Abstract:

Magnoliaceae, an assemblage of early diverged angiosperms, comprises two subfamilies, speciose Magnolioideae with about 300 species in varying numbers of genera and monogeneric Liriodendroideae with two species in Liriodendron. This family occupies a pivotal phylogenetic position with important insights into the diversification of early angiosperms, and shows intercontinentally disjunct distribution patterns between eastern Asia and Americas. Widespread morphological homogeneity and slow substitution rates in Magnolia s.l. resulted in poorly supported phylogenetic relationships based on morphology or molecular evidences, which hampers our understanding of the genus’ temporal and spacial evolution. Here, based on the newly generated genome skimming data for 48 Magnolia s.l. species, we produced robust Magnolia phylogenies using genome-wide markers from both plastid genomes and SNP data. Contrasting the plastid and nuclear phylogenies revealed extensive cyto-nuclear conflicts in both shallow and deep relationships. ABBA-BABA and PhyloNet analyses suggested hybridization occurred within sect. Yulania, and sect. Magnolia, which is in concordance with the ploidy level of the species in these two sections. Divergence time estimates and biogeographic reconstruction indicated that the timing of the three tropical Magnolia disjunctions coincided with the Mid-Eocene cooling climate and/or Late-Eocene climate deterioration, and two temperate disjunctions occurred much later, possibly during the warm periods of Miocene, hence supporting the boreotropical flora concept of Magnolia s.l..

Key words:

Magnoliaceae, Phylogenomics, Plastid, Hybridization, Biogeography