The role of phenotypic plasticity and resource polymorphism on the evolution of fish populations

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Understanding the mechanisms underlying species diversification and speciation was first addressed in Darwin's The Origin of Species, and reviews published over the past few years have highlighted that this question is still one the most challenging and exciting issues in evolutionary ecology. It has been shown that plasticity promotes the origin of novel phenotypes through the capacity of single genotypes to produce different phenotypes in response to varying environmental conditions. Phenotypic plasticity has been proposed as a mechanism for the expression of resource polymorphism, i.e., when individuals of the same population exhibit differences in morphology, behaviour, and physiological traits associated with differential niche use. Resource polymorphisms could in turn lead to genetic differentiation and ultimately to adaptive radiation. However, testing these recent theoretical developments in natural systems is still one of the most challenging tasks in evolutionary ecology. The long-term objective of my research program is to study how phenotypic plasticity and resource polymorphism promote adaptive radiation. I use the brook trout, Salvelinus fontinalis, from Canadian Shield lakes as the model species. Brook trout exhibits a subtle resource polymorphism, and our results suggest that these lakes represent the early stages of evolutionary divergence of this species. This makes them of particular interest for understanding the processes involved in the early steps of ecological speciation. The proposed research is built on 15 years of work in this system and will allow us to 1) improve our understanding on the role of temperature in the evolution of resource polymorphism in ectotherms, 2) test the functional relationship between phenotype–environment in two discrete ecotypes, and 3) identify the mechanisms underlying the transmission of adaptive traits in fishes. In addition to being done on natural populations, the proposed research projects are conceptually original and will collectively contribute to a better understanding of the mechanisms of adaptive radiation in animals. Furthermore, the proposed research will allow to train two M.Sc. and two Ph.D. candidates as well as 10 research assistants. These students will acquire solid conceptual and practical skills, which are highly sought by employers like public organizations, private industries, and academic institutions.