Date of Award


Degree Type

Honors College Thesis

Academic Program

Biological Sciences BS


Biological Sciences

First Advisor

Brian Kreiser, Ph.D.

Advisor Department

Biological Sciences


When species hybridize, mitochondrial and nuclear introgression can take place. This is commonly observed in freshwater fish species, such as the Fundulus notatus complex, which is composed of F. notatus, F. olivaceus, and F. euryzonus. The broadstripe topminnow, F. euryzonus, is only found in the Amite and Tangipahoa Rivers in the Lake Pontchartrain drainage, where it overlaps in distribution with F. olivaceus. Previous studies determined that F. euryzonus in the Tangipahoa River system possesses mitochondrial DNA (mtDNA) from F. olivaceus as a result of hybridization between the two species. The goal of this thesis was to re-examine an existing data set of single nucleotide polymorphisms (SNPs) to determine if this mitochondrial discordance has manifested itself in changes in the nuclear genome between populations of F. euryzonus in the Amite and Tangipahoa Rivers. This was conducted using a sliding window analysis to look for genome regions with very high (>0.95) or low (<0.01) weighted fixation index (FST) values and further analyzing regions that included three or more windows in a series. Sliding window groups were assigned to scaffolds within the genome of F. heteroclitus, and the roles of the genes were determined using the UniProt knowledge base. Sixty-nine sliding window groups were identified, which contained a total of 403 annotated genes belonging to 12 functional groups. Ten genes were found to be associated with the mitochondria, and four of these genes (NMES1, UQCRC1, NDUFB4, and SMIM20) were specifically related to the electron transport chain. Given the functional significance of these genes, it is suggested that natural selection could be acting upon F. euryzonus in the Tangipahoa River as a consequence of mitonuclear discordance.

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Biology Commons