New insights into intergeneric relationships of Hickeliinae (Poaceae: Bambusoideae) revealed by complete plastid genomes.

The Hickeliinae (Poaceae: Bambusoideae) is an ecologically and economically significant subtribe of tropical bamboos restricted to Madagascar, Comoros, Reunion Island, and a small part of continental Africa (Tanzania). Because these bamboos rarely flower, field identification is challenging, and inferring the evolutionary history of Hickeliinae from herbarium specimens is even more so. Molecular phylogenetic work is critical to understanding this group of bamboos. Here, comparative analysis of 22 newly sequenced plastid genomes showed that members of all genera of Hickeliinae share evolutionarily conserved plastome structures. We also determined that Hickeliinae plastome sequences are informative for phylogenetic reconstructions. Phylogenetic analysis showed that all genera of Hickeliinae are monophyletic, except for , which is paraphyletic and forms two distant clades. The type species of (Clade II) is endemic to Reunion Island and is not closely related to other sampled species of endemic to Madagascar (Clade VI). Clade VI (Malagasy ) is sister to the  +  clade (Clade V), and both clades have a clumping habit with short-necked pachymorph rhizomes. The monotypic is remarkable in having the longest floret in Bambuseae and forms a distinct Clade IV. Clade III, which has the highest generic diversity, consists of , , , and , which are also morphologically diverse. This work provides significant resources for further genetic and phylogenomic studies of Hickeliinae, an understudied subtribe of bamboo.