Mitochondrial gene diversity of Skistodiaptomus mississippiensis in impoundments of the Upper Coastal Plain near Aiken, South Carolina, USA

Abstract

Genetic diversity of the calanoid copepod Skistodiaptomus mississippiensis was assessed by sequencing a 348-base pair fragment of a mitochondrial gene, cyto- chrome b apoenzyme, from 165 copepods in ponds from the Savannah River and Edisto River watersheds near Aiken, South Carolina, USA. Eight ponds were sampled, including four on the Savannah River Site (SRS) that had been used to cool effluent from nuclear reactors. All of the ponds were man-made, and the potential times since establishment of the copepod populations ranged from 10- 70yr. Skistodiaptomus mis- sissippiensis is nearly unknown from natural habitats of the area, but high genetic diversity within and among populations in the man-made ponds suggests that the spe- cies colonized from local sources. Haplotypes were not randomly distributed among ponds or between drainages. Results of a nested cladistic analysis revealed that pri- mary routes of colonization were most likely due to contiguous range expansion of haplotypes predominant within the area. Among abandoned cooling ponds of the SRS, the larger ponds showed greater proportions of haplotypes confined to the Savannah River drainage. These haplotypes were poorly represented in the two smaller ponds,