Phylogeny of Fargesia (Poaceae: Bambusoideae) and infrageneric adaptive divergence inferred from three cpDNA and nrITS sequence data

Fargesia, a temperate woody bamboo genus, is one of the largest genera and constitutes a taxonomically problematic group due to unusual life cycles and the rarity of flowering. We explored phylogenetic relationships within Fargesia and its allies based on sequence data from three cpDNA regions (matK, psbA-trnH and trnL-trnF) and one nuclear region (nrITS). A representative sample of 49 species, including 36 Fargesia and nine Yushania, were sampled, and maximum parsimony, maximum likelihood and Bayesian inference were used to reconstruct the phylogeny of Fargesia. The results suggest that Fargesia is polyphyletic, with F. crassinoda and F. damuniu in the Thamnocalamus clade, F. ampullaris, F. semiorbiculata, F. gyirongensis and F. collaris in the Drepanostachyum+Himalayacalamus clade, and the rest of species of Fargesia and all sampled species of Yushania in a Fargesia+Yushania clade, which was further divided into weakly supported Fargesia spathe and non-spathe clades. Species in the Fargesia spathe clade have the derived spathe-like leaf sheath syndrome, which may have evolved as a result of an adaptive advantage of compressed inflorescences in colder temperatures.