Date of Award


Publication Type

Master Thesis

Degree Name



Great Lakes Institute for Environmental Research

First Advisor

Cristescu, Melania (Biological Sciences)


Environmental Sciences.



Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.


This thesis analyzes genetic patterns across botryllid tunicate invasions in North America - encompassing the violet tunicate Botrylloides violaceus and the golden-star tunicate Botryllus schlosseri. I investigate these species entry and spread on the continent by using the mitochondrial cytochrome c oxidase subunit I (COI) gene, and 13 (B. violaceus) and 12 (B. schlosseri) nuclear polymorphic microsatellite loci. Considerable genetic differentiation was detected both within and among East and West coast locales. Also, there was substantial variation in the degree of genetic diversity maintained in introduced populations, which showed, in general, signatures of long-distance dispersal. Taken together, these results indicate the invasions were founded from multiple source regions. Also, post-introduction spread along the coasts appears to occur predominantly through human-mediated dispersal of sexually-produced propagules. I relate these findings to knowledge of the life-history attributes of B. schlosseri and B. violaceus, and to available records of their introductions to North America.