ddRAD analyses reveal a credible phylogenetic relationship of the four main genera of Bambusa-Dendrocalamus-Gigantochloa complex (Poaceae: Bambusoideae)

The Bambusa-Dendrocalamus-Gigantochloa complex (BDG complex) is the most diversified and phylogenetically recalcitrant group of the paleotropical woody bamboos. Species of this complex occur in tropical and subtropical Asia and most of them are of great economic, cultural and ecological value. The lack of resolution achieved through the analyses of previous molecular datasets has long confounded its phylogenetic estimation and generic delimitation. Here, we adopted a ddRAD-seq strategy to investigate phylogenetic relationships of the four main genera (Bambusa, Dendrocalamus, Gigantochloa, and Melocalamus) in the BDG complex. A total of 102 species were sampled, and SNP data were generated. Both MP and ML analyses of the ddRAD-seq data resulted in a well-resolved topology with Gigantochloa and Melocalamus confirmed as monophyletic, and Melocalamus resolved as sister to the rest of the complex. Bambusa and Dendrocalamus were both resolved as paraphyletic. The phylogenetic relationships were mostly supported by morphological evidence including characters of the branch complement, rachilla, lodicules, filaments and stigma. We also generated and assembled complete plastid genomes of 48 representative species. There were conflicts between the plastome and the ddRAD topologies. Our study demonstrated that RAD-seq can be used to reconstruct evolutionary history of lineages such as the bamboos where ancient hybridization and polyploidy play a significant role. The four genera of the BDG complex have a complex evolutionary history which is likely a product of ancient introgression events.