Plastid phylogenomics shed light on intergeneric relationships and spatiotemporal evolutionary history of Melocanninae (Poaceae: Bambusoideae)

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, <i>Cephalostachyum </i>and <i>Schizostachyum</i>, were paraphyletic. Species of <i>Cephalostachyum</i> were resolved in two successive basal clades, while <i>Annamocalamus</i> was embedded in the <i>Schizostachyum</i> clade. Different plastid regions provided inconsistent signals for the relationship of <i>Melocanna</i> and <i>Pseudostachyum</i>. 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: <i>in situ</i> 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 via 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 <i>Schizostachyum</i>.