Honors Theses

Date of Award

Spring 5-1-2021

Document Type

Undergraduate Thesis



First Advisor

Peter Zee

Second Advisor

Brad Jones

Third Advisor

Wayne Gray

Relational Format



Local adaptation occurs in populations when multiple subsets of the same population are exposed to different environmental conditions causing the beneficial evolution of each species in its respective environment (Delph 2018). PURPOSE: Using Pseudomonas fluorescens as a model organism, this project sought to understand how an individual’s relative fitness will be affected after undergoing local adaptation in three different environments. METHODOLOGY: To conduct this experiment, three identical strains of SBW25 and three identical strains of lacZ were grown up in three separate environments. Each environment contained an M9 minimal salt media supplemented with either dextrose, xylose, or a 50/50 mixture of each. After two days of growing in their respective media, six microliters were transferred to a new environment with six mL of fresh media. At the end of fourty-eight days, six strains of Pseudomonas Fluorescens had formed via artificial selection. I then calculated the relative fitness of each of the newly formed strains, as well as the original ancestors, in each of the three separate environments. RESULTS: The main finding of this project was that the XE strain saw the most gains in relative fitness compared to any evolved strain or the ancestral strain. The competitive advantages conferred by DXE and DE were small, if not nonexistent, compared to the gains conferred by XE. CONCLUSIONS: Local adaptation seems to be most advantageous when occurring in the presence of a resource that was previously not preferred by the ancestor. That is, adaptation occurring in a poor environment seems to lead to the generation of the most beneficial adaptations.

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