title: Evolutionary history of Purple cone spruce (Picea purpurea) in the Qinghai-Tibet Plateau: homoploid hybrid origin and Pleistocene expansion.
abstract: Hybridization and introgression can play an important role in speciation. Here, we examine their roles in the origin and evolution of Picea purpurea, a diploid spruce species occurring on the Qinghai-Tibet Plateau (QTP). Phylogenetic relationships and ecological differences between this species and its relatives, P. schrenkiana, P. likiangensis and P. wilsonii, are unclear. To clarify them, we surveyed sequence variation within and between them for 11 nuclear loci, three chloroplast (cp) and two mitochondrial (mt) DNA fragments, and examined their ecological requirements using ecological niche modelling. Initial analyses based on 11 nuclear loci rejected a close relationship between P. schrenkiana and P. purpurea. BP&P tests and ecological niche modelling indicated substantial divergence between the remaining three species and supported the species status of P. purpurea, which contained many private alleles as expected for a well-established species. Sequence variation for cpDNA and mtDNA suggested a close relationship between P. purpurea and P. wilsonii, while variation at the nuclear se1364 gene suggested P. purpurea was more closely related to P. likiangensis. Analyses of genetic divergence, Bayesian clustering and model comparison using approximate Bayesian computation (ABC) of nuclear (nr) DNA variation all supported the hypothesis that P. purpurea originated by homoploid hybrid speciation from P. wilsonii and P. likiangensis. The ABC analysis dated the origin of P. purpurea at the Pleistocene, and the estimated hybrid parameter indicated that 69% of its nuclear composition was contributed by P. likiangensis and 31% by P. wilsonii. Our results further suggested that during or immediately following its formation, P. purpurea was subject to organelle DNA introgression from P. wilsonii such that it came to possess both mtDNA and cpDNA of P. wilsonii. The estimated parameters indicated that following its origin, P. purpurea underwent an expansion during/after the largest Pleistocene glaciation recorded for the QTP.
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystem, College of Life Science, Lanzhou University, Lanzhou, 730000, China.|Key Laboratory for Bio-resources and Eco-environment, College of Life Science, Sichuan University, Chengdu, 610065, China.
authors.forename: Yongshuai
authors.initials: Y
authors.lastname: Sun
authors.affiliation: School of Biology, University of St Andrews, Mitchell Building, St Andrews, Fife, KY16 9TH, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Abbott
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystem, College of Life Science, Lanzhou University, Lanzhou, 730000, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystem, College of Life Science, Lanzhou University, Lanzhou, 730000, China.
authors.forename: Long
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystem, College of Life Science, Lanzhou University, Lanzhou, 730000, China.
authors.forename: Jiabin
authors.initials: J
authors.lastname: Zou
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystem, College of Life Science, Lanzhou University, Lanzhou, 730000, China.
authors.forename: Jianquan
authors.initials: J
authors.lastname: Liu
mesh_terms: D001499:Bayes Theorem; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D017753:Ecosystem; D008040:Genetic Linkage; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D006824:Hybridization, Genetic; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D028222:Picea / Q000145:classification* / Q000235:genetics; D017422:Sequence Analysis, DNA; D018609:Tibet
chemical_list: D018742:DNA, Chloroplast; D004272:DNA, Mitochondrial; D018744:DNA, Plant
keywords: Picea; Pleistocene expansion; Qinghai‐Tibet Plateau; homoploid hybrid speciation; hybridization; introgression