The job of immune genes is to fight off pathogens. However, pathogens don’t take this beating lying down. Pathogens adapt to evade the immune genes, forcing the immune genes to counter-adapt in return. To improve your chances against infection in this evolutionary arms race, would it not be neat if you could borrow immune genes that evolved in another species? Hybridization could facilitate this. Through repeated hybridization, genes can flow between species: a process known as introgression. In a study led by Tomasz Gaczorek and Wiesław Babik, published in Molecular Ecology, we test to what extent the important immune genes of the major histocompatibility complex (MHC) are exchanged between different crested newt species. It turns out that MHC genes introgress more extensively than random genes – exactly what you would expect if natural selection were to favor exotic immune genes.

Reference: Gaczorek, T., Marszałek, M., Dudek, K., Arntzen, J.W., Wielstra, B., Babik, W. (2023) Interspecific introgression of MHC genes in Triturus newts: evidence from multiple contact zones. Molecular Ecology 32(4): 867-880.