Rhynchospora hamadryadis 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 hamadryadis W. W. Thomas sp. nov.

Figs 3 C – D , 4 B , 5 , 6

Type.

BRAZIL – Bahia • Mun. Poções. Fazenda Boa Esperança , 7.5 km S of Morrinhos (6.1 km E of Poções on road to Ilhéus) on forested slope; 14 ° 36 ’ 40 ” S, 40 ° 20 ’ 13 ” W; 7 Feb. 2004; W. W. Thomas, A. M. Amorim, P. Fiaschi., J. L. Paixão & S. Sant’Ana 13954; holotype: CEPEC [ 102299 ]; isotypes: K, MO, NY, RB [ 692412 ], RB [ 693118 ], US .

Diagnosis.

Rhynchospora hamadryadis is unusual in having mostly short, unbranched secondary axes branching off the primary axis of each synflorescence. Otherwise, it is similar to Rhynchospora panicoides Schrad. ex Nees.

Description.

Plants glabrous, rhizomatous, the rhizomes 1.5–2 mm in diameter, the internodes congested or occasionally to 6 cm. Culms slender and arching, 18–45 cm long, 0.7–1 mm wide. Leaves mostly or all basal; basal leaves 3–7, linear, the sheaths 2–3 cm long, often difficult to distinguish from blade, the blades 20–35 × 0.2–0.4 cm; cauline leaves 0–1, the sheath 15–20 mm long, the summit of the sheath concave. Synflorescence a series of 3–4 elongate, compact, corymbose inflorescences of 1–9 spikelets, each inflorescence subtended by a linear, leaf-like bract, the bracts at each more distal node diminishing in size; basal bract with the sheath 14–20 mm long, the blade 18–24 × 0.15–0.35 cm; terminal inflorescence largest, the primary axis 18–65 × 0.25 mm, the basal secondary axis longest, 70–110 × 0.3–0.4 mm, each secondary axis terminating in a cluster of 3–6 spikelets. Mature spikelets (without fruit deforming shape) brown, lenticular (slightly flattened), broadly obpyriform, 2.8–3.8 (– 4.5) × 2.2–2.6 mm, the basal 6–7 glumes distichous, carinate, cucullate, the apex acute, mucronate, the basal fertile glume ca 2.2–2.5 × ca 2.5 mm, the mucro ca 0.3–0.4 mm. Hypogynous bristles ca 2–2.5 mm long, two-thirds as long as to slightly exceeding the nutlet and style base, densely short-plumose on the distal two thirds, sparsely so on the basal third. Nutlet broadly to very broadly elliptic to obovate in outline, deeply lenticular, 1.7–2.4 × 1.45–1.7 mm, the surface golden tan and very lightly tuberculate, the summit slightly arched; persistent style base triangular, 0.4–0.5 × 0.6–0.7 mm, the surface dull grey and irregularly textured.

Distribution and habitat.

Rhynchospora hamadryadis is known from three localities, all in the deciduous seasonal forest zone ( Thomas and Barbosa 2008) at 495 to 900 m elevation in southern Bahia and adjacent Minas Gerais (Fig. 5 ). This is a low, open forest with many lianas and giant bromeliads. Locally, it is known as “ mata de cipó ” and is exceedingly scarce.

Etymology.

In Greek and Roman mythology, a hamadryad was a woodnymph bonded to a certain tree and who died when the tree died. Martius (1906) recognized five phytogeographic regions in Brazil and used Hamadryades to describe the seasonal arid vegetation of the interior of north-eastern Brazil.

Preliminary IUCN conservation assessment.

Rhynchospora hamadryadis is known from three locations, all in the highly endangered deciduous seasonal tropical forest. It has an Extent of Occurrence of 659.5 km 2 and an Area of Occupancy of 16 km 2 (Fig. 5 ). Both values indicate that the species should be considered as Endangered: EN B 1 ab (iii) + B 2 ab (iii). While the known localities near Boa Nova are now part of the Refúgio de Vida Silvestre de Boa Nova and are probably protected, the location in Minas Gerais remains unprotected and a decline in the area, extent and / or quality of the habitat is therefore inferred.

Additional material examined.

BRAZIL – Bahia • Boa Nova, Fazenda Cotermaia , entrance 1.2 km E of Boa Nova on road to Dario Meira; 14 ° 22.419 ’ S, 40 ° 11.305 ’ W; 810 m; 18 May 2001; W. W. Thomas et al. 12493; CEPEC [ 89604 ], NY, SPF [ 205632 ] • 14 ° 22.389 ’ S, 40 ° 11.309 ’ W; 790 m; 25 Oct. 2001; W. W. Thomas et al. 12640; CEPEC [ 92010 ], NY • 3.3 km E of Boa Nova on road to Dario Meira ; 14 ° 22.983 ’ S, 40 ° 11.177 ’ W; 850–900 m; 15 Oct. 2000; W. W. Thomas et al. 12286; CEPEC [ 89012 ], NY • 14 ° 22.98 ’ S, 40 ° 11.17 ’ W; 865 m; 20 Nov. 2000; S. C. Sant’Ana et al. 1017; CEPEC [ 86937 ], NY, SPF [ 205657 ] • Jequié, Serra do Castanhão , 14.5 km S of Jequié on BR 116, then 7.2 km W; 13 ° 56.522 ’ S, 40 ° 11.468 ’ W; 775 m; 23 Oct. 2001; W. W. Thomas et al. 12547; CEPEC [ 91012 ], NY – 3, SPF [ 205643 ] . – Minas Gerais • Salto da Divisa [on both sides of the state line with Bahia: Itagimirim], Estação Repetidora de Salto da Divisa [ Serra do Bogodo ], 7.1 km E of Salto da Divisa; 16 ° 01 ’ 43 ” S, 39 ° 55 ’ 17 ” W; 495 m, 31 Jan. 2004; W. W. Thomas et al. 13735; CEPEC [ 103138 ], NY, RB [ 686946 ] .

Taxonomic notes.

Rhynchospora hamadryadis is unusual in having mostly short, unbranched secondary axes branching off the primary axis of each synflorescence. This gives the appearance of a narrow, elongate synflorescence. The only other species to have similar inflorescences is R. panicoides , a much more robust species; while R. hamadryadis has 1–9 spikelets per inflorescence, R. panicoides usually has over 30 per inflorescence. See key to the species of R. sect. Pleurostachys below.

Figures

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).

Figure 6. Rhynchospora hamadryadis. A. Plant habit. B. Synflorescence in fruit. C. Spikelet. D. Spikelet with mature nutlet. E. Developing nutlet showing bristles and filaments, and style with 2 stigmas. F. Spikelet scale. G. Nutlet, face view and side view. A – G from W. W. Thomas et al. 13954 (isotype, NY). Drawn by Bobbi Angell.