Conservation genetics and distribution of the Yazoo Darter (Etheostoma raneyi)

The Yazoo Darter is a range-restricted endemic fish in north-central Mississippi. Because the limited and fragmented range of this species puts it at risk of extinction, the Yazoo Darter has been classified as vulnerable or sensitive by several agencies and conservation organizations. However, the actual conservation status of this species is uncertain. Information necessary for conservation management is relatively sparse and is scattered among published and unpublished sources, particularly collection records. I have consolidated all known collection records for this species into a standardized database which has not only yielded valuable information presented here, but will provide a resource for future management efforts. In addition, I have used genetic methods to quantify contemporary population structure, genetic variation, and gene flow throughout the range of the species, estimated contemporary migration rates and effective population sizes, and have compared them to historic estimates before habitat modification and fragmentation. I also used genetic methods to try to detect and determine when population declines occurred. Results indicate that the Yazoo Darter is distributed unevenly across the two major river drainages within its range and that the species is at greater risk of extirpation due to anthropogenic disturbance in the Yocona River drainage. Most genetic variation is partitioned among populations and each tributary of the two major river drainages that we sampled constituted a genetically distinct population. Since habitat modification began about 150 years ago, effective population sizes have declined severely and populations have become genetically isolated resulting in decreased genetic variation. All populations are small enough in size and geographic range to be at risk of extirpation due to stochastic factors.