title: Origin and speciation ofPicea schrenkianaandPiceasmithianain the Center Asian Highlands and Himalayas.
abstract: Elucidating the evolutionary history of current species diversity, especially trees with large effective population sizes and long generation times, is a complicated exercise confounded by gene flow and incomplete lineage sorting. In the present study, we aim to determine the origin and speciation ofPicea schrenkianaandPicea smithianausing population genetic data from chloroplast (cp), mitochondrial (mt), and nuclear (nr) genomes. These two species occur in the Central Asian Highlands and Himalayas, respectively, where they are isolated from other Asian congeneric species by the Qinghai-Tibet Plateau (QTP) or adjacent deserts. Previous studies based on both morphological and molecular evidence suggest that they have contrasting phylogenetic relationships withPicea likiangensisorPicea wilsoniiwhich are closely related and both located in the QTP. We examined genetic variation among 16 loci of three genomes from 30 populations of these four species. At both cpDNA loci and mtDNA loci,P. schrenkianaappeared to be closely related toP. likiangensis, although statistical support for this was weak. However, phylogenetic analyses and speciation tests based on the nuclear data from 11 loci provided evidence thatP. schrenkianaandP. smithianaare sister species. These two species diverged around five million years ago (Mya) while the divergence between them and theP. likiangensis-P. wilsoniiclade occurred about 18.4 Mya. We also detected gene flow accompanying these speciation events. Our results highlight the complex speciation histories of these alpine conifers due to interspecific gene flow and/or incomplete lineage sorting, and the importance of the early QTP uplifts in promoting the origin of these important conifer species in the Asian highlands.
authors.affiliation: State Key Laboratory of Grassland Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000 China.
authors.forename: Lili
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Grassland Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000 China.
authors.forename: Yongshuai
authors.initials: Y
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Grassland Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000 China.
authors.forename: Jiabin
authors.initials: J
authors.lastname: Zou
authors.affiliation: State Key Laboratory of Grassland Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000 China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yue
authors.affiliation: State Key Laboratory of Grassland Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000 China.
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Grassland Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000 China.
authors.forename: Jianquan
authors.initials: J
authors.lastname: Liu
keywords: Gene flow; P. smithiana; Picea schrenkiana; Population genetic data; Speciation test