Highly heterogeneous generic delimitation within the temperate bamboo clade (Poaceae: Bambusoideae): evidence from GBSSI and ITS sequences

Abstract

AbstractThere is much debate about the phylogenetic relationships within the temperate bamboo clade inferred from morphological and anatomical data. To investigate these relationships, internal transcribed spacer (ITS) and partial granule‐bound starch synthase I gene (GBSSI) sequences were obtained from 47 species representing the two widely accepted subtribes and 26 genera of the temperate bamboo clade. All analyses of the DNA data using maximum parsimony and Bayesian reference confirm that the temperate bamboos form a robust monophyly with 100% bootstrap support. Our results suggest that the Racemobambosinae is not a member of the temperate clade. The two major subtribes, Arundinariinae and Shibataeinae, are each rejected as monophyletic. This is somewhat unexpected as the definition of the subtribes is based on the inflorescence types that have been widely accepted. Our results also suggest that, in the temperate clade, Arundinaria s.l., Pleioblastus, Chimonobambusa, Sinobambusa, and even the “well‐defined” Phyllostachys, are not monophyletic. Therefore, most genera, as currently delimited, within the temperate clade are highly heterogeneous. Using GBSSI, ITS, and GBSSI‐ITS combined data it is revealed that Phyllostachys and Shibataea are closely related and that the combination of Menstruocalamus and Qiongzhuea and even some species of Sinobambusa into Chimonobambusa is warranted. Brachystachyum is not supported as being derived within Semiarundinaria. This implies that many morphological characters used for subtribal divisions and generic delimitation in the current systems of bamboo classification are homoplastic and that their evolutionary meaning should be reevaluated.