Collaborative Research: SG: The importance of X-chromosomes in speciation: Are genes that do not introgress concentrated on the X chromosome?

为了理解新物种是如何进化的，我们需要了解参与这一过程的基因以及这些基因在基因组中的位置。物种形成是由导致个体群体之间生殖不相容的基因引起的，早期的研究表明这些基因位于X染色体上。这个项目将研究X染色体在两种密切相关的蟋蟀进化中的作用。这两种蟋蟀仍然能够产生一些杂交后代并交换遗传信息。这些物种的种群共同出现在美国东北部，在那里，它们形成了一个广泛的自然杂交区，在那里，基因已经交换了数千代。研究人员将调查物种之间的遗传混合率，并确定它在基因组中的位置。这项研究将解决X染色体包含导致生殖隔离的基因的假设，通过测试X染色体是否显示物种之间的遗传交换率较低。位于低遗传交换区域内的特定基因也将被确定，以进一步了解新物种进化所需的条件。这是一个合作研究项目，将主要在文科，本科学院进行，并将为本科生的培训和指导提供大量的机会。外联活动包括科学教育讲习班和活动，将针对STEM领域代表性不足的初中和高中学生。拟议的研究将测试X染色体在物种形成中的重要性，以及在田野蟋蟀，Gryllus firmus和G. pennaclicus，反映了差异渐渗和/或最近的选择。该项目有三个主要目标。首先，X染色体将使用杂交回交和种内杂交作图;将评估这些X连锁染色体标记的分化模式。其次，将从基因组区域获得基因序列，这些基因组区域显示物种之间基因交换和分化的不同速率。基因组区域的低速率的基因流和高分化可能窝藏基因负责生殖隔离和物种的身份。绝对和相对措施的遗传分化和估计的选择将计算高分化地区和低分化的控制区。这些结果将用于测试基因组是否由高分化区域和低分化区域的拼凑物组成。第三个目标是基于观察，有两个蟋蟀物种之间的单向不兼容，但这一“规则”是打破一些人口杂交。如果高度分化的区域是生殖隔离的原因，那么在产生后代的配对和不产生后代的配对之间应该存在一致的基因组差异。 结果将提供重要的见解的基因组结构的物种形成，X染色体在生殖隔离和不同的适应中的作用，并将有助于正在进行的辩论基因组岛的分化。

To understand how new species evolve we need to understand the genes involved in the process and where these genes are located in the genome. Speciation results from genes that cause reproductive incompatibilities between groups of individuals, and earlier studies have suggested these genes are located on the X chromosome. This project will investigate the role of the X chromosome in the evolution of two closely related species of field crickets. These two cricket species are still capable of producing some hybrid offspring and exchanging genetic information. Populations of these species co-occur in the Northeastern U.S., where they form an extensive natural hybrid zone, in which genes have been exchanged for thousands of generations. The researchers will investigate rates of genetic mixing between the species, and determine where it occurs across the genome. This research will address the hypothesis that the X chromosome contains the genes that lead to reproductive isolation, by testing whether the X chromosome shows a lower rate of genetic exchange between species. Specific genes located within regions of low genetic exchange will also be identified to further our understanding of what is required for new species to evolve. This is a collaborative research project that will be mainly conducted at a liberal arts, undergraduate college and will provide substantial opportunity for training and mentoring of undergraduate students. Outreach includes science education workshops and activities, and will target underrepresented, middle and high school students in STEM fields.The proposed research will test both the importance of the X chromosome in speciation and whether observed islands of differentiation in the field crickets, Gryllus firmus and G. pennsylvanicus, reflect differential introgression and/or recent selection. The project has three main objectives. First, the X chromosome will be mapped using hybrid backcrosses and within species crosses; patterns of differentiation for these X-linked chromosome markers will be assessed. Second, gene sequences will be obtained from genome regions that show varying rates of gene exchange and differentiation between species. Genome regions with low rates of gene flow and high differentiation might harbor genes responsible for reproductive isolation and species identities. Absolute and relative measures of genetic differentiation and estimates of selection will be calculated for high differentiation regions and for control regions with low differentiation. These results will be used to test if the genome is composed of a patchwork of high and low differentiation regions. The third objective is based on the observation that there is a one-way incompatibility between the two cricket species, but that this 'rule' is broken in some population crosses. If regions of high differentiation are responsible for reproductive isolation, then there should be consistent genomic differences between pairs that produce offspring and those that do not. Results will provide important insights into the genomic architecture of speciation, the role of the X chromosome in reproductive isolation and divergent adaptation, and will contribute to ongoing debates about genomic islands of differentiation.