GEOGRAPHIC-VARIATION OF PADDLEFISH ALLOZYMES AND MITOCHONDRIAL-DNA

North American paddlefish Polyodon spathula historically occurred in t he Mississippi, Saint Lawrence, and Alabama rivers, as well as several other Gulf of Mexico coastal drainages. Recent population declines in some locations and the local extirpations of others purportedly have been due to habitat loss, overharvest, and other biotic and abiotic ch anges to riverine ecosystems. Mitigation for these declines has emphas ized hatchery production and supplemental stocking programs, which use a number of geographical sources for parental stock. To investigate p hylogeographic relationships within and among several watersheds, we s urveyed allozyme and mtDNA variation among 189 individuals collected f rom six regions of the Mississippi River drainage plus the Mobile Bay and Pearl River drainages. Paddlefish exhibited lower levels of alleli c and haplotypic diversity than other freshwater species, a characteri stic shared with other ''primitive'' fishes. Allozyme variation at 64 presumptive loci was segregated into two major groups: a Mobile Bay dr ainage group and a group from the Mississippi River and Pearl River dr ainages. More subtle population divergences were observed among major regional tributaries within the Mississippi River, although a clear an d unambiguous level of geographical clustering was not delineated. Fur thermore, several of the localities harbored ''private,'' but rare, po lymorphisms. These results demonstrate that the populations are suffic iently divergent to warrant differential management considerations for any rehabilitation, restoration, or protection measures.