Honors Program Theses


Honors Program Thesis (UNI Access Only)

First Advisor

Peter Berendzen


Reptiles--Adaptation--Mississippi Embayment; Reptiles--Mississippi Embayment--Genetics; Amphibians--Adaptation--Mississippi Embayment; Amphibians--Mississippi Embayment--Genetics; Fishes--Adaptation--Mississippi Embayment; Fishes--Mississippi Embayment--Genetics;


The Mississippi River represents one of the most prominent geographic barriers in eastern North America. The Mississippi River is so large and diverse that it can be divided into six different sections. This study focuses on the southern-most section and its surrounding plain, the Mississippi Embayment. This region has been repeatedly impacted by glacial events and sea level advances and retreats. Multiple studies on the geographic distribution of genetic variation within organisms have revealed a repeated pattern of divergence across the Mississippi River. However, the question remains did all these organisms respond in unison to a single pervasive event or did each respond individually to repeated events? This study is a meta-analysis that involved taking vast amounts of DNA sequence data from previously published studies of aquatic and terrestrial organisms on either side of the Mississippi River. The sequence data were downloaded and assembled into datasets. These datasets were then analyzed using traditional and new methods to determine the timing of events that isolated populations east and west of the Mississippi river. The new methods take into account population differences between organisms including population size, generation time, and mutation rate. Comparisons among analyses were made and hypotheses were generated to determine the possible number of event(s) that correspond to the divergence of organisms across the Mississippi Embayment. The analyses revealed between two and four events that can be attributed to sea level rises and retreats from the Gulf of Mexico during respective eras throughout the history of North America. Determining and recording the evolutionary history of the distribution of organisms provides insight into how communities have been formed and could provide insight into how future climate change will impact the flora and fauna.

Year of Submission



Department of Biology

University Honors Designation

A thesis submitted in partial fulfillment of the requirements for the designation University Honors

Date Original


Object Description

1 PDF file (viii, 44 pages)



File Format


Off-Campus Download