Meeting Abstract
Rapid change in head and body shape has accompanied the repeated and independent invasion of oceanic threespine stickleback into freshwater habitats in regions deglaciated approximately 13,000 years ago. Recent research has made clear that phenotypic and genetic divergence can occur in decades. A remaining challenge is to link stickleback genomic architecture to causal genes that underlie shape evolution. To address this we used natural populations of stickleback that colonized freshwater ponds created by the 1964 Alaska earthquake on islands in the Gulf of Alaska and Prince William Sound. These very young populations already show phenotypic and genotypic divergence from their marine ancestors. We used a large dataset of single nucleotide polymorphisms (SNPs) generated via RAD-seq to determine patterns of linkage disequilibrium (LD) in a network analysis of loci across the genome. We compared these genomic patterns with loci found to be associated with phenotypic variation identified with a genome wide association (GWA) approach. These analyses uncover several unique clusters of loci in LD which suggests that multiple evolutionary phenomena, i.e. chromosomal inversions, selection, admixture or epistatic fitness interactions, create local and widespread LD patterns in the stickleback genome. Furthermore, the LD patterns help to interpret our GWA findings and suggest that rapid phenotypic evolution may be underlain by many loci across the genome but that these loci significantly covary because of LD. The young stickleback populations present a rare opportunity to link rapid phenotypic evolution and the genomic architecture that shapes it in a natural context.
