Amphipods of the genus Diporeia dominate the benthic macroinvertebrate community in deep waters of the Laurentian Great Lakes, and have been selected as an indicator of ecological condition for the Great Lakes.  However, the taxonomy of Diporeia is not completely resolved, the genus being thought to comprise as many as eight species.  This study examined the diversity of the mitochondrial cytochrome c oxidase subunit I (COI) gene in populations of Diporeia spp. in Lake Superior.  COI sequences were obtained from Diporeia collected at eight sites located in nearshore and offshore zones of eastern, central, and western regions of Lake Superior. 

Results/Conclusions

A total of 59 COI haplotypes were identified from 236 individuals.  The mean sequence divergence was 0.58%, which is consistent with the presence of a single species in Lake Superior.  A single haplotype accounted for 36% of individuals, and was present at all sites, whereas 49 haplotypes were unique to individual sites.  Sequence divergence of COI between Diporeia from Lake Superior and those collected at five sites in Lakes Michigan, Huron and Ontario averaged 1.69%, with no spatial overlap of haplotypes between Lake Superior and the other lakes.  These results indicate the existence of a distinct lineage in Lake Superior, and a lack of gene flow between Superior and the lower Great Lakes.  Clarification of the taxonomy of Diporeia will aid in understanding the spatial and temporal variations that have been observed in the abundance of these amphipods, and facilitate their effective use as an ecological indicator. 

_{This abstract does not necessarily reflect EPA policy.}