Systematics of Chusquea section Chusquea, section Swallenochloa, section Verticillatae, and section Serpentes (Poaceae: Bambusoideae)

A classification of the neotropical bamboo genus Chusquea into four sections is proposed, and detailed descriptions of 25 species are presented. Chusquea, comprising approximately 120 species, is restricted to the New World, where it is found from Mexico through Central America, along the Andes to Chile and Argentina, and eastward into Brazil. The aggregate altitudinal range of its species is from sea level to more or less 4,000 m, but the majority of Chusquea species inhabit the lush, misty montane forests of Central and South America. The shrubby, high altitude species with intravaginal branching, formerly segregated as the genus Swallenochloa, are incorporated into Chusquea as section Swallenochloa (14 species). Two other smaller natural subgroups known from lower elevations are formally classified as section Verticillatae (5 species) and section Serpentes (4 species). These three sections are well defined, primarily on morphology of the buds, branches, and foliage leaves. The remainder of Chusquea species are provisionally included in section Chusquea. Anatomical and morphological evidence supporting this classification are presented, and additional comments on cyctology and ecology are included. Preliminary phylogenetic analyses in the form of cladograms are provided for the three well defined sections;From this study a pattern of diversification in the genus has emerged, based on modification of habit and branching. The development of the unique bud complement in Chusquea, which consists of one large central bud, subtended by 2-many smaller, independent subsidiary buds, was a major evolutionary step. Once multiple, independent buds could be produced, almost any combination of bud number and branching pattern became possible, thus permitting extreme variation in vegetative morphology. This potential for vegetative plasticity may account for the extensive speciation that has occurred in Chusquea