Indigofera uniseminalis Rzed. & R. Grether, 2018

Rzedowski, Jerzy & Grether, Rosaura, 2018, Two new species of the genus Indigofera (Papilionoideae, Leguminosae) from central Mexico, Phytotaxa 372 (4), pp. 256-262 : 259-261

Indigofera uniseminalis Rzed. & R. Grether , sp. nov. ( Fig. 2 )

Frutex vel herba perennis ad 1 m alta ; caules plerumque non ramosi; folia numerosa dense instructa 5–9 cm longa, foliolis (19–)23–35 linearibus ad oblongis 7–13(–17) mm longis, 1.5–4(–4.5) mm latis, supra glabris, subtus strigosis; racemi spiciformes (5–) 9–16 cm longi floribus numerosis deflexis; calyx campanulatus ca. 1.5 mm longus dense strigosus; corolla aurantiaca 6–6.5 mm longa, vexillo strigoso, carina ad apicem strigosa ; fructus plerumque numerosi ovoidei, subsphaerici vel ellipsoidei, 3.5–5 mm longi, strigosi monospermi.

Type:— MÉXICO. Guanajuato: municipio de Victoria, Puerto de Trancas, 2000 m, matorral arbustivo, 14 August 1990 (fl, fr), E. Ventura & E. López 8538 (holotype IEB, isotype MEXU).

Shrub or herbaceous plant ligneous in the base, 0.8–1 m high; stems generally not ramified, angled, densely strigulose with fine dolabriform trichomes less than 0.3 mm long, glabrescent; foliage dense and crowded; leaves commonly numerous, 5–9 cm long, stipules triangular, 1 mm long, persistent, petioles 1–1.5 cm long, leaflets (19–)23–35, linear to oblong, apical one frequently oblanceolate, opposite, 7–13(–17) mm long, 1.5–4(–4.5)mm wide, apex obtuse to truncate and mucronulate, base cuneate, membranous, glabrous on adaxial face, strigose with dolabriform trichomes on abaxial face, petiolules 0.8–1 mm long, stipels triangular, 0.3–0.4 mm long; inflorescences in axillary spiciform racemes (5–) 9–16 cm long, frequently longer than leaves, moderately dense and with numerous flowers, axis strigose, bracts triangular-subulate, 0.5–1 mm long, strigose, early deciduous, pedicels 1–1.5 mm long, strigose; flowers deflexed in anthesis, calyx campanulate, ca. 1.5 mm long, densely strigose with dolabriform trichomes, teeth triangular, ca. 0.5 mm long, corolla orange, standard 6–6.5 mm long, 4–4.5 mm wide, obovate, sessile, base attenuate, densely strigose with dark brown dolabriform trichomes on abaxial face, folded, wings 3–5.5 mm long, 1–1.5 mm wide, glabrous, keel strigose on upper portion with white and brown dolabriform trichomes, as long as the standard, its petals ca. 6 mm long, ca. 2 mm wide, fused in upper portion, with spur at midpoint ca. 0.5 mm long, free at base, claw ca. 1 mm long; androecium 5.5–7 mm long, anthers basifixed, ca. 0.5 mm long, mucronulate; ovary strigose with 1 ovule, style curved, glabrous, stigma capitate; fruits commonly numerous, ovoid, subglobose or ellipsoid, reflexed, 3.5–5 mm long, apex apiculate, beak 1.5–2.5 mm long, pericarp hard and thick, green when fresh, brown when dried, strigose, but margins glabrous; seed 1, globose to reniform, 2.5–2.6 mm long, 2–2.3 mm wide, 1.5–1.6 mm thick, testa light brown.

Discussion: —On account of its ellipsoid to subglobose one-seeded fruits, this new species resembles I. sphaerocarpa A. Gray (1853: 37) and I. jaliscensis Rose (1905: 310) . Main differences among the three species are indicated in Table 2.

Indigofera uniseminalis is assigned to sect. Indigofera , according to the preliminary infrageneric treatment of the genus by Schrire (1995: 223), where he included sect. Dispermae Rydberg (1923: 138) as a synonym. This latter group comprised species with 1–3(–4) seeded pods.

Habitat: — Indigofera uniseminalis is an uncommon plant growing in oak forests, pine-oak forests, and in the secondary vegetation nearby. As far as we know, its geographic distribution is restricted to the Sierra Gorda of northeastern Guanajuato, where it occurs at elevations of 1800–2000 m.

Phenology: —The plant blooms in July and August and it has been collected with fruits in July and October.

Etymology: —The name of the species refers to the one-seeded fruits.

Additional specimens examined (paratypes): — MÉXICO. Guanajuato: municipio de Victoria, Mesas del Tigre , 1800 m, matorral arbustivo, 17 August 1990 (fl, fr), E. Ventura & E. López 8594 ( IEB) ; municipio de Victoria, 13 km al W de Xichú , sobre la carretera a San Luis de la Paz, 1800 m, cañada con vegetación de encinar, 30 October 1986 (fr), J. Rzedowski 41553 ( ENCB, IEB) ; municipio de Xichú, Agua Zarca del Pinal , 2000 m, bosque de encino-pino, 15 October 1987 (fr), R. Santillán 482 ( IEB, MEXU, UAMIZ) .

Figures

FIGURE 2. Indigofera uniseminalis. A. Fruiting branch. B. Inflorescence. C. Leaflet, abaxial and adaxial views. D. Open calyx. E. Standard, abaxial view. F. Wings. G. Keel. H. Androecium. I. Gynoecium and vexillary stamen. J. Legume with persistent calyx. K. Seed, lateral view. L. Seed, ventral view. A, J–L drawn from J. Rzedowski 41553 (IEB); B–I drawn from E. Ventura y E. López 8538 (IEB). Illustration by Anabel Duarte.