Eriosema elegans Fort.

Fortuna-Perez, Ana Paula, Silva, Marcos José Da, Cândido, Elisa Silva, Vargas, Wanderleia De, Cobra, Thiago & Vatanparast, Mohammad, 2017, Eriosema elegans (Leguminosae, Papilionoideae): A new species from the Highlands of Goiás State, Brazil, Phytotaxa 296 (1), pp. 81-87 : 82-85

Eriosema elegans Fort. -Perez & M.J. Silva, spec. nov. ( Fig. 1 )

Diagnostic Characters: Subshrubs up to 70 cm tall; stipules caducous; leaves 3–foliolate, the leaflets conspicuously 3–nerved with the adaxial surface puberulous and the abaxial surface glabrous; racemes 15–25 cm long with flowers laxly distributed, and secretory-base trichomes in leaflets. It is morphologically similar to Eriosema glabrum but differs by the features cited in Table 1.

Type:— BRAZIL. Goiás: Alto Paraíso de Goiás, Parque Nacional Chapada dos Veadeiros, imediações do alojamento Lobo Guará em Cerrado sensu stricto, 6 Jan 2016, 14º 9’ 27.4” S, 47º 46’ 57” W, alt. 1.122 m, fl. fr., M. J. Silva et al. 7228 (holotype UFG!; isotypes: BOTU!, OUPR!, NY!) .

Subshrub ca. 70 cm tall, stems erect, little-branched, striate, glabrescent to strigose. Stipules caducous. Stipels absent. Leaves trifoliolate, leaflets three-nerved, midrib prominent, the two lateral veins marginal and near-convergent at apex; petiole 5–10 mm long. Leaflets 4–8 × 0.8–1.5 cm, adaxial surface puberulous, abaxial surface glabrous, narrowly elliptic to narrowly obovate, apex acute, mucronate, base acute, margin entire. Racemes 12–25 cm long (including peduncle), with up to 25 flowers laxly distributed along the rachis, axes villous. Flowers 13–15 mm long, pedicel 5–9 mm long. Calyx 5–lobed, villous, margin entire, punctate; tube 3–3.5 mm long, lobes 2–6 mm long. Corolla yelloworange, the standard 16–18 × 9–10 mm (excluding claw), obovate to narrowly obovate, multi-veined, punctate, apex retuse or slightly emarginate, base auriculate, auricles 0.5–1 mm long, adaxial surface sparsely sericeous, abaxial surface glabrous, claw 1.3–2 mm; wing petals 10–11 × 3–3.1 mm (excluding claw), elliptical to oblong, apex rounded, glabrous, slightly auriculate, claw 2.5–3 mm long; keel petals 9–11 × 4–4.5 mm (excluding claw), obovate, falcate to broadly elliptical, apex rounded, glabrous to puberulous at the apex in both surface, black trichomes, claw 3–3.5 mm long; stamens 10–15 mm long; anthers uniform, 0.5–1 mm long, elliptical; ovary 10 mm long, sericeous; style curved; stigma minute. Fruit oblong, black to brown, 1.8–2.5 × 0.7–10 cm, punctate, with white trichomes but glabrescent, margin hirsute. Seeds 2–7 mm long, oblong, smooth, black.

Additional Specimens Examined (Paratypes):— BRAZIL. Goiás: Alto Paraíso de Goiás, Parque Nacional Chapada dos Veadeiros ( PNCV), imediações do alojamento Lobo Guará em Cerrado sensu stricto, 14º 9’ 27.4” S, 47º 46’ 57” W, 30 July 2016 (fr), A. P. Fortuna-Perez et al. 2655 ( BOTU, UFG).

Distribution and Habitat: — Eriosema elegans is known only from the type locality ( Fig. 2 ) where it grows in open areas of Cerrado vegetation sensu stricto in clayey soil; it occurs together with other legume species such as Centrosema bracteosum Benth. (1837: 55) , Chamaecrista setosa ( Vogel 1837: 51) Irwin & Barneby (1982: 650) and Bauhinia goyazensis Harms (1903: 21) .

Phenology: —The species was collected with flowers and fruits in January, and with fruits in July.

Etymology: —The specific epithet elegans was chosen due to the pleasing appearance of the new species.

Conservation Status: —Since the new species is known only from the locality of type we prefer to consider its conservation status as Data Deficient (DD) according to IUCN Red List criteria ( IUCN 2014).

Taxonomic Comments: — Eriosema elegans can be confused with E. glabrum Mart. ex Benth. and E. glaziovii Harms because both have three leaflets, the inflorescence surpassing the leaves, and conspicuous veins in the leaflets. It can be differentiated from both species especially by the characters listed in Table 1. Additionally, E. elegans is unique among trifoliolate Eriosema species in Brazil in having a peculiar type of trichome on the adaxial leaflet surface, referred as secretory-base trichomes (see secretory structure studies section bellow).

Secretory Structure Studies: — Eriosema elegans exhibits vesicular glands ( Fig. 3C ), idioblasts in the mesophyll ( Fig. 3A ), and a peculiar type of trichome on the adaxial leaflet surface, referred to here as secretory-base trichomes ( Fig. 3A ); these have been reported only from the unifoliolate species E. grearii Cândido & Fort. -Perez ( Cândido et al. 2016). The secretory-base trichomes are multicellular, unbranched, uniseriate trichomes, composed of an elongated, acuminate apical cell with thick lignified walls, three intermediate cells with thick lignified walls, and a large basal cell ( Fig. 3A, C ). The vesicular glands have bulky heads and one-celled peduncles embedded in epidermis depressions ( Fig. 3C ).

In contrast, Eriosema glabrum does not have the secretory-base trichomes, but has vesicular glands ( Fig. 3B ), besides non-glandular, multicellular, unbranched and uniseriate trichomes with one elongated acuminate apical cell and one basal cell ( Fig. 3B ). The two species also differ in trichome density: in E. elegans , tector trichomes are sparsely distributed ( Fig. 3E ), while in E. glabrum trichomes are practically absent, being restricted to the midrib ( Fig. 3F ). Eriosema glaziovii also does not have the secretory-base trichomes as cited in Table 1, only tector trichomes.

Figures

FIGURE 1. Eriosema elegans. A. Flowering branch. B. Detail of the adaxial surface of the leaflet. C. Detail of the abaxial surface of the leaflet. D. Calyx opened out. E. Petals: Standard, wing petals and keel petals. F. Gynoecium, note the sericeous trichomes. G. Staminal sheath. H. Fruit (M.J. Silva et al. 7228). Drawn by Jesiani Rigon.

FIGURE 2. Distribution map of Eriosema elegans. The new species has been recorded only from the state of Goiás, Midwest of Brazil (Ecoregions of the world modified from Olson et al. 2001).

FIGURE 3. Optical micrographs and SEM of Eriosema elegans and E. glabrum. A. Secretory-base trichomes on the adaxial leaflet surface (black arrow). B. Non-glandular trichomes common to all species of the genus (black arrow) and vesicular glands on the abaxial leaflet surface (black asterisk) in E. glabrum. C. Vesicular glands and secretory-base trichomes (white arrow) in E. elegans. D. Details of vesicular glands with eight cells in head embedded in the epidermis depressions in E. elegans (white asterisk). E. Overview of the abaxial surface of leaflets of E. elegans. F. Overview of the abaxial surface of leaflets of E. glabrum.