Rhynchospora barbosae W. W. Thomas, 2024

Thomas, William Wayt, Silva Filho, Pedro Joel Silva da & Reginato, Marcelo, 2024, Rhynchospora section Pleurostachys (Cyperaceae): a phylogeny and three new species from the dry forests of Bahia and Espírito Santo, Brazil, Plant Ecology and Evolution 157 (3), pp. 257-269 : 257-269

Rhynchospora barbosae W. W. Thomas sp. nov.

Figs 2 , 3 A – B , 4 A , 5

Type.

BRAZIL – Espírito Santo • Mun. Santa Teresa, 1.5 km N of São João do Petrópolis on ES- 80, then 600 m W on dirt road and 300 m on foot to Reserva Valão São Bras ; 19 ° 48 ’ 10 ” S, 40 ° 41 ’ 21.7 ” W; 160 m; 22 Sep. 2016; W. W. Thomas, M. R. Barbosa, F. Z. Saiter & E. F. Oza 16619; holotype: JPB [ JPB 63492 ]; isotypes: G, K, MBML, MO, NY, P, RB .

Diagnosis.

Rhynchospora barbosae is unique in having leaf blades less than 1 cm wide and nutlets 2.4–2.6 mm long.

Description.

Plants glabrous, rhizomatous, the rhizomes 2.5–4 mm in diameter, the internodes 1.5–6 cm. Culms arching, 30–56 cm long, 1–1.7 mm wide. Leaves basal or on basal portion of fertile culm, usually 3–6, the older leaves dying as culms mature; sheaths tight, 3–3.8 cm long, the summit of the sheath concave or “ V ” shaped; blades 29–57 × 0.8–0.9 cm, linear. Synflorescence a series of 3–4 inflorescences, each subtended by a leaf-like bract, the bracts at each more distal node diminishing in size, the basal bract with a sheath 12–15 mm long, the blade linear, 30–43 × 6–8 mm; inflorescences corymbose grouped into 2–3 basal longer lateral branches and 2–4 shorter distal branches forming a terminal cluster and comprising 17–35 spikelets, each lateral branch with 2–5 spikelets; lower lateral branches greatly exceeding the central axis; lowest inflorescence with central axis 50–56 × ca 0.5 mm long, the portion distal to the lowest lateral branch 13–25 mm long; basal lateral branch 20–39 × ca 0.2 mm long. Mature spikelets lenticular (slightly flattened), brown, ellipsoid to ovoid, 3–3.2 (– 4.2) × 2.3–2.5 mm, the basal 6–7 glumes distichous, carinate, cucullate, the apex acute and mucronate, the mucros separating from the glume below apex. Hypogynous bristles ca 1.7–1.8 mm long, densely short-plumose on the distal two thirds, sparsely so on the basal third. Nutlet broadly elliptic to broadly obovoid in outline, deeply ellipsoid to nearly globose, 2.4–2.6 × 1.8–1.9 mm, the summit straight to slightly arched, the persistent style base triangular, (0.9 –) 1.1–1.2 × 0.9–1 mm, the surface shiny, smooth to lightly and irregularly textured.

Distribution and habitat.

Rhynchospora barbosae is known from a single area of Atlantic Forest in the state of Espírito Santo, Brazil (Fig. 5 ). The only collections are from an intact tropical seasonal semi-deciduous forest ( Thomas and Barbosa 2008) at 160 m on a forested slope, usually among rocks.

Etymology.

The species is named in honour of Dr Maria Regina de Vasconcellos Barbosa, a co-collector of the type. She is a Brazilian botanist and Senior Professor at the Federal University of Paraíba. She is a brilliant teacher and is an expert on the Rubiaceae and on the vegetation of north-eastern Brazil.

Preliminary IUCN conservation assessment.

