Date Written

2015

Document Type

Distinction Paper

Degree Name

Biology-BA

Department

Biology & Earth Science

Advisor

Simon Lawrance, Ph.D.

First Committee Member

Jeffrey Lehman, Ph.D.

Second Committee Member

Jennifer Bennett, Ph.D.

Keywords

MHC Diversity, Mate Choice, African Penguins, Parasite Resistance

Subject Categories

Genetics | Zoology

Abstract

Background: The major histocompatibility complex (MHC) is highly polymorphic, functioning to maintain a proper immune system within all vertebrates. High diversity within exon 2 of the MHC class II gene has been linked to increases in both parasite resistance and overall fitness. Organisms mate with individuals who will provide them with a high diversity of MHC class II alleles. The role MHC diversity plays in mating of African penguins (Spheniscus demersus) has recently been a topic of debate due to their endangered species status. The purpose of this study is to determine the effects of MHC class II diversity on female mate choice within a captive population of African penguins at Mystic Aquarium. Methods: DNA was extracted from penguin blood samples. Exon 2 of the MHC class II gene was amplified through PCR. The results were run on a DGGE, as well as sequenced. The sequences were analyzed to determine individual MHC alleles and compare the allelic combinations within the population. The MHC alleles of mating pairs and parent-offspring relationships were analyzed. Results: Of the twenty-eight penguins sampled, nine were homozygous, while nineteen were heterozygous. Three alleles were identified within this population, Spde001, Spde002, and Spde003. The allelic combinations produced four genotypes: nine Spde001/Spde001, three Spde001/Spde002, eleven Spde001/Spde003, and five Spde002/Spde003. A lineage map connecting mating pairs and offspring was constructed from the genotypes. Discussion: The Mystic Aquarium population showed reasonable amounts of diversity based on frequency of heterozygotes and patterns of mate choice. Heterozygosity with regard to MHC was more common than homozygosity and presumably would result in greater fitness. Through mating pair analysis, it was concluded that ten of the females chose male mates that were dissimilar from themselves, while one female chose an MHC similar male mate. The result of this dissimilar mating is that African penguins are producing heterozygous offspring. MHC-mediated mate choice is a tactic used by many organisms to ensure increased fitness for their offspring, and it appears as though African penguins utilize this method as well. Despite levels of heterozygosity and dissimilar mate choice, the distribution of genotypic frequencies were no different than what would be expected in Hardy-Weinberg equilibrium (X2df=5 = 8.7, P=0.12) (i.e., random mating).

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