Major clades and a revised classification of Magnolia and Magnoliaceae based on whole plastid genome sequences via genome skimming

With more than 300 species, the Magnoliaceae family represents a major Magnoliid lineage that is disjunctly distributed in Asia and the New World. The classification of Magnolia s.l. has been highly controversial among taxonomists, varying from one genus with several subgenera, sections, and subsections to several (up to 16) genera. We conducted a comprehensive phylogenetic study of Magnoliaceae on the basis of sequences of the complete chloroplast genomes with a broad taxon sampling of 86 species. The phylogenetic analyses strongly support 15 major clades within Magnolia s.l. due to the non-monophyly of subgen. Magnolia, the previous subgeneric treatment that recognizes three subgenera, is not supported. Based on the phylogenetic, morphological, and geographic evidence, we recognize two subfamilies in Magnoliaceae: Liriodendroideae and Magnolioideae, each with one genus, Liriodendron and Magnolia, respectively. Magnolia is herein classified into 15 sections: sects. Magnolia, Manglietia, Michelia, Gwillimia, Gynopodium, Kmeria, Maingola, Oyama, Rytidospermum, Splendentes, Talauma, Tuliparia, Macrophylla, Tulipastrum, and Yulania.