Date of Graduation

5-2018

Document Type

Thesis

Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level

Undergraduate

Department

Animal Science

Advisor

Douglas, Marlis

Reader

Douglas, Michael

Second Reader

Rosencrans, Charles

Abstract

Darters are small, benthic fishes that live in freshwater rivers and streams and belong to the family Percidae. Pleistocene glaciations fragmented many darter species, resulting in speciation, but new species are often hard to detect if they are morphologically identical to pre-existing species. Intraspecific hybridization and resulting introgression, which occur frequently in glaciated areas, further complicate identification by introducing heterospecific genomes into mitochondrial DNA, making it difficult to accurately resolve phylogenetic relationships. The results of Bossu and Near’s 2009 study highlight this issue, showing a large degree of incongruence between mitochondrial and nuclear gene trees.

This study analyzed samples from 50 collection sites along the White River Drainages in the Ozark Highlands region of Arkansas, and area that is high in both species richness and habitat diversity. SVDQuartets analysis genrerating bootstap values for 1000 iterations recovered 12 species of Etheostoma, including 3 from the E. spectabile species complex, which was surprisingly non-monophyletic for the represented taxa. However, the relationships shown in the tree are consistent with previous studies which concluded that heterospecific DNA is being introgressed into the E. spectabile complex, although the sister-species relationships recovered differ from those found in Bossu and Near. The relationships displayed in this tree reveal the tendency for hybridization and introgression to occur between members of E. spectabile and other Etheostoma, however, sampling size and sampling area are both small, and further analysis is needed that includes more individuals and a broader sampling across a wide range of darter habitats to determine if these relationships are representative of the clade as a whole.

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