Meeting Abstract
Epigenetic potential, defined as the capacity for epigenetically-mediated phenotypic plasticity, may play an important role during range expansions. During range expansions, populations may encounter relatively novel challenges, including pathogens, while experiencing lower genetic diversity due to bottlenecks and/or founder effects. Phenotypic plasticity may allow individuals to rapidly cope with these challenges. Here, we asked whether one form of epigenetic potential (i.e. the abundance of CpG sites within gene promoters) varied among native and introduced populations of house sparrows (Passer domesticus) in three microbial surveillance genes: Toll-like Receptors 1B (TLR1B), 2A (TLR2A), and 4 (TLR4). Evidence suggests that increased expression of TLR2 and TLR4 may play a role in house sparrow range expansions, and that methylation at one CpG site within the putative promoter region of TLR4 was a predictor of TLR4 expression. We characterized i) total CpG sites, ii) total additions of CpG sites, and iii) losses of CpG sites in TLRs 1B, 2A, and 4. We hypothesized that introduced populations would have more total CpG sites via more additions and fewer losses of CpG sites (or overall higher epigenetic potential). We found that introduced populations had a higher total number of CpG sites in TLR2A and TLR4, but not in TLR1B. Additionally, the lower number of CpG sites was related to the lower genetic diversity of these introduced populations. Surprisingly, we found that low genetic diversity predicted a higher number of additions in CpG sites in TLR2A and fewer losses of CpG sites in TLR4. This suggests that selection is acting on CpG sites in introduced populations and that epigenetic potential may facilitate house sparrow range expansions.
