Format: ORAL

Jialiang Li1, Wentao Wang1, Kangshan Mao1

1 College of Life Sciences, 29 Wangjiang Road, Chengdu 610064, Sichuan, P.R. China

As one of the largest families of gymnosperms, Cupressaceae comprises above 162 species (32 genera, seven subfamilies), and is the only gymnosperm group occurring on all continents except Antarctica. The world-wild distribution and high species diversity make this family an ideal example for exploring evolutionary history of the global intercontinental floras. Here we conducted a comprehensive phylogenomic study of Cupressaceae using more than 2000 single copy nuclear genes with a nearly complete sampling of species. Species tree reconstruction suggest that all genera and subfamilies were well-supported monophylies. Unexpectedly, we found the subfamily Athrotaxidoideae, which was sister to the remaining four subfamilies except Cunninghamioideae and Taiwanioideae in previous studies, was clustered with Sequoiodeae. Results of concordance analysis showed a high level of gene tree conflict of the ancestral node of Athrotaxidoideae and Sequoiodeae, suggesting it might have experience rapid speciation event and/or hybridization. PhyloNet analyses suggested three reticulation events within Cupressaceae at subfamily level. Molecular clock estimation revealed that two diverse evolutionary lineages (the tribe Cupresseae and Callitris), which together comprise ~70% of the species of Cupressaceae, underwent rapid diversification around the Cretaceous-Paleogene (K-Pg) boundary. A diversification rate shift was also detected along the ancestral branch of the tribe Cupresseae, corresponding a rate shift in phenotypic evolution. Biogeographical analyses suggest that the current distribution pattern of Cupressioideae and Callitroideae is largely associated with the breakup of Pangea, yet the detailed spatiotemporal evolutionary history is different from previous studies. In short, our phylogenomic survey suggest that the evolutionary history of Cupressaceae is more complex than previously thought.