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Sexual selection, condition dependence and meiotic drive

性选择、条件依赖性和减数分裂驱动

基本信息

批准号：
NE/R010579/1
负责人：
Andrew Pomiankowski
金额：
$ 80.73万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FR010579%2F1
关键词：
Sexual selection condition dependence meiotic

项目摘要

In many species, females show strong sexual preferences to mate with particular males - those with elaborate and exaggerated sexual ornaments. These traits are thought to be honest signals of male genetic quality. But what is the nature of the "good genes" benefits that females derive from mate preference?We will address this fundamental question using the stalk-eyed fly, an iconic example of extreme sexually-selected morphological evolution. Male flies have greatly exaggerated eyespan and females prefer to mate with males with the most extreme eyespan. Of great interest, stalk-eyed flies harbour a selfish genetic element on the X chromosome that causes sex-ratio distortion through meiotic drive. In normal male meiosis, the X and Y chromosomes segregate equally into sperm. But the meiotic drive element produces a toxin that attacks the Y chromosome, causing Y-bearing sperm to die. So all sperm contain the drive X chromosome, and only female offspring are produced. Meiotic drive persists in populations of stalk-eyed flies because of the two-fold advantage the element gains in meiosis (it is passed on to all offspring, whereas other genes are only passed to half the offspring). But its spread is limited because it has overt deleterious effects on the fitness of the organism. Most obviously, it is bad because it kills half of a male's sperm. But it is also bad because the genes causing meiotic drive exist in an "inversion" - a part of the X chromosome that has been flipped around and is orientated in the opposite direction. Inversions cannot undergo normal processes like genetic recombination, and tend to accumulate deleterious mutations. We hypothesise that females gain benefits from avoiding mating with meiotic drive males, as they have low genetic quality. We will test the prediction that females discriminate against drive males. Preliminary work supports this, as drive males have small eyespan. We will investigate this further by exposing males to a range of environmental stresses that are typical of those experienced in the wild, to test whether the sexual ornament is an "honest" signal of genetic quality, in turn explaining why females use it to select a mate. We will characterise in depth how meiotic drive disrupts fertility (by measuring reproductive organ size, sperm allocation and sperm competition) and survival components of fitness, again under variable environmental stress. An interesting prediction is that the rest of the genome has evolved counter-adaptations to drive that will ameliorate loss of performance. We will investigate evidence for this at both the organismal and genomic levels. Evolutionary responses will be tracked at the sequence level by creating high-quality reference genomes of drive and non-drive chromosomes and investigating genomic signatures of changes that are deleterious or beneficial to fitness. Intensive laboratory experiments will be backed up by extensive field investigations of female mating behaviour and male trait distribution of drive-carrying flies in the wild, and how the frequency of drive varies with environmental stress under field conditions. All these strands contribute to our overarching goal: to show how sexual selection, on males and females, interacts with a chromosomal region with clear deleterious effects on organismal fitness.

在许多物种中，雌性表现出强烈的性偏好，与特定的雄性交配-那些精心制作和夸张的性装饰。这些特征被认为是男性遗传质量的真实信号。但是，雌性从择偶偏好中获得的“好基因”的本质是什么呢？我们将使用茎眼蝇来解决这个基本问题，这是极端性选择形态进化的一个标志性例子。雄性果蝇的眼距非常大，雌性果蝇更喜欢与眼距最大的雄性果蝇交配。令人感兴趣的是，有柄眼果蝇的X染色体上有一个自私的遗传因子，通过减数分裂驱动导致性别比例扭曲。在正常的男性减数分裂中，X和Y染色体均等地分离成精子。但是减数分裂驱动元件产生一种毒素，攻击Y染色体，导致携带Y染色体的精子死亡。所以所有的精子都含有驱动X染色体，只有雌性后代才能产生。减数分裂驱动力在有柄眼果蝇种群中持续存在，因为该元素在减数分裂中获得了双重优势（它传递给所有后代，而其他基因只传递给一半后代）。但它的传播是有限的，因为它对有机体的健康有明显的有害影响。最明显的是，它是坏的，因为它杀死了一半的男性精子。但这也是不好的，因为导致减数分裂驱动的基因存在于“倒位”中--X染色体的一部分被翻转过来，方向相反。倒位不能经历像基因重组这样的正常过程，并且倾向于积累有害的突变。我们假设，女性获得的好处，避免与减数分裂驱动男性交配，因为他们有低的遗传质量。我们将测试女性歧视男性的预测。初步的工作支持这一点，因为驱动男性有小的眼睛跨度。我们将进一步研究这一点，将雄性暴露在一系列环境压力下，这些压力是野生环境中所经历的典型压力，以测试性装饰是否是遗传质量的“诚实”信号，从而解释为什么雌性使用它来选择配偶。我们将深入探讨减数分裂驱动如何破坏生育力（通过测量生殖器官大小，精子分配和精子竞争）和生存组成部分的健身，再次在可变的环境压力。一个有趣的预测是，基因组的其余部分已经进化出了反适应，以改善性能的损失。我们将在生物体和基因组水平上调查这一点的证据。通过创建驱动和非驱动染色体的高质量参考基因组，并研究对适应性有害或有益的变化的基因组特征，将在序列水平上跟踪进化反应。密集的实验室实验将支持广泛的实地调查的女性交配行为和男性特征分布的驱动器携带苍蝇在野外，以及如何驱动器的频率变化与环境压力在现场条件下。所有这些线索都有助于我们的总体目标：显示雄性和雌性的性选择如何与染色体区域相互作用，对生物体的适应性产生明显的有害影响。