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Willi, Yvonne
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Willi, Yvonne
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Voici les éléments 1 - 10 sur 17
- PublicationMétadonnées seulement
- PublicationMétadonnées seulementThe Influence of Genetic Drift and Selection on Quantitative Traits in a Plant Pathogenic Fungus(2014)
;Stefansson, Tryggvi S ;McDonald, Bruce AGenetic drift and selection are ubiquitous evolutionary forces acting to shape genetic variation in populations. While their relative importance has been well studied in plants and animals, less is known about their relative importance in fungal pathogens. Because agro-ecosystems are more homogeneous environments than natural ecosystems, stabilizing selection may play a stronger role than genetic drift or diversifying selection in shaping genetic variation among populations of fungal pathogens in agro-ecosystems. We tested this hypothesis by conducting a QST/FST analysis using agricultural populations of the barley pathogen Rhynchosporium commune. Population divergence for eight quantitative traits (QST) was compared with divergence at eight neutral microsatellite loci (FST) for 126 pathogen strains originating from nine globally distributed field populations to infer the effects of genetic drift and types of selection acting on each trait. Our analyses indicated that five of the eight traits had QST values significantly lower than FST, consistent with stabilizing selection, whereas one trait, growth under heat stress (22°C), showed evidence of diversifying selection and local adaptation (QST>FST). Estimates of heritability were high for all traits (means ranging between 0.55?0.84), and average heritability across traits was negatively correlated with microsatellite gene diversity. Some trait pairs were genetically correlated and there was significant evidence for a trade-off between spore size and spore number, and between melanization and growth under benign temperature. Our findings indicate that many ecologically and agriculturally important traits are under stabilizing selection in R. commune and that high within-population genetic variation is maintained for these traits. - PublicationMétadonnées seulement
- PublicationMétadonnées seulementAn assay for quantitative virulence in Rhynchosporium commune reveals an association between effector genotype and virulence(2014)
;Stefansson, Tryggvi S; ;Croll, DMcDonald, Bruce A - PublicationMétadonnées seulementDrift load in populations of small size and low density(2013-3-20)
; ;Griffin, PVan Buskirk, J - PublicationMétadonnées seulement
- PublicationMétadonnées seulementLocal adaptation and evolutionary potential along a temperature gradient in the fungal pathogen Rhynchosporium commune(2013)
;Stefansson, Tryggvi S ;McDonald, Bruce A - PublicationMétadonnées seulement
- PublicationMétadonnées seulement
- PublicationAccès libreThe evolution of quantitative traits in reponse to drought in "Arabidopsis lyrata"(2013)
; 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.
During this thesis I have investigated these questions using the Arabidospsis lyrata 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.