Alien gene introgression promotes rapid adaptation: an unconscious experiment on Fire-bellied toad (Bombina bombina) at the northern edge of its distribution range

外来基因渗入促进快速适应：对火腹蟾蜍（Bombinaombina）分布范围北缘的无意识实验

基本信息

批准号：
274681367
负责人：
Professor Dr. Ralph Tiedemann, Ph.D.
金额：
--
依托单位：
Institut für Biochemie und Biologie
依托单位国家：
德国
项目类别：
Priority Programmes
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/274681367?language=en
关键词：
Alien gene introgression promotes rapid

项目摘要

This proposal focusses on genomic sources of adaptive variation for rapid change (thematic group 3), by evaluating particular hypotheses, i.e., (1) small isolated populations at the margin of a species distribution might be constrained by a lack of standing genetic variation and (2) introgression of allochthonous alleles may enhance the adaptive potential of such populations. In case of introgression, heterozygosity and allelic diversity increase instantly and sexual reproduction creates mosaic genotypes combining different sets of authochthonous and allochthonous alleles, providing the raw material for rapid adaptation. Our study organism is the Fire-bellied toad Bombina bombina, which occurs in Europe in two distinct evolutionary lineages, i.e., a southern lineage distributed in the Balkan states and Austria, and a northern lineage reaching from Ukraine through Poland to the edges of the northern distribution range in Northern Germany and Southern Sweden. Initial genetic analyses at 20 unlinked genetic loci unraveled an introgression of southern lineage (putatively Austrian) genotypes into three local northern lineage populations, presumably due to independent unofficial (and illegal) release by amateur herpetologists. Interestingly, these introgressed populations (1) are fixed for introgressed alleles at several loci and (2) have a positive population trend, such that they outperform local authochthonous populations. This scenario provides a replicated unconscious experiment, mimicking long-distance dispersal and subsequent introgression from a southern lineage (potentially adapted to warmer summer conditions) to a northern population. We will perform genomic scans (RAD-seq) and expression profiling (RNA-seq) for both the authochthonous and the introgressed Bombina populations to discern, on a genomic scale, introgressed alleles/expression patterns from authochthonous ones. In genome-wide association studies (GWAS), we will relate these patterns to fitness related traits (body size, mass, condition). These data will be fed into theoretical models developed by our collaborator (Prof. Stephan) to discern the relative importance of selective sweeps vs. polygenic selection in rapid adaptation. In-depth analysis of candidate genes (including MHC and heat shock protein genes) will unravel the functional classes, in which introgressed (allochthonous) alleles will be favored by selection, and in which ones authochthonous alleles are maintained. This will provide us with a causal understanding of the reason, why introgressed populations of the Fire-bellied toad at the northern edge of the distribution range outperform the non-introgressed ones. Ultimately, the project focusses on the relevance of introgression as a mechanism to increase the amount of standing genetic variation and thus to contribute adaptive genetic material for rapid adaptation.

该提案通过评估特定假设，重点关注快速变化的适应性变异的基因组来源（主题组3），即（1）物种分布边缘的小型孤立种群可能受到缺乏常备遗传变异的限制，并且（ 2）异地等位基因的渗入可能增强此类群体的适应潜力。在基因渗入的情况下，杂合性和等位基因多样性立即增加，有性生殖产生结合不同组原源和异源等位基因的镶嵌基因型，为快速适应提供原材料。我们的研究生物是火腹蟾蜍 Bombinaombina，它以两种不同的进化谱系出现在欧洲，即分布在巴尔干国家和奥地利的南部谱系，以及从乌克兰穿过波兰到达北部边缘的北部谱系。分布范围德国北部和瑞典南部。对 20 个不相关的遗传位点进行的初步遗传分析揭示了南部谱系（假定为奥地利）基因型向三个当地北部谱系种群的渗入，这可能是由于业余爬行动物学家独立的非官方（且非法）释放所致。有趣的是，这些基因渗入群体（1）在多个位点的基因渗入等位基因是固定的，并且（2）具有积极的群体趋势，使得它们优于当地的原生群体。这种情况提供了一个复制的无意识实验，模仿长距离扩散和随后从南方谱系（可能适应较温暖的夏季条件）向北方种群的渗入。我们将对原产地和基因渗入的 Bombina 种群进行基因组扫描 (RAD-seq) 和表达谱分析 (RNA-seq)，以在基因组规模上辨别原地基因渗入的等位基因/表达模式。在全基因组关联研究 (GWAS) 中，我们将这些模式与健康相关特征（体型、质量、状况）联系起来。这些数据将被输入到我们的合作者（Stephan 教授）开发的理论模型中，以辨别快速适应中选择性扫描与多基因选择的相对重要性。对候选基因（包括 MHC 和热休克蛋白基因）的深入分析将揭示其功能类别，其中渗入（异源）等位基因将受到选择的青睐，而哪些原源等位基因被保留。这将使我们对分布范围北部边缘火腹蟾蜍基因渗入种群的表现优于非基因渗入种群的原因有一个因果性的理解。最终，该项目的重点是基因渗入作为一种机制的相关性，以增加常备遗传变异的数量，从而为快速适应贡献适应性遗传物质。