Collaborative Research: Patterns of Larval Dispersal and Postsettlement Selection Shaping Connectivity of Oyster Populations Along an Ecotone

当栖息地在生长和/或繁殖方面存在空间异质性时，种群的持久性和局部适应的规模取决于幼虫的连通性和定居后的选择。不幸的是，对于大多数物种和大多数海洋生态系统来说，限制招募和基因流动的定居前后作用因素的相对重要性仍然未知。部分原因是幼虫行为和水文学之间的相互作用很难研究，因此只能间接推断扩散限制。此外，许多海洋物种不适合进行定居后选择的强有力的空间测试，并且这些实验难以在与高分散物种相关的大空间尺度上完成。因此，只有少数自然系统产生了区分定居前和定居后对基因流的限制的结果，因此我们对产生遗传和表型种群结构的机制的理解是零碎的。这项研究的智力价值在于，它在栖息于佛罗里达州东部半连通泻湖的河口物种中实现了这一双重目标，那里的环境变量、群落组成和潜在的幼虫扩散媒介存在纬度梯度。北大西洋西部海岸线的大部分地区都包括被障壁岛包围的浅泻湖，但只有少数研究测量了河口之间的连通性，而且没有测量泻湖之间的连通性。该项目以之前对东部牡蛎 Crassostrea Virginica 的重要研究为基础，整合了沉降前和沉降后的测量结果。移民的高分辨率基因识别将用于每三年构建 30 个人口之间的连接矩阵。将测试扩散模式与假设的扩散向量和约束之间的统计关联。队列分析将用于测试整个海岸的基因型特异性生存率的空间变化。此外，每年都会在田野公共花园中测量定居后的相对存活率和表现，并对当地个体、移民和杂交种进行比较。最后，将比较群体内和群体间杂交的受精效率，以检验配子不相容性限制基因流的假设。结果将被整合到模型中，这些模型描述了扩散和选择之间的空间和/或时间动态平衡，定义了沿着生态交错带的局部适应的空间规模，并确定了可能影响共同分布物种的非生物基因流限制。这项研究的更广泛影响源于其对多样性和渔业管理的重要栖息地以及代表性不足群体的参与的关注。所研究的牡蛎种群栖息在佛罗里达州东部的泻湖，该泻湖拥有美国所有河口中最高的多样性，但该海岸线正在快速发展。此外，卡纳维拉尔角泻湖还拥有北美最古老的海洋保护区。了解该保护区对周围捕捞种群的影响取决于其边界的扩散和栖息地质量，这两个方面都在这里进行了研究。这项研究还将支持一名博士生，她将专注于论文选择的衡量标准。这名研究生是一名女性非裔美国人，致力于研究海洋进化生态学，这一目标跨越两个少数族裔代表性极低的领域。 P.I.一直有兴趣吸引下一代学者。目前，四名本科生在 Hare 实验室从事与佛罗里达生态交错带相关的项目。其中三名本科生是女性，第四名是非裔美国人。美国国家科学基金会的资助将允许本科生的参与范围扩大到包括佛罗里达州的夏季实地工作。以前在 Hare 实验室工作的本科生获得了霍华德休斯奖学金并为出版物做出了贡献（Gaines 等人，2005 年）。马里兰大学的非洲裔美国人毕业生数量比全国排名前 20 的大学中的任何一所都要多。这为 Hare 实验室的招募提供了大量的少数族裔候选人。 P.I.有着将初级研究成果整合到遗传学入门讲座中的历史。研究结果也通过实验室网页发布来传播。

Population persistence and the scale of local adaptation are determined by both larval connectivity and post-settlement selection when habitats are spatially heterogeneous for growth and/or reproduction. Unfortunately, the relative importance of factors acting before and after settlement that limit recruitment and gene flow is still unknown for most species and most marine ecosystems. This is partly because the interactions between larval behavior and hydrography are difficult to study, so dispersal constraints are only inferred indirectly. In addition, many marine species are not amenable to strong spatial tests of post-settlement selection and these experiments are difficult to accomplish at the large spatial scales relevant to high dispersal species. Consequently, only a handful of natural systems have yielded results that distinguish pre- and post-settlement constraints on gene flow such that our understanding of mechanisms generating genetic and phenotypic population structure is piece meal. The intellectual merit of the study is that it achieves this dual goal in an estuarine species inhabiting semi-connected lagoons along eastern Florida where there is a latitudinal gradient in environmental variables, community composition, and potential larval dispersal vectors. Much of the western North Atlantic coastline includes shallow lagoons enclosed by barrier islands, but only a handful of studies have measured connectivity among estuaries, and none among lagoons. This project builds on significant previous research on the eastern oyster, Crassostrea Virginica to integrate pre- and post-settlement measurements. High resolution genetic identification of migrants will be used to construct a connectivity matrix among 30 populations in each of three years. Statistical associations will be tested between dispersal patterns and hypothesized dispersal vectors and constraints. Cohort analysis will be used to test for spatial variation in genotype-specific survivorship along the entire coast. Also, in each of two years, relative postsettlement survivorship and performance will be measured in field common gardens in which local individuals, migrants and hybrids are compared. Finally, fertilization efficiency of within- and between-population crosses will be compared to test the hypothesis that gamete incompatibilities limit gene flow. The results will be integrated in models that describe the spatially and/or temporally dynamic balance between dispersal and selection, define the spatial scale of local adaptation along the ecotone, and identify abiotic gene flow constraints that may affect codistributed species.The broader impacts of this study derive from its focus on important habitats for diversity and fisheries management, and on the involvement of underrepresented groups. The oyster populations under study inhabit eastern Florida lagoons that possess the highest diversity of any estuary in the United States, yet this coastline is undergoing rapid development. In addition, the Cape Canaveral lagoons contain the oldest marine protected area in North America. Understanding the impact of this reserve on surrounding fished populations hinges on dispersal across its boundaries and on habitat quality, both of which are studied here. This study will also support one PhD student who will focus on the measurements of selection for her dissertation. The graduate student is a female African-American who endeavors to study marine evolutionary ecology, a goal spanning two fields with extremely low minority representation. The P.I. has a continuing interest in attracting the next generation of scholars. Currently four undergraduates work in the Hare lab on projects related to the Florida ecotone. Three of the undergraduates are women and the fourth an African-American. Funding from NSF will allow undergraduate participation to be expanded to include summer field work in Florida. Previous undergraduates working in the Hare lab have obtained Howard Hughes fellowships and contributed to publications (Gaines et al. 2005). The University of Maryland graduates more African-Americans than any of the top 20 universities in this country. This provides a large pool of minority candidates for possible recruitment to the Hare lab. The P.I. has a history of integrating primary research results into lectures in introductory genetics. Research results are also disseminated via lab web page postings.