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，遗传差异和物种形成的问题尤其复杂，因为基因交流的障碍通常是允许差异发生的关键，比陆地系统中的障碍要微妙得多。然而，物种可以而且确实在海洋中迅速形成。我使用种群遗传学来确定推动水生生物遗传多样性和物种形成的基本过程。通过比较几个物种的遗传结构模式，我问，在浮游生物中作为幼虫扩散的能力是否为观察到的模式提供了最好的解释。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移或自然选择等过程变得不同的可能性？或者，增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对进化的影响，我将重点放在北大西洋的海洋无脊椎动物动物群上，因为这些物种中的许多都受到了最近整个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被从太平洋或东北大西洋分散到北极各地的殖民者完全取代。这些新来的人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，重建驱动现代遗传结构模式的过程。这项研究将为推动种群间遗传差异积累的机制提供有价值的见解，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.