Framework Phylogeny, Evolution and Complex Diversification of Chinese Oaks

Oaks (QuercusL.) are ideal models to assess patterns of plant diversity. We integrated the sequence data of five chloroplast and two nuclear loci from 50 Chinese oaks to explore the phylogenetic framework, evolution and diversification patterns of the Chinese oak's lineage. The framework phylogeny strongly supports two subgeneraQuercusandCerriscomprising four infrageneric sectionsQuercus,Cerris,IlexandCyclobalanopsisfor the Chinese oaks. An evolutionary analysis suggests that the two subgenera probably split during the mid-Eocene, followed by intergroup divergence within the subgenusCerrisaround the late Eocene. The initial diversification of sections in the subgenusCerriswas dated between the mid-Oligocene and the Oligocene-Miocene boundary, while a rapid species radiation in sectionQuercusstarted in the late Miocene. Diversification simulations indicate a potential evolutionary shift on sectionQuercus, while several phenotypic shifts likely occur among all sections. We found significant negative correlations between rates of the lineage diversification and phenotypic turnover, suggesting a complex interaction between the species evolution and morphological divergence in Chinese oaks. Our infrageneric phylogeny of Chinese oaks accords with the recently proposed classification of the genusQuercus. The results point to tectonic activity and climatic change during the Tertiary as possible drivers of evolution and diversification in the Chinese oak's lineage.