Population Structure of the Endangered Robust Redhorse (Moxostoma robustum) Based on Mitochondrial DNA Control Region Sequence

Moxostoma robustum, the robust redhorse, is an endangered species of suckerfish. Before rediscovery in 1991, the robust redhorse had been believed extinct for 122 years. In 1994, a small population of robust redhorse was discovered in the Oconee River of Georgia. Then in 1988, 5 robust redhorse were discovered in the Savannah River (Georgia). Wildlife officials are now trying to save the robust redhorse by the introduction of hatchery reared fish. It is of interest to know whether the fish collected from these two rivers represent different genetic stocks of robust redhorse. This project attempted to address this question by sequencing the mitochondrial DNA (mtDNA) control region of 20 Oconee River fish and the 5 fish collected from the Savannah River. Sequence data for a 302 base pair (bp) portion of the control region was obtained for Oconee and Savannah River robust redhorse. Five polymorphic sites were observed in this 302 by region. Three of these polymorphic sites exhibit fixed genetic differences between the fish collected from the two river populations. This evidence suggests that the two river populations of robust redhorse are genetically distinct and diverged about 200,000 years ago. In light of these results, wildlife officials should respect these genetic differences and establish separate brood-stocks of robust redhorse for the Oconee and Savannah Rivers.