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The genomic landscape of adaptive radiation in the Jaera albifrons species complex

Jaera albifrons 物种复合体中适应性辐射的基因组景观

基本信息

批准号：
NE/M015661/1
负责人：
Stuart Piertney
金额：
$ 42.88万
依托单位：
University of Aberdeen
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FM015661%2F1
关键词：
genomic landscape adaptive radiation Jaera

项目摘要

Understanding how one species splits to become two species is of fundamental importance for our understanding of the evolution of life on Earth and the origins of biological diversity. Darwin described this speciation process as "the mystery of mysteries", and considerable effort has gone into understanding the mechanisms that may cause two populations to eventually become incompatible if they tried to reproduce. A lot of effort has focussed on populations that become species through gradual genetic change in isolated populations, and there has been much success in gauging how different two DNA sequences will become after a prolonged period of separation. A bigger challenge has been to explain how two populations may become species if they are not isolated. This is especially pertinent in the marine environment where gene flow should prevent any genetic differences accumulating, but this is clearly not what happens. One theory to explain this is that strong natural selection may operate on certain regions of the genome which effectively shelters these areas from the homogenizing effects of gene flow. These regions - called genomic islands of divergence - will get bigger and bigger until eventually the whole genome is incompatible and two species have formed from one.Recent advances in our ability to look for areas of genetic differences across the entire genetic make-up of individuals and populations means we can finally test this hypothesis and look for these islands of divergence and what genes they may encompass.The aim of this project is to examine this landscape of genome wide divergence among several species of intertidal isopods (Jaera) that have progressed down the route towards speciation to different extents. This provides a very novel way of following the speciation process from beginning through to end. We will look at how different the species are at all points across the genome to identify the regions, and the genes within them, that are showing exceptionally high differences.In Jaera it is known that parts of the chromosomes translocate in the different species, and we will use these as candidate regions for where we might expect a genomic island of divergence to form. We can test this by overlaying the data on genetic differentiation on mapped genomes that we characterise within a family of individuals.We also know that reproduction between species is prevented because courtship behaviour is very specific with males using the hairs on their legs to stimulate females in a very specific way. Females stimulated in the wrong way will not allow mating to occur. We have identified some gene regions that control the patterns of hairs on the legs, and so may represent important genes that promote speciation. Again we will test whether these regions coincide with areas of the genome that display elevated divergence.Finally, it is accepted as norm that most genetic differences between species are a consequence of differences in DNA sequence that then affects the proteins that genes encode. Less emphasis has been given to examining how switching a gene on and off may influence speciation. We will look at which genes are switched on and off in the legs of Jaera during embryonic develop, and identify differences among species that may explain why their legs look very different. This will assess the extent to which there is a direct link between behavioural isolating mechanisms that prevent breeding and the timing of genes being switched on during development. We can also assess whether these differentially expressed genes also fall within the regions of the genome with elevated genomic divergenceOverall this project will provide important new information on the nature, number and size of genomic regions underlying species differences in the J. albifrons species complex, and yield broad insight into the mechanisms that cause species to diverge.

了解一个物种如何分裂成两个物种对于我们理解地球上生命的进化和生物多样性的起源至关重要。达尔文将这种物种形成过程描述为“谜团中的谜团”，并且已经投入了大量精力来了解可能导致两个种群在试图繁殖时最终变得不相容的机制。大量的努力集中在通过孤立种群的逐渐遗传变化而成为物种的种群上，并且在测量两个DNA序列在长时间分离后会变得多么不同方面取得了很大的成功。一个更大的挑战是解释如果两个种群不是孤立的，它们是如何成为物种的。这一点在海洋环境中尤其重要，因为在那里，基因流动应该防止任何遗传差异的积累，但显然情况并非如此。解释这一现象的一种理论是，强自然选择可能作用于基因组的某些区域，从而有效地保护这些区域免受基因流动的负面影响。这些区域--被称为基因组差异岛--会变得越来越大，直到最终整个基因组不相容，两个物种从一个基因组形成。个体和种群的数量增加意味着我们最终可以检验这一假设，并寻找这些分歧岛以及它们可能包含的基因。是检查这几种潮间带等足类动物（Jaera）的基因组广泛分歧的景观，已经进展到不同程度的物种形成的路线。这提供了一个非常新颖的方法，从开始到结束跟踪物种形成过程。我们将研究物种在基因组中各个点的差异，以确定区域，以及其中的基因，这些区域显示出异常高的差异。在Jaera中，已知部分染色体在不同物种中易位，我们将使用这些区域作为候选区域，我们可能期望形成基因组差异岛。我们可以通过将遗传分化的数据叠加在绘制的基因组上来验证这一点，我们在一个家庭中绘制了基因组，我们还知道物种之间的繁殖被阻止，因为求偶行为是非常特殊的，雄性用腿上的毛发以一种非常特殊的方式刺激雌性。以错误的方式刺激雌性不会允许交配发生。我们已经确定了一些控制腿上毛发图案的基因区域，因此可能代表了促进物种形成的重要基因。我们将再次检验这些区域是否与基因组中表现出高度分化的区域相吻合。最后，物种之间的大多数遗传差异是DNA序列差异的结果，然后影响基因编码的蛋白质，这是公认的标准。很少有人强调研究基因的开启和关闭如何影响物种形成。我们将研究在胚胎发育过程中，Jaera的腿中哪些基因被打开和关闭，并确定物种之间的差异，这可能解释为什么它们的腿看起来非常不同。这将评估防止繁殖的行为隔离机制与发育过程中基因开启的时间之间的直接联系。我们还可以评估这些差异表达的基因是否也属于基因组差异升高的基因组区域。总的来说，该项目将提供有关白额胡蜂物种复合体中物种差异的基因组区域的性质，数量和大小的重要新信息，并对导致物种分化的机制产生广泛的见解。