Microsatellite DNA markers for the study of horseshoe crab (Limulus polyphemus) population structure

Twenty‐two microsatellite DNA loci were identified and characterized for horseshoe crabs (Limulus polyphemus) collected from two Atlantic coast and one Gulf of Mexico site. These markers revealed a high degree of genetic diversity (8–35 alleles per locus), heterozygosity (25.0% to 100.0%), and allelic heterogeneity (69.8% of comparisons). Considerable regional differentiation was observed as genetic distances (chord) ranged between 0.25 and 0.45, and all F_ST values (0.014–0.092) were significant. These preliminary findings are consistent with patterns of regional differentiation observed using