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Effect of rapid environmental change on genetic diversity through space and time: selective sweeps and industrial melanism in peppered moths

快速环境变化对空间和时间遗传多样性的影响：胡椒蛾的选择性清除和工业黑化

基本信息

批准号：
NE/H024352/1
负责人：
Ilik Saccheri
金额：
$ 52.2万
依托单位：
University of Liverpool
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH024352%2F1
关键词：
Effect rapid environmental change genetic

项目摘要

Adaptive responses to rapid environmental change are typically associated with strong selection for extreme phenotypes. In the simplest case, when the positively selected phenotype derives from a single mutation of recent origin, it will be associated with a unique extended haplotype for the mutant chromosome, such that when the favoured allele spreads, it will do so in linkage with a large part of its parent haplotype. This hitch-hiking process is expected to lead to loss of genetic variation in the region flanking the target of selection. The size of the chromosomal region affected, and the rate at which nucleotide diversity declines within it, depends on the opportunity for recombination with alternative haplotypes, and therefore upon the local frequency of alternative haplotypes, the number of generations for recombination to occur, the population size and the crossover rate. The replacement of the typical morph of the peppered moth, Biston betularia, by the black carbonaria morph within 40 generations in 19th c. England, driven by the effects of smoke pollution on the relative visibility of the two morphs to bird predators, is predicted to have generated a strong hitch-hiking effect. The opportunity for recombination with alternative haplotypes is likely to have varied spatially along the carbonaria frequency cline between urban manufacturing areas in northwest England and adjacent rural North Wales. In the industrial heartlands of northern England, where carbonaria was near fixation for about 70 generations, the diversity of carbonaria haplotypes should have changed relatively little. By contrast, during the post-1970 decline of carbonaria, probably fuelled in large part by typical immigrants from the rural west, the prediction is for linkage disequilibrium either side of the carbonaria locus to have been progressively eroded over time, and for genetic diversity to have been at least partially restored. Having recently isolated the genomic region containing the carbonaria switch locus, we are now ideally positioned to examine the genetic consequences of the rise and subsequent fall of the carbonaria morph. A special feature of this study is that the evolutionary dynamics will be analysed with respect to both space and time, by integrating genetic information not only from samples collected at a series of positions along the cline but also from historical material preserved in entomological collections. The value of this approach is twofold. Firstly, it allows for more powerful dissection of the interacting processes of selection and dispersal, whose impacts on genetic diversity and linkage disequilibrium are expected to vary in space and time. Secondly, it provides documentary evidence of a clinal selective sweep, as opposed to a historical reconstruction based purely on a contemporary snapshot. One hundred DNA polymorphisms spanning a 3Mb region centred around the carbonaria locus will be assayed in a sample of about 1000 moths representing the population along the cline transect, in recent generations as well as ancestral generations going back to 19th c. Analysis of these data will reveal the age and identity of the original mutant haplotype, and establish whether the carbonaria phenotype has just one or multiple mutational origins. Patterns in genetic diversity will be explained with respect to selection, immigration and time, and contrasted between carbonaria and typical haplotypes. By providing the most detailed reconstruction to date of a clinal selective sweep our study will make a substantial contribution to the understanding of science. Beyond evolutionary biologists, this is relevant both to the general public, who are already familiar with the story of industrial melanism in peppered moths, and to environmental policy makers who need to appreciate the evolutionary ramifications of environmental change.

对快速环境变化的适应性反应通常与对极端表型的强烈选择有关。在最简单的情况下，当正选择的表型来自最近起源的单一突变时，它将与突变染色体的唯一扩展单倍型相关联，这样当所青睐的等位基因传播时，它将与其亲本单倍型的很大一部分连锁。这种搭便车的过程预计将导致选择目标两侧区域的遗传变异的丧失。受影响的染色体区域的大小以及其中核苷酸多样性下降的速度取决于与替代单倍型重组的机会，因此取决于替代单倍型的局部频率、发生重组的世代数、种群规模和交叉率。在公元19世纪的英国，由于烟雾污染对两种变种对捕食性鸟类的相对能见度的影响，在19世纪的英国，典型的花椒蛾Biston betularia变种被黑色碳藻变种取代，预测产生了强烈的搭便车效应。在英格兰西北部的城市制造业地区和邻近的北威尔士农村之间，与替代单倍型重组的机会可能在空间上沿着碳酸盐频率斜面变化。在英格兰北部的工业腹地，碳藻在那里有大约70代人几乎是固定的，碳藻单倍型的多样性应该变化相对较小。相比之下，在1970年后碳线虫的下降--很可能在很大程度上是由来自西部农村的典型移民推动的--预测是，碳线虫基因座两侧的连锁不平衡随着时间的推移而逐渐受到侵蚀，遗传多样性至少已部分恢复。在最近分离了包含碳链开关基因的基因组区域后，我们现在处于理想的位置来研究碳链突变的上升和随后下降的遗传后果。这项研究的一个特点是，将从空间和时间两个方面分析进化动态，不仅整合了在斜坡沿线一系列位置收集的样本的遗传信息，还整合了保存在昆虫学收藏中的历史材料。这种方法的价值是双重的。首先，它允许更有力地剖析选择和扩散的相互作用过程，其对遗传多样性和连锁不平衡的影响预计在空间和时间上是不同的。其次，它提供了克隆体选择性扫荡的文件证据，而不是纯粹基于当代快照的历史重建。100个DNA多态分布在以碳线虫基因座为中心的3MB区域，将在代表近几代人和19世纪以前祖先世代的约1000只蛾样本中进行分析。对这些数据的分析将揭示原始突变单倍型的年龄和身份，并确定碳线虫表型是只有一个还是多个突变来源。遗传多样性的模式将从选择、迁徙和时间方面进行解释，并与碳假单倍型和典型单倍型进行对比。通过提供迄今为止最详细的克隆选择性扫描重建，我们的研究将对理解科学做出实质性贡献。除了进化生物学家，这对已经熟悉胡椒蛾工业黑化故事的普通公众和需要理解环境变化的进化后果的环境政策制定者都是相关的。