Macropsychanthus nitidus Fonseca-Cortes & L. P. Queiroz 2023, comb. et stat. nov.
Creators: name: Fonseca-Cortés, Andrés
name: Snak, Cristiane
name: Queiroz, Luciano Paganucci De
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Fabales
Fabaceae
Macropsychanthus
Macropsychanthus nitidus

description: Macropsychanthus nitidus Fonseca-Cortés & L.P. Queiroz, comb. et stat. nov.
Basionym: Dioclea rostrata var. nitida Benth., Fl. Bras. 15(1): 168. 1859. Type: Brazil, Mato Grosso?, ‘ Salto do Curaú, rio Pardo’, Riedel 452 (560) (lectotype designated by Queiroz & Snak (2020): LE! [00002539]; isolectotypes: A! [00066322], F! [0059202F], K! [000502901], NY! [01583820]). Fig 1.
Erect to procumbent shrub to 2 m tall; branches terete, grey, hollow in the young ones, glabrous or canescent sericeous. Stipules 0.1–0.2 × 0.1–0.2 cm long, basifixed, triangular, canescent or fulvous sericeous. Leaves spirally arranged; petiole 2–6 cm long, terete, canaliculate, brown, glabrous to canescent sericeous; rachis 0.5–2.0 cm long, terete, glabrous to canescent sericeous; stipels absent; petiolules 0.5–1.0 cm long, cylindrical, canescent or fulvous sericeous; leaflets coriaceous, conduplicate, elliptical or ovate, base cuneate to rounded, apex extended into a 0.5–0.7 cm long acumen, mucronate; primary venation pinnate, secondary veins 8–11 pairs, brochidodromous, upper surface glabrous, shinning, lower surface densely argenteous sericeous; terminal leaflet 8–13 × 3–6 cm; lateral leaflets 6–13 × 2.8–5.0 cm. Inflorescence 20–40 cm long, axillary or terminal, pseudoracemose, straight, erect, glabrous to canescent sericeous; inflorescence peduncle 2–15 cm long; brachyblasts 0.5–1.2 cm long, straight, pedicellate, 1.3–3.0 cm apart along the inflorescence rachis; first order bract (at brachyblast attachment) 2–4 × 1–2 mm, erect, lanceolate, canescent or fulvous sericeous; second order bract (at the pedicel attachment) 0.1–0.2 × 0.1–0.2 cm, ovate, fulvous sericeous; bracteoles (at calyx base) two, opposite, 2–3 × 2–3 mm, rounded, fulvous or dark brown sericeous; pedicel 0.4–0.5 cm long, fulvous sericeous. Flowers 1.0– 1.5 cm long; pedicels 0.4–1.0 cm long, canescent or fulvous sericeous; calyx 0.5–1.0 × 0.4–0.7 cm, campanulate, slightly gibbous behind the upper lobe, argenteous sericeous; upper lobe 0.3–0.5 × 0.3–0.5 cm, rounded, entire or emarginated; lateral lobes 0.3–0.5 × 0.2–0.4 cm, falcate; lower lobe 0.5–0.5 × 0.2–0.4 cm, lanceolate; petals glabrous, lilac, standard petal 1.0–1.6 × 0.8–1.2 cm, ovate, with two callosities in the base and two basal auricles, claw 0.2–0.5 × to 0.1 cm; wing petals 1.0–1.5 × 0.6–1.0 cm, lower lobe rounded and rounded apex, claw 0.3–0.5 × to 0.1 cm, with a dorsal spur at the base of the claw; keel petals 0.8–1.2 × 0.8–1.2 cm, semilunar, distal margin straight, claw 0.3–0.5 × to 0.1 cm; androecium 0.8–1.2 cm long, pseudomonadelphous, fertile stamens 5 on longer filaments, anthers ovate, staminodes 5 on shorter filaments, anthers ovate; intrastaminal nectariferous disk shortly cylindrical; ovary sessile, ovoid, 2–3-ovulate, densely canescent sericeous, style 0.7–2.0 cm, linear, the basal part canescent sericeous; stigma capitate. Legume 12–13 × 3–4 × 0.3–0.6 cm, woody, obovate, laterally compressed, brown puberulous, woody inside, 2–3-seeded Seeds 2.0–2.4 × 1.7–2.0 × 0.3–0.6 cm, ovoid, laterally compressed, smooth, hilum circular.
