Phenotypic plasticity in the hepatic transcriptome of the European common frog (Rana temporaria): the interplay between environmental induction and geographical lineage on developmental response.

Phenotypic plasticity might facilitate adaptation to new environmental conditions through the enhancement of initial survival of organisms. Once a population is established, further adaptation and diversification may occur through adaptive trait evolution. While several studies have found evidence for this mechanism using phenotypic traits, much less is known at the level of gene expression. Here, we use an islands system of frog populations that show local adaptation and phenotypic plasticity to pool drying conditions in development time until metamorphoses. We examined gene expression differences in Rana temporaria tadpole livers with respect to pool drying at the source population and in response to simulated pool drying in the laboratory. Using a MAGEX cDNA microarray and quantitative real-time polymerase chain reaction (qPCR), we identified an increase in several gene transcripts in response to artificial pool drying including thyroid hormone receptor alpha and beta, carbamoyl phosphate synthetase 1, ornithine transcarbamylase and catalase. In addition, these gene transcripts also showed greater abundance in island populations that developed faster. Hence, the gene transcripts were related to both constitutive response (higher levels in island populations that developed faster) and plastic response (increased abundance under decreasing water levels). This pattern is in accordance with genetic accommodation, which predicts similarities between plastic gene expression and constitutive expression in locally adapted populations.