Patterns of parent and offspring gene expression reflect canalization, not plasticity, in response to environmental stress
Parenting buffers offspring from hostile environments, but it is not clear how or if the genes that underlie parenting change their expression under environmental stress. We recently demonstrated that for the subsocial carrion beetle, Nicrophorus orbicollis, temperature during parenting does not affect parenting phenotypes. Here, we ask if transcriptional changes associated with parenting are likewise robust to environmental stress. The absence of a transcriptional response for parenting under stress would suggest that the genetic programs for parenting and being parented are canalized. Conversely, a robust transcriptional response would suggest that plasticity of underlying gene expression is critical for maintaining behavioral stability, and that these mechanisms provide a potential target for selection in the face of environmental change. We test these alternatives by characterizing gene expression of parents and offspring with and without parent-offspring interactions under a benign and a stressful temperature. We found that parent-offspring interactions elicit distinct transcriptional responses of parents and larvae irrespective of temperature. We further detected robust changes of gene expression in beetles breeding at 24 degrees C compared to 20 degrees C irrespective of family interaction. However, no strong interaction between parent-offspring interaction and temperature was detected for either parents or larvae. We therefore conclude that canalization, not plasticity of gene expression, most likely explains the absence of behavioral plasticity under thermal stress. This result suggests that species may not have the genetic variation needed to respond to all environmental change, especially for complex phenotypes.