(2260) Proposal to conserve the name Piresia against Reitzia (Poaceae, Bambusoideae)

Abstract

Piresia Swallen and Reitzia Swallen are two genera of Neotropical herbaceous bamboos that belong to the grass tribe Olyreae and include, respectively, five (Carvalho & al. in Syst. Bot. 37: 134–138. 2012) and only one described species (Judziewicz & al. in Amer. Bamboos: 314–316. 1999). Piresia presents a wide distribution in South America, occurring as a clear disjunction between the Amazon basin and the Atlantic forest in northeast Brazil, from the state of Pernambuco to Bahia (Judziewicz & al., l.c.; Carvalho & al., l.c.). On the other hand, Reitzia ranges in a smaller area, covered exclusively by Atlantic forest, and it was originally considered by Swallen (l.c. 1956) as endemic to the state of Santa Catarina, in south Brazil, being afterwards cited for Sao Paulo (Clark in Wanderley & al., Fl. Sao Paulo 1: 49. 2001) and Rio de Janeiro, both in southern Brazil (Oliveira & al. in Almeida & Teixeira, Anais I Semin. Nac. Bambu, ed. 2: 62–68. 2011). In the original publication of Piresia (Swallen, l.c. 1964), it was considered closely related to Reitzia, based on glumes of fertile spikelet 3-nerved, and differing from it by glume nerves prominent, fruit pubescent and culms biform (vs. glume nerves faint, fruit glabrous and culms all alike in Reitzia). Piresia has raceme-like inflorescences in culms of two types: aerial ones, bearing broad and flat leaf blades at the top; and fertile ones, often decumbent, shorter, bladeless or with very much reduced leaf blades, usually hidden among leaf litter or even burrowing through it (Soderstrom in Brittonia 34: 199–209. 1982; Soderstrom & Calderon in Biotropica 6: 141–153. 1974), while Reitzia also includes raceme-like inflorescences, but only at the apex of aerial culms, partially covered by the leaf blades (Judziewicz & al., l.c). There are other characters described in Clayton & al. (Grass Base; http://www.kew.org/data/grasses-db/www/imp08878.htm, accessed 23 Jun 2013) that are quite similar between Piresia and Reitzia, such as the number of culms, shape and distribution of the leaves in the culms, the number and position of male and female spikelets in the inflorescences (the female being terminal, with two male adjacent), the absence of glumes in male spikelet, as well as three lodicules and three stamens. Beside this, Reitzia shares with some members of Piresia bisexual and not typically dimorphic spikelets, being unusual among genera of herbaceous bamboos, which display predominantly unisexual and dimorphic spikelets (Soderstrom & Calderon, l.c.). This little differentiation between male and female spikelets of Reitzia occurs especially in species of Piresia from the Atlantic forest (Carvalho & al., l.c.), as well as in Diandrolyra Stapf, another herbaceous bamboo genus endemic to the same Brazilian biome (Oliveira & Clark in Novon 19: 209–215. 2009). Based especially on the type and position of the inflorescence, Clayton & Renvoize (Genera Graminum: 64–65. 1986) considered Piresia to be close to Diandrolyra, while Reitzia was treated together with Maclurolyra Calderon & Soderstr. and Rehia Fijten. However, recent phylogenetic studies in Olyreae did not indicate a relationship between Piresia and Diandrolyra (Oliveira & al., subm.). Ongoing studies on the systematics and evolution of Piresia based on multiple approaches (Carvalho, Estud. Biossistematicos Piresia [thesis, UEFS, Bahia]: 232. 2013) have shown that the diversity of this genus is high, as early suggested by Clayton & Renvoize (l.c.), including at least nine undescribed species. Using five regions of plastid and nuclear DNA, Carvalho (l.c.) identified Reitzia as nested in a clade together with the species of Piresia, but without clear resolution of their relationships. In order to resolve the status of the group as monophyletic, Piresia and Reitzia will likely be considered a single genus, and there are many more species that resemble the morphology of Piresia than