Sticklebacks (Gasterosteus aculeatus L.) on the Norwegian coast: fresh water colonisation, divergence rates and adaptive speciation

This project will investigate how historical contingency and evolutionary mechanisms interact to prime ecological and physiological adaptation, which may ultimately result in speciation in the threespined stickleback. This primarily marine species has fou nded numerous anadromous- and stationary populations in fresh waters, living with- or without piscivorous predators, due to the glaciostatic uplift and its phylogeographic structure. By studying neutral genetic markers at both the regional- (mtDNA) and lo cal scales (micro-satellites), in comparison with datings of lake-isolation, we will assess the evolutionary history of a large number of stickleback populations. This will be achieved through a nested-cladistic analysis and historical demography. Adaptiv e specialisation associated with adoptation of new freshwater niches (studied using stable isotopes and feeding behaviour) will be contrasted with the marine ancestors by scoring a suite of armour and trophic traits, and life-history variables. The geneti c basis for variation in traits exposed to natural selection, will be assessed by markers associated with QTL´s as determined by previous mapping efforts. If physiological adaptations to freshwater niches increases with elapsed time in freshwater, then sa ltwater- and thermal-tolerance should be temporally associated with other traits also being exposed to natural selection. Common-garden experiments using half-sib designs will be conducted to estimate trait heritability, and to evaluate adaptive divergenc e (i.e. a Qst/Fst analysis) in wild populations. Saltwater- and thermal tolerance, and expression of candidate genes, including heat-shock proteins and prolactin genes, will be studied on offspring from experimental crosses. The joint effort to compare ma ny stickleback populations along the coast of both Norway and Canada, using the very same protecol, offers a unique possibility to study divergence rates and speciation in the threespine stickleback complex.