Grant: Discovery Grants Program - Individual

Understanding how animals have evolved to cope with environmental stress in the past allows us to better predict how they might respond to future change. My laboratory studies the mechanisms fish have used to adapt to changes in environmental salinity, a variable that has a strong effect on their distribution and abundance. While we understand a great deal about how fish can cope with changes in salinity within a lifetime, we know much less about how fish populations evolve in response to salinity change and what might limit their evolutionarily potential. To better understand how salinity tolerance evolves and the traits required for fish to successfully colonize freshwater we will work with two groups of Canadian fish: the stickleback and killifish. In our first set of experiments, we will test the effects of hybridization on upper salinity tolerance and salinity preference by comparing Banded Killifish (Fundulus diaphanus) populations hybridizing with the more salinity-tolerant Common Killifish (Fundulus heteroclitus) to populations that do not interbreed. In our second set of experiments, we will study the molecular mechanisms associated with the Common Killifish's exceptionally high salinity tolerance; this species can survive in salinities four times more concentrated than seawater. We will compare the Common Killifish's transcriptomic response to hypersaline seawater acclimation in the gill to that of the less-tolerant Banded Killifish and their inter-specific hybrids to identify the molecular mechanisms associated with tolerance evolution and determine how these are regulated. In our third set of experiments, we will study the factors facilitating or limiting freshwater colonization by comparing species of Atlantic Canadian stickleback that have, and have not, colonized freshwater lakes in the past. We will test if salinity tolerance during early life and the ability to thrive in freshwater during cold winters is associated with successful historical colonization. The research conducted by the six undergraduate honours, two masters and one doctoral student trained as part of this grant will clarify how fish have evolved to cope with changes in water salinity and identify limitations in tolerance that might constrain species distributions in the future.