Term of Award

Fall 2022

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 of Biology

Committee Chair

Aaron Schrey

Committee Member 1

Jay Hodgson

Committee Member 2

Michele Guidone

Committee Member 3

Lynn Martin

Committee Member 3 Email



Epigenetic buffering, as an environmentally induced increase in variance of epigenetic states that increases phenotypic variation to buffer populations against decreased fitness, may be a factor that resolves the genetic paradox of introduced species. DNA methylation is a molecular mechanism that could facilitate epigenetic buffering by changing in response to environmental stress. Therefore, epigenetic buffering can be detected through increased variance in DNA methylation in novel or heterogeneous environments. Introduced house sparrows (Passer domesticus) have well-documented phenotypic changes with low genetic diversity, high epigenetic diversity, and high variance in DNA methylation that provide a characteristic signature of epigenetic buffering. Here, we screened DNA methylation among introduced and native house sparrows from multiple widely separated geographic locations to test for evidence of epigenetic buffering. We used epiRADseq to detect differentially methylated regions and estimate total DNA methylation. We found that introduction history explained the patterns of DNA methylation among introduced and native house sparrows in a manner that supports epigenetic buffering. Recently introduced house sparrows had the highest variance in DNA methylation, and the most significantly different methylated sites. Established introduced house sparrows also had higher variance than native house sparrows. House sparrows from British Columbia and Brazil were more similar to recently introduced sparrows in methylation patterns, while the older established introduced sparrows, South Africa and Florida USA, were more similar to native house sparrows. We show that variance in DNA methylation is highest in the novel environments for the house sparrow. As environmental novelty encompasses intense stress and potentially heterogeneous environments, we suggest that epigenetic buffering is likely an important phenomenon for response to such conditions.

Research Data and Supplementary Material