Mechanisms underlying the evolution of salinity tolerance in fish

为了更好地了解生物多样性的起源和维持，并帮助我们预测种群可能如何应对未来的环境变化，需要了解动物如何应对环境变化。对鱼类的分布和丰度有重大影响的一个变量是环境盐度。虽然我们对允许鱼类在一生中应对盐度短期变化的机制了解很多，但我们对鱼类种群如何随着盐度变化而演变的了解要少得多。我的学生和我将研究两种加拿大鱼类，四刺鱼(Apeltes Square Racus)和带状剑鱼(Fundulus Diaphanus)，作为研究对淡水耐受性增强的进化的模型系统。我们之所以选择这些鱼类，是因为它们在种群和物种之间存在耐盐性的多样性，它们可以很容易地从野外采集并在实验室进行研究，并且它们与两个拥有广泛基因组资源的模式物种--三刺鱼(Gastersteus Aculeatus)和普通千里鱼(Fundulus Exuleatus)--关系密切，这将为我们的遗传分析提供便利。我们将首先测试自然种群之间的耐盐性的差异。接下来，我们将利用先进的基因组和转录分析技术，结合经典的生理和数量遗传技术，进行综合实验，以确定与淡水耐受性增强相关的生理、分子和遗传机制。这些研究将使我们能够测试在导致淡水耐受性的机制中是否存在平行的证据，这些机制分别与它们的姊妹种尖吻对虾和异色对虾的耐性有关。然后，我们将确定适应等位基因的来源，并具体检验这一假说，即华山松和华山松之间的渐进式杂交导致了华山松种群对淡水的更高耐受性的进化。五名本科生和三名硕士学生将在这项资助的过程中接受培训，这项研究的成果将对我们理解动物如何适应和适应环境的变化做出宝贵的贡献。**

An understanding of how animals cope with changes in their environment is needed to better understand the origins and maintenance of biodiversity and help us predict how populations might respond to future environmental change. One variable that has a strong effect on the distribution and abundance of fish is environmental salinity. While we understand a great deal about the mechanisms allowing fish to cope with short-term changes in salinity within a lifetime, we know much less about how fish populations evolve in response to salinity change. My students and I will examine two species of Canadian fish, the Fourspine stickleback (Apeltes quadracus) and the Banded Killifish (Fundulus diaphanus), as models systems in which to study the evolution of increased tolerance to freshwater. We have chosen these fish because there is diversity in salinity tolerance among populations and species, they can be easily collected from the wild and studied in the lab, and they are closely related to two model species with extensive genomic resources, the Threespine Stickleback (Gasterosteus aculeatus) and the Common Killifish (Fundulus heteroclitus), which will facilitate our genetic analyses. We will first test for differences in salinity tolerance among natural populations of A. quadracus and F. diaphanus. Next, we will conduct integrative experiments to determine the physiological, molecular and genetic mechanisms associated with increased freshwater tolerance using cutting-edge genomic and transcriptomic analyses paired with classical physiological and quantitative genetic techniques. These studies will allow us to test for evidence of parallelism in the mechanisms leading to freshwater tolerance between A. quadracus, F. diaphanus and their sister species G. aculeatus and F. heteroclitus, respectively. We will then determine the origin of adaptive alleles and specifically test the hypothesis that introgressive hybridization between F. diaphanus and F. heteroclitus has led to the evolution of higher freshwater tolerance in F. heteroclitus populations. Five undergraduate and three master's students will be trained during the course of this grant and publications stemming from this research will make valuable contributions to our understanding how animals can adapt, and acclimate, to changes in their environment. **