The data set corresponds to genotypes of individuals belonging to Lampsilis siliquoidea and L. radiata which are two closely related freshwater mussel species [Bivalvia: Unionidae]. Individual genotypes consist of seven microsatellite loci developed by Eackles and King 2002. Genotypes were used to asses population genetic structure above and below waterfalls in the lower Great Lakes (USA) and to investigate the degree of hybridization between these two species. 

Lampsilis siliquoidea and L. radiata tissue samples from sites across much of their geographic ranges were collected by the authors or kindly provided by colleagues from various agencies and institutions in the USA and Canada. Genomic DNA was extracted from 0.10-0.25 cm³ of tissue or from 200 ml of lysis buffer from each sample using a modified alcohol extraction method following Wilson (1997). Seven microsatellite loci developed for L. abrupta (Eackles and King 2002) that amplify across Lampsilis species were used. Each microsatellite locus was amplified via a polymerase chain reaction (PCR) in a 10 ml reaction containing the following concentrations: 10.0-20.0 ng/ml of extracted genomic DNA, 0.3 mM dNTPs, 10mM Tris-HCl buffer (pH 8.3), 2.5-3 mM MgCl₂, 0.2 mM each fluorescently-labeled primer and 1U Taq polymerase. The amplification conditions as follows: initial heating at 94°C for 2 min, then 30 cycles of 94°C for 40 s, annealing at 53-57°C for 40 s, and a 1 min extension time at 72°C followed by a final extension of 10 min at 72°C. All PCR products were screened on 7% polyacrylamide gels in a LI-COR NEN® Global IR2 DNA Sequencer System, using fluorescently labeled primers. Allele size was determined by comparing amplified products to 50-350 bp size standards (LI-COR Biotechnology Division).Locus C2 (Eackles and King 2002) has a compound trinucleotide repeat motif and it showed two alleles that only differed in length by one base-pair (scored in this study as 157 and 158; these alleles are 19 bp longer than the length reported by Eackles and King (2002) due to an M13 tail that is added with florescent dye). These alleles were cloned using TOPO TA Cloning kit (ThermoFisher Scientific) following the manufacturer’s manual. Transformed clones were sequenced using Sanger sequencing by TACGen, CA. That demonstrated that they are two different alleles, identified as 157 and 160.