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Demography and speciation history of the homoploid hybrid pine Pinus densata on the Tibetan Plateau
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China. (Graduate School, Chinese Academy of Sciences, Beijing 100049, China)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). (Arcum)
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2012 (English)In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 21, no 19, 4811-4827 p.Article in journal (Refereed) Published
Abstract [en]

Pinus densata is an ecologically successful homoploid hybrid that inhabits vast areas of heterogeneous terrain on the south-eastern Tibetan Plateau as a result of multiple waves of colonization. Its region of origin, route of colonization onto the plateau and the directions of introgression with its parental species have previously been defined, but little is known about the isolation and divergence history of its populations. In this study, we surveyed nucleotide polymorphism over eight nuclear loci in 19 representative populations of P. densata and its parental species. Using this information and coalescence simulations, we assessed the historical changes in its population size, gene flow and divergence in time and space. The results indicate a late Miocene origin for P. densata associated with the recent uplift of south-eastern Tibet. The subsequent differentiation between geographical regions of this species began in the late Pliocene and was induced by regional topographical changes and Pleistocene glaciations. The ancestral P. densata population had a large effective population size but the central and western populations were established by limited founders, suggesting that there were severe bottlenecks during the westward migration out of the ancestral hybrid zone. After separating from their ancestral populations, population expansion occurred in all geographical regions especially in the western range. Gene flow in P. densata was restricted to geographically neighbouring populations, resulting in significant differentiation between regional groups. The new information on the divergence and demographic history of P. densata reported herein enhances our understanding of its speciation process on the Tibetan Plateau.

Place, publisher, year, edition, pages
John Wiley & Sons, 2012. Vol. 21, no 19, 4811-4827 p.
Keyword [en]
coalescent simulation, effective population size, gene flow, hybrid speciation, isolation history, nucleotide diversity
National Category
URN: urn:nbn:se:umu:diva-61180DOI: 10.1111/j.1365-294X.2012.05712.xISI: 000309234300014OAI: diva2:566707
Available from: 2012-11-09 Created: 2012-11-07 Last updated: 2016-05-19Bibliographically approved
In thesis
1. Hybridization and Evolution in the Genus Pinus
Open this publication in new window or tab >>Hybridization and Evolution in the Genus Pinus
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Gene flow and hybridization are pervasive in nature, and can lead to different evolutionary outcomes. They can either accelerate divergence and promote speciation or reverse differentiation. The process of divergence and speciation are strongly influenced by both neutral and selective forces. Disentangling the interplay between these processes in natural systems is important for understanding the general importance of interspecific gene flow in generating novel biodiversity in plants. This thesis first examines the importance of introgressive hybridization in the evolution of the genus Pinus as a whole, and then focusing on specific pine species, investigates the role of geographical, environmental and demographical factors in driving divergence and adaptation.

By examining the distribution of cytoplasmic DNA variation across the wide biogeographic range of the genus Pinus, I revealed historical introgression and mtDNA capture events in several groups of different pine species. This finding suggests that introgressive hybridization was common during past species’ range contractions and expansions and thus has played an important role in the evolution of the genus. To understand the cause and process of hybrid speciation, I focused on the significant case of hybrid speciation in Pinus densata. I established the hybridization, colonization and differentiation processes that defined the origin of this species. I found P. densata originated via multiple hybridization events in the late Miocene. The direction and intensity of introgression with two parental species varied among geographic regions of this species. During the colonization on Tibetan Plateau from the ancestral hybrid zone, consecutive bottlenecks and surfing of rare alleles caused a significant reduction in genetic diversity and strong population differentiation. Divergence within P. densata started from the late Pliocene onwards, induced by regional topographic changes and Pleistocene glaciations. To address the role of neutral and selective forces on genetic divergence, I examined the association of ecological and geographical distance with genetic distance in Pinus yunnanensis populations. I found both neutral and selective forces have contributed to population structure and differentiation in P. yunnanensis, but their relative contributions varied across the complex landscape. Finally, I evaluated genetic diversity in the Vietnamese endemic Pinus krempfii. I found extremely low genetic diversity in this species, which is explained by a small ancestral population, short-term population expansion and recent population decline and habitat fragmentation.

These findings highlight the role of hybridization in generating novel genetic diversity and the different mechanisms driving divergence and adaptation in the genus Pinus

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2013. 49 p.
Adaptation, biogeography, coalescent simulation, cytoplasmic genome, demographic history, genetic diversity, hybridization, migration, Pinus, population structure, selection, speciation
National Category
Evolutionary Biology
Research subject
evolutionär genetik
urn:nbn:se:umu:diva-80998 (URN)978-91-7459-702-8 (ISBN)
Public defence
2013-10-25, KBC-huset, KB3B1, Stora Hörsalen, Umeå Universitet, Umeå, 13:00 (English)
Available from: 2013-10-04 Created: 2013-09-30 Last updated: 2013-09-30Bibliographically approved

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Wang, BaoshengIngvarsson, PärWang, Xiao-Ru
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