HLA-C and infection: In order to test this hypothesis, we specifically (i) estimated MHC‐I and MHC‐II allele diversity in rufous‐collared sparrows in a latitudinal gradient in South America (from Colombia to Cape Horn in Chile), (ii) explored signals of positive selection on MHC alleles, (iii) investigated the associations among MHC allele diversity and latitude/infection, and (iv) analyzed the associations among parasite infection status and latitude/biomes.