Will gene flow save endangered Arabis floodplain species from extinction?

生态系统退化加剧和全球气候变化使越来越多的物种濒临灭绝。它们还重新洗牌了物种的边界，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和拯救濒危物种，但也可能加速它们的灭绝。因此，确定基因流是否有益是保护生物多样性的基础。本研究的目标是将实验遗传学和理论种群基因组学方法相结合，以确定中欧洪泛平原濒危的狭长异株物种阿拉比斯与其同域亲缘箭虫之间的基因流的进化意义。马尾松仅限于河流泛滥平原，在那里它能抵抗常规洪水带来的巨大波动，并通过种子库持续存在，这一生活史特征已被证明对种群遗传学过程产生了多种后果。箭竹是一种同样濒临灭绝的适应干旱的物种，到目前为止还没有在洪泛区环境中的报道。最早的遗传分析表明，箭虫已经开始在洪泛区的栖息地定居，并自然地与沼虾杂交，产生了可生育的后代，从而实现了种间基因流动。为了确定基因流动是否有利，并提高马尾松的抗逆性，我们将区分正选择和负选择对两个杂交物种中基因流动速度的影响。具体地说，我们将1)进行群体基因组分析以重建导入的历史，2)绘制控制生态相关表型(如耐涝、抗旱、生存、不亲和)的基因座，3)进行转录组分析以更好地了解与耐涝有关的遗传功能，4)开发理论工具来推断适应性导入的速率，同时考虑种子库的影响，以及5)量化所涉及的导入基因的选择类型和强度。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.