Trade‐offs in expressed major histocompatibility complex diversity seen on a macroevolutionary scale among songbirds

To survive organisms must defend themselves against pathogens. Classical Major Histocompatibility Complex (MHC) genes play a key role in pathogen defense by encoding molecules involved recognition. MHC gene diversity influences the variety of pathogens individuals can recognize and respond to has consequently been popular genetic marker for disease resistance ecology evolution. However, is predominantly estimated using genomic DNA (gDNA) with little knowledge expressed diversity. This limits our ability interpret adaptive significance variation diversity, especially species very many such as songbirds. Here, we address this issue phylogenetic comparative analyses number class I alleles (MHC-I diversity) gDNA complementary (cDNA), that is, alleles, across 13 songbird species. We propose three theoretical relationships could be expected between MHC-I on macroevolutionary scale test which these are best supported. In doing so, show significantly fewer than available expressed, suggesting optimal achieved modulating expression. Understanding relationship essential interpreting an evolutionary context.