COS 239-1 - CANCELLED - Mutation load and adaptability to future climate change in two ptarmigan species

Abstract: We generated whole genome re-sequencing data from ten populations of two cold-adapted avian sister species: rock ptarmigan (Lagopus muta) and willow ptarmigan (Lagopus lagopus), to best capture their Holarctic distribution. We investigate the genomic basis of climate influenced adaptation, using differentiation outlier scans and gene-environment association analysis. Using the current associations between genetic variants and climate we utilized prediction models to assess the adaptive capacity of each population to future climate change, by estimating the degree of genetic offset (maladaptation) to projected future climate scenarios. We also investigated how past declines in effective population size and increasing genetic drift have affected the accumulation of deleterious mutations and the efficacy of purifying selection by combining demographic modeling and the distribution of fitness effects of new mutations.
We show that isolated island populations have experienced historical bottlenecks and now have lower levels of genetic diversity and thus lower effective population sizes. These populations are also more heavily burdened by relative and realized mutational load and the reduced efficacy of purifying selection. In spite of this, we do find a number of genes associated with climate variables putatively involved in climate adaptation, but the offset between current adaptability and what would be needed under future climatic changes is large. We assert that the ability of some populations to adapt in time is highly uncertain.