia sousae is an endemic apparently restricted to Los Tuxtlas region (Veracruz, Mexico), in mountains of volcanic origin. The species occurs in high evergreen forest and tropical rain forest on steep slopes, up to 700 m above sea level, showing a patchy distribution, with only a slight disturbance over the area ( Fig. 2 .) .

Etymology: —The specific epithet is a tribute to Dr. Mario Sousa, a distinguished botanist responsible for the training of many taxonomists in Mexico and other countries around the word, recognized specialist of the Legume family and coordinator of that family for Flora Mesoamericana. His knowledge allowed him to point out that this new species was probably different from others described from the same region.

Phenology: —Flowering from April to September fruiting from September to March.

Taxonomic notes:—Within sect. Rhynchosia , R. sousae is similar to R. amabilis Grear and has been confused in the region with R. precatoria (Humb. & Bonpl. ex Willdenow 1809: 755–756) De Candolle (1825: 385) . The three species have ovate-rhombic to rhombic or deltoid to rhombic-lanceolate, sometimes ovate leaflets; inflorescence equalling or not surpassing the caulinar leaves; fruits densely ferruginous-puberulous or villosulose, remaining brown and yellowish-ferruginous with age, and seeds red or bicolor variable to the red and black area at one end. The distinguishing characters between these taxa are summarized in Table 1.

The specimen Nee & Calzada 22769 * (MEXU) has fruits with viscid-hirsute glandular pubescent (multicellular hairs and bulbous gland base), a characteristic only present in R. quercetorum Standl. (1937: 555) of the sect. Rhynchosia . This last species is found in Costa Rica, Panama to western Colombia. This pubescent type probably should be associated to environmental conditions of mountains of volcanic origin. In Mesoamerica and Central America this type of pubescence can be observed in different species not taxonomically related to each other: i.e. R. monticola Grear (1978: 92) , R. discolor M. Martens & Galeotti (1843: 199) , R. potosina Brandegee (1911: 181) , R. edulis Griseb. (1874: 123) . In the latter species, this type of pubescence has been detected in some Central American and Bolivian specimens.

Additional specimens examined (paratypes): — MEXICO. Veracruz: Catemaco, 1 km al S de la Estación Biológica Los Tuxtlas, 3August 1986, R . Cedillo 364 ( MEXU); Las Cabañas a 5 km al N de la desviación de la carretera a Jicacal , 22 October 1974, C . Calzada 1600 ( MEXU); Playa Escondida and environs, remnants of Selva Alta , 18º 35’ N, 95º 04´W, 27 January 1984, S . Solheim & S . Reisfield 1419 ( MEXU). Coatzacoalcos, Zona de Salvaguarda-Pemex- La Cangrejera, a 8 km al S-SE de Coatzacoalcos, 1 April 1999, A . Hanan Alipi et al. 1283 ( MEXU). Pajapan , 5 km NW of Pajapan, SE slopes of Cerro San Martín Pajapan , 18º 17’ 30” N, 94º 43´W, 3 November 1981, M . Nee & J. I . Calzada 22769 * ( MEXU). San Andrés Tuxtla, cerro El Vigía, Estación de Biología Tropical Los Tuxtlas , 21 October 1982, G . Ibarra Manríquez 337, ( MEXU); Estación de Biología Tropical Los Tuxtlas , 18º 34’ N, 95º 04´/ 95º 09´W, lote 67, 22 March 1984, G . Ibarra Manríquez 1393 ( MEXU); cima cerro El Vigía, Estación de Biología Tropical Los Tuxtlas , 18º 34’ N, 95º 04´/ 95º 09´W, 23 June 1986, G . Ibarra Manríquez & S . Sinaca Colín 2910 ( MEXU); entre La Palma y desviación a Playa Escondida , carr. Catemaco-Montepío, 14 August 1998, A . Campos & C . León 5347 ( MEXU); 4 September 1983, R . Cedillo Trigos & G . Ibarra Manríquez 2553 ( MEXU); 18º 35’ N, 95º 05’W, 21 October 1974, J. I . Calzada 1597 ( MEXU 309676 ); 1 km al S de la Estación Biológica Los Tuxtlas, 3 August 1986, R . Cedillo 3643 ( MEXU); Tropical rain forest on ridge above UNAM Bio Reserve Headquarters, ca. 20 km by air NNK of Sontecomapan, Los Tuxtla regions, 11 September 1975, G . Webster et al. 20392 ( MEXU) .

Figures

FIGURE 1. a–n. a. Habit. b. Upper leaf surface. c. Lower leaf surface. d. Inflorescence. e. Sepals. f. Standard. g. Detail of the glanddotted. h. Wings. i. Claw. j. Androecium. l. Gynophore. m. Fruit. n. Seed, hilar view and side view.

FIGURE 2. Map distribution of Rhynchosia amabilis, R. precatoria and R. sousae.