The genetics of reproductive isolation and speciation in north Atlantic sea urchins

新物种的起源仍然是进化生物学中最核心和最难以捉摸的问题。 在海洋环境中，遗传分化和物种形成的问题特别复杂，因为遗传交换的障碍通常是允许分化发生的必要条件，而这些障碍比陆地系统要微妙得多。无论是沿着生态边界的沿着不同的选择，还是配子不相容性的进化，以防止杂交（即，强化）预计将在海洋物种形成过程中发挥关键作用，但这些力量究竟如何抵消基因流动的负面影响一直存在争议。 我的研究利用下一代测序技术的令人兴奋的进展来研究基因组水平上的物种差异。 我专注于两种广播产卵海胆在大西洋西北部，人口重叠和杂交频繁发生之间的接触区。 杂交区是研究物种形成过程中选择作用的理想“天然实验室”，因为具有混合祖先的个体的命运可以在他们从一个生态环境迁移到另一个生态环境时被追踪。通过实验室和实地研究，我和我的学生（i）将确定有多少不同的基因参与了整个杂交区的生殖隔离进化，（ii）评估适应不同栖息地作为生殖隔离机制的作用，（iii）更好地理解加强配子识别分子的作用，这些分子可能已经进化到阻止杂交的发生。本提案中概述的实验将扩展我们对种群水平上生殖隔离驱动因素的认识，并有助于对多样化选择、基因流动和遗传漂变的对立力量在物种形成过程中的相对重要性有一个普遍的理解。

The origin of new species remains the central and most elusive question in evolutionary biology. In marine environments, the problem of genetic divergence and speciation is especially complex, because the barriers to genetic exchange that are generally essential for allowing divergence to occur are far more subtle than in terrestrial systems. Both divergent selection along ecological boundaries, and the evolution of gamete incompatibilities to prevent hybridization (i.e., reinforcement) are expected to play key roles in the process of speciation in the sea, but exactly how these forces counteract the homogenizing effects of gene flow has long been debated. My research uses exciting advances in next generation sequencing techniques to investigate species divergence at the level of the genome. I focus on a contact zone between two species of broadcast spawning sea urchins in the northwest Atlantic, where populations overlap and hybridization frequently occurs. Hybrid zones are ideal “natural laboratories” for examining the role of selection in the process of speciation, because the fate of individuals with mixed ancestry can be traced as they move and from one ecological setting to another. Using both laboratory and field studies my students and I (i) will determine how many different genes are involved in the evolution of reproductive isolation across the hybrid zone, (ii) assess the role of adaptation to different habitats as a mechanism of reproductive isolation, and (iii) better understand the role of reinforcement at gamete recognition molecules that may have evolved to prevent hybridization from occurring. The experiments outlined in this proposal will extend our knowledge of the factors driving reproductive isolation at the population level, and contribute to a general understanding of the relative importance that the opposing forces of diversifying selection, gene flow and genetic drift play in the process of speciation.