Mimosa melosa J. Gelma, L.P. Queiroz & Van den Berg, 2023

Do Nascimento, Janaína Gelma A., Rocha, Lamarck, Dutra, Valquíria F., De Queiroz, Luciano P. & Berg, Cássio Van Den, 2023, Four new species of Mimosa sect. Batocaulon ser. Cordistipulae (Leguminosae) from Bahia, Brazil, Phytotaxa 599 (5), pp. 265-279 : 273-276

4. Mimosa melosa J. Gelma, L.P. Queiroz & Van den Berg , sp. nov. Figs. 4A–G , 5 .

Type:— BRASIL, Bahia: Mun. Pil„o Arcado, Brejo do Zacarias, ca. 30 km de Pil„o Arcado , 10°05’55’’S, 42°54’41’’W, 8 December 2005 (fl.), J.G.A. Nascimento 557 (holotype: HUEFS [barcode 000234325]!; isotype: HUEFS [barcode 000248806]!) .

Affinis M. xiquexiquensi Barneby (1991: 279) sed habitu erecto usque 1.5 m alto (nec decumbenti), floribus in capitulis ellipsoideis (nec spicis elongatis), inflorescentia fasciculata (nec axillar sejuncta) differt.

Subshrubs 1–1.5 m tall, erect; branches cylindrical, viscid, vilose, with filiform trichomes, 0.1–0.3 mm long, and capitate-filiform glandular trichomes, 0.5–2 mm long. Internodes 14–16 mm long. Stipules 4–5 × 1–1.3 mm, lanceolate, chartaceous or subcoriaceous, base truncate, apex acuminate, pilose, margin ciliate, 1–3-veined. Petiole 2–5 mm long, rachis 35–40 mm long, with small prickles, first interpinnal segment 3–5 mm long, remaining segments 2–3 mm long; pinnae 10–16 pairs, median pinna 5–6 mm long, decreasing in size toward to the leaf base; leaflets 10–12 pairs per pinna (median pinnae), membranaceous, 1.5–2 × 1–1.2 mm, oblong, apex obtuse, base rounded, both surfaces sericeous, margin ciliate, 3-veined. Capitula ellipsoid, 6–12 mm long, 25–30-flowered, 2–3-fascicled in efoliate terminal pseudoracemes; peduncle 12–15(–25) mm long, vilosulous, mixed with capitate-filiform glandular trichomes; bracts 0.4–0.5 × 0.2–0.25 mm, membranaceous, obovate, slightly clawed. Flowers sessile; calyx white, 0.6–0.7 mm long, campanulate, lobes with apex truncate; corolla white with pink a rim, glabrous, subtubular, membranaceous, tube 1–1.2 mm long, lobes 1–1.2 mm long, acuminate; stamens 6, filaments dark-pink, connate ca. 2 mm long at the base, three longer 4–5 mm, three shorter 3–4 mm long, anthers 0.4–0.6 mm long, globose, yellow; ovary 0.6–0.8 mm long, dense capitate-setiform trichomes, stipitate, stipe ca. 0.3 mm long, 3–6-ovulate; style 1–1.2 mm long. Fruit and seeds unknown.

Distribution, habitat and phenology:— Mimosa melosa is known from only two collections from a single population in Pil„o Arcado municipality, Bahia, Brazil ( Figure 5 ). The specimens were collected on inland sand dunes on the banks of the S„o Francisco River, growing in open areas between clumps of vegetation, at 420 m of elevation, with flowers in September and December.

Conservation:— As there is a lack of information on the distribution of M. melosa in this area, we propose that this species be categorized as Data Deficient (DD). The S„o Francisco dunes are formed by extensive aeolian deposits, which can exceed 100 m in height, covered by caatinga vegetation ( Rocha et al. 2004). The soils are sandy and deep, with very low fertility ( Velloso et al. 2002). The dune area is apparently well preserved, with little human disturbance, such as the extraction of wood for fire making, which threatens the stability of the dunes.

Etymology:—The epithet melosa refers to the vernacular name of this species, giving the sensation of viscosity when touched.

Notes:— Mimosa melosa is morphologically related to M. xiquexiquensis , both have leaves with (8–)14–18(–22) pairs of pinnae and 11–12 pairs of leaflets per pinna. Mimosa melosa can be differentiated by erect habit, 1–1.5 m tall (vs. prostrate habit, ca. 0.5 m tall in M. xiquexiquensis ), smaller petioles, 2–5 mm long (vs. petioles usually larger, 5–7 mm long) and inflorescence units as ellipsoid capitula grouped in fascicles along a terminal efoliate pseudoraceme (vs. solitary and axillary elongate spikes) ( Table 4).

The region of the S„o Francisco river dunes includes a very differentiated biota with a high number of endemic species of plants and animals ( Rocha et al. 2004; Queiroz et al. 2017). The endemic plant species are usually distributed throughout this area. However, the Mimosa melosa - Mimosa xiquexiquensis pair seems to be an example of geographical speciation within the dunes, with M. melosa occurring in the northern part of the dunes and M. xiquexiquensis in the southern part, but in similar habitats. Many of the endemic plant species have been recently described from this area, such as Aeschynomene sabulicola Queiroz & Cardoso (2008: 750) , Rhynchosia franciscana Queiroz & Cardoso (2018: 975) and Pterocarpus monophyllus Klitgaard et al. (2000: 989) .

Paratype:— BRAZIL. Bahia: Mun. Pil„o Arcado, Brejo do Zacarias , 28 September 2005 (fl.), L.P. Queiroz et al. 10968 ( HUEFS) .

Figures

FIGURE 4. Mimosa melosa. A. reproductive branch. B. portion of the branch showing stipules. C. detail of the branch indument, showing glandular trichomes. D. pinnae in adaxial surface. E–F. leaflets showing adaxial (E) and abaxial (F) surfaces. G. flower (Drawing from Nascimento 557, holotype—HUEFS, by Carla Lima).

FIGURE 5. Distribution map of new species of Mimosa ser. Cordistipulae from Bahia.