Mimosa flabellifolia Barneby (1991: 226)

Borges, Leonardo Maurici & Antar, Guilherme Medeiros, 2016, Four they are! Broadening the description of Mimosa flabellifolia (Leguminosae Mimosoideae), a rare species from the Brazilian Cerrado, Phytotaxa 243 (2), pp. 155-162 : 156-159

Mimosa flabellifolia Barneby (1991: 226) Figs. 1–3

Type:— BRAZIL. Goiás: [Pindorama de Tocantins], campo cerrado em solo concrecionario, próximo a Pindorama de Goiás, 11º14’ S, 47º28’ W, 21 April 1978, fr., R.P. Orlandi 77 (holotype: RB photo! (2 sheets) , isotypes: NY! [fragmentary] , HRB [?] ).

Subshrubs 20–30(–50) cm tall; the thin, ribbed, green to reddish branches spreading from the xylopodium; individuals sparsely clustered. Plants completely glabrous except by some sessile glandular trichomes ca. 0.03–0.05 mm diam. on branches apexes, floral bract’s margins and calice’s rim. Leaves 1-jugate; stipules 0.5–0.8 mm × 0.1–0.2 mm, lanceolate, persistent; petioles 0.8–1 mm long, ca. 0.4 mm diam., grooved on adaxial surface, the pulvinus 0.4–0.5 mm long, terminal projection 0.5–0.7 × 0.1 mm, lanceolate; rachillas 10–16 mm long, ca. 0.2 mm diam., slightly recurved; leaflets in (1–) 2 pairs per pinna, the basal ones 2.8–3.8 × 1.3–2 mm and the larger distal ones 4.5–5.9 × 2.1–3 mm, all narrowly-obovate to obovate, 0.3–0.5 mm apart, veins 3-palmate, but usually only the midrib is perceived as prominent on the abaxial surface, apex rounded and mucronate to obtuse, base slightly inequilateral, rounded; the prominent paraphyllidia 0.3–0.4 × ca. 0.1 mm, subulate. Racemes 3.3–3.5 × 3.5–3.8 mm, globose, 1-axillary to a young leaf that may fully develop only after the anthesis of its associated raceme; peduncles 8.2–9.5 mm long; floral bracts 0.7–1 × ca. 0.3 mm, ellipsoid-acuminate, slightly cymbiform, 1-nerved, glabrous except by the margins with a few glandular trichomes; flowers 4-merous, diplostemonous, basal ones staminate only; pedicel 0.1–0.2 mm long; calyx 0.3–0.5 mm long, cupulate, tube 0.2–0.4 mm long, lobes 0.1–0.2 mm long, rim ciliate with a few glandular sessile trichomes less than 0.5 mm long; corolla 1.7–2.2 mm long, campanulate, glabrous, lobes 0.9–1.1 × 0.6–0.7 mm, narrowly ovate, 1-nerved, vein branching at the acute apex; filaments 3.8–5 mm long, glabrous, fused ca. 0.1 mm at base, apparently white; anthers ca. 0.4 × 0.4 mm, glabrous; ovary 0.5–0.6 × ca. 0.3 mm, compressed, elliptic, glabrous, stipe ca. 0.2 mm long, glabrous; style 5.2–6 mm long, glabrous; stigma porate, glabrous. Fruit a craspedium 24–35.7 × 6.2–8.75 mm, elliptic to narrowly oblong, constricted between articles, papery, dark brown, apex obtuse to rounded, obliquely aristate, base cuneate, sometimes rounded; pedicel 3–6.5 × 0.5–0.6 mm; replum ca. 0.5 mm wide; valves breaking into 1–3(–5?, Barneby 1991) articles, 6.6–12 × 5.4–7.95 mm, monospermic, oblong to elliptic, truncate at the breaking region, colliculate over each seed; sparsely puberulous with sessile glandular setae ca. 0.05 mm diam.; seeds not seen.

Additional specimens examined: — BRAZIL. Tocantins: Ponte Alta do Tocantins, estrada Ponte Alta do Tocantins–Rio da Conceição , próximo à fazenda do Sr. Luis Piriquito, 10°59’08,9’’ S, 47°11’02,4’’ W, 29 January 2015, fl., G.M. Antar et al. 701 ( SPF! NY! [To be distributed]) .

Distribution: — Mimosa flabellifolia is endemic to Jalapão and nearby areas in the state of Tocantins, Brazil. It occurs in sandy soils of open cerrado vegetation, at elevations from 450 to 600 m. Populations are small, apparently rare and formed by sparsely clustered individuals.

Conservation status: —CR. GeoCAT analysis indicates EOO as 0.344 km 2 and AOO as 8000 km 2. Both values place Mimosa flabellifolia in the critically endangered category ( IUCN 2012). It is important to note, however, that the species was collected only twice in a botanically underexplored area. Therefore, it is possible for its areas of occurrence and extension to be larger. Nonetheless, the fact that only two populations with few sparsely distributed individuals are known rises the threaten concern of M. flabellifolia .

Notes: —The type specimens of Mimosa flabellifolia were collected as part of the RADAM Brasil project, which had as one of its goals to survey the Brazilian Vegetation. Specimens collected during the project were stored at the HRB herbarium and duplicates were sent to other herbaria, including RB. We were not able to check the HRB collection, but it is very likely that it houses an isotype of M. flabellifolia .

Barneby (1991) indicates that the proximal anterior leaflet is commonly lacking in the species. However, all leaves of Antar et al 701 bear four leaflets organized in two pairs. The photograph of the isotype at RB also appears to have both basal leaflets, although study of the specimen itself is necessary. Nonetheless, we believe that Barneby’s impressions are artificial, based on the scant collection he studied and the ease with which leaflets fall.

According to Barneby (1991: 226), the racemes of Mimosa flabellifolia may form “a lax terminal pseudoraceme, the lowest ones subtended by a leaf, the upper bracteate”. Nonetheless, the specimens and images we studied, particularly the recently collected specimens, exhibit all racemes subtended by leaves, which may not be fully expanded during anthesis. In some cases, similar to what is seen in the type material, those leaves may have fallen. At present, it is not possible to evaluate if the development of leaves continues parallel to fruit maturation, since leaves subtending fruits are not present in the type material, and Antar et al. 701 has only flowers.

Figures

FIGURE 1. Mimosa flabellifolia. A. Sparsely clustered individuals. B. Shoot apex with inflorescences. All from Antar et al. 701. Photographs by G.M.Antar.

FIGURE 2. Mimosa flabellifolia. A. Branch bearing leaves and inflorescences. B. Leaf. C. Floral bract. D. Flower.All based on Antar et al. 701. Drawing by Laura Montserrat.

FIGURE 3. Known points of occurrence of Mimosa flabellifolia, both outside of the Estação Ecológica Serra Geral do Tocantins (ee; white area). · Antar et al. 701. ▲ Approximate type collection site. States: BA—Bahia; MA—Maranhão; PI—Piauí; TO—Tocantins.