The genetic legacy of an Asian oyster introduction and its disease-causing parasite

在20世纪，太平洋牡蛎长牡蛎（Crassostrea gigas）被有意地从亚洲沿海的原生栖息地引入到六大洲的河口。虽然引进的太平洋牡蛎被广泛养殖，从而可以为当地创造经济财富，但它们有时会超越本地牡蛎，并可能携带微生物、动物和植物搭便车，对当地经济和当地河口的生态功能产生负面影响。本研究利用世界范围内的种群遗传调查，全面评估了太平洋牡蛎引种的途径和来源。同时，该研究还评估了一种搭便车原生生物（nelsonhaplosporidium nelsoni）的途径和来源，该原生生物在美国东海岸的弗吉尼亚牡蛎（Crassostrea virginica）中引起MSX（多核球体X）疾病。这项研究的一个目标是制定管理策略，以对抗太平洋牡蛎及其相关入侵者的负面影响，并最大限度地减少未来的入侵。第二个目标是尽量减少破坏性单孢子虫寄生虫种群生物学的不确定性，从而增加管理贝类健康、恢复和商业的政策制定者的信心。通过量化巨噬线虫的途径和来源，本项目可以为应对巨噬线虫及其相关入侵者的负面影响以及减少未来入侵提供策略。此外，对沿美国东海岸的尼尔森氏杆菌种群内部和种群之间的扩散进行量化，将为防止这种破坏性病原体通过水产养殖持续扩散的区域生物安全措施的有效性提供视角。此外，该项目也适用于培养本科生和K-12学生批判性思维和研究经验的项目。该项目为6-9名本科生提供了进行研究的机会，包括为更广泛的本科生社区举办为期两天的生物信息学研讨会，并为K-12学生参与公民科学研究提供了持续的机会。关于巨噬线虫的来源、途径和载体的大量信息主要基于历史文献，但没有研究全面测试过这些历史记录是否正确，使用全球人口遗传调查。利用来自五大洲41个居群的14K单核苷酸多态性（SNPs），发现了高水平的空间遗传分化，在本地范围和非本地区域的源居群之间存在差异。初步的遗传数据表明，寄生原生生物尼尔森单孢子虫（Haplosporidium nelsoni）与进口到美国大西洋海岸线的巨线虫一起到达美国，然后感染了当地的弗吉尼亚单孢子虫，但尼尔森单孢子虫的本地源种群、途径和载体仍不清楚。该项目结合了高通量测序技术和基于近似贝叶斯计算（ABC）的模型来回答以下问题：来自本地和非本地地区的巨线虫的种群基因组模式是什么？nelsonhaplosporidium在亚洲和北美长牡蛎和北美东部的C. virginica中的种群基因组模式是什么？C. gigas和H. nelsoni的源种群和入侵途径是什么？确定巨噬线虫的来源位置、途径和载体，将为研究人员提供与巨噬线虫一起运输的数十种其他非本地物种的入侵历史的零模型。目前还没有得到验证？矢量地图吗?与现代或历史运输记录中产生的相似的C. gigas的历史运输。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

During the 20th century, the Pacific oyster Crassostrea gigas was deliberately introduced from its native range of coastal Asia to the estuaries of six continents. While the introduced Pacific oysters are widely aquacultured and thus can generate local economic wealth, they sometimes outcompete native oysters, and can carry microbial, animal and plant hitchhikers that negatively impact local economies and the ecological functioning of local estuaries. This study comprehensively assesses the pathways and sources of Pacific oyster introductions using a worldwide, population genetic survey. Simultaneously, the study also assesses the pathways and source of one hitchhiking protist (Haplosporidium nelsoni) that causes the disease MSX (multinucleated sphere X) in the Virginia oyster (Crassostrea virginica) along the eastern seaboard of the United States. One goal of this research is to generate management strategies that combat the negative impacts of the Pacific oyster and its associated invaders, and minimize future invasions. A second goal is to minimize some uncertainty about the population biology of the devastating Haplosporidium parasite, and thus, increase confidence of policy makers who are managing shellfish health, restoration and commerce. By quantifying the pathways and sources of C. gigas, this project may inform strategies to combat negative impacts of C. gigas and its associated invaders, as well as minimize future invasions. Moreover, quantifying dispersal within and among populations of H. nelsoni along the US East Coast will provide perspective on the effectiveness of regional biosecurity measures in preventing the ongoing dispersal of this destructive pathogen via aquaculture. In addition, the project lends itself well to programs that foster critical thinking and research experience among both undergraduate and K-12 students. The project provides opportunities for 6-9 undergraduates to perform research, includes a 2-day workshop on bioinformatics for the wider undergraduate community, and facilitates ongoing opportunities for K-12 students to participate in citizen-science research.There is a wealth of information on the source, pathways and vectors of C. gigas based largely on historical documents but no study has comprehensively tested whether these historical accounts are correct using a worldwide, population genetic survey. Using 14K single-nucleotide polymorphisms (SNPs) from 41 populations across five continents a high level of spatial genetic differentiation was found within the native range and differences in source populations among non-native regions. Preliminary genetic data indicated that the parasitic protist, Haplosporidium nelsoni arrived with C. gigas imports to the US Atlantic coastline and then infected the native C. virginica, however the native source populations, the pathways and vector from which H. nelsoni arrived remain unknown. This project couples high-throughput sequencing technologies and Approximate Bayesian Computing (ABC)-based models to answer the following: What are the population genomic patterns among C. gigas from native and non-native regions? What are the population genomic patterns of Haplosporidium nelsoni among Asian and North American Crassostrea gigas and eastern North American C. virginica? What were the source populations and invasion pathways of C. gigas and H. nelsoni? Identifying source locations, pathways and vectors of introduction of C. gigas will provide researchers with a null-model of invasion history for dozens of other non-native species that were transported with C. gigas. Currently, there are no verified ?vector maps? for historical shipments of C. gigas that are similar to those generated from modern-day or historical shipping records.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.