Meeting Abstract
During range expansions, epigenetic mechanisms may mediate phenotypic responses to environmental cues, enabling organisms to adjust to conditions at novel sites. In particular, we expect that the number of CpG sites within the genome, one genetic mechanism underlying epigenetic potential, may be important for success at range edges because methylation could titrate gene expression contingent on environmental conditions. Previously we found that this form of epigenetic potential was higher in introduced compared to native populations of house sparrows (Passer domesticus) for two immune genes (Toll-like receptors 2A and 4). Here, we took a next-generation sequencing approach (ddRadSeq and EpiRadSeq) to investigate how this same form of epigenetic potential, as well as resultant DNA methylation, varied across five sites in the ~60 year-old Kenyan house sparrow range expansion. We found that CpG sites increased towards the edge of the invasion, even when accounting for genetic diversity among sites. This pattern was driven by more losses of CpG sites in birds from the core. Additionally, DNA methylation levels towards the range edge, when we considered only sequences proximal to CpG sites that were lost to mutation in core birds. This pattern is significant because DNA methylation across the whole genome decreased towards the range-edge. These results provide further evidence that epigenetic potential influences house sparrow range expansions, perhaps providing greater phenotypic plasticity later to be assimilated genetically in as populations adapt to new conditions.
