Senior Project Advisor

Peterson, Merrill A., 1965-

Document Type


Publication Date

Winter 2004


Speciation research, Reinforcement theory, Leaf beetles


Reinforcement theory is a controversial mechanism by which speciation can occur through reduced hybrid fitness promoting the evolution of reproductive isolating mechanisms. Populations within a hybrid zone may be at differing relative abundances which may affect their risk of hybridization and strength of sexual isolation. The effect of relative abundance has been seldom examined in studies of reinforcement. Chrysochus cobaltinus and C. auratus leaf beetles from a zone of secondary contact in central Washington were run in various multi-choice mating trials to determine if lab results were indicative of those occurring in nature and whether relative abundance had an effect on risk of hybridization, pairwise sexual isolation (PSI) and overall isolation (IPSI). Results from lab experiments were found to be representative of those in nature. Relative abundance had a significant effect on both the risk of hybridization. In addition, our results suggested that overall sexual isolation and that as a species became rarer, they also became choosier. This sets the stage for further research on hybridization risk and relative abundance to be taken into the field setting, and indicates that studies of reinforcement should consider not only relative abundance, but also the relationship between relative abundance and choosiness, to better understand the risk of hybridization.



Subjects - Topical (LCSH)

Chrysomelidae; Hybridization; Evolution (Biology); Isolating mechanisms


student projects; term papers




Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Rights Statement