Mechanisms underlying the evolution of salinity tolerance in fish

点击翻译按钮获取中文摘要

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.