Historical biogeography and plastome evolution of Commelinaceae Mirb. (Commelinales) corroborate the East Gondwanan origins

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BackgroundCommelinaceae are a Pantropical monocot family comprising ca. 36 genera and 810 species. Due to the high morphological variation and limited sampling, the relationships within the family remain unclear. Previous studies, which relied on limited genetic loci or low-resolution sequencing, have not fully resolved these relationships. Additionally, there is a need to investigate the historical biogeography of Commelinaceae using genomic data. To address these issues, we assembled twelve Commelinaceae plastomes and inferred their biogeographical pathways using both newly generated and previously published data.ResultsOur results indicate that all members of the subfamily Commelinoideae have shortened accD and rpoA genes, which do not affect functionality. In contrast, members of the subf. Cartonematoideae possess intact forms of both genes. Phylogenetic analyses based on 79 plastid protein-coding genes provide much-needed insight into the placement of some key genera that had previously remained unplaced or were erroneously placed elsewhere within the family. Of these, our results support the monophyly of the subtribe Streptoliriinae, the non-monophyly of the subtr. Coleotrypinae, and the need to recognise a broader circumscription of Aneilema R.Br. (including Rhopalephora Hassk.). Our biogeographic analysis shows that the ancestor of Commelinaceae originated in the Australian region around 104.8 million years ago (Mya), thus revealing an East Gondwanan origin. We also found that four major dispersal events have shaped the intercontinental diversification of this family: (1) from the Australian to the Ethiopian region ca. 81.4 Mya; (2) from the Ethiopian to the Oriental + Palearctic region ca. 50.4 Mya; (3) from the Oriental + Palearctic to the Neotropical region ca. 50.4 Mya; and (4) from the Neotropical to the Ethiopian region ca. 32.3 Mya.ConclusionsWe identified genetic events, such as inversions and IR expansion, which shed light on the genomic evolution of Commelinaceae. Our findings support taxonomic updates, and future work will integrate comprehensive phylogenomic and morphological datasets to deepen our understanding of morphological evolution and biogeographic history within Commelinaceae, establishing a robust foundation for systematic revisions in the family.