Phylogenomics of Tricalysia Based on Angiosperms353 Target Capture Data

Tricalysia, (Rubiaceae) a diverse genus of tropical African understory shrubs and small trees, offers a rich system to answer evolutionary questions about biogeography, speciation, and trait evolution. Phylogenetic relationships within the genus remain poorly resolved, limiting taxonomic clarity and obscuring evolutionary patterns. In this study, we use a target-capture approach using the Angiosperm 353 probe set to reconstruct a robust phylogenetic tree of Tricalysia with coalescent species tree approaches, sampling broadly across the genus and generating data for hundreds of nuclear loci. Phylogenetic and systematic analyses using both concatenated maximum likelihood and coalescent-based species tree methods reveal strong support for several major clades, while also indicating that current morphological sectional classifications do not fully reflect evolutionary history. Biogeographic patterns indicate that diversification in Tricalysia is related to aridification during the Late Miocene Cooling event and rapid fluctuations during the glacial/interglacial cycles in the Plio-Pleistocene. Our results provide a well-supported phylogenetic hypothesis for understanding the history of Tricalysia while offering new insights into the evolutionary processes that have shaped this African genus.