Date of Graduation

5-2024

Document Type

Thesis

Degree Name

Bachelor of Science in Biology

Degree Level

Undergraduate

Department

Biological Sciences

Advisor/Mentor

Zhuang, Xuan

Committee Member/Reader

Beaulieu, Jeremy

Committee Member/Second Reader

Luu, Khoa

Abstract

Convergent evolution provides valuable insights into how natural selection shapes species traits. Genomic analysis of lineages that display convergent traits has the potential to identify candidate genes for environmental adaptations across the scope of entire genomes. One remarkable example of convergent evolution is the independent development of antifreeze proteins (AFPs) in phylogenetically distant polar fish lineages. While AFPs themselves are relatively well studied, the full genomic context of adaptation to freezing conditions in these fish lineages remains largely unexplored. Leveraging the whole genome sequences previously assembled in our lab, along with other high-quality genomes available in GenBank, I examined the genomes of freeze-resistant species and related non-resistant species across four teleost fish lineages: Pleuronectidae, Cottidae, Labridae, and Notothenioidei. Screening for orthogroup expansion and positive selection produced eight promising candidate genes identified in three or more of these lineages. Of these, RHO, Hsp70, and TP53BP1 have the clearest potential relation to the freezing and cold resistant traits that are characteristic of species that possess antifreeze proteins (AFP+ species). Further investigation of these genes could lead to insights into the mechanisms that facilitate tolerance to these extreme environments.

Keywords

Genomics; Adaptive Evolution; Convergent Evolution; Freeze Resistance

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