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Demographic histories of four spruce (Picea) species of the Qinghai-Tibetan Plateau and neighboring areas inferred from multiple nuclear loci
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Functional Genomics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.ORCID iD: 0000-0003-3344-6036
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Functional Genomics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Functional Genomics.
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2010 (English)In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 27, no 5, 1001-1014 p.Article in journal (Refereed) Published
Abstract [en]

Nucleotide variation at 12 to 16 nuclear loci was studied in three spruce species from the Qinghai-Tibetan Plateau (QTP), Picea likiangensis, P. wilsonii and P. purpurea, and one species from the Tian Shan mountain range, P. schrenkiana. Silent nucleotide diversity was limited in P. schrenkiana and high in the three species from the QTP, with values higher than in boreal spruce species, despite their much more restricted distributions compared to that of the boreal species. In contrast to European boreal species that have experienced severe bottlenecks in the past, coalescent-based analysis suggests that DNA polymorphism in the species from the QTP and adjacent areas is compatible with the standard neutral model (P. likiangensis, P. wilsonii, P. schrenkiana) or with population growth (P. purpurea). In order to test if P. purpurea is a diploid hybrid of P. likiangensis and P. wilsonii, we used a combination of approaches, including model based inference of population structure, Isolation-with-Migration models and recent theoretical results on the effect of introgression on the geographic distribution of diversity. In contrast to the three other species, each of which was predominantly assigned to a single cluster in the Structure analysis, P. purpurea individuals were scattered over the three main clusters and not, as we had expected, confined to the P. likiangensis and P. wilsonii clusters. Furthermore the contribution of P. schrenkiana was by far the largest one. In agreement with this, the divergence between P. purpurea and P. schrenkiana was lower than the divergence of either P. likiangensis or P. wilsonii from P. schrenkiana. These results, together with previous ones showing that P. purpurea and P. wilsonii share the same haplotypes at both chloroplast and mitochondrial markers, suggest that P. purpurea has a complex origin, possibly involving additional species.

Place, publisher, year, edition, pages
2010. Vol. 27, no 5, 1001-1014 p.
Keyword [en]
Picea, Qinghai Tibetan Plateau, effective population size, divergence time, introgression, speciation
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-121399DOI: 10.1093/molbev/msp301ISI: 000276994800004PubMedID: 20031927OAI: oai:DiVA.org:uu-121399DiVA: diva2:305229
Available from: 2010-03-23 Created: 2010-03-23 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Conifer Evolution, from Demography and Local Adaptation to Evolutionary Rates: Examples from the Picea genus
Open this publication in new window or tab >>Conifer Evolution, from Demography and Local Adaptation to Evolutionary Rates: Examples from the Picea genus
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Evolutionary process can be inferred at three different levels: the species level, the population level and the molecular level. In this thesis, I applied approaches at these three levels and aimed to get a comprehensive picture of conifer evolution, from speciation and demography to geographic variation and local adaptation, and then to the molecular evolution of proteins and small regulatory RNAs.

Spruce species have been observed to possess a large number of trans-species shared polymorphisms. Using an “Isolation with migration” model, we found that the large effective population size of spruce retained these shared polymorphisms, inheriting them from the common ancestor. Post-divergence gene flow only existed between Picea abies and P. glauca, and between P. wilsonii and P. schrenkiana. The combination of Tajima’s D and Fay & Wu’s H at most of loci suggested an ancient and severe bottleneck for most species except P. breweriana.

Furthermore, I investigated the effect of local selection in two parallel clines, which is one of the major forces that can cause divergence or even speciation. The timing of bud set and growth cessation was found correlated with latitude in populations of P. abies and P. obovata. Using allele frequency spectrum analyses we identified three genes under local selection in both species including two circadian-clock genes GI and PRR7, and one photoperiodic gene FTL2. This indicated that parallel evolution could occur through groups of genes within related pathways. Clinal variation at expression level provided stronger evidence of selection in FTL2, which has previously been associated with bud set in P. abies.

Finally we focused on the molecular evolution of mRNA and small regulatory RNAs in P. abies. With the help of Next-Generation sequencing, we have achieved in spruce the first de novel assembly of the needle transcriptome and a preliminary characterization of sRNA populations. Along with features common in plants, spruce also exhibited novelties in many aspects including lower substitution rate and protein evolutionary rate, dominance of 21-nt sRNA, and a large proportion of TIR-NBS-LRR genes as sRNA sources and targets.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 947
Keyword
Speciation, Demographics, clinal variation, convergent evolution, transcriptome, small regulatory RNA
National Category
Evolutionary Biology Genetics
Research subject
Biology with specialization in Evolutionary Functional Genomics; Biology with specialization in Evolutionary Genetics
Identifiers
urn:nbn:se:uu:diva-177482 (URN)978-91-554-8411-8 (ISBN)
Public defence
2012-09-14, Lindahlsalen, EBC, Norbyvägen 18A, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2012-08-24 Created: 2012-07-13 Last updated: 2013-01-22Bibliographically approved
2. Conservation Genetics and Speciation in Asian Forest Trees
Open this publication in new window or tab >>Conservation Genetics and Speciation in Asian Forest Trees
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tropical forests are important because they are the home of millions of species at the same time as they perform ecosystem services and provide food, cash income and raw materials for the people living there. The present thesis elucidates questions relevant to the conservation of selected forest trees as it adds to the knowledge in the phylogeny, population structure, genetic diversity and adaptation in these species.

