Date of this Version
The Prairie Naturalist 43(3/4): 84–91; December 2011
We provided an early characterization of the genetic structure of the grass carp (Ctenopharyngodon idella) population as it expands its distribution in both the Missouri and Mississippi River basins. Further, we provided initial comparisons of allelic richness at 17 polymorphic microsatellite markers between 56 grass carp from the USA, and six from the Yangtze River in China. The number of alleles per locus ranged from two to eight and size ranges of alleles for fish collected from the invaded and native ranges were similar (P ≤ 0.001; 107–226 bp) to those previously reported in the literature. Distance-based clustering methods did not suggest significant groupings by river reaches. Using allele frequencies, we identified a possible population bottleneck (heterozygosity excess in the Missouri River upstream sample group) between the uppermost Missouri River reach and all other samples which may indicate a difference in the level of diversity between the locations. Within population allelic diversity (AS) was 1.56, 2.27, and 1.39 for samples from the Missouri River in South Dakota and Nebraska, samples from the Missouri River in Missouri, and samples from the Mississippi River respectively. Despite isolation from the native population and exposure to a novel environment, in the nearly 50 years since their first introduction from China, the genome at these 17 microsatellite loci has diverged little from fish collected in their native range. We found only weak evidence to suggest that grass carp throughout the Missouri and upper Mississippi River basins are reproductively isolated from one another at this time. Range expansion can result in divergent genetic structure of subpopulations, which may provide clues about the mechanism of invasion success and inform fisheries scientists how to focus management efforts most effectively. These results provided a unique glimpse at a species early in the process of range expansion in the USA and provide a benchmark for future assessments of grass carp genetic structure in the Great Plains.