Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Neff, Bryan D.

Abstract

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.

Summary for Lay Audience

Many organisms prefer mates that are genetically dissimilar to themselves at certain genes. This produces offspring with multiple functional variants of the molecules these genes code for, which could be advantageous. The Major Histocompatibility Complex (MHC) genes are an example of a set of genes in which organisms look for mate dissimilarity. 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 one of the MHC genes. I found evidence that positive selection promotes genetic diversity at the MHC in bluegill. 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.

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