Mucuna chiapaneca M. Sousa & T.M. Moura, 2016

Sousa, Mario & Moura, Tânia Maria De, 2016, Mucuna chiapaneca (Leguminosae-Papilionoideae) a new species from Mexico, Phytotaxa 246 (3), pp. 198-202 : 198-200

Mucuna chiapaneca M. Sousa & T.M. Moura , sp. nov. ( Fig. 1 )

M. tapantianae N. Zamora et T. M. Moura affinis a qua differt stipellis aliquot persistentibus (versus absentes), inflorescentia rachidi secundaria sine nodulis, recta et rachidi pedicellis distichis sine spatiis inter paria (versus nodulos manifestos et rhachim pedicellis distichis cum spatiis sinuosis inter paria), fructibus cum partibus floralibus persistentibus (versus partes florales cito caducas). Habitat in sylvis borealibus caducifoliis.

Type:— MEXICO. Chiapas: Jitotol, along the Rio Hondo 6.5 km North of Jitotol along road to Pichucalco, 1700 m, 27 October 1971 (fl.), D. E. Breedlove & R. F. Thorne 21422 (holotype: MEXU!, isotype: DS!).

Liana. Leaf-bearing portion of stems with sparse, adpressed hairs; stipules lanceolate, caducous. Leaves alternate, trifoliolate, 22 × 13–14 cm; pulvinus 5–8 × 2–3 mm; petiole 7–10 cm long, with sparse, erect hairs (sometimes glabrous); stipels persistent, acicular, ca. 2 mm long; rachis 2.5–3.5 cm long, with sparse, erect hairs; petiolule 1 cm long, with sparse, erect hairs; leaflet blades glabrous on both surfaces; lateral leaflets 9–10 × 4.5–5 cm, asymmetric at base, cuspidate at apex; terminal leaflets elliptic to obovate, 9.5–10 × 4.5–8.5 cm, acute at base, cuspidate at apex. Inflorescence an axillary, pendent pseudoraceme, peduncle reported as up to 2.5 m long, with a sparse indumentum of short, adpressed hairs; bracts caducous; rachis ca. 5 cm long, secondary axis neither nodose nor evident, pedicels 5–6.5 cm long. Flowers 4.5–5 cm long; calyx 1.5 cm long, sericeous; 4-lobed, the adaxial lobe formed by two connate sepals, 5 × 7 mm, retuse at apex, lateral lobes 5 × 2 mm, acute at apex, abaxial lobe 8 × 3 mm, acute at apex; corolla reported as cream or greenish-yellow; standard 4 × 3 cm, oval, truncate at base, 2 auricles 2 mm long, claw 8 mm long; the wings 3 × 1 cm, obovate, auriculate at base (auricle 1 mm long), claw 9 mm long; keel petals 4 × 1.5 cm, oblong, auriculate at base, acute at apex, claw 1 mm long; wing and keel petals pubescent at base, stamen diadelphous, filaments 4–4.8 cm long, glabrous; anthers dimorphic, either basifixed, oblong, ca. 4 mm long, or sub-basifixed, subglobose, ca. 2 mm long, gynoecium ca. 4.3 cm long, style 3.8 cm long, sericeous, the hairs becoming sparse at apex; ovary 1.2 × 0.3 cm, with a dense indumentum; stigma peltate, villous. Fruits legume, opening along one suture, 1–(2–3)-seeded, when 1-seeded, ovate-oblique, long atenuate at base, 7–8 × 5 cm, rostrate at the apex, when 2–3-seeded, oblong, 11.5–14.5 × 3.6–5 cm, short attenuated at base, short rostrate, constricted between the seeds, laterally compressed, covered with dark brown (umber) pilose long ascending soft non irritant trichomes. Seeds (immature) 1–3 per fruit, 2.7 × 2.3 cm, globose, laterally compressed, black; hilum circling almost all the seed circumference.

