The evolution of quantitative traits in reponse to drought in "Arabidopsis lyrata"

In spite of the great advances in population genetic and quantitative genetics over the last decades, many central questions of these fields are still not satisfactorily answered. In particular, we still have a poor understanding of how species are limited in their adaptation to changing environmental conditions and to habitats present beyond their natural distribution. In addition, our knowledge about the effect of habitat heterogeneity on the maintenance of genetic variation remains poor. In the context of global climate changes, many species will have to respond to different environmental conditions in order to survive. Therefore, understanding species’ ability to adapt and how high levels of the genetic variance necessary for adaptation can be maintained within populations is highly important. Such knowledge will be very useful for building new conservation strategies. <br>During this thesis I have investigated these questions using the <i>Arabidospsis lyrata</i> plant system. Its ability to grow on different substrates and the development of comprehensive genomic resources makes it a powerful system for studying adaptation. Several seed families occurring in a heterogeneous landscape and across two latitudinal clines in North America were raised in a common garden environment and in two different treatments: wet and dry. By measuring several traits all related to drought adaptation and by performing intense linear and multivariate statics, I discovered that genetic constraints and low levels of genetic variation are limiting northern populations to adapt to higher latitudes. In addition, I observed that habitat heterogeneity did not greatly impact the adaptive potential of this species. Results of this thesis offer a greater understanding of adaptive limits met at distribution edges. This new knowledge will help constructing models evaluating the impact of global changes on many plant and animal populations.

Thèse de doctorat : Université de Neuchâtel, 2013