The last decades have seen an increase of emerging infectious diseases, in humans, livestock, and wildlife – the current Covid-19 pandemic being just one popular example. When investigating these diseases, researchers tend to focus on the pathogens, but the host also plays a critical role in the determination of infection outcome, for instance through immunity. Sexual selection is a strong evolutionary force that can facilitate or inhibit adaptation to environmental challenges. When populations face novel pathogens, sexual selection can influence their ability to persist by impacting the spread of traits that confer disease resistance. The major histocompatibility complex (MHC) encodes proteins that recognize pathogens and activate the immune system, allowing the organism to fight against the pathogen. Many vertebrates preferentially mate with partners that carry beneficial MHC alleles, conferring higher resistance to their offspring. By understanding the role of sexual in the evolution of disease resistance, we can better protect global diversity, and identify which species are in more dire need of conservation.
Currently, amphibians are one of the most threatened animal groups, with 41% of the species declining. This is of high concern for humans, as amphibians control the overgrowth of pests, are an important food source, and are the source of many medical advances. In addition to habitat destruction, the disease chytridiomycosis is a major cause of extinction. While it has been recently found that the MHC genes of individuals in infected populations is under strong selection, it is unclear which evolutionary force is driving it. Thus, understanding the evolutionary dynamics of MHC could be critical for preserving amphibian diversity. However, there is a lot of fundamental knowledge missing when it comes to the amphibian MHC, for instance, it is currently unknown whether MHC dependent mate choice occurs in amphibians. This makes them the perfect organism to study this issue.
In this project I explore the role of sexual selection in the evolutionary dynamics of amphibian resistance to chytridiomycosis (an emerging infectious disease that is causing population declines and extinctions worldwide) with poison frogs (a species-rich group in which the strength of sexual selection differs between species). I start by reviewing the current knowledge on the amphibian MHC. Then I test whether mate preferences are influenced by MHC or by the infection status of both partners. Finally, I use theoretical models to predict under which circumstances sexual selection can accelerate the evolution of disease resistance. This project provides fundamental scientific knowledge on the relationship between sexual selection and the evolution of disease immunity against an extremely lethal pathogen by exploring the interaction between chytridiomycosis and amphibian MHC. It builds on the recent insights that natural selection drives MHC evolution in amphibians, and originally explores the role of sexual selection in this process in a uniquely integrated experimental, theoretical, and ecological fashion.
