Epigenetic Potential in Native and Introduced Populations of House Sparrows (Passer domesticus)

Abstract

Synopsis 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 while experiencing lower genetic diversity. Phenotypic plasticity via epigenetic potential might be selectively advantageous at the time of initial introduction or during spread into new areas, enabling introduced organisms to cope rapidly with novel challenges. Here, we asked whether one form of epigenetic potential (i.e., the abundance of CpG sites) in three microbial surveillance genes: Toll-like receptors (TLRs) 1B (TLR1B), 2A (TLR2A), and 4 (TLR4) varied between native and introduced house sparrows (Passer domesticus). Using an opportunistic approach based on samples collected from sparrow populations around the world, we found that introduced birds had more CpG sites in TLR2A and TLR4, but not TLR1B, than native ones. Introduced birds also lost more CpG sites in TLR1B, gained more CpG sites in TLR2A, and lost fewer CpG sites in TLR4 compared to native birds. These results were not driven by differences in genetic diversity or population genetic structure, and many CpG sites fell within predicted transcription factor binding sites (TFBS), with losses and gains of CpG sites altering predicted TFBS. Although we lacked statistical power to conduct the most rigorous possible analyses, these results suggest that epigenetic potential may play a role in house sparrow range expansions, but additional work will be critical to elucidating how epigenetic potential affects gene expression and hence phenotypic plasticity at the individual, population, and species levels.

Long‐distance dispersal in the short‐distance dispersing house sparrow (Passer domesticus)

“…These types of long‐distance dispersal events highlight the potential for colonization of new habitats by house sparrows, which may be an important and hitherto overlooked part of this species success as a global colonizer and invasive species (Anderson, 2006 ; Hanson et al., 2020 ). Future studies may utilize these observations to investigate if individual phenotypic differences in, for example, morphology (Skjelseth et al., 2007 ), physiology (Nafstad et al., 2023 ; Pepke et al., 2022 ), or life‐history characteristics (Pärn et al., 2009 ; Saatoglu et al., 2024 ) underlie longer‐than‐expected dispersal distances (Tufto et al., 2005 ) in a species with very low flight efficiency (Claramunt, 2021 ).…”

The importance of eco-evolutionary dynamics for predicting and managing insect range shifts

“…One interesting idea is that the evolution of 'epigenetic potential' (i.e. proportion of the genome available for new epigenetic modifications) may be an important mechanism of plasticity evolution during range shifts [47], a hypothesis that remains untested in insects.…”

The Mutagenic Consequences of DNA Methylation within and across Generations

“…Therefore, the number of CpG sites represent a genetic constraint, and CpG depletion likely has many impacts on fitness [ 143 ]. For instance, high levels of phenotypic plasticity might be favored under certain conditions, such as in invasive species or naturally expanding populations coping with novel environmental conditions [ 144 , 145 ]. In these situations, depletion of CpG sites may impede the ability for individuals, populations, or species to cope with novel environments; thus, CpG sites may be selected to prevent the erosion of plasticity.…”