Mitochondrial DNA Variation Reveals Significant Rangewide Genetic Heterogeneity in Paddlefish

We sequenced the complete mitochondrial DNA D-loop region of 338 Paddlefish from 12 sampling locations throughout the range of Paddlefish including 8 within the Mississippi River drainage and 4 from isolated Gulf Coast drainages. In total, 39 unique haplotypes were observed, with 3 to 15 haplotypes per location. We found significant genetic heterogeneity among locations with the majority of pairwise comparisons (50 of 66) significant at ɑ=0.05 and 44% significant after a Bonferroni correction (ɑ=0.0008). All pairwise comparisons with the Alabama River were significant, including comparison with the Tombigbee River which joins the Alabama to form the Mobile River. Similarly, Grand Lake, OK and Arkansas River, AR were each distinct from all other locations. Grand Lake had the lowest number of haplotypes and lowest haplotype and nucleotide diversity, which is similar to a previously published study of nuclear DNA, indicating perhaps a reduced effective population size due to stocking (i.e. Ryman-Laikre effect). Furthermore, values of genetic differentiation for all comparisons with Grand Lake were large (Φ_st = 0.18 to 0.64). Patterns of genetic structure in Paddlefish are affected by dams, which isolate populations and increase genetic drift among populations, and past stocking practices which transferred fish among rivers.