Roles of demography and natural selection in molecular evolution of trees, focus on Pinus sylvestris
1University of Oulu, Faculty of Science, Department of Biology
|Online Access:||PDF Full Text (PDF, 0.4 MB)|
|Persistent link:|| http://urn.fi/urn:isbn:9789514287688
|Publish Date:|| 2008-04-01
|Thesis type:||Doctoral Dissertation
|Defence Note:||Academic dissertation to be presented, with the assent of the Faculty of Science of the University of Oulu, for public defence in Kuusamonsali (Auditorium YB210), Linnanmaa, on April 11th, 2008, at 12 noon
Research Associate Professor Thomas Bataillon
Professor Craig Primmer
Natural selection, mutation, recombination, demographic history and chance all have a role in evolution. In natural populations, the outcome of these forces is seen as adaptations, differences between geographic varieties, and as genetic diversity in populations—both at the phenotypic and molecular levels. In this thesis I wanted to examine the roles of the evolutionary forces shaping molecular genetic diversity in trees, with emphasis on a boreal conifer, Scots pine (Pinus sylvestris).
Phylogeographic history and past population size changes have a dominant role in molecular diversity of P. sylvestris. The effect of the Last Glacial Maximum (37 000–16 000) was observed in the distribution of mitochondrial DNA variation. In contrast, nuclear DNA was not much affected by the last glacial period. Instead, more ancient demographic events that took place millions of years ago can still be observed in the variation of P. sylvestris nuclear DNA.
Not much evidence of positive natural selection was found in pines or trees in general. This is in contrast to strong natural selection that is observed at the phenotypic level. Positive selection is difficult to prove, especially when the genome is still affected by demographic history. Mutation–drift equilibrium may rarely be reached in tree populations.
Acta Universitatis Ouluensis. A, Scientiae rerum naturalium
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