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Impact of Geography and Climate on the Genetic Differentiation of the Subtropical Pine Pinus yunnanensis
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing, People’s Republic of China.
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, People’s Republic of China.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2013 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 8, no 6, e67345- p.Article in journal (Refereed) Published
Abstract [en]

Southwest China is a biodiversity hotspot characterized by complex topography, heterogeneous regional climates and rich flora. The processes and driving factors underlying this hotspot remain to be explicitly tested across taxa to gain a general understanding of the evolution of biodiversity and speciation in the region. In this study, we examined the role played by historically neutral processes, geography and environment in producing the current genetic diversity of the subtropical pine Pinus yunnanensis. We used genetic and ecological methods to investigate the patterns of genetic differentiation and ecological niche divergence across the distribution range of this species. We found both continuous genetic differentiation over the majority of its range, and discrete isolated local clusters. The discrete differentiation between two genetic groups in the west and east peripheries is consistent with niche divergence and geographical isolation of these groups. In the central area of the species' range, population structure was shaped mainly by neutral processes and geography rather than by ecological selection. These results show that geographical and environmental factors together created stronger and more discrete genetic differentiation than isolation by distance alone, and illustrate the importance of ecological factors in forming or maintaining genetic divergence across a complex landscape. Our findings differ from other phylogenetic studies that identified the historical drainage system in the region as the primary factor shaping population structure, and highlight the heterogeneous contributions that geography and environment have made to genetic diversity among taxa in southwest China.

Place, publisher, year, edition, pages
plosone , 2013. Vol. 8, no 6, e67345- p.
National Category
URN: urn:nbn:se:umu:diva-79435DOI: 10.1371/journal.pone.0067345ISI: 000321424400097OAI: diva2:643698
Available from: 2013-08-28 Created: 2013-08-19 Last updated: 2013-09-30Bibliographically 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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