Replicated Ecological Speciation in Extreme Habitats: Patterns, Mechanisms, and Consequences of Multi-Trait Divergence

硫化氢是一种剧毒气体，即使在低浓度下对大多数动物也是致命的。在墨西哥南部，Poecilia属的小型活鱼独立地定居在多个硫化物泉水中，那里的硫化氢自然浓度很高。这些鱼为研究脊椎动物如何在对大多数其他生物致命的条件下生存提供了机会。硫化物泉水的适应还导致硫化物生态型和非硫化物生态型之间的生殖隔离，为新物种如何进化提供了洞察力。这项建议的目标是在硫化物和非硫化物生境的复制对中确定表型和遗传分化的趋同模式。这种比较将揭示调节硫化物耐受性的性状和潜在的基因变化。这项研究解决了三个基本问题：(1)复杂的表型是如何沿着复制的环境梯度进化的？量化野生捕获个体的表型变异(包括行为、生理和形态特征)将确定硫化物和非硫化物鱼类复制对中适应性特征差异的收敛模式。分析普通园养个体相同的表型性状，将有助于阐明可遗传分化和表型可塑性如何相互作用来表达自然界的表型。(2)性状差异背后的基因组变化是什么？下一代测序技术(RNA-Seq)将被用来识别表现出差异选择或差异表达特征的基因，这将被用来识别与极端环境相适应的候选基因。(3)在不同的环境条件下表现出的不同性状对生殖隔离的功能后果是什么？比较实验室饲养的鱼暴露在硫化或非硫化条件下的生长速度，将提供适应硫化物与以移民丧失生存能力形式的生殖隔离之间的直接联系。了解有机体？对自然产生的压力环境的反应最终可以用来更好地理解生物对人类改变的环境反应的原因和后果。该项目促进了科学家和来自美国和墨西哥的学生在研究和教育方面的合作。该项目为鱼类生物学家建立了一个公共推广平台，以与鱼类爱好者组织互动，作为向非专业公众传播研究成果的一种手段。

Hydrogen sulfide is a highly toxic gas that is lethal for most animals, even at low concentrations. In southern Mexico, small livebearing fish of the genus Poecilia have independently colonized multiple sulfidic springs, where hydrogen sulfide naturally occurs in high concentrations. These fish provide an opportunity to study how vertebrates have managed to survive in conditions that are lethal for most other organisms. Adaptation in sulfide springs also leads to reproductive isolation between sulfidic and non-sulfidic ecotypes, providing insights about how new species evolve. The objectives of this proposal are to identify convergent patterns of phenotypic and genetic differentiation in replicated pairs of sulfidic and non-sulfidic habitats. This comparison will reveal both traits and the underlying genetic changes that mediate sulfide tolerance. The research addresses three basic questions: (1) How do complex phenotypes evolve along replicated environmental gradients? Quantifying phenotypic variation (including behavioral, physiological, and morphological traits) in wild-caught individuals will identify convergent patterns of adaptive trait divergence in replicated pairs of sulfidic and non-sulfidic fish. Analyzing the same phenotypic traits in common garden-raised individuals will shed light on how heritable differentiation and phenotypic plasticity interact to express phenotypes in nature. (2) What are the genomic changes underlying trait divergence? Next generation sequencing technologies (RNA-Seq) will be used to identify genes that show signatures of divergent selection or differential expression, which will be used to identify candidate genes underlying adaptation to the extreme environments. (3) What are the functional consequences of the divergent traits expressed under different environmental conditions for reproductive isolation? Comparing growth rates of laboratory-reared fish exposed to either sulfidic or non-sulfidic conditions will provide a direct link between adaptation to sulfide and reproductive isolation in the form of immigrant inviability. Understanding organisms? responses to naturally occurring stressful environments can ultimately be used to better understand causes and consequences of organismal responses to anthropogenically altered environments. The project fosters collaboration in research and education between scientists and students from the United States and Mexico. This project establishes a public outreach platform for fish biologists to interact with fish hobbyist organizations as a means to disseminate research findings to the lay public.