Date of Award


Degree Type

Honors College Thesis

Academic Program

Marine Biology BS


Biological Sciences

First Advisor

Jacob Schaefer, Ph.D.

Advisor Department

Biological Sciences


Character displacement is a pattern that can be used to explain differences between similar species in sympatric and allopatric situations. Gause’s Principle explains that a niche can only be occupied by one species at a time, so character displacement may be a way for similar species in the same habitat to shift resource use and compensate in order for the species to coexist. The Southeastern United States offers a unique opportunity to study this pattern because the diversity of freshwater fauna is quite high. However, the question of “How did this region become so diverse?” remains unanswered. One way for speciation to have increased diversity would involve changing an organism’s biology, specifically its body morphology through character displacement. The study of how an organism’s body is related to environmental factors is ecomorphology. In order to test if character displacement could have contributed to the high diversity in the Southeast, two similar species from one of the most diverse groups in this region (darters) were used, Percina sciera and Percina nigrofasciata. Geometric morphometrics was used to measure and analyze differences in body shape between individuals in sympatric and allopatric drainage systems. The largest difference seen was between the two species and while it was not considered as significant as the other results, there was a difference seen in the interaction between treatment (sympatric vs. allopatric) and species. The expanded caudal peduncle seen in the shift from P. sciera to P. nigrofasciata could be explained by the fish expanding their niche to include different habitats, such as faster flowing habitats. Future studies should look at individual drainages instead of major drainage systems to look for smaller scale changes between sympatric and allopatric individuals.

Included in

Evolution Commons