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Genomic patterns of introgression between hybridising birch species due to range shifts caused by climate change in the Scottish Highlands

由于苏格兰高地气候变化引起的范围变化，杂交桦树种之间的基因组渗入模式

基本信息

批准号：
NE/G01504X/1
负责人：
Richard Buggs
金额：
$ 35.25万
依托单位：
Queen Mary University of London
依托单位国家：
英国
项目类别：
Fellowship
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%2FG01504X%2F1
关键词：
Genomic patterns introgression between hybridising

项目摘要

Scientists are certain the global warming is occurring at an alarming rate, but we do not yet fully understand the effects this will have on the living world. There is good evidence that many natural species are gradually moving the ranges in which they live, to stay in environmental conditions to which they are adapted. For many species in the UK, this means moving northwards, or up mountains. One consequence of this is that some species are forced into close contact with their relatives. This arrangement can work well if they are unable to have sex together, and the two species can often coexist in the same area. But where sex is possible, things get complicated. Sexual reproduction between two species is called hybridisation, and can result in the two species merging into a single new species, or one species eliminating the other. Which of these outcomes occurs depends on many factors, including how fit the two species are relative to each other and how successful the hybrid offspring are. This project plans to investigate this in two birch tree species growing in the UK. Downy birch is common and currently expanding its range up mountains where it meets its relative, dwarf birch, which is nationally scarce. The two species can hybridise together even when they are far apart, because they are wind pollinated. They produce hybrids that grow up and hybridise with their parents. As downy birches advance up the mountains, the dwarf birches have no where left to go. We need to know how long this has been happening in the past and how quickly it is happening in the present. We can get a window on this from historical records, but these can often be patchy. Another way is to look at the DNA of the two species and look for signs of past hybridisation. Because the species hybridise so much, bits of the dwarf birch genome will be found inside the downy birch genome wherever the two species have met, even if it was a long time ago. This means that we can discover where the two species first met, and how far dwarf birch has been pushed back by downy birch. For this to work, we have to look at very many sections of DNA, all over the genomes of these two wild tree species. Until recently, this would have been impossible, but new technology lets us do this relatively easily and cheaply. We can read many parts of the DNA sequences of the two species and discover where they differ, then go back and look for these differences in areas where they have hybridised. For every tree we look at, we can find which sections of the genome are from downy birch and which are from dwarf birch. Looking more closely at that data, we can use mathematics to map which sections of the genome are moving around and which are not. In another approach to this, we can use our DNA sequence data to design sticky tags that are targeted to one species or the other. When we attach these tags to dyes, we can 'paint' the genomes of individual plants and use microscopes to look at the mixtures of the two species that they contain. Then we can look even closer, and investigate the function of genes in the sections from different species. We expect different sections of the genomes to behave in different ways, due to the genes they contain. Some sections will be so integral to a species' identity that they cannot part with them. Others will be selected by the environment and move to wherever they are needed, regardless of the species. Still others will be neutral, and drift around at random; these are the best markers of historical hybridisation and species range movements. Scientists have only just started to be able to work on the question of which parts of genomes can move freely between species, even though we have been interested in it for a long time. So this work will make an important contribution to our knowledge of how species evolve and remain separate, as well as helping us to understand how global warming will affect rare species.

科学家们确信全球变暖正在以惊人的速度发生，但我们还没有完全了解这对生物世界的影响。有充分的证据表明，许多自然物种正在逐渐迁移它们生活的范围，以留在它们适应的环境条件下。对于英国的许多物种来说，这意味着向北迁移或上山。这样做的一个后果是，一些物种被迫与它们的亲属密切接触。这种安排可以很好地工作，如果他们不能在一起发生性关系，这两个物种往往可以在同一地区共存。但如果性是可能的，事情就变得复杂了。两个物种之间的有性繁殖被称为杂交，可以导致两个物种合并成一个新的物种，或者一个物种消灭另一个物种。这些结果中的哪一个发生取决于许多因素，包括两个物种相对于彼此的适应程度以及杂交后代的成功程度。该项目计划在英国生长的两种桦树品种中调查这一点。绒毛桦树很常见，目前正在向山上扩展，在那里它遇到了它的亲戚，矮桦树，这是全国罕见的。这两个物种即使相距很远也能杂交，因为它们是风媒传粉的。它们产生的杂交种长大后与它们的父母杂交。当长满绒毛的桦树向山上进发时，矮桦树无处可去。我们需要知道这种情况在过去发生了多久，现在发生的速度有多快。我们可以从历史记录中找到一个窗口，但这些往往是不完整的。另一种方法是观察两个物种的DNA，寻找过去杂交的迹象。因为这两个物种杂交的频率很高，所以无论这两个物种在哪里相遇，都会在绒毛桦树的基因组中发现矮桦树基因组的片段，即使是很久以前。这意味着我们可以发现这两个物种第一次相遇的地方，以及矮桦被绒毛桦推了多远。为了使这个工作有效，我们必须研究DNA的许多部分，遍布这两种野生树种的基因组。直到最近，这是不可能的，但新技术让我们相对容易和便宜地做到这一点。我们可以读取这两个物种的DNA序列的许多部分，发现它们的不同之处，然后回头在它们杂交的区域寻找这些差异。对于我们观察的每一棵树，我们都能发现基因组的哪些部分来自绒毛桦，哪些来自矮桦。更仔细地观察这些数据，我们可以用数学来绘制基因组的哪些部分在移动，哪些没有。在另一种方法中，我们可以使用我们的DNA序列数据来设计针对一个物种或另一个物种的粘性标签。当我们将这些标签附着在染料上时，我们可以“绘制”单个植物的基因组，并使用显微镜观察它们所包含的两种物种的混合物。然后我们可以更近距离地观察，研究不同物种切片中基因的功能。我们预计基因组的不同部分会以不同的方式表现，这是由于它们包含的基因。有些部分对一个物种的身份是如此不可或缺，以至于他们不能与它们分开。其他的将被环境选择，并移动到任何需要它们的地方，不管是什么物种。还有一些是中性的，随机漂移;这些是历史杂交和物种范围运动的最佳标记。科学家们才刚刚开始能够研究基因组的哪些部分可以在物种之间自由移动的问题，尽管我们对此感兴趣已经很久了。因此，这项工作将对我们了解物种如何进化和保持分离做出重要贡献，并帮助我们了解全球变暖将如何影响稀有物种。