Eight new taxa and two new reports of Bambuseae (Poaceae: Bambusoideae) from Colombia

Morphological characters support the description of seven new species and one variety of Bambusoideae from Colombia belonging to four genera of woody bamboos: Arthrostylidium, Chusquea, Guadua, and Rhipidocladum. The new species and variety are described, illustrated, and compared with putatively related species. They are Arthrostylidium auriculatum, A. chiribiquetensis, A. punctulatum, A. virolinensis, Rhipidocladum abregoensis, Guadua angustifolia var. nigra, Chusquea antioquensis, and C. arachniforme. A revised key to the South American species of Arthrostylidium is presented. Two genera of woody bamboos previously unknown in Colombia are documented to occur there. Otatea, thought to be restricted to Mexico and Central America, is found in northern Colombia, and Merostachys, widespread but with its diversity concentrated in southeastern Brazil, is reported from north-central Colombia. Among the Andean countries, Colombia possesses a high diversity of woody bamboos. Londofio (1990) reported a total of 45 described species in seven genera for Colombia; just a few years later, Clark (1995) reported an estimated 63 species in eight genera for the country, without referring explicitly to the additional genus. Based on fieldwork by Londofio in 1994 and by Londofio and Clark over several years in the Andean region of Colombia, as well as examination of herbarium specimens, we here report that woody bamboo diversity in Colombia comprises nine genera and 62 described species, including those in the present paper, with an estimated species diversity of 90 including undescribed taxa. In this paper, we describe seven species and one variety new to science, and document the occurrence of two genera previously unknown in Colombia. Two of the species, Arthrostylidium auriculatum and Rhipidocladum abregoensis, are known only from a single collection, but in each case, the plants were in flower, and qualitative differences are sufficient to distinguish them from related congeners. We present a key to the species of Arthrostylidium Ruprecht in South America, revised from Judziewicz and Clark (1993) to include the four species described here. Tables comparing A. virolinensis with the other three species of the genus with zig-zag/flexuous synflorescences, and R. abregoensis with two similar, narrow-leaved congeners are included. Our interpretation of reproductive morphology follows that of Stapleton (1997) and Judziewicz et al. (in press). The spikelet is considered to be an inflorescence, based on which an aggregation of spikelets is here termed a synflorescence. The stalk of the spikelet is therefore a peduncle, and the axis of the spikelet is the rachis. The principal axis of the synflorescence is referred to as the main axis, and the branches are paraclades. A coflorescence is a set of one to several paraclades derived from a single axis; in our taxa, a coflorescence may consist of a single spikelet, a first-order paraclade bearing spikelets, or a first-order paraclade with higher orders of branching. We also note that in Rhipidocladum McClure and Arthrostylidium, the glumes, sterile lemmas, and fertile lemmas are not always morphologically very distinct from each other (Clark & Londonfo, 1991). The glumes and sterile lemmas of Chusquea Kunth also intergrade frequently (Clark, 1996). We here refer to all of the empty bracts at the base of a spikelet as glumes, and all synflorescence bracts enclosing a bud as gemmiparous bracts.