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Among-year variation in selection during early life stages and the genetic basis of fitness in Arabidopsis thaliana
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.ORCID iD: 0000-0001-9573-2463
2018 (English)In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 27, no 11, p. 2498-2511Article in journal (Refereed) Published
Abstract [en]

Incomplete information regarding both selection regimes and the genetic basis of fitness limits our understanding of adaptive evolution. Among-year variation in the genetic basis of fitness is rarely quantified, and estimates of selection are typically based on single components of fitness, thus potentially missing conflicting selection acting during other life-history stages. Here, we examined among-year variation in selection on a key life-history trait and the genetic basis of fitness covering the whole life cycle in the annual plant Arabidopsis thaliana. We planted freshly matured seeds of >200 recombinant inbred lines (RILs) derived from a cross between two locally adapted populations (Italy and Sweden), and both parental genotypes at the native site of the Swedish population in three consecutive years. We quantified selection against the nonlocal Italian genotype, mapped quantitative trait loci (QTL) for fitness and its components, and quantified selection on timing of germination during different life stages. In all 3years, the local Swedish genotype outperformed the nonlocal Italian genotype. However, both the contribution of early life stages to relative fitness, and the effects of fitness QTL varied among years. Timing of germination was under conflicting selection through seedling establishment vs. adult survival and fecundity, and both the direction and magnitude of net selection varied among years. Our results demonstrate that selection during early life stages and the genetic basis of fitness can vary markedly among years, emphasizing the need for multiyear studies considering the whole life cycle for a full understanding of natural selection and mechanisms maintaining local adaptation.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018. Vol. 27, no 11, p. 2498-2511
National Category
Evolutionary Biology
Identifiers
URN: urn:nbn:se:uu:diva-302861DOI: 10.1111/mec.14697ISI: 000434152100002PubMedID: 29676059OAI: oai:DiVA.org:uu-302861DiVA, id: diva2:968058
Funder
Swedish Research Council, 2016-05435Available from: 2016-09-12 Created: 2016-09-12 Last updated: 2018-08-31Bibliographically approved
In thesis
1. Selection during Early Life Stages and Local Adaptation in Arabidopsis thaliana
Open this publication in new window or tab >>Selection during Early Life Stages and Local Adaptation in Arabidopsis thaliana
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organisms are often adapted to their local environment, but the role of early life stages in adaptive differentiation among populations remains poorly known. The aim of my thesis was to investigate the contribution of early life stages to the magnitude and genetic basis of local adaptation, and to identify the underlying adaptive traits. For this, I used two natural populations of the annual plant Arabidopsis thaliana from Italy and Sweden, and a Recombinant Inbred Line (RIL) population derived from a cross between these populations. By combining greenhouse and field experiments, Quantitative Trait Loci (QTL) mapping, and path analysis, I examined (1) the genetic basis of seed dormancy, (2) the contribution of differential seedling establishment to local adaptation, (3) among-year variation in selection during seedling establishment, (4) direct and indirect effects of seed dormancy and timing of germination on fitness, and (5) the adaptive value of the seed bank.

I found that both the level and the genetic basis of seed dormancy were affected by the maternal environment. One major-effect QTL was identified in all maternal environments, which overlaps with the dormancy gene DELAY OF GERMINATION 1 (DOG1).

Selection through seedling establishment success contributed strongly to local adaptation and genetic tradeoffs, and varied among years. Variation in seedling establishment and overall fitness among RILs could be explained by genetically based differences in seed dormancy and timing of germination. Seed dormancy affected fitness throughout the life cycle, by affecting the proportion of germinated seeds, and indirectly via effects on timing of germination, plant size and flowering time.

My results suggest that a considerable portion of A. thaliana seeds enter the seed bank. I found genetic differences in dormancy cycling behaviour between the two populations, which could contribute to local adaptation. The value of a seed bank should be higher at the Swedish study site than at the Italian study site due to lower rate of seed mortality in the soil.

Overall, the results of this thesis demonstrate that early life stages contribute strongly to both the magnitude and the genetics of local adaptation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. p. 51
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1425
Keywords
Dormancy cycling, Germination timing, Maternal effects, Natural variation, QTL mapping, Seed bank, Seed dormancy, Structural Equation Modeling
National Category
Evolutionary Biology Ecology Botany
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-302862 (URN)978-91-554-9687-6 (ISBN)
Public defence
2016-10-28, Zootissalen, Villavägen 9, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2016-10-05 Created: 2016-09-12 Last updated: 2016-10-11

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Postma, Froukje M.Ågren, Jon

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