Freshwater Fish Group
The freshwater fishes are amazingly variable in shape, behaviour and life history. In temperate areas such as Scandinavia the freshwater fishes had to invade suitable habitats after the last glaciation, dispersing from various glacial refugia as the ice retracted. The landscape that the fishes entered was complex, with rivers, streams and lakes. Useful habitat types are often found as isolated patches, and dispersal corridors between patches are often blocked by barriers kinds (mountains, waterfalls, etc.). This lead to reduced gene flow among populations, and given differences in selection pressure this may lead to genetic and phenotypic differentiation and local adaptation.
The freshwater landscape is complex, and the immigration history of the different freshwater fishes has also been complex. So, even if the number of freshwater fish species in Scandinavia is relatively small the overall biodiversity is large. Populations of the various species differ strongly in morphology and life history, and often for unknown reasons. What is less well appreciated is that marine fishes that are closely associated with the complex littoral zone experiences some of the same challenges as freshwater fishes. Unfortunately, many of these small-sized fishes are not at all studied. It is therefore of interest to extend studies into the marine realm, focusing on species that have not up to now been the focus of management and thus also research.
In our group much of our research effort aims at understanding why there is so large variation among populations freshwater fish. Until recently evolution was believed to progress relatively slowly, hence difficult to observe and study in contemporary populations whose dynamics are driven by faster ecological processes. This idea has led to a view that evolutionary change can be ignored for the effective management of fish populations. Nevertheless, there has been a major shift in the way the time scales of ecological and evolutionary processes are viewed. Evolutionary dynamics can clearly affect ecology in the same way as ecology always affects evolution. Thus, ecology and evolution may be commensurate in time and interact through feedbacks. We therefore try to study evolutionary and ecological processes at the same time.
We approach these kinds of questions using a wide range of study organisms (three-spine stickleback, perch, pike, brown trout, grayling, Atlantic salmon, corkwing wrasse) and approaches.
In our investigations we use a combination of methods:
- Classical field observations linked with field experiments (such as mark-recapture techniques).
- Behavioural studies – mainly using telemetry or passive tags.
- Population genetics, based on genotyping or sequencing of relevant genetic markers and genes.
- Population dynamics, using analysis of time series of various kinds (methods are statistical time series analysis and mathematical models).
- Controlled laboratory experiments (common garden studies for quantitative and molecular genetic analyses).
- Functional genetic methods (sequencing, gene expression).
In all modern research collaboration is needed, and we maintain extensive collaborations both internally and externally (in Norway and the rest of the world). To do science today is really a collaborative effort.