Discovery of the first succulent bamboo (Poaceae, Bambusoideae) in a new genus from Laos' karst areas, with a unique adaptation to seasonal drought

Phylogenomic analyses reveal reticulate evolution between Neomicrocalamus and Temochloa (Poaceae: Bambusoideae)

Neomicrocalamus and Temochloa are closely related to bamboo genera. However, when considered with newly discovered and morphologically similar material from China and Vietnam, the phylogenetic relationship among these three groups was ambiguous in the analyses based on DNA regions. Here, as a means of investigating the relationships among the three bamboo groups and exploring potential sources of genomic conflicts, we present a phylogenomic examination based on the whole plastome, single-nucleotide polymorphism (SNP), and single-copy nuclear (SCN) gene datasets. Three different phylogenetic hypotheses were found. The inconsistency is attributed to the combination of incomplete lineage sorting and introgression. The origin of newly discovered bamboos is from introgressive hybridization between Temochloa liliana (which contributed 80.7% of the genome) and Neomicrocalamus prainii (19.3%), indicating that the newly discovered bamboos are closer to T. liliana in genetics. The more similar morphology and closer distribution elevation also imply a closer relationship between Temochloa and newly discovered bamboos.

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 Nastus, which is paraphyletic and forms two distant clades. The type species of Nastus (Clade II) is endemic to Reunion Island and is not closely related to other sampled species of Nastus endemic to Madagascar (Clade VI). Clade VI (Malagasy Nastus) is sister to the Sokinochloa + Hitchcockella clade (Clade V), and both clades have a clumping habit with short-necked pachymorph rhizomes. The monotypic Decaryochloa 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 Cathariostachys, Perrierbambus, Sirochloa, and Valiha, which are also morphologically diverse. This work provides significant resources for further genetic and phylogenomic studies of Hickeliinae, an understudied subtribe of bamboo.