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Mechanism of adaptation to environmental change: parallel evolution of melanism in the peppered moth

适应环境变化的机制：胡椒蛾黑色素的平行进化

基本信息

批准号：
NE/J022993/1
负责人：
Ilik Saccheri
金额：
$ 53.63万
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：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ022993%2F1
关键词：
Mechanism adaptation environmental change parallel

项目摘要

The genetic raw material that allows a population to respond adaptively to environmental change must come from one of three different sources: 1) genetic variation already present in the population; 2) immigration from another population that has the necessary genetic variation; or 3) spontaneous mutation within the population that produces a beneficial trait. Because a novel phenotypic trait may be produced through a variety of alternative genetic and developmental pathways, adaptive responses to the same environmental change in different populations could involve the same or different genetic changes. Furthermore, the idea that many adaptations are controlled by a restricted subset of genetic master switches or 'hotspots' implies that the origin of phenotypic novelty is to some extent predictable. This overall process influences the likelihood of a novel trait appearing in a population and therefore on the rate of adaptation. However, there are very few well worked examples of mutational origins and the existence of genomic hotspots for adaptation in natural populations.This research aims to expand our understanding of these phenomena in the context of industrial melanism in the peppered moth. This species provides excellent material for studying the mechanism of adaptation. It is widely known that in 19th century Britain till the 1970s, a black coloured variety of this moth, which had never been seen before, replaced the light coloured 'typical' form. The reason for this is that high levels of coal soot in the air caused darkening of the surfaces which peppered moths rest on during the day-time. This made the typical form much more visible than the black form to bird predators, and so the genetic variants producing the typical form rapidly declined. What is less well known is that essentially the same change happened at around the same time in the peppered moth populations of mainland Europe and eastern North America. Were these parallel changes in the separate populations made possible by the same mutation spreading around the world or by different, home-grown, mutations? If there were different mutations, did they occur in the same or different genes?For the British peppered moth population, recent genetic studies have shown that all black peppered moths (called carbonaria) are descended from just one mutant ancestor from the 19th century. Surprisingly, the obscure chromosomal region where the carbonaria gene was found turns out to also control very different colour patterns in butterflies, which hints at a deeply conserved mechanism, perhaps a hotspot. Our objective is to similarly discover the original genetic source of the black peppered moths in mainland Europe and in N America. Preliminary evidence already suggests that they are different from the UK carbonaria and also that they may be much older. This latter possibility is significant because it would mean that, in some populations, the genetic variation for the black form existed before industrialisation.We will take three complementary approaches to this problem: 1) Use parent-offspring families to work out whether the chromosomal regions controlling the black morphs are the same or different between populations. 2) Compare DNA sequence variation associated with black and typical moths in population samples, including early 20th century museum specimens through to modern day specimens. This will tell us if the black moths in Europe and N America come from different ancestors, and whether these ancestors came into being relatively recently, or have a much more ancient history. 3) Measure the activity of the genes that we find during the critical period of melanin production, shortly before the adult moth emerges from the pupa. The findings of this research will add significantly to our understanding of how natural populations adapt to rapid environmental change, which is important to anticipating the consequences of human activity.

使种群能够适应环境变化的遗传原材料必须来自三个不同来源之一：1）种群中已经存在的遗传变异; 2）来自另一个具有必要遗传变异的种群的移民;或3）种群内产生有益性状的自发突变。由于一种新的表型性状可能是通过多种不同的遗传和发育途径产生的，因此不同种群对相同环境变化的适应性反应可能涉及相同或不同的遗传变化。此外，许多适应性是由遗传主开关或“热点”的有限子集控制的想法意味着表型新奇的起源在某种程度上是可预测的。这一整体过程会影响一种新特征在种群中出现的可能性，从而影响适应的速度。然而，有很少的突变起源和基因组热点的存在，以适应在自然population.This研究的目的是扩大我们的理解，这些现象的背景下，工业黑化胡椒蛾的例子。本种为研究适应机制提供了极好的材料。众所周知，在19世纪世纪的英国直到20世纪70年代，这种蛾的黑色变种，以前从未见过，取代了浅色的“典型”形式。这是因为空气中大量的煤烟导致白天飞蛾栖息的表面变暗。这使得典型形式比黑色形式更容易被鸟类捕食者看到，因此产生典型形式的遗传变异迅速下降。鲜为人知的是，欧洲大陆和北美东部的胡椒蛾种群在同一时间发生了基本相同的变化。这些在不同人群中发生的平行变化，是由传播到世界各地的相同突变造成的，还是由不同的本土突变造成的？如果有不同的突变，它们是发生在相同的基因还是不同的基因上？对于英国胡椒蛾种群，最近的遗传研究表明，所有的黑胡椒蛾（称为carbonaria）都是从世纪的一个突变祖先传下来的。令人惊讶的是，发现carbonaria基因的模糊染色体区域也控制着蝴蝶中非常不同的颜色模式，这暗示了一种高度保守的机制，也许是一个热点。我们的目标是类似地发现欧洲大陆和北美黑胡椒蛾的原始遗传来源。初步证据已经表明，它们与英国的carbonaria不同，而且它们可能更古老。后一种可能性是重要的，因为这意味着，在某些种群中，黑色形态的遗传变异在工业化之前就存在了。我们将采取三种互补的方法来解决这个问题：1）使用父母后代家庭来确定控制黑色形态的染色体区域在种群之间是相同还是不同。2)比较种群样本中与黑色和典型蛾相关的DNA序列变异，包括世纪早期的博物馆标本到现代标本。这将告诉我们欧洲和北美的黑蛾是否来自不同的祖先，以及这些祖先是相对较近的，还是有更古老的历史。3)测量我们在黑色素产生的关键时期发现的基因的活性，在成年蛾从蛹中出来之前不久。这项研究的结果将大大增加我们对自然种群如何适应快速环境变化的理解，这对于预测人类活动的后果至关重要。