title: Phylogenetic relationships, possible ancient hybridization, and biogeographic history of Abies (Pinaceae) based on data from nuclear, plastid, and mitochondrial genomes.
abstract: Abies, the second largest genus of Pinaceae, consists of approximately 48 species occurring in the north temperate region. Previous molecular phylogenetic studies improved our understanding of relationships within the genus, but were limited by relying on only DNA sequence data from single genome and low taxonomic sampling. Here we use DNA data from three genomes (sequences of internal transcribed spacer of nrITS, three chloroplast DNA intergenic spacers, and two mitochondrial intergenic spacers) from 42 species to elucidate species relationships and construct the biogeographic history of Abies. We further estimated the divergence times of intercontinental disjunction using a relaxed molecular clock calibrated with three macro-fossils. Our phylogenetic analyses recovered six robust clades largely consistent with previous classifications of sections. A sister relationship between the eastern Asian and Europe-Mediterranean clades was highly supported. The monophyly of section Balsamea, disjunct in Far East and western North America, is supported by the nrITS data but not by the cpDNA data. Discordance on placement of section Balsamea between the paternally inherited cpDNA and maternally inherited mtDNA trees was also observed. The data suggested that ancient hybridization was likely involved in the origin of sect. Balsamea. Results from biogeographic analyses and divergence time estimation suggested an origin and early diversification of Abies in an area of high latitude around the Pacific during the Eocene. The present disjunction in eastern Asia and Europe-Mediterranean area of Abies was likely the result of southward migration and isolation by the Turgai Strait in the Late Eocene. An 'out-of-America' migration, for the origin of an eastern Asian and western North American disjunct species pairs in section Amabilis was supported. The results suggested a western North American origin of the section with subsequent dispersal across the Bering Land Bridge (BLB) to Japan during the Middle Miocene.
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, PR China. Electronic address: qpxiang@ibcas.ac.cn.
authors.forename: Qiao-Ping
authors.initials: QP
authors.lastname: Xiang
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, PR China; University of the Chinese Academy of Sciences, Beijing 100039, PR China.
authors.forename: Ran
authors.initials: R
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, PR China; University of the Chinese Academy of Sciences, Beijing 100039, PR China.
authors.forename: Yi-Zhen
authors.initials: YZ
authors.lastname: Shao
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, PR China; University of the Chinese Academy of Sciences, Beijing 100039, PR China.
authors.forename: Zu-Yu
authors.initials: ZY
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Xiao-Quan
authors.initials: XQ
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Xian-Chun
authors.initials: XC
authors.lastname: Zhang
mesh_terms: D028202:Abies / Q000145:classification* / Q000235:genetics; D001208:Asia; D001499:Bayes Theorem; D005075:Biological Evolution; D018744:DNA, Plant / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005060:Europe; D005580:Fossils; D054628:Genome, Chloroplast; D054629:Genome, Mitochondrial; D018745:Genome, Plant; D006824:Hybridization, Genetic; D016013:Likelihood Functions; D008957:Models, Genetic; D009656:North America; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D018744:DNA, Plant; D021903:DNA, Ribosomal Spacer
keywords: Ancient hybridization; Genome conflict; Northern hemisphere disjunction; Out of western North America; Section Balsamea