University of Oulu

Flowering time and natural selection in Arabidopsis lyrata

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Author: Riihimäki, Mona-Anitta1
Organizations: 1University of Oulu, Faculty of Science, Department of Biology
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.8 MB)
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Language: English
Published: 2005
Publish Date: 2005-08-12
Thesis type: Doctoral Dissertation
Defence Note: Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, for public discussion in Kuusamonsali (Auditorium YB210), Linnanmaa, on August 22nd, 2005, at 12 noon
Reviewer: Professor Olavi Junttila
Docent Irma Saloniemi


Arabidopsis lyrata is a close outcrossing relative of Arabidopsis thaliana, the model organism of plant physiology and molecular biology. I studied variation in flowering time and the factors shaping the variation within and between A. lyrata populations in different environments. The role of the two important proximate factors determining flowering time, day length and temperature, were studied in climate chambers. The southern A. lyrata populations were found to flower in high frequency and quicker than northern A. lyrata populations in all studied environments, but the reaction of northern populations on long day length was found to be stronger than that of southern populations. Differences in vernalization requirement between A. lyrata populations were found in outdoor common garden, but in the climate chambers the results of vernalization experiments were not consistent. Strength and direction of selection on flowering time and other life history traits were studied in alpine and lowland A. lyrata populations in Scandinavia. Differences in selection were found both between populations and between years. Grazing sheep caused high levels of damage in inflorescences in the alpine population. In the lowland population there was less herbivory, caused by insects and hares. The difference in selection on flowering traits in the two study populations might be partly caused by selective grazing. Completely outcrossing mating system in A. lyrata is due to well developed self-incompatibility system. However, biparental inbreeding is likely to exist in natural populations and it may lead to spatial structuring of genetic variation within populations. I studied the effects of biparental inbreeding on components of fitness in A. lyrata in three different environments. I found inbreeding depression after sib-mating to be substantial. Stressful environment reduced the overall performance of the plants, but had no effect on the magnitude of inbreeding depression. A literature survey indicates that the observed levels of inbreeding depression in self-incompatible A. lyrata were higher than those of self-compatible species. This suggests that self-compatible species have purged some of their genetic load. The genetic basis of flowering time variation in A. lyrata can be further studied by using A. thaliana molecular tools.

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Series: Acta Universitatis Ouluensis. A, Scientiae rerum naturalium
ISSN-E: 1796-220X
ISBN: 951-42-7794-5
ISBN Print: 951-42-7793-7
Issue: 441
Copyright information: © University of Oulu, 2005. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.