Date of Award

2026

Document Type

Thesis

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Dr. Jory Brinkerhoff

Abstract

Lyme disease, caused by the bacterium Borrelia burgdorferi and transmitted by the blacklegged tick Ixodes scapularis, is the most common vector-borne illness in the United States. Whereas Lyme disease is concentrated in the northeastern US, I. scapularis exists in the southeast as well, and the ticks in these regions generally separate into northern and southern evolutionary lineages. Although recent analyses suggest unidirectional and limited gene flow from north to south due to behavioral, ecological, and environmental barriers, the mechanisms underlying the persistence of this limited gene flow remain unclear. This study examines whether bird-mediated dispersal may facilitate south-to-north gene flow in I. scapularis, addressing a potential pathway that could influence the spread of tick populations and associated disease risk. Phylogenetic analysis using the mitochondrial 16S rDNA marker from avian-associated ticks collected at five northern U.S. sites was conducted, and resulting sequences were compared to reference sequences. Results show no evidence of south-to-north gene flow and instead support clear separation between northern and southern clades. These findings are consistent with existing evidence that ecological and behavioral barriers limit genetic exchange, suggesting that bird-mediated dispersal does not contribute significantly to gene flow between these populations. However, low-level gene flow that escapes detection cannot be ruled out completely.

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