Date of Award
Master of Science
The marsh rice rat (Oryzomys sp.) is a semiaquatic rodent native to wetlands in the southeastern United States. The northwestern-most part of the rice rat’s range extends to Illinois where rice rats are found in wetlands across the southern part of the state. Recent studies have shown that rice rats in the United States can be divided into two species: O. palustris and O. texensis, but the taxonomic status of rice rats in Southern Illinois is unclear. To resolve this, I sequenced cytochrome-b and the control region, two regions of mitochondrial DNA, for 16 rice rats and constructed a phylogeny using these new sequences and previously obtained O. palustris and O. texensis sequences. In contrast to previous morphological assessments, I found that rice rats in Southern Illinois should be classified as O. texensis. This would extend the range of O. texensis north and west from its current extent. Further investigation using nuclear loci will be needed to confirm this classification.
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