The prevalence of genetic introgression in speciation

背景：物种间遗传交换的重要性（即来自一个物种的基因渐渗） 物种通过杂交中间体进入另一个物种）是进化论中争论不休的话题。 生物学家虽然有些人声称基因交换是普遍存在的，但其他人声称它是极其罕见的。目前， 几乎没有数据从数量上支持这两种情况。 广泛的长期目标：拟议的对自然发生的混合区的研究将量化 物种间遗传交换的普遍性，以了解频率和进化后果 基因交换。该提案利用这些在混合区进行的自然实验， 基因组，我可以绘制复杂的行为特征的遗传学，这些特征在杂交后代之间存在差异。 物种由于行为性状的遗传作图已被证明是非常困难的，通过传统的手段，混合 测绘为在这些重要问题上取得进展提供了独特的机会。 具体目标：本研究的目标1是绘制六个自然杂交区的基因渗入流行图， 这是第一次被记录下来。AIM2将使用来自杂交区的混合果蝇来绘制基因图谱 在生态学上重要的温度偏好特征的基础上。目标3将使用混合苍蝇从另一个 杂交区，以绘制配偶偏好的复杂行为特征的基因。 方法：在自然生境中采集果蝇，并进行饲养 在实验室条件下，并拥有无与伦比的分子遗传和基因组工具库。这 一项提案提出了一种新的模型，用于识别基因组中的渗入等位基因，这种方法只 在杂交两个亲本物种都具有高质量基因组组装的生物体中是可行的。的 在这些混合物分析中鉴定的基因将用CRISPR介导的基因功能验证。 替代品混合作图和基因组编辑的初步结果都很有希望。 健康相关性：人类混合物图谱是用于识别 致病基因变异然而，后续的实验来测试基因的功能， 疾病不能在人类身上进行。因此，混合物映射方案从未经过验证 从鉴定与疾病相关的变异的群体水平到功能性 分子遗传水平，表现为表型状态。这个提议是创新的，因为它 开发新的计算方法来识别具有复杂祖先的基因组区域，然后将 通过基因组编辑将这些基因组模式转化为可测量的表型差异。 影响：这项研究的结果将提供第一个广泛的情况下，渗入模式的看法， 物种在自然界中杂交，并将利用这些模式的混合物解剖的遗传基础， 导致生殖隔离的物种之间的行为差异。

Background: The importance of genetic exchange between species (i.e. introgression of genes from one species into another through hybrid intermediates) is a constant subject of debate among evolutionary biologists. While some claim genetic exchange is pervasive, others claim that it is extremely rare. Currently, there is little data quantitatively supporting either of these scenarios. Broad, long-term objective: The proposed study of naturally occurring hybrid zones will quantify the prevalence of genetic exchange between species to understand the frequency and evolutionary consequences of gene exchange. The proposal takes advantage of these natural experiments in hybrid zones to find admixed genomes with which I can map the genetics of complex behavior traits that differ between the hybridizing species. Since genetic mapping of behavior traits has proven very difficult by conventional means, admixture mapping provides a unique opportunity to make progress on these important questions. Specific aims: Aim 1 of the study is to map the prevalence of introgression in six natural hybrid zones, four of which are documented here for the first time. Aim 2 will used admixed flies from a hybrid zone to map genes underlying the ecologically important trait of temperature preference. Aim 3 will use admixed flies from another hybrid zone to map genes underlying the complex behavioral trait of mate preference. Method: Fruit flies from the genus Drosophila can be collected in their natural habitat and also maintained under laboratory conditions, and have an unmatched arsenal of molecular genetic and genomic tools. This proposal presents a novel model for identifying introgressed alleles in the genome, an approach that is only feasible in hybridizing organisms for which both parental species have high quality genome assemblies. The genes identified in these admixture analyses will be functionally validated with CRISPR-mediated gene replacements. Preliminary results for admixture mapping and genome editing are both promising. Health-relatedness: Admixture mapping in humans is a primary approach used for the identification of disease-causing gene variants. However, follow up experiments to test the function of genes correlated with disease cannot be performed in humans. Admixture mapping protocols have therefore never been validated end-to-end from the population level at which variants correlated with disease are identified, to the functional molecular genetic level where the phenotypic state is manifested. This proposal is innovative because it develops new computational methods to identify genomic regions with complex ancestry, and then connects these genomic patterns to measurable phenotypic differences via genome editing. Impact: The results from this study will provide the first broad view of patterns of introgression in cases where species interbreed in nature, and will leverage those patterns of admixture to dissect the genetic basis of behavioral differences between species that cause reproductive isolation.