Collaborative Research: Local adaptation across latitudes: microgeographic scales, gene flow, and correlates of countergradient growth variation

智力优势：适应性遗传变异的地理模式知识对物种保护至关重要，但在海洋系统中，我们对这一现象的理解几乎为零。直到最近，人们一直认为，由于大多数海洋物种具有高度分散或流动的生命阶段，局部适应只能在广泛的地理范围内发生。这一观点得到了种群间相对较低水平的遗传变异的支持，该水平的遗传变异由中性于选择的DNA标记的调查所索引。表型变异在很大程度上可能源于环境，特别是对环境条件高度敏感的生理性状。在对大西洋银鱼和其他物种的研究的刺激下，这些长期持有的信念正在迅速改变。银边显示了高度结构化的局部适应的戏剧性证据，在北美东海岸的纬度上，一系列与气候变化密切相关的共同进化的生理和形态特征。然而，来自分子遗传学调查的初步数据表明，整个纬度范围内都有广泛的基因流动。该项目将解决两个核心问题。第一个问题涉及当地适应的微观地理。它的比例有多高？它是如何受到基因流动的影响的？它是否与海岸线的自然特征密切相关？在相同的梯度上，多个性状是否具有相似的协变性？第二个问题集中在生长率的进化上，这一特征不仅在银边，而且在许多其他分类群中都表现出强烈的逆梯度纬度变化。最近的实验表明，生长速度可以非常迅速地进化，以应对大小选择性死亡，包括捕鱼造成的遗传变化。这个项目将考察增长率演变的相关性。我们将研究生长速度的权衡如何影响动物的发育、行为、形态和抵御疾病的能力。这项研究综合了生物地理学、生理学、数量和分子遗传学、行为学、免疫学和发育生物学。它利用自然和实验进化的种群，从而允许对假设进行严格的测试，这在大多数其他海洋物种中是不可能的。更广泛的影响：这个项目将一名高级调查员的经验与两名新兴的少数族裔背景的初级教员的技能结合在一起。参与该项目的学生将有一个独特的机会体验海洋保护的生态学和分子遗传学方法。由于亚麻池海洋实验室对银边圈养种群的持续维护和提供，该项目提供了通过学生研究项目、班级演示和参观让公众参与科学的绝佳机会。此外，我们最近发现的选择性捕捞的进化效应引起了全世界的广泛宣传和兴趣，这是一个极好的机会，可以增加公众对进化原理及其如何影响当代社会问题的理解。

Intellectual merit: Knowledge of geographic patterns in adaptive genetic variation is crucial to species conservation, yet in marine systems our understanding of this phenomenon is virtually nil. Until recently, the belief has been that because most marine species have highly dispersive or mobile life stages, local adaptation could occur only on broad geographic scales. This view is supported by comparatively low levels of genetic variation among populations as indexed by surveys of DNA markers neutral to selection. Phenotypic variation is expected to be largely of environmental origin, especially for physiological traits that are highly sensitive to environmental conditions. Stimulated by studies of the Atlantic silverside (Menidia menidia) and other species, these long-held beliefs are rapidly changing. The silverside shows dramatic evidence of highly structured local adaptation in a suite of coevolving physiological and morphological traits tightly associated with climate change across latitudes along the east coast of North America. Yet preliminary data from molecular genetic surveys suggest extensive gene flow along the entire latitudinal range. This project will address two central problems. The first concerns the micro-geography of local adaptation. How finely scaled is it? How is it influenced by gene flow? Is it closely tied to physical features of the coastline? Do multiple traits co-vary similarly along the same gradient? The second problem focuses on the evolution of growth rate, a trait that strongly displays countergradient latitudinal variation not only in the silverside but also in numerous other taxa. Recent experiments show that growth rate can evolve very rapidly in response to size-selective mortality, including genetic changes caused by fishing. This project will examine the correlates of growth rate evolution. We will study how trade-offs with growth rate influence development, behavior, morphology, and the ability of animals to defend against disease. This research integrates biogeography, physiology, quantitative and molecular genetics, behavior, immunology, and developmental biology. It draws upon natural and experimentally evolved populations, thereby allowing rigorous testing of hypotheses that would be impossible in most other marine species. Broader Implications: This project unites the experience of a senior investigator with the skills of two emerging junior faculty of minority background. Students working on the project will have a unique opportunity to experience both ecological and molecular genetic approaches to marine conservation. Because of the continuous maintenance and availability of captive populations of the silverside at the Flax Pond Marine Laboratory, this project provides excellent opportunities for engaging the public in science through student research projects, class demonstrations, and tours. In addition, the extensive worldwide publicity and interest generated by our recent findings on evolutionary effects of size-selective fishing represent an excellent opportunity to increase public understanding of the principles of evolution and how they affect contemporary societal issues.