Abstract: Monochoria C. Presl is a genus of Pontederiaceae and confined to the Old World, with species mainly distributed in tropical and subtropical Africa, Asia, and Australia. However, phylogenetic relationships and biogeography within Monochoria are yet to be fully resolved. Here, we sequenced 14 Monochoria plastomes, representing around eight of the ~10 species of Monochoria, and two plastomes from related genera. We undertook comparative analyses and phylogenetic reconstructions of Monochoria using these and other available sequences. We found the plastomes of Pontederiaceae to be highly conserved in structure, and identified six regions as mutational hotspots among species of Monochoria. Our data strongly support the monophyly of Monochoria and two main clades within the genus. We confirm that Monochoria australasica Ridl. is sister to the rest of the genus and that Monochoria korsakowii (Regel & Maack) defines the second split within Monochoria. In addition, we inferred the African endemic species Monochoria africana (Solms) N. E. Br. to be closely related to Monochoria plantaginea (Roxb.) Kunth and an undetermined specimen from Australia (Monochoria sp. AU63). Estimation of divergence times and biogeography implied that the African species M. africana originated in Asia, and the most recent common ancestor of Monochoria was distributed in Australasia/Asia at approximately 15 Ma, followed by diversification in Asia during the late Miocene and Pliocene. Long-distance dispersal, likely mediated by migratory birds, to Africa and Australia during the Pliocene and Pleistocene, might have contributed to the extant transoceanic distribution of the genus. Additionally, based on our phylogenetic results, we revised the description of Monochoria valida G. X. Wang & Nagam here.

Key words: biogeography, Monochoria, phylogenomics, plastid genome