Etymology:— The species name remarks the state of Chiapas, Mexico in which this species grows. Phenology:— Flowering in June to October and fruiting in August. Distribution and ecology:— Species endemic to Chiapas, Mexico, on the Jitotol, Ridge in the Northern Highlands of Chiapas ( Fig. 2 ); in two different forests, one the Montane Rain Forest, and the other in Pine-Oak-Liquidambar forest, both forests are close each other. Mucuna chiapaneca was determined in the study by Zuill & Lathrop (1975) as M. argyrophylla . The new species is present at elevations between 1700 and 1920 m.

Conservation Status:— Mucuna chiapaneca has a restricted extent of occurrence (EOO= 57,000 km 2, CR) and area of occupancy (AOO= 24,000 km 2, EN). Moreover, this species is reported to few localities to Chiapas, Mexico. Although there are native forests in this area, none specimen of M. chiapaneca was registered to a protected area and the environment, where this species occurs, is disturbed as a whole due to the presence of roads, and agricultural spots. Therefore, according to IUCN criteria (2014) M. chiapaneca is assessed as endangered [(EN B1B2ab(iii)].

Additional specimens examined (Paratypes):— MEXICO. Chiapas: Pueblo Nuevo Solistahuacán, Rincón Chamula, Slopes with Pinus and Quercus , 20 August 1969 (fl., fr.) O.F. Clarke 298 (DS, ENCB, MEXU); Selva Negra, ca. 3 mi N of Pueblo Nuevo Solistahuacán, 3 June 1970 (fl.) R.F. Thorne & E. Lathrop 40252 (DS, ENCB); vicinity of Pueblo Nuevo Solistahuacán, 125 km NE of Tuxtla Gutiérrez, 22–30 June 1963 (fl.), S.S. Tillet 636–67 ( US); above Pueblo Nuevo Solistahuacán, 15 August 1967 (fl.) A.S. Ton 2833 (DS, MEXU); on slopes 3 km northwest of Pueblo Nuevo Solistahuacán, 22 August 1970 (fl.) H. Zuill 276 (DS).

Discussion:— A very distinguished characteristic for M. chiapaneca is the persistent floral parts at the base of the fruits; not noticed for the other species of this genus. Mucuna chiapaneca is similar to M. tapantiana and slight similar to M. argyrophylla , especially in the colour of the corolla and the short wing petals (these are usually shorter than the standard petal but including the claw they are almost of the same length). Both M. tapantiana and M. argyrophylla , however, have a nodose secondary inflorescence axis (whilst M. chiapaneca does not), and peduncle up to 1 m long (whilst in M. chiapaneca it is up to 2.5 m long). Mucuna chiapaneca has stipels whilst M. tapantiana has not. The flowers in M. tapantiana are slightly shorter (4–4.5 cm long) than in M. chiapaneca (4.5–5 cm long); and the fruits in M. tapantiana are ornamented by discrete lamellae (versus no ornamented in M. chiapaneca ). Among the species occurring in Mexico, M. chiapaneca is easily distinguished from M. argyrophylla by a dense sericeous, argenteus indumentum on the abaxial surface of its leaflets (versus glabrous leaflets in M. chiapaneca ).

An account of the accepted names of Mucuna occurring in Mexico, including some diagnostic characters, is presented in the Table 1.

Although we presented here six species occurring in Mexico, a special attention to the representatives of M. subg. Stizolobium occurring in this Country is still necessary. Moreover, Ruiz (2009) commented the possibility of M. holtonii becomes a synonym of M. mollis ; however, observations of these species in loco are necessary for unveiling it.

Figures

FIGURE 1. Mucuna chiapaneca. A. Leaf and the pendent inflorescence; B. calyx; C. standard petal; D. wing petal; E. keel petal; F. androecium; G. gynoecium; H. pendent inflorescence with flowers on the floral rachis; I. branch bearing 2–3-seeded fruits, including persistent flower part remains at their base; J. fruit margin showing the pilose ascending trichomes; K. stipule; L. stipels. Flowering material, stipels and stipule from the type Breedlove & Thorne 21422 (MEXU); gynoecium from Thorne & Lathrop 40252 (DS). DRAWN BY RAMIRO CRUZ.

FIGURE 2. Geographical distribution map of Mucuna chiapaneca. Created using Diva GIS.