College of Graduate Studies: Theses & Dissertations

Term of Award

Summer 2026

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Biology

Committee Chair

Joshua Gibson

Committee Member 1

Michele Guidone

Committee Member 2

Scott Harrison

Abstract

Speciation is an evolutionary process resulting in the divergence of populations into reproductively isolated species, a key concept that supplies our planet with an abundance of biodiversity. Mechanisms for speciation center on obstacles to fertilization and include post-zygotic barriers, such as intrinsic deleterious interactions, that arise in hybrid systems where genetic variants are combined. Genes from separate parent lineages are often incompatible due to the co-evolution of paired genes within a singular species not matching their complement genes in another species, and the result is a reduction in fitness of the hybrid when these genes come together. The mitochondrial OXPHOS pathway is a candidate pathway for observing this mismatching effect due to enzyme complexes relying on a combination of nuclear and mitochondrial DNA to function properly. Nasonia parasitoid wasps exhibit a higher rate of evolution in their mitochondrial genome relative to their nuclear genome, an observation that makes Nasonia hybrids strong contenders for investigating the underlying genetics and physiological deficiency that results from incompatible allele interactions. Prior studies have investigated these impacts in N. vitripennis (NV) and N. giraulti (NG) hybrids, and results indicate extreme mortality associated with the species-specific origin of cytoplasmic maternal factors, where hybrids with an NG mitochondrial background exhibit significantly higher rates of marker transmission ratio distortion (MTRD) and mortality. Our study aims to incorporate an introgressed region of nuclear alleles in Nasonia hybrids to rescue offspring from cytonuclear incompatibilities, low physiological output, and associated mortality. We hypothesize that integrating mitochondrial-matching alleles in Nasonia hybrids will increase ATP production and complex I activity, and decrease MTRD. Physiology studies were not completed due to recurring issues with assays and mitochondrial isolates, but a timeline of modifications to the protocol were still presented for the record. For genetic studies, we concluded that incorporating mitochondrial-matching alleles results in a complete rescue of mortality associated with a problem locus on chromosome 5. We also discovered a Mendelian ratio of alleles at a marker further down the chromosome in hybrids with and without the introgressed region, indicating a localization of the mortality locus to the distal end of chromosome 5.

Research Data and Supplementary Material

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