Local Adaptation at the Transcriptome Level in Brown Trout: Evidence from Early Life History Temperature Genomic Reaction Norms

Abstract

Local adaptation and its underlying molecular basis has long been a key focus in evolutionary biology. There has recently been increased interest in the evolutionary role of plasticity and the molecular mechanisms underlying local adaptation. Using transcriptome analysis, we assessed differences in gene expression profiles for three brown trout (Salmo trutta) populations, one resident and two anadromous, experiencing different temperature regimes in the wild. The study was based on an F2 generation raised in a common garden setting. A previous study of the F1 generation revealed different reaction norms and significantly higher QST than FST among populations for two early life-history traits. In the present study we investigated if genomic reaction norm patterns were also present at the transcriptome level. Eggs from the three populations were incubated at two temperatures (5 and 8 degrees C) representing conditions encountered in the local environments. Global gene expression for fry at the stage of first feeding was analysed using a 32k cDNA microarray. The results revealed differences in gene expression between populations and temperatures and population × temperature interactions, the latter indicating locally adapted reaction norms. Moreover, the reaction norms paralleled those observed previously at early life-history traits. We identified 90 cDNA clones among the genes with an interaction effect that were differently expressed between the ecologically divergent populations. These included genes involved in immune- and stress response. We observed less plasticity in the resident as compared to the anadromous populations, possibly reflecting that the degree of environmental heterogeneity encountered by individuals throughout their life cycle will select for variable level of phenotypic plasticity at the transcriptome level. Our study demonstrates the usefulness of transcriptome approaches to identify genes with different temperature reaction norms. The responses observed suggest that populations may vary in their susceptibility to climate change.

Transcriptional and biochemical markers in transplanted Perca flavescens to characterize cadmium- and copper-induced oxidative stress in the field

“…Studies have reported specific genomic reaction norms in response to changes of environmental conditions such as temperature in brown trout (Meier et al, 2014) or salinity in eels (Côté et al, 2014). To our knowledge, our's is the first study reporting a genomic reaction norm to metals using reciprocal transplant experiments directly in the natural environment.…”

“…When attempting to test hypotheses aimed at identifying possible ecological drivers, traits and genes involved in the adaptation to changing environmental conditions, one approach involves the comparison of the transcription levels of genes among different exposure conditions (Côté et al, 2014;Hoffmann and Daborn, 2007;Meier et al, 2014). Among natural populations, variation in gene expression has been shown to play a prominent role in ecological adaptation (Derome and Bernatchez, 2006;Pavey et al, 2011;St-Cyr et al, 2008).…”

Biological invasions, climate change and genomics

“…; Meier et al. ). A few of them have considered populations from native and invaded parts of their range to assess whether there are differences in plastic responses to the different environmental conditions encountered in invasive situations.…”

Life history and genetic characterisation of sea troutSalmo truttain the Adriatic Sea

“…Therefore, the threshold size and growth rate triggering seaward migration would seem to vary among populations adapted to different local conditions (Jonsson & Jonsson, 2009). More recently, transcriptomic studies suggested the influence of epigenetic mechanisms acting on the migration propensity (Meier et al, 2014;Morán, Marco-Rius, Megías, Covelo-Soto, & Pérez-Figueroa, 2013). More recently, transcriptomic studies suggested the influence of epigenetic mechanisms acting on the migration propensity (Meier et al, 2014;Morán, Marco-Rius, Megías, Covelo-Soto, & Pérez-Figueroa, 2013).…”