Will gene flow save endangered Arabis floodplain species from extinction?

生态系统日益退化和全球气候变化使越来越多的物种面临灭绝的危险。它们还重新划分了物种边界，有利于新的基因流动模式的出现。基因流动可以增强适应能力，拯救濒危物种，但也会加速它们的灭绝。本研究的目的是将联合收割机实验遗传学与理论种群基因组学方法相结合，探讨欧洲中部河漫滩的狭株濒危种南芥（Arabisnemorensis）与其同域近缘种南芥（A.箭形。A. nemorensis局限于河流泛滥平原，在那里它抵抗定期洪水造成的巨大波动，并通过种子库持续存在，这是一种生活史特征，已被证明对种群遗传过程有多方面的影响。A.箭形虫是一种同样濒危的适应干旱的物种，迄今为止还没有关于洪泛区环境的报告。首先遗传分析表明A. sagittata已经开始在河漫滩栖息地定居，它自然地与A. nemorensis，导致生育后代，从而使种间基因流。为了确定基因流动是否是有利的，并促进A。nemorensis，我们将解开积极和消极的选择对两个杂交物种的基因流率的影响。具体来说，我们将1）进行群体基因组学分析，以重建渗入的历史，2）绘制控制生态相关表型的基因座（例如耐淹性、耐旱性、生存力、不亲和性），3）进行转录组分析以更好地理解对耐淹性重要的遗传功能，4）开发理论工具来推断适应性渐渗的速率，同时考虑种子库的影响，以及5）量化在所涉及的渐渗基因处的选择的类型和强度。通过设计和验证新的方法来推断种子库物种中基因流动的进化意义，该项目将有助于支持旨在保护植物生物多样性的全球努力。

Increased ecosystem degradation and global climate change place an increasing number of species in danger of extinction. They also reshuffle species boundaries, favoring the emergence of novel patterns of gene flow. Gene flow can enhance adaptation and rescue endangered species, but it can also accelerate their extinction. Determining whether gene flow is beneficial is therefore fundamental for the preservation of biodiversity.The goal of this study is to combine experimental genetics with theoretical population genomics approaches to determine the evolutionary significance of gene flow between Arabis nemorensis, an endangered stenoecious species of Central European floodplains, and its sympatric relative A. sagittata. A. nemorensis is confined to river floodplains, where it resists the massive fluctuations imposed by regular flooding and persists via seed banks, a life history trait that has been shown to have manifold consequences on population genetics processes. A. sagittata is an equally endangered drought-adapted species that was so far not reported in floodplain environments. First genetic analyses have shown that A. sagittata has begun to colonize floodplain habitats and that it naturally hybridizes with A. nemorensis, resulting in fertile offspring and thus enabling interspecific gene-flow. To determine whether gene flow is advantageous and promote resilience in A. nemorensis, we will disentangle the effects of positive and negative selection on the rate of gene flow in each of the two hybridizing species. Specifically, we will 1) conduct a population genomics analysis to reconstruct the history of introgressions, 2) map loci controlling phenotypes of ecological relevance (e.g. flooding tolerance, drought tolerance, viability, incompatibility), 3) perform a transcriptome analysis to better understand the genetic function important for flooding tolerance, 4) develop theoretical tools to infer the rates of adaptive introgression while accounting for the effects of seed banking, and 5) quantify the type and strength of selection at the involved introgressed genes. Through the design and validation of novel approaches to infer the evolutionary significance of gene flow in seed banking species, this project will contribute to support global efforts aiming at preserving plant biodiversity.