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，小型的白鲟属活鱼已经独立地在多个硫化物泉中定居，那里的硫化氢天然存在于高浓度中。这些鱼提供了一个机会，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。硫化物温泉的适应也导致了硫化物和非硫化物生态类型之间的生殖隔离，提供了关于新物种如何进化的见解。本建议的目标是确定趋同模式的表型和遗传分化的复制对硫化物和非硫化物的栖息地。这种比较将揭示介导硫化物耐受性的性状和潜在的遗传变化。研究解决了三个基本问题：（1）复杂的表型是如何沿着重复的环境梯度进化的？量化表型变异（包括行为，生理和形态特征）在野生捕捞的个人将确定收敛模式的适应性性状分歧复制对硫化物和非硫化物鱼。分析相同的表型性状在普通花园提出的个人将揭示遗传分化和表型可塑性如何相互作用，以表达表型的性质。(2)性状分化背后的基因组变化是什么？下一代测序技术（RNA-Seq）将用于鉴定显示出不同选择或差异表达特征的基因，这些基因将用于鉴定适应极端环境的候选基因。(3)在不同的环境条件下，不同的性状在生殖隔离方面的功能后果是什么？比较实验室饲养的鱼类暴露于硫化物或非硫化物条件下的生长速度，将提供一个直接的联系，以适应硫化物和生殖隔离的形式移民的无能。了解有机体？对自然发生的压力环境的反应最终可以用于更好地理解生物体对遗传改变的环境的反应的原因和后果。该项目促进美国和墨西哥科学家和学生之间的研究和教育合作。该项目为鱼类生物学家建立了一个公共外展平台，与鱼类爱好者组织进行互动，作为向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.