Evolution of Hybrid Incompatibilities in Gene Regulatory Networks

EVOLUTION OF HYBRID INCOMPATIBILITIES IN GENE REGULATORY NETWORKS SEPTEMBER 2013 ALEXANDER Y. TULCHINSKY, B.S., VIRGINIA COMMONWEALTH UNIVERSITY, RICHMOND M.S., VIRGINIA COMMONWEALTH UNIVERSITY, RICHMOND Ph.D., UNIVERSITY OF MASSACHUSETTS, AMHERST Directed by: Adam H. Porter Under the Dobzhansky-Muller model, postzygotic isolation results from incompatibility between interacting genes. Evidence points to regulatory networks as a rich source of incompatibilities that impact hybrid fitness. Pleiotropy is a natural feature of regulatory networks because regulatory elements generally have multiple targets. Both pleiotropy and hybrid incompatibility arise due to genetic interactions; therefore we can expect an intimate association between them. In the following chapters, I investigate the relationship between pleiotropy and hybrid incompatibility in the context of regulatory networks. In chapter one, I extend a general network-based study of hybrid incompatibility by incorporating a sequence-based thermodynamic model of transcriptional regulation. In the absence of pleiotropy, hybrid misregulation of a positively selected trait evolves quickly as a consequence of non-recognition or spurious binding in regulatory