Rhynchospora barbosae is known from three localities in a ca 15 km strip of semi-deciduous forest in the municipality of Santa Teresa, Espírito Santo (Fig. 5 ). The Atlantic Forest of Brazil has been identified as one of the World’s biodiversity “ hotspots ” ( Myers et al. 2000), in part, because of continuing deforestation. Overall, the Atlantic Forest has been reduced to less than 11 percent of its original extent ( Ribeiro et al. 2009), with the dry forests suffering the most. The Extent of Occurrence for this species is 8.05 km 2, a value that would be considered CR. The Area of Occupancy is 12.0 km 2, a value just large enough that it would suggest that EN is the proper Red List category. The municipality of Santa Teresa, however, has been well collected and there are few remaining semi-deciduous forests in the region, and the little that is left is under pressure. While the species is collected from three localities, we consider them to comprise a single location. Since the location is unprotected and anthropogenic pressure on the semi-deciduous forests in the region is high, we assess R. barbosae as Critically Endangered: CR B 1 ab (iii).

Additional material examined.

BRAZIL – Espírito Santo • Mun. Santa Teresa, IFES Campus Santa Teresa, mata do São Brás , abaixo do ponto de captação de água, Folhas verdes escuras, rígida, dentro da mata, solo raso; 19 ° 48 ’ 11 ” S, 40 ° 41 ’ 20.4 ” W; 350 m; 2 Sep. 2015; E. F. Oza, F. Z. Saiter, F. Falk & J. Ribeiro 6; MBML [ 50636 ] • Comunidade do Milanês, São João de Petrópolis, propriedade de Thiago Rosado / IFES Santa Teresa , em grotão com solo profundo e muita matéria orgânica; 19 ° 47 ’ 38.4 ” S, 40 ° 39 ’ 54 ” W; 250 m; 6 Apr. 2016; E. F. Oza, F. Z. Saiter, F. Falk & J. Ribeiro 16; MBML [ 50637 ] • Várzea Alegre ( Mata do Fausto , próximo ao colégio), interior de mata, ambiente seco; 27 Jul. 2000; V. Demuner et al. 1303; MBML [ 013251 ], NY • Escola Agrícola ; 19 ° 49 ’ 55.2 ” S, 40 ° 36 ’ 46.8 ” W; 155 m; 4 Apr. 2003; P. Fiaschi et al. 1468; CEPEC, MBML [ 21036 ], NY, SPF [ 157828 ] .

Taxonomic notes.

The only other species with large nutlets similar in size to those of Rhynchospora barbosae is R. calyptrocaryoides (R. Gross) W. W. Thomas with nutlets 2.4–3.2 mm long. Rhynchospora calyptrocaryoides , however, is a much more robust plant, with leaf blades 15–90 × 2–2.4 cm compared to 29–57 × 0.8–0.9 cm in R. barbosae . Rhynchospora macrantha (Kunth) W. W. Thomas has achenes that overlap in size with those of R. barbosae (2.1–2.6 × 1.5–2.1 mm vs 2.4–2.6 × 1.8–1.9 mm). It, however, is also much more robust and has large, open panicles with solitary spikelets at the end of each branch. The remaining species of Rhynchospora sect. Pleurostachys have achenes 0.8–2.4 mm long. See key to the species of R. sect. Pleurostachys below.

Figures

Figure 2. Rhynchospora barbosae. A. Plant habit. B. Synflorescence in fruit. C. Detail of one branch of synflorescence. D. Synflorescence in flower. E. Spikelet prior to anthesis. F. Spikelet scale. G. Nutlet, side view, top view, and detail of bristle. A – G from W. W. Thomas et al. 16619 (isotype, NY). Drawn by Bobbi Angell.

Figure 3. Photographs of Rhynchospora barbosae and R. hamadryadis in the field. A. R. barbosae habit. B. R. barbosae synflorescence with mature nutlets. C. R. hamadryadis habit. D. R. hamadryadis, developing synflorescence. A – B from W. W. Thomas et al. 16619 (isotype, NY); C from W. W. Thomas et al. 13735 (NY); D from W. W. Thomas et al. 13954 (isotype, NY).

Figure 4. Nutlet photographs. A. Rhynchospora barbosae. B. R. hamadryadis. C. R. eremica. A from W. W. Thomas et al. 16619 (isotype, NY); B from W. W. Thomas et al. 13954 (isotype, NY); C from W. W. Thomas et al. 13748 (isotype, NY). Scale bars = 0.5 mm.

Figure 5. Distribution map of Rhynchospora barbosae (black circles), R. hamadryadis (grey squares), and R. eremica (white triangle).