Divergence in the sea: comparative population genetics of north Atlantic marine invertebrates

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，比陆地系统要微妙得多。 然而，物种可以而且确实在海洋中迅速形成。 我使用群体遗传学来确定驱动水生生物遗传多样性和物种形成的基本过程。 通过比较几个物种之间的遗传结构模式，我问是否有能力分散的浮游生物幼虫提供了最好的解释所观察到的模式。 高扩散潜力是否会导致高种群连通性，并降低任何一个种群通过随机遗传漂变或自然选择等过程在遗传上变得独特的可能性？ 或者，生长和地理分布的历史是否在今天的遗传结构模式上留下了持久的印记？ 如果是这样的话，这些过去的事件对种群间遗传差异的积累或新物种的形成有多重要？ 为了分离生物学和历史的进化影响，我专注于北大西洋的海洋无脊椎动物群，因为这些物种中的许多物种都受到了更新世冰川进退模式的深刻影响。 在此期间，西北大西洋的大部分海洋潮间带群落完全被从太平洋或东北大西洋分散到北极的殖民者所取代。 这些新来者带来了新的遗传物质，通过应用结合理论，我将使用DNA序列来回顾过去，并重建驱动现代遗传结构模式的过程。 这项研究将提供宝贵的见解，以了解推动种群间遗传差异积累的机制，并分离出物理和生物因素对海洋物种形成过程的相对重要性。

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. Nevertheless, species can and do form rapidly in the sea. I use population genetics to identify the fundamental processes that drive genetic diversification and speciation in aquatic organisms. By comparing patterns of genetic structure among several species, I ask whether the ability to disperse as larvae in the plankton provides the best explanation for the patterns observed. Does high dispersal potential lead to high population connectivity and reduce the likelihood that any one population will become genetically distinct through processes like random genetic drift or natural selection? Or, has the history of growth and geographic distribution left a lasting signature on the present-day patterns of genetic structure? If so, how important were these past events to the accumulation of genetic differences among populations or to the formation of new species? To isolate the evolutionary influences of biology and history I focus on the marine invertebrate fauna of the north Atlantic because many of these species have been profoundly influenced by recent patterns of glacial advance and retreat throughout the Pleistocene. During this time much of the marine intertidal community of the northwest Atlantic was completely replaced by colonizers that dispersed across the Arctic from the Pacific or the northeast Atlantic. These new arrivals brought with them new genetic material, and by applying coalescent theory I will use DNA sequences to look back in time and reconstruct the processes driving modern day patterns of genetic structure. This research will provide valuable insights into the mechanisms driving the accumulation of genetic divergence among populations and isolate the relative importance of both physical and biological factors to the process of speciation in the sea.