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

在生物多样性热点地区的所有物种中，有多达40%的物种具有较小的地理分布范围和较小的种群规模。这些特有物种受到环境变化的威胁，面临灭绝的巨大危险。此外，还有灭绝的遗传风险，因为遗传漂变和近亲繁殖导致遗传变异的丧失，这降低了未来适应新环境条件的进化潜力。对两种拟南芥Arabidopsis pedemontana和A. cebennensis是地方性的，分布范围小，分别在皮埃蒙特的科蒂安阿尔卑斯山脉和法国的Cevennes和Massif Central。本项目研究了这两个特有种的基因组变异模式和基因组组成与具有更大分布范围和更高遗传变异水平的密切相关物种的差异。这将通过分析这些物种的许多个体的完整基因组序列来实现。调查将揭示特有物种是否比其近亲遭受更高的遗传负荷和更低的适应潜力，以及哪些基因特别受这种情况的影响。此外，还将研究重要的表型性状，包括水分利用效率、对土壤类型的适应性和硫甙含量，这些性状在抗草食动物中起作用。将研究特有种及其近亲对不同胁迫处理的表型反应，并通过转录组测序表征基因表达模式。基因表达的差异将与物种的遗传距离进行比较，并采用群体遗传和统计方法进行分析，以确定有助于差异适应的基因。在特有种中，经常观察到从异交到自花受精的过渡。通过使用群体遗传分析和种内杂交，将检查自花受精的程度。将进行与近亲的种间杂交，以在长期内鉴定在物种间遗传分化中起作用的新基因。该项目将有助于更好地了解在迅速变化的环境中特有植物的演变和保护。

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.