Adaptive immunity and mate selection
The immune system plays a crucial role in the life of every multicellular organism, due to constant attacks from pathogens. As a result, there is natural selection for an optimal immune gene repertoire, and sexual selection for optimisation of the immune capacity of progeny, which can only be achieved through the choice of an immunologically optimal mate.
Displaying bluethroat male. Photo: Bjørn Aksel Bjerke.
Parasites and pathogens are ubiquitous in nature and the ability to mount an immune response against foreign attacks is therefore crucial for survival in all organisms across the tree of life. In vertebrates, a cluster of immune genes called the major histocompatibility complex (MHC) plays an important role in fighting intra- and extra-cellular parasites and pathogens. There is evidence for mate preferences based on similarity of MHC genotypes, often conveyed by body odours, from many species including humans. Passerine birds are characterized by unusually variable MHC, but the consequences of MHC-variation for mate choice are poorly understood. Recent results from the bluethroat strongly suggest female MHC-preferences for optimally dissimilar genetic sires, resulting in extra-pair offspring with an intermediate MHC variability. The primary objective of this project is to test the optimal MHC hypothesis as applied to passerine mating systems, suggesting that multiple mating is a female strategy to adjust suboptimal social mate choice with respect to MHC compatibility.
Financing: Natural History Museum
- Johnsen, A., Andersen, V., Sunding, C. & Lifjeld, J. T. 2000. Female bluethroats enhance offspring immunocompetence through extra-pair copulations. Nature 406: 296-299.
- Fossøy F., Johnsen A. & Lifjeld, JT. 2008. Multiple genetic benefits of female promiscuity in a socially monogamous passerine. Evolution, 62: 145-156.
- Fossøy F., Johnsen A. & Lifjeld, JT. 2009. Cell-mediated immunity and multi-locus heterozygosity in bluethroat nestlings. Journal of Evolutionary Biology, 22: 1954-1960.
- Rekdal, S. L., Anmarkrud, J. A., Johnsen, A. & Lifjeld, J. T. 2018. Genotyping strategy matters when analyzing hypervariable major histocompatibility complex—Experience from a passerine bird. Ecology and Evolution 8: 1680-1692.
- Rekdal, S. L., Anmarkrud, J. A., Lifjeld, J. T. & Johnsen, A. 2019. Extra-pair mating in a passerine bird with highly duplicated major histocompatibility complex class II: Preference for the golden mean. Molecular Ecology 28: 5133-5144.
- Rekdal, S., Anmarkrud, J. A., Lifjeld, J. T., Johnsen, A. 2021. Elevated phytohaemagglutinin-induced skin-swelling response at an intermediate number of MHC class II alleles in bluethroat nestlings. Journal of Avian Biology 52:e02734.