The Ecology of Genome Evolution - Connecting Population Genetics and Reproductive Biology

遗传变异是进化的燃料，了解其在野生种群中的分布和维持是进化生物学的核心目标。随着我们试图了解人口将如何适应不断变化的环境条件，这一目标重新变得突出起来。遗传多样性受到种群大小的影响，这是保护生物学家关注的一个关键问题。然而，其他因素也会影响野生种群的遗传多样性，如果我们要了解物种过去是如何进化的，以及它们未来将如何进化，了解这些因素是至关重要的。在这方面涉及的两个因素是物种的繁殖结构和基因重组的速度，这是在所有有性繁殖物种中发生的一种机制，通过这种机制，遗传物质在一对染色体之间交换，导致父母和后代拥有不同的基因组合。重组是一个非常重要的过程，已被证明与更高水平的遗传多样性相关。我将研究重组和交配系统在决定遗传多样性如何在果蝇黑腹果蝇中分布和维持方面所起的作用。D.黑腹鱼是一种模式物种，在许多研究领域都有成功的应用。它的自然种群引起了人们的极大兴趣，因为它已经成为一个世界性的物种，在过去的几千年里适应了许多新的环境。与人类一样，它被认为起源于非洲，相对较近地殖民于世界其他地区，非洲以外的种群与非洲相比遗传多样性较低，因为创建新种群的个体数量较少。我将收集该物种范围内的苍蝇，包括欧洲、北美和非洲，因为这种物种被认为比欧洲更晚到达美国--几百年而不是几千年前。我将利用我们对果蝇基因组的广泛知识，通过检查每个种群的遗传多样性水平，进行迄今为止野外最大的遗传变异性研究之一。这将使我能够看到范围扩大和适应新栖息地对遗传多样性的影响，以及基因重组的影响。通过检查基因组中发生这一过程的不同区域，我将探索重组和遗传多样性之间的关系，并评估种群是否在这些参数如何相关的方面存在差异。我还将从男性和女性的角度来研究交配系统如何影响遗传多样性。首先，我们知道许多物种的雄性都是色彩鲜艳的，或者展示精致的展示来吸引雌性。雄性果蝇面临着类似的压力，挑剔的雌性果蝇只与它们认为合适的雄性交配。因此，被选中的雄性可能会生下很多后代，而其他雄性可能没有后代。这减少了生育下一代的男性数量，从而减少了男性遗传的基因变异数量。通过测量雄性的这种性选择的强度以及不同种群之间的差异，我将研究这如何影响野生环境中的遗传变异性。其次，在物种很好地适应其栖息地和营养资源丰富的种群中，雌性将有足够的能量产生大量的卵。当营养来源不足时，例如在物种刚建立或对资源的竞争激烈的环境中，一些雌性可能无法产卵。这减少了对下一代有贡献的雌性数量，从而减少了雌性遗传的可变性。我将通过观察卵子发育的模式来检查不同种群的雌性是否为繁殖做好了准备，看看雌性繁殖状态如何影响野外的遗传多样性。

Genetic variation is the fuel of evolution, and understanding its distribution and maintenance in wild populations is a core aim of evolutionary biology. This aim has gained renewed prominence as we try to understand how populations will adapt to changing environmental conditions. Genetic diversity is influenced by population size, and this is a key concern for conservation biologists. However, other factors will influence genetic diversity in wild populations, and understanding these is vital if we are to understand how species have evolved in the past, and how they will do so in future. Two factors implicated in this respect are the breeding structure of the species and the rate of genetic recombination, a mechanism occurring in all sexually reproducing species by which genetic material is exchanged between pairs of chromosomes, resulting in parents and offspring having different combinations of genes. Recombination is a very important process and has been shown to be correlated with higher levels of genetic diversity. I will examine the role that recombination and the mating system play in determining how genetic diversity is distributed and maintained in the fruit fly Drosophila melanogaster. D. melanogaster is a model species that is successfully used in many areas of research. Its natural populations are of great interest because it has become a cosmopolitan species, adapting to many new environments over the last few thousand years. Like humans, it is thought to have originated in Africa, colonising the rest of the world relatively recently, and populations outside Africa have low genetic diversity compared to those in Africa due to small numbers of individuals founding new populations. I will collect flies around the species' range, including Europe and North America as well as Africa, because the species is thought to have reached America more recently than Europe - several hundred rather than several thousand years ago. I will use our extensive knowledge of the fruit fly genome to carry out one of the largest studies of genetic variability in the wild to date, by examining levels of genetic diversity in each population. This will allow me to look at the effects on genetic diversity of range expansion and adaptation to new habitats, as well as the influence of genetic recombination. By examining regions of the genome that differ in the rate at which this process occurs, I will explore the relationship between recombination and genetic diversity, and assess whether populations vary in terms of how these parameters are related. I will also look at how the mating system influences genetic diversity, from both the male and female perspectives. Firstly, we know males of many species are brightly coloured or exhibit elaborate displays to attract females. Male fruit flies experience similar pressures, with choosy females only mating with males they deem suitable. Chosen males may therefore father many offspring, whilst others have none. This reduces the number of males fathering the next generation, and thus the number of genetic variants passed on by males. By measuring how strong this sexual selection on males is and how it varies between populations, I will examine how this affects genetic variability in the wild. Secondly, in populations where the species is well adapted to its habitat and nutritional resources are abundant, females will have enough energy to produce large numbers of eggs. When nutritional sources are low, for example in environments where the species is newly established or competition for resources is high, some females may not be able to produce any eggs. This reduces the number of females contributing to the next generation, and thus the genetic variability passed on by females. I will examine whether females in different populations are prepared for breeding by looking at patterns of egg development, to see how female reproductive status influences genetic diversity in the wild.