We investigated the genetic diversity and speciation of four spruce species around the Qinghai-Tibetan Plateau (QTP), Western China, and one from Taiwan. Nucleotide diversity was low in P. schrenkiana and the Taiwanese P. morrisonicola but higher in P. likiangensis, P. purpurea and P. wilsonii. This can be explained by the population bottlenecks that were detected in the two former species by coalescent-based analysis. The phylogenetic relationships between the five species were difficult to interpret, possibly because other Asian spruce species might have been involved. However, all species are distinct except P. purpurea, which likely has a hybrid origin. 

The rate of bud set and expression of the FTL2 gene in response to photoperiod in the southernmost growing spruce species, P. morrisonicola, was studied. We found that in this species, although growing near the equator, bud set appears to be induced mainly by a shortening of photoperiod, similarly to its more northerly growing spruce relatives. In addition, seedlings originating from mother trees growing at higher elevations showed a trend towards earlier bud set than seedlings originating from mother trees at lower altitudes.

We also studied the population structure and genetic diversity in the endemic white cedar (Dysoxylum malabaricum) in the Western Ghats, India. Overall, no increase in inbreeding that could be related to human activities could be detected. Populations appear to have maintained genetic diversity and gene flow in spite of forest fragmentation over the distribution range. However, there is a severe lack of juveniles and young adults in several populations that needs to be further addressed. Finally, we recommend conservation units based on population structure.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 45 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1047
National Category
Natural Sciences
Research subject
Biology with specialization in Evolutionary Functional Genomics
Identifiers
urn:nbn:se:uu:diva-198798 (URN)978-91-554-8676-1 (ISBN)
Public defence
2013-06-14, Friessalen, EBC, Norbyvägen 14, Uppsala, 12:30 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency
Available from: 2013-05-22 Created: 2013-04-25 Last updated: 2013-08-30
3. Neutral and Adaptive Processes Shaping Genetic Variation in Spruce Species
Open this publication in new window or tab >>Neutral and Adaptive Processes Shaping Genetic Variation in Spruce Species
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Population genetic analyses can provide information about both neutral and selective evolutionary processes shaping genetic variation. In this thesis, extensive population genetic methods were used to make inferences about genetic drift and selection in spruce species. In paper I we studied four species from the Qinghai-Tibetan Plateau (QTP): Picea likiangensis, P. purpurea, P. wilsonii and P. schrenkiana. Big differences in estimates of genetic diversity and Ne were observed in the more restricted species, P. schrenkiana, and the other more widely distributed species. Furthermore, P. purpurea appears to be a hybrid between P. likiangensis and P. wilsonii. In paper II we used Approximate Bayesian Computation (ABC) to find that the data support a drastic reduction of Ne in Taiwan spruce around 300-500 kya, in line with evidence from the pollen records. The split from P. wilsonii was dated to between 4-8 mya, around the time that Taiwan was formed. These analyses relied on a small sample size, and so in Paper III we investigated the impact of small datasets on the power to distinguish between models in ABC. We found that when genetic diversity is low there is little power to distinguish between simple coalescent models and this can determine the number of samples and loci required.

In paper IV we studied the relative importance of genetic drift and selection in four spruce species with differing Ne: P. abies, P. glauca, P. jezoensis and P. breweriana. P. breweriana, which has a low Ne, exhibits a low fraction of adaptive substitutions, while P. abies has high Ne and a high fraction of adaptive substitutions. The other two spruce, however, do not support this suggesting other factors a more important. In paper V we find that several SNPs correlate with both a key adaptive trait (budset) and latitude. The expression of one in particular (PoFTL2) correlates with budset and was previously indentified in P. abies. These studies have helped characterise the importance of different population genetic processes in shaping genetic variation in spruce species and has laid some solid groundwork for future studies of spruce.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 30 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1078
Keyword
spruce, population genetics, adaptation, evolution, picea, approximate bayesian computation, cline
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-207714 (URN)978-91-554-8760-7 (ISBN)
Public defence
2013-10-31, Lindahlsalen, Evolutionary Biology Centre, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2013-10-10 Created: 2013-09-18 Last updated: 2014-01-23

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