Plastome characterization and its phylogenetic implications on Lithocarpus (Fagaceae)

The plastome of Fagaceae is generally conserved. Nevertheless, genes related to metabolism, photosynthesis, and energy were under strong positive selection in Lithocarpus, likely driven by environmental pressures and local adaptation. The plastome-based phylogeny confirmed the monophyletic status of Lithocarpus and revealed a phylogeographic pattern indicating limited seed-mediated gene flow in the ancestral lineage. The prevalence of cytonuclear discordance in Lithocarpus and other Fagaceae genera suggests that ancient introgression, incomplete lineage sorting, and asymmetrical seed- and pollen-mediated geneflow might contribute to this discordance. Future studies are essential to test these hypotheses and further elucidate the divergence patterns of this unique Asian evergreen lineage.