Researcher ORCID Identifier

0000-0002-8437-6544

Graduation Year

2024

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Sarah Budischak

Reader 2

Findley Finseth

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Terms of Use for work posted in Scholarship@Claremont.

Rights Information

© 2024 Ella Wasson

Abstract

Host-parasite relationships foster antagonistic coevolutionary forces that confer selective pressures on host genomes, promoting the host’s ability to combat parasitic infection. In conjunction, immune genes are widely recognized as genomic hotspots of adaptive evolution, yet the specific mode of selection experienced by an immune gene is mediated by its function. The present study investigated whether rates of adaptive evolution were higher in immune versus non-immune genes within a coccidia-infected Peromyscus maniculatus population from Claremont, CA. It further interrogated whether the type of immune gene influenced observed evolutionary patterns. Lastly, it aimed to identify immune genes exhibiting signatures of selection. Comparisons of the mean Tajima’s D for 63 non-immune genes and 63 immune genes (comprising 21 innate, 21 adaptive, and 21 cytokines) were conducted. Contrary to theoretical expectations, rates of adaptive evolution in immune genes were equivalent to those of non-immune genes. Further, immune gene designation did not affect any observed patterns. This supports that wildlife systems experience complex factors that exert diverse pressures on host genomes. Notably, the distributions of mean Tajima’s D values were elevated across all gene group designations, supporting either: 1) heterozygote immune advantage or 2) a recent population contraction. Furthermore, Tajima’s D testing identified several immune genes exhibiting signatures of balancing selection, supporting previous work on the selective pressures acting on immune genes. The present findings underscore the utility of genomics in disease ecology, elucidating the complex evolutionary forces acting on wildlife systems while additionally shedding light on the selective pressures acting on host immune genes.

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