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

当生境在生长和/或繁殖的空间异质性时，种群的持久性和局部适应的规模由幼虫的连通性和定居后的选择决定。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因素的相对重要性仍然未知。这在一定程度上是因为很难研究幼虫行为和水文地理学之间的相互作用，因此只能间接地推断扩散限制。此外，许多海洋物种不受定居后选择的强大空间测试的影响，这些实验很难在与高分散物种相关的大空间尺度上完成。因此，只有少数几个自然系统产生了区分定居前和定居后对基因流动的限制的结果，以至于我们对产生遗传和表型种群结构的机制的理解是零碎的。这项研究的学术价值在于，它在居住在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传播媒介存在纬度梯度。北大西洋西部的大部分海岸线包括被屏障岛包围的浅泻湖，但只有少数几项研究测量了河口之间的连通性，没有一项研究测量过泻湖之间的连通性。该项目以先前对东部牡蛎Crassostrea Virgiica的重大研究为基础，综合了定居前和定居后的测量结果。将使用移民的高分辨率遗传识别，在每三年一次的30个人口中构建一个连接矩阵。将测试扩散模式与假设的扩散载体和约束之间的统计关联。队列分析将被用来测试整个海岸的特定基因存活率的空间差异。此外，在每两年的每一年，将在实地普通花园中测量相对定居后的存活率和表现，并在其中比较当地个体、迁徙和杂交个体。最后，将比较种群内和种群间杂交的受精效率，以检验配子不亲和性限制基因流动的假设。研究结果将被整合到描述扩散和选择之间的空间和/或时间动态平衡的模型中，确定沿交错带局部适应的空间尺度，并确定可能影响共同分布物种的非生物基因流动限制。这项研究的更广泛影响来自其对多样性和渔业管理的重要生境的关注，以及对代表性不足群体的参与。研究中的牡蛎种群生活在佛罗里达州东部的泻湖上，那里的多样性是美国所有河口中最高的，但这条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。了解这个保护区对周围鱼类种群的影响取决于跨越其边界的扩散和栖息地质量，这两个方面都在这里进行研究。这项研究还将支持一名博士生，她将专注于选择论文的衡量标准。这名研究生是一名女性非裔美国人，她努力研究海洋进化生态学，这一目标跨越了两个领域，少数民族代表性极低。在吸引下一代学者方面，P.I.一直很感兴趣。目前有四名本科生在黑尔实验室从事与佛罗里达交错带相关的项目。其中三名本科生是女性，第四名是非裔美国人。来自NSF的资金将允许本科生的参与范围扩大到包括佛罗里达州的暑期实地考察。之前在黑尔实验室工作的本科生已经获得了霍华德·休斯奖学金，并为出版物做出了贡献(Gaines等人。2005)。马里兰大学毕业的非裔美国人比美国排名前20的任何一所大学都多。这为Hare实验室可能的招募提供了大量的少数族裔候选人。P.I.有将主要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张贴进行传播。

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.