Tracking signatures of adaptive diversification
About the project
We will study the adaptive diversification in the polymorphic / euryhaline threespine stickleback at genomic and phenotypic scales during colonization from the ocean to freshwater. Four lateral plate morphs are found, where a completely plated morph dominates in the ocean, a partially plated morph in brackish water, and a low plated morph in freshwater. In a few lakes, a fourth morph lacking lateral plates can be found. This salinity gradient is viewed as an evolutionary temporal transect where populations adapt to local selection pressures, and where hybridization and adaptive introgression occur in contact zones. We aim at detecting selection on phenotypes in the wild, search for signatures of selection, adaptive introgression and drift along the genome, and illuminate how phenotypes are linked to genomic divergence, studying mechanisms behind heterogenous genomic divergence in a framework of evolutionary parallelism. We apply a SNP genome-scan, searching for outlier loci under selection as compared with phenotypic data. Also, we sequence 3 regions of the Ectodysplasine gene (Eda) associated with directional selection on lateral plates. First, we contrast two salinity gradients/hybrid zones with complete, partial and low morph present partly under geneflow. Secondly, we compare 10 lakes of low plated morphs with 10 ocean sites of completely plated morphs in absence of gene-flow. Third, we study directional selection by analysing completely plated- to no-plated morphs, adding 10 lakes with the no-plated morph. Further, we link (non)adaptive phenotypes to genotypes, and reveal patterns of polymorphism around loci and how this translates into phenotypes and morphs. Finally, we model the fitness of morphs and alleles in contrasting environments. Thus, we may identify genomic islands of divergence, implying hotspots for evolution, and model the build-up of genomic and reproductive isolation along the colonization/adaptation trajectory of sticklebacks.
This project funded by The Research Council of Norway.
Laboratory of Biodiversity and Evolutionary Genomics (Belgium)
Max Planck Institute for Evolutionary Biology (Germany)
Start: 15.4.2010. End: 14.04.2014 (Edit: Extended).