Landscape genomics, climate change and adaptation

The central aim of the project is to determine the genetic responses to environmental variation. Specifically, we will test the hypothesis that differential gene expression and/or coding sequence evolution is involved in the evolution of local adaptation along a natural environmental temperature gradient in Drosophila subobscura. We will also test the hypothesis that these locally adapted genes are retained within chromosomal inversions which themselves exhibit clinal variation associated with temperature variation. Given this, we predict:1. Differential gene expression contributes to local adaptation along an environmental gradient in Drosophila subobscura. Specifically, we predict differences in response to high and low temperature stress and a trade-off between these responses.2. Signatures of selection will be detected as allele frequency outliers and/or clinal patterns. We will assess the proportion of these signatures associated with loci showing adaptive expression differences (i.e. those where selection may act on cis-regulatory sequences).3. Loci showing differential expression or the influence of selection are found within inversions more often than expected by chance.To test these predictions, we will complete the following objectives:1. Establish field enclosed populations, with environmental data loggers embedded in the field enclosure, across six sites including southern and northern populations close to the latitudinal range limits.2. Reciprocally transplant individuals from the most southern and northern study populations. This common garden experiment will allow us to differentiate between adaptive and acclimatisation responses.3. Sample males from each of these 8 populations in situ at three different thermal profiles corresponding to local heat stress, cold stress, and a benign temperature.4. Analyze these samples for differential gene expression using RNA-seq (Illumina) to determine whether there is locally adapted gene expression.5. Perform outlier analyses on the resulting sequence data to test for coding changes associated with local adaptation.6. Locate candidate genes using in situ hybridization to assess their association with chromosomal inversions.