Early Life History Transcriptome Differences and Temperature Adaptation in Brown Trout

Studies of local adaptation in salmonids have been a major focus for many years and there is a considerable amount of evidence suggesting that salmonids are adapted to local environments. Given these adaptations, a major concern today is whether salmonids have evolutionary potential to cope with predicted climate changes. In this study we apply transcriptomic tools to assess differences in gene expression profiles for three brown trout (Salmo trutta) populations experiencing different temperature regimes. A previous study with F1 offspring from these populations, raised in a common garden setting, suggested that fry were adapted to local temperature conditions. In this study an F2 generation was established for these populations. Offspring were raised in a common garden setting at two different temperatures representing temperature regimes of their local environments. Subsequently, global gene expression was analyzed using a 32k cDNA microarray. Our results reveal that there are differences in gene expression between populations, temperatures and population x temperature interactions, the latter of which indicate local adaptation. We aim to identify the physiological pathways explained by these differences and derive temperature reaction norms at the transcriptomic level to identify the genes underlying temperature adaptation. These genes will serve as candidates for future studies assessing the impact of climate change on brown trout populations.