Etymology: —The specific epithet makes allusion to the shiny indumentum of the lower leaflet surface.
Distribution and habitat: — Macropsychanthus nitidus is known only in the Mato Grosso and Rondônia Brazilian states (Fig. 3). It occurs in savanna vegetation of the Cerrado phytogeographical domain, a mostly open vegetation with mixed grassy and shrubby layers on sandy soils and latosols.
Addtional examined material:— BRAZIL. Mato Grosso: Reserva do Cabaçal. Chapada dos Parecis, após a Comunidade Casulo Mulher. 15° 04´20´´ S 58° 26´16´´ W, 546 m, 2 September 2015, Lima et al. 8068 (RB!, INPA!, HUEFS!); Reserva do Cabaçal, Chapada dos Parecis, Fazenda Gozen, 15° 01´21´´ S 58° 23´23´´ W, 581 m, 2 September 2015, Lima et al 8090 (RB!, HUEFS!, INPA!); Tangará da Serra, próximo ao Rio Verde (Chapada dos Parecis) 14° 23´S 58° 18´W, Messias Santos 209 (INPA!); Sararé Radambrasil, folha SD21-YC, ponto, vegetação de caatinga amazônica baixa, 28° 13´50´´ S 58° 55´W, 3 August 1978, J.M. Pires & Santos 16357 (INPA!, RB!, MG!).
Conservation Status: —The AOO got an area of 5,738 km 2 and the EOO an area of 16 km 2. Macropsychanthus nitidus meets the requirements of endangered species, it is only known from four localities, most of the collections were done in the last century, and actually the areas in which the species grows has been mainly converted for soy production (Valdiones et al. 2022). Consequently, we assign the Endangered (EN) category (B2aii) (IUCN 2022).
Notes
Bentham (1837) described Dioclea rostrata based on the specimen collected by M. Wied s.n. (BR-0000005197040 and BR-0000005197378) and included it in Dioclea sect. Pachylobium (now subgenus Macropsychanthus). Later, Bentham (1859) cited an additional specimen (Gardner 1557, K) from the Araripe range in Ceará state and placed the species in sect. Platylobium, he also described the variety D. rostrata “β” nitida with the basis of Riedel 452 (560). In his unpublished PhD thesis, Maxwell (1969) followed Bentham (1859) and retained D. rostrata in the sect. Platylobium. Since he could not examine the type of D. rostrata, he proposed it as a synonym of D. bicolor based on Gardner 1557 (K). For D. rostrata var. nitida he suggested the unpublished combination Dioclea nitida (Benth.) R.H. Maxwell. Finally, Queiroz and Snak (2020) proposed D. rostrata and D. rostrata var. nitida as synonyms of M. bicolor.
The analysis of the Wied specimens (BR) showed the presence of stipels, and keel petals with rounded apex. The presence of stipels and the shape of the keel form suggest a closer relationship with the species of the subgenus Macropsychanthus. However, the lack of a direct analysis of the type collection prevents us to determine if this taxon corresponds to another species of Macropsychanthus subg. Macropsychanthus or to a species only known for the type collection. Despite this, it is clear that Wied specimen belongs to subgenus Macropsychanthus and does not correspond either to M. bicolor or to M. nitidus both of the subgenus Platylobium. On the other hand, Gardner 1557 (K) actually corresponds to M. bicolor.
Macropsychanthus nitidus is unique in the subgenus Macropsychanthus by the combination of the leaf rachis to 2 cm, leaflet undersurface sericeous argenteus and keel apex straight. This species could be confused with M. erectus and M. bicolor, for which we include the mains differences of the three species in Table 1 and Figure 2.
description: Published as part of Fonseca-Cortés, Andrés, Snak, Cristiane & Queiroz, Luciano Paganucci De, 2023, Macropsychanthus nitidus: a new rank and combination for dioclea rostrata var. nitida (leguminosae, papilionoideae), pp. 293-298 in Phytotaxa 619 (4) on pages 294-297, DOI: 10.11646/phytotaxa.619.4.4, http://zenodo.org/record/8430575