Two new species of Rhynchospora (Cyperaceae) from Bahia, Brazil, and new combinations in Rhynchospora section Pleurostac
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Abstract. Recent molecular phylogenies have demonstrated that Pleurostachys (Cyperaceae) should be recognized as a section within Rhynchospora. Here all accepted species of Pleurostachys are transferred to Rhynchospora sect. Pleurostachys, five new combinations are made, and one new name provided. Rhynchospora austrobahiensis and R. contraligularis are described as new species endemic to the Atlantic forest of southern Bahia, Brazil. They are distinct from all other species of sect. Pleurostachys by having spikelets that are never clustered and basal leaves over 1 cm wide. The summit of the inner band of the leaf sheath on R. austrobahiensis is concave to triangular while that of R. contraligularis is arched with a distinct, chartaceous contraligule. Both species are illustrated and compared to other species of Rhynchospora sect. Pleurostachys. Keywords: Atlantic forest, Brazil, Cyperaceae, Pleurostachys, Rhynchospora, taxonomy. Resumo. Filogenias moleculares recentes demonstraram que Pleurostachys (Cyperaceae) deveria ser reconhecido como uma seção dentro de Rhynchospora. Aqui, todas as espécies aceitas de Pleurostachys são transferidas para Rhynchospora sec. Pleurostachys, cinco novas combinações são feitas e um nome novo é fornecido. Rhynchospora austrobahiensis e R. contraligularis são descritas como espécies novas endêmicas da mata atlântica do sul da Bahia, Brasil. Elas são distintas de todas as outras espécies de seção Pleurostachys por terem espiguetas que nunca são agrupadas e folhas basais com mais de 1 cm de largura. O cimo do lado interno da bainha da folha de R. austrobahiensis é côncavo a triangular, enquanto o da R. contraligularis é arqueado com um contraligula cartáceo e distinto. Ambas são ilustradas e comparadas com outras espécies de Rhynchospora sec. Pleurostachys.
Rhynchospora is characterized by simple spikelets, usually with spirally arranged scales, bisexual flowers, lenticular nutlets subtended by perianth bristles, and a persistent style base. Pleurostachys was first treated as a section within Rhynchospora by Bentham and Hooker (1883). Characters that distinguish this section from the rest of Rhynchospora include an inflorescence comprising a series of axillary synflorescences, distichously (or subdistichously) arranged spikelet scales, flattened perianth bristles that are densely papillose-ciliolate along the margins, and a decurrent style base (Thomas & Alves, 2008). Although Kükenthal (1952) treated 30 species, Alves and Thomas (2015) recognized 14 species, 11 of which are endemic to Brazil’s Atlantic coastal forest. Recent studies have increased the number
of accepted species to 16. Modern collections have greatly increased the number of specimens available for study, revealing at least seven undescribed species, two of which are described here. Most authors have maintained Pleurostachys as a separate genus closely allied to Rhynchospora Vahl (Boeckeler, 1875; Clarke, 1908; Pfeiffer, 1925; Koyama, 1961; Kükenthal, 1952; Eiten, 1976; Bruhl, 1995; Goetghebeur, 1986, 1998; Soros & Bru
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