Brongniartia dulce Dorado, 2024

Dorado, Óscar & Florentino, Alexis, 2024, A new species of Brongniartia (Fabaceae: Faboideae) from southwestern Oaxaca, México, Phytotaxa 665 (1), pp. 75-80 : 76-78

Brongniartia dulce Dorado , sp. nov. Fig. 1 .

Brongniartia dulce is similar to B. intermedia but differs from it by having stipules (0.7–)1–2.1 × (0.6–) 0.8–2.2 cm, rounded, somewhat hemicordate, commonly persistent; bracteoles conspicuous, narrowly elliptic; flowers in dense racemes, sometimes solitary, never on leafless flowering branches; calyx 1.1–1.4 × 0.4–0.5 cm; standard 1.6–1.7 cm long; petals red marron, except whitish towards the distal part of keel petals.

TYPE:— México, Oaxaca. Santiago Tapextla, 4 km al noreste del plantel EIBO No. 237, en camino de terracería hacia San Isidro, después seguir 250 m al noroeste, dentro de potrero. Mpio. de Santiago Tapextla. Ó. Dorado 10701, J. M. de Jesús-Almonte, G. Cuevas, V. Peñaloza y R. Acevedo. 25 de febrero 2023 (Holotype MEXU, isotype: HUMO).

Shrub to 1.5 m tall, commonly branching near the base, branches often gray with numerous whitish lenticels, branchlets and foliage hirtelous, with hairs 0.05 mm long, whitish. Stipules (0.7–)1–2.1 × (0.6–) 0.8–2.2 cm, rounded, somewhat hemicordate, rarely lanceolate, commonly persistent, even after the spring; one of the pair of the stipules is larger than the other, lower lobe more or less equally developed, forming a 180° angle with the longitudinal axis, base truncate, apex truncate or sometimes rounded; venation often conspicuous, texture coriaceous, pubescence scarcely hirtelous. Leaves (4.7–) 8–16.2 cm long; petiole (0.9–) 1–1.8 cm; rachis (3.5–) 4.7–11.2 cm; 7–9 foliolate; leaflets 3.2–7(–8.2) × 2.9–4.5(–6.5) cm, opposite, or sometimes subopposite; petiolule 3–4 mm long, obscure or yellowish, hairs 0.05 mm long, texture rather thin; venation often no visible due to the density of the indumentum, base acute, obtuse or rounded, apex rounded or acute and apiculate. Inflorescences in dense racemes, sometimes solitary flowers, never on leafless flowering branches; bracteoles conspicuous, narrowly elliptic, 1/10 to 1/8 of the length of the sepals, opposite, hirtelous, usually persistent with white hairs, more dense towards the base at the level of their articulation at the calyx; peduncle 0.8–1.7 cm long, hairs 0.02–0.05 mm, hirsute; calyx 1.1–1.4 × 0.4–0.5 cm, campanulate, densely to sparsely hirsute, the two vexillar lobes 5–7 × 2–2.3 mm, connate along 1/10 of their length, lateral lobes 5–7 × 2–2.8 mm, carinal [keel] lobes 5–6 × 1.8–2.2 mm. Petals red marron except the whitish keel at the distal part.; standard 1.6–1.7 (including the claw) × 1.5 cm, widely ovate to trapezoidal or suborbicular, with a yellowish-green macula; standard inclination angle with respect to the keel and wing petals 85–100°, claw 3–4 mm, auricles forming a 135° angle with the claw; wing petals 1.3–1.5 (including the claw) × 0.5–0.6 cm, obliquely elliptical, vexillar side slightly curved, claw 1.5–2 mm long, auricle forming a 45°–55° angle with the claw; keel petals 1.2–1.3 (including the claw) × 0.5–0.6 cm, lunate, vexillar side of the keel curved and whitish upwards, claw 2.3–2.5 mm long, auricle forming a 120°–130° angle with the claw; androecium 1.4–1.5 cm long; ovary 8.2–8.5 mm long, style 6.5–7 mm long. Fruit 7.3–8 × 1.5–1.6 cm, oblong or rarely obovate, brown to dark brown when mature, mucro 1–3 mm long, with 7 or 8 seeds per fruit; seeds 9–10 × 6–7 × 2.5–2.8 mm, light brown.

Additional specimens examined: — MEXICO: Oaxaca: Mpio. Santiago Tapextla, Jamiltepec, sobre la carr. de terracería a Tapextla , 1 km antes de llegar a la comunidad, 13 Mar 2010, D. Alavés 134 ( MEXU!) ; 1.4 km al noreste del plantel EIBO No. 237, en camino de terracería hacia San Isidro , 92 m elev., 16.364986°, -98.421097°, 13 Ago 2022, O. Dorado 10639, 10640, 10641, 10642, 10643, 10644, J. M. de Jesús-Almonte, G. Cuevas, A. Florentino y A. Burgos ( MEXU, HUMO) ; 1.4 km al noreste del plantel EIBO No. 237, en camino de terracería hacia San Isidro , 73 m elev., 16.352617°, -98.437294°, 25 Feb 2023, O. Dorado 10695, 10696, 10697, J. M. de Jesús-Almonte, G. Cuevas, V. Peñaloza y R. Acevedo ( MEXU, HUMO) ; 4 km al noreste del plantel EIBO No. 237, en camino de terracería hacia San Isidro , seguir 60 m al noroeste, dentro de potrero, 73 m elev., 16.352617°, -98.437294°, 25 Feb 2023, Ó. Dorado 10698, 10699, J. M. de Jesús-Almonte, G. Cuevas, V. Peñaloza y R. Acevedo ( MEXU, HUMO) ; 4 km al noreste del plantel EIBO No. 237, en camino de terracería hacia San Isidro , seguir 120 m al noroeste, dentro de potrero, 73 m elev., 16.352617°, -98.437294°, 25 Feb 2023, O. Dorado 10700, J. M. de Jesús-Almonte, G. Cuevas, V. Peñaloza y R. Acevedo ( MEXU, HUMO) ; 4.1 km al noreste del plantel EIBO No. 237, en camino de terracería hacia San Isidro , 73 m elev., 16.352617°, -98.437294°, 25 Feb 2023, O. Dorado 10702, J. M. de Jesús-Almonte, G. Cuevas, V. Peñaloza y R. Acevedo ( MEXU, HUMO) .

Distribution and habitat: —Known only from the vicinity of the type locality in southwestern Oaxaca, close to the border with Guerrero; also common in some disturbed areas with SDTFW and Woodlands at 70–90 m above sea level; in this habitat grows: Poponax sp. Raf. (1838: 118), Tauroceras cornigerum (L.) Britton & Rose (1928: 86), Gliricidia sepium (Jacq.) Kunth ex Walpers (1842: 679) , Diphysa Jacquin (1760: 7) , Caesalpinia Plum. Ex L. (1753: 380) , Mimosa L. (1753: 516), and Piscidia L. (1759: 1155), among others.

Phenology: —The species presents leaves (at the end of May), flowers and fruits in spring (from February to March).

Specific epithet: — The epithet honors Dra. Dulce M. Arias , a scientist specializing in the southern Mexican flora, especially for Morelos, where her research is outstanding. She has also been very instrumental in documenting the flora of southern México ; she is an example of women in science.

IUCN Red List category: — Brongniartia dulce is the only species of the genus found in southwestern Oaxaca near the border with Guerrero. The area where it has been collected is undergoing to deforestation, mainly due to increasing agriculture practices. About seventy-five individuals were counted/recorded in two locations about 800 m. Brongniartia dulce is assessed as Endangered, EN B2 ac (ii, iii, iv) according to IUCN (2012) criteria.

Discussion: —Within the genus there are four main types of bracteoles and two of stipules. Referring to bracteoles: 1) elliptic to ovate, including Brongniartia intermedia Moric. (1836: 253) and B. dulce ; 2) linear and large, not minute (characteristics in the PG), represented by B. balsensis J. Jiménez & K. Vega (2009: 360–363) ; 3) enclosed the calyx, as in: B. bracteolata Micheli (1903: 249–250) , B. goldmanii Rose (1909: 269) , B. lupinoides (Kunth) Taubert (1895: 613) , B. parryi Hemsl. (1879: 254–255) and B. diffusa Rose (1899: 194) ; 4) minute, 1(–3) mm, linear–subulate, sometimes deciduous. Regarding stipules: 1) not hemicordate (more than two times larger than wider) and 2) hemicordate (the same large and wide) as present in PG and B. dulce . Therefore, the morphological closer species of B. dulce could be B. intermedia .

The bracteoles of B. dulce are narrowly elliptic, small, and do not enclosing the calyx, along with hemicordate stipules ( Table 1, A). This species has a combination of characteristics that is not seen elsewhere in the genus. Brongniartia intermedia has similarly shaped bracteoles, but the stipules of this species are small. The bracteoles of B. balsensis are linear-subulate and stipules that are elliptical ( Tab. 1, B). Other taxa in the genus have broadly elliptical bracteoles that enclose the calyx but may be early deciduous, along with small, elliptical stipules ( Tab. 1, C). The PG, comprising 29 taxa (24 species), is well characterized by the minute or inconspicuous bracteoles and large, hemicordate stipules ( Tab. 1, D).

Figures

FIGURE 1. Brongniartia dulce (Illustration by Gerardo Cuevas and Óscar Dorado). A. Branch with leaves and stipules, B. Hemicordate stipule, C. Bracteoles (closed and open), D. Leaflets (abaxial surface), E. Flowers, F. Standard (front, back and lateral view), G. Wings petals, H. Keel petals, I. Calyx and androecium, J. Fruits mature and immature, K. Seed, L. Stem, M. Whole plant.