DNA methylation predicts immune gene expression in introduced house sparrows (Passer domesticus)

Populations undergoing range expansions are often faced with novel selective pressures, and to cope with such challenges, populations must either adapt quickly or exhibit phenotypic plasticity. This latter option allows for rapid phenotypic adjustments and persistence in novel environments, and thus could be advantageous at range‐edges. Our previous research on house sparrows in Kenya—a site of ongoing range expansion— and a growing literature suggests that invasion success is facilitated by epigenetic regulation of gene expression. Previously, we found (i) differences in the expression of a microbial surveillance gene (i.e. Toll‐like receptor 4—TLR4), and (ii) extensive variation in genome‐wide DNA methylation among house sparrows across Kenya. Here, our goal was to investigate whether these two observations are related, specifically whether DNA methylation within a target sequence upstream of the TLR4 transcription start site is associated with variation in TLR4 expression. We found t...