Worker transcriptome is more strongly affected by environmental conditions than queens, with negligible influence of habitat in a small acorn ant.

Urbanisation alters the environment of organisms, creating new challenges and opportunities. In ants, urbanisation has been shown to increase resistance to temperature and to pollutants. Ant queens are expected to be more protected from environmental variation compared to workers thanks to social buffering effects. We assessed how urbanisation and social buffering affect gene expression in workers and queens of the ant Temnothorax nylanderi, a species that inhabits both environments. We tested whether whole body gene expression differed between urban and forest colonies and whether this differential expression was more pronounced in workers compared to queens due to social buffering. We further examined whether differential expression held after rearing colonies under a common garden laboratory setup. We found that habitat had no clear influence on gene expression in queens and workers, whereas, as expected, the number of differentially expressed genes between workers and queens was large (2830 genes). We also found 661 genes differentially expressed between the colonies that remained in the field and those that were reared in the laboratory for eight months. The effect of rearing conditions on gene activity was greater in workers than in queens, supporting the idea that queens are partially protected from environmental variation. We found minimal transcriptional differences between habitats which is intriguing because of the previously observed phenotypic differences. We provide, for the first time, support at the level of gene expression that laboratory rearing conditions induce major changes in gene expression and that queens undergo social buffering during such environmental change.