The transcriptome of the ant <i>Temnothorax nylanderi</i> is not affected by urbanisation but by rearing conditions

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. Here we assessed how urbanisation affects gene expression in workers and queens of the ant Temnothorax nylanderi, a species that inhabits both city and forest habitats. We further examined whether there was a differential expression between two distinct conditions, in the field or after laboratory rearing for 8 months. As expected, the number of differentially expressed genes (DEGs) between workers and queens was large (2830 genes). However, we found that habitat (city or forest) had no clear influence on gene expression in queens and workers of T. nylanderi even when individuals were directly collected from the field. Interestingly, we also found 661 DEGs between field colonies and laboratory-reared ones. The effect of rearing conditions on gene activity was greater in workers than in queens, suggesting that queens are more resilient to environmental changes. The lack of transcriptional differences between habitats is intriguing because of the previously observed differences in life-history traits between city and forest populations.