Mechanisms underlying the evolution of salinity tolerance in fish

为了更好地理解生物多样性的起源和维持，并帮助我们预测种群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很大影响的一个变量是环境盐度。虽然我们对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应对盐度变化的进化知之甚少。我和我的学生将研究两种加拿大鱼类，四棘棘鱼（Apeltes quadracus）和带状鳉鱼（Fundulus diaphanus），作为研究淡水耐量增加的进化的模型系统。我们之所以选择这些鱼，是因为它们在种群和物种之间具有多样性的耐盐性，它们可以很容易地从野外收集和实验室研究，并且它们与具有广泛基因组资源的两种模式物种——三刺棘鱼（Gasterosteus aculeatus）和普通鳉鱼（Fundulus heteroclitus）密切相关，这将有助于我们的遗传分析。我们将首先测试两种自然种群的耐盐性差异。接下来，我们将进行综合实验，利用尖端的基因组和转录组学分析以及经典的生理和定量遗传技术，确定与淡水耐受性增加相关的生理、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平行的证据，在A. quadracus， F. diaphanus和它们的姐妹物种G. aculeatus和F. heteroclitus之间分别。然后，我们将确定适应性等位基因的起源，并专门测试F. diaphanus和F. heteroclitus之间的渐渗杂交导致F. heteroclitus种群中更高的淡水耐受性进化的假设。五名本科生和三名硕士生将在这项资助的过程中接受培训，这项研究的出版物将对我们理解动物如何适应和适应环境的变化做出有价值的贡献。**

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. **