Data from: Epigenetic potential and DNA methylation in an ongoing House Sparrow (Passer domesticus) range expansion

During range expansions, organisms can use epigenetic mechanisms to adjust to conditions in novel areas by altering gene expression and enabling phenotypic plasticity. Here, we predicted that the number of CpG sites within the genome, one form of epigenetic potential, would be important for successful range expansions because DNA methylation can modulate gene expression, and consequently plasticity. We asked how the number of CpG sites and DNA methylation varied across five locations in the ~70 year-old Kenyan house sparrow ( Passer domesticus ) range expansion. We found that the number of CpG sites was highest towards the vanguard of the invasion and decreased towards the range core. Analysis suggests that this pattern may have been driven by selection, favoring birds with more CpG sites at the range edge. However, we cannot rule out other processes including non-random gene flow. Additionally, DNA methylation did not change across the range expansion, nor was it more variable. We hypothesize that as new areas are colonized, epigenetic potential may be selectively advantageous early but eventually be replaced by less plastic and perhaps genetically-canalized traits as populations adapt to local conditions. While further work is needed on epigenetic potential, this form (CpG number) appears to be a promising mechanism to investigate as a driver of expansions via capacitated phenotypic plasticity in other natural and anthropogenic range expansions.