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

知识价值：了解适应性遗传变异的地理模式对物种保护至关重要，但在海洋系统中，我们对这一现象的了解几乎为零。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移动的生命阶段，因此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中相对较低水平的遗传变异的支持，这是由对选择中立的DNA标记的调查得出的。表型变异预计很大程度上是由环境因素引起的，特别是对环境条件高度敏感的生理性状。在对大西洋银鱼（Menidia Menidia）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。银鱼在一系列与北美东海岸纬度气候变化密切相关的共同进化的生理和形态特征中表现出高度结构化的局部适应。然而，分子遗传学调查的初步数据表明，在整个纬度范围内存在广泛的基因流动。这个项目将解决两个核心问题。第一个是关于地方适应的微观地理。它有多精细？它是如何受到基因流的影响的？它与海岸线的物理特征密切相关吗？多个特征是否沿着相同的梯度相似地共同变化？第二个问题集中在生长速率的进化上，这一特征不仅在银腹草中，而且在许多其他分类群中都表现出强烈的反梯度纬度变化。最近的实验表明，由于体型选择性死亡，包括捕鱼引起的基因变化，生长速度可以迅速变化。本项目将研究增长率演变的相关因素。我们将研究生长速率的权衡如何影响动物的发育、行为、形态和抵御疾病的能力。这项研究整合了生物地理学、生理学、定量和分子遗传学、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，从而允许对大多数其他海洋物种不可能进行的假设进行严格的测试。更广泛的影响：该项目结合了一位高级研究员的经验和两位新兴的少数族裔背景的初级教师的技能。参与该项目的学生将有独特的机会体验生态和分子遗传学方法来保护海洋。由于亚麻池海洋实验室持续维护和圈养的银边鱼种群的可用性，该项目通过学生研究项目、课堂演示和参观为公众参与科学提供了极好的机会。此外，我们最近关于大小选择性捕鱼的进化效应的发现引起了全世界广泛的宣传和兴趣，这是一个很好的机会，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.