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Paleotropical woody bamboos (PWB) are phylogenetically and taxonomically intractable. Because previous studies included deficient samples or lacked informative characters for tree construction, phylogenetic relationships within the PWB remain incompletely resolved. This study presents the most extensively sampled phylogeny of the PWB with 18 plastid regions and a sample of 144 (35%) ingroup species representing 40 (85%) genera and 8 outgroup species. Results confirmed Melocanninae as the earliest diverging lineage from the rest of the group, and Hickeliinae (including Nastus s.str.) and Racemobambosinae are separately placed within the PWB. Bambusinae is phylogenetically heterogeneous and consists of the Dinochloa-Greslania-Mullerochloa-Neololeba-Sphaeroambos (DGMNS) assemblage, Temburongia simplex, and the core Bambusinae. The core Bambusinae may be redefined to include a basal grade, which contains Kinabaluchloa, Holttumochloa, Bonia, Neomicrocalamus, Temochloa, Soejatmia and an unidentified taxon, and the Bambusa-Dendrocalamus-Gigantochloa (BDG) complex. The BDG complex is extremely diverse in morphology and is subdivided into six subclades. Within the Melocanninae, Davidsea, Neohouzeaua and Ochlandra are closely related to Schizostachyum. Phylogenetic relationships are mostly supported by morphological and geographical evidence. In addition, novel interpretations are provided in the redelimitation of some taxa.

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Melocanninae is sister to other subtribes of Paleotropical woody bamboos with some 90 species mainly concentrated in Asia. However, phylogenetic relationships within the subtribe are poorly known. Here, we filled the gaps in complete plastome data of Melocanninae, reconstructed the phylogeny of Melocanninae, and further estimated divergence time and ancestral distribution range. Our results showed that the two major genera, Cephalostachyum Munro and Schizostachyum Nees, were paraphyletic. Species of Cephalostachyum were resolved in two successive basal clades, whereas Annamocalamus H. N. Nguyen, N. H. Xia, & V. T. Tran was embedded in the Schizostachyum clade. Different plastid regions provided inconsistent signals for the relationship of Melocanna and Pseudostachyum. Conservative loci supported a successive divergence rather than sister relationship between them and the difference may be caused by long‐branch attraction. We infer that Melocanninae originated in the East Himalaya to northern Myanmar in the early Miocene. Three routes were revealed in forming its present biogeographic pattern: in situ diversification on the Asian mainland, dispersing southwest to Sri Lanka and to the Western Ghats in South India, and spreading southeast to Malesia and Oceania by way of the Indo‐China Peninsula. The rapid uplift of the Tibetan Plateau and the intensification of Asian monsoons since the Miocene and the sea level fall events since the Late Miocene might be potential driving forces for diversification of Melocanninae and, particularly the latter event, for the species radiation of Schizostachyum.

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Holttumochloa has previously only been recorded from Malaysia. Here we describe and illustrate a new species, Holttumochloa hainanensis sp. nov., from the lowland montane forests of Diaoluo Mountain on the Island of Hainan, South China. Morphologically, H. hainanensis is similar to Holttumochloa korbuensis, but can be clearly distinguished from it in having larger culms covered by white wax, longer leaf blades, larger pseudospikelets and anthers. Furthermore, molecular phylogeny based on the nuclear gene GBSSI corroborates the identification of the new species and its affinity. The biogeographical significance of the new record of Holttumochloa in South China is also highlighted in this study.

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