Evolutionary Genetics of Fishes

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My research program focuses on understanding the factors that influence the evolution of different forms (morphs) that arise in the same population as the result of variation in the environment (food availability and habitat) where the fish live. This is important because we still do not understand how biodiversity is generated and specifically how genetic variation can become partitioned between populations when they begin to diverge genetically into different species. I examine different morphs of Arctic charr (Salvelinus alpinus) from Iceland that differ in body size and shape (phenotype) and live in different environments, which are sometimes in the same lake. Arctic charr continue to be models for this work because of the remarkable variation in their appearance, the ability to capture them from many lakes and produce experimental families. Icelandic charr also have a relatively simple evolutionary history, which makes it easier to disentangle the different factors involved in their evolution. My proposed research is organized into three sections. Firstly, I will test if the body shape and size of fish is the result of environmental features such as food type (natural selection) or random processes (genetic drift and gene flow) not related to the improved performance of fish with a certain phenotype. I will also test if the relationship between phenotype and environment is influenced by population size and the amount of genetic variation of the fish in the population to see if small populations have limited potential to evolve and respond to environmental change. This will involve repeated capture of individually tagged Arctic charr from nineteen small populations that live in lava caves in northern in Iceland. I will also test if the same patterns of morph phenotype and what the fish eat are the same across six Icelandic lakes, which would indicate that body shape is the result of natural selection. Secondly, I will search for genes that influence body morphology and size within morphs and see how these differ between morphs. Here I will look for associations between genes and the phenotype of offspring produced from two parents (families) and wild fish from many unknown families. I will test if the genetic differences between morphs from the same lake are the same as those between morphs in other lakes and if different traits are controlled by different genes. Thirdly, I will test if the genes found to be associated with morphology are located in areas of the genome that have diverged between morphs. This would suggest that the genes discovered are important for the evolution of different morphs. The knowledge generated by this research is essential to tackling the question of whether new species can arise from morphs living together in the same area. **