Understanding local adaptation in a freshwater salmonid fish: evolution of a research programme

Linking ecology and evolution can be challenging, particularly as these fields evolve rapidly tracking technological and theoretical developments. Thus, it is important for practitioners of different biological disciplines to understand new opportunities and challenges. Since theory and methods evolve, so will research programmes—often tracking opportunity. Here, we describe a research programme where we have investigated the population biology of grayling Thymallus thymallus in a Norwegian alpine landscape over three decades. Starting with classical ecological studies, we identified a set of populations that had evolved population-specific phenotypic traits over a relatively short time span (10–30 generations). These observations led us into evolutionary studies at various levels of biological organization, using population and quantitative genetic, transcriptomic and proteomic approaches. Overall, the results show that the populations exhibit evolutionary responses to local-scale differences in environment (mainly water temperature during early development). Further, plastic responses are important in the early phase of population diversification. Population genomic studies are now becoming possible following the completion of an annotated genome. This will help us and others in addressing questions about the genetic architecture of traits important for local adaptation, thus emphasizing that combining ecological and evolutionary approaches is more important and interesting than ever