Genomics of Thermal Adaptation in Redband Trout

Previous work has demonstrated local adaptation in populations of redband (Oncorhynchus mykiss) trout occupying desert and montane habitats.  To further elucidate the genetic mechanisms of thermal adaptation, gametes were collected from a single representative wild population adapted to each of warm and cool climates.  Gametes were fertilized to produce progeny of a pure warm adapted line, pure cool adapted line, and their F1 crosses.  Fish from each of these lines were reared in constant conditions at the Hagerman Fish Culture Experiment Station until they reached an average of 5 grams, and then were divided into treatment and control groups.  Fish in treatment tanks experienced diel temperature cycles that reached a maximum of 28.5°C in the afternoon and a minimum of 17.0°C at night.  Control tanks were held at a constant temperature of 15°C (spring water).  Mortality was measured throughout the duration of the experiment (6 weeks) from three replicate tanks for each line.  Tissue samples were collected throughout the experiment, with fin clips collected from all survivors and mortalities in the treatment tanks, and liver and gill tissue from both control and treatment tanks at various time periods (24 hours, 72 hours, 7 days, 30 days).  DNA was extracted from fin clips of individuals that survived or died in treatment tanks and were screened with numerous SNP markers throughout the genome.  Results of this genome scan are being used to identify the gene regions involved in thermal adaptation in this species.  Gene expression data is also being collected from liver and gill samples.