Major histocompatibility complex does not affect mating patterns in bluegill sunfish (Lepomis macrochirus)

In many species, individuals prefer mates that are genetically dissimilar at the major histocompatibility complex (MHC). This is likely because it improves offspring resistance to pathogens. Here I provide the first genotypic characterization of the MHC class II peptide binding region in bluegill (Lepomis macrochirus), a species of sunfish, and examine its effect on mating patterns. I hypothesized females would choose to mate with MHC dissimilar males leading to an increase in the resulting offspring’s fitness. I captured females and males during spawning and sequenced the DNA of these fish at the MHC class II putative peptide binding region. I found evidence that positive selection promotes genetic diversity at the MHC in bluegill, with a 5:2 ratio of non-synonymous to synonymous mutations. I found no evidence, however, that MHC genotypes affected mating patterns, either between females and parental males (social mates) or between females and cuckolder males (extra-pair mates). Given that parental males provide sole parental care to the eggs in their nest, the quality of male parental care may outweigh any potential benefit of MHC-based mate choice in bluegill