The interaction of genetic drift and adaptive evolution in two endemic plant species, Arabidopsis pedemontana and A. cebennensis

点击翻译按钮获取中文摘要

Up to 40% of all species in hotspots of biodiversity harbor species with a small geographic distribution range and small population sizes. Such endemic species are threatened by environmental change and exposed to a substantial danger of extinction. In addition, there is an genetic risk of extinction because genetic drift and inbreeding cause the loss of genetic variation, which reduces the evolutionary potential for future adaptation to new environmental conditions. The two species Arabidopsis pedemontana and A. cebennensis are endemic with small distribution ranges in the Cottian Alps of the Piedmont, and in the Cevennes and Massif Central, France, respectively. This project investigates how the two endemic species differ in their patterns of genomic variation and genomic composition from closely related species with a much larger distribution range and a higher level of genetic variation. This will be achieved by analysing the complete genome sequence of many individuals of these species. The investigations will reveal whether the endemic species suffer from a higher genetic load and a lower adaptive potential than their close relatives, and which genes are particularly affected by this situation. In addition, important phenotypic traits will be investigated that include water use efficience, adaptation to soil type and glucosinolate content, which play a role in herbivore resistance. The phenotypic reaction of the endemic species and their close relatives to different stress treatments will be investigated and the gene expression patterns will be characterised by transcriptome sequencing. Differences in gene expression will be compared with the genetic distance of the species and analyzed with population genetic and statistical approaches to identify genes that contribute to differential adaptation. In endemic species, a transition from outcrossing to self-fertilization is frequently observed. By using population genetic analyses and intraspecific crosses the extent of self-fertilization will be examined. Interspecific crosses with close relatives will be conducted to identify in the long-term new genes that play a role in the genetic differentiation between the species. The project will contribute to an improved understanding of the evolution and conservation of endemic plants in a rapidly changing environment.