Evolutionary causes of variation in immune function

Studies of a wide diversity of organisms have shown that immune genes are among the most important targets of natural selection. However, most previous studies have focused on macroevolutionary patterns (across species). In contrast, little is known about recent (microevolutionary) adaptations of the immune system. In the present project, whole-genome re-sequencing data from 31 bank voles from southern Sweden will be analysed to identify signatures of recent positive selection, with a focus on immune genes. Key questions include: What is the relative importance of selection on immune genes vs other genes? Which types of immune genes are the main targets of recent selection?

One potentially important factor generating genetic variation in the immune system is adaptation to the local pathogen community, but this has rarely been quantified at the genome-wide level (except in humans). To address this question, the existing whole genome re-sequencing data from bank voles in southern Sweden will be complemented with data from northern Sweden and/or eastern Poland. The combined data will then be used for analyses of population differentiation and population-specific signatures of selection.

Besides genetic variation there are also often differences between the sexes in immune function. Moreover, conflicting selection pressures on immune defence in males and females could potentially help maintain variation in immune genes. As a first step to address this issue, the present project will test for differences in expression of immune genes between males and females.