Range-Wide Genetic Study of the Suwannee Bass

Suwannee bass have the smallest range of all the black basses.  For decades, they were believed to only inhabit the Ochlockonee and Suwannee River drainages in Florida and Georgia.  Over the last 15 years, additional populations have been discovered in the Wacissa, Wakulla, and St. Marks Rivers in Florida, leading to speculation that these populations were created in the late 20^th century through unsanctioned angler releases.  Tissue samples were collected from Suwannee bass inhabiting six streams in northern Florida and multiple techniques were used to resolve genetic relationships across the species range and investigate the possibility that the recently discovered populations were introduced.  Nuclear DNA variation (11 polymorphic microsatellite loci and three allozyme loci) indicated there was significant genetic differentiation between the fish inhabiting the Suwannee River drainage and those from the four streams to the west (i.e., the Ochlockonee River collection plus the three recently discovered populations).  Analysis of molecular variance found more than half of the nuclear genetic variation was partitioned between these two groups of collections.  The fish from the two regions also had different ND2 gene sequences and private RFLP haplotypes, indicating that there were consistent patterns of differentiation in the nuclear and mitochondrial genomes.  The recently discovered populations were found to be genetically similar to fish from the Ochlockonee River and displayed genetic signals consistent with their having passed through genetic bottlenecks, as would be expected if these populations had originated from the release of a small number of individuals.  However, the Ochlockonee River also had the genetic signature of a bottleneck, providing an example of a natural population of Suwannee bass that is likely to have experienced natural bottlenecks due to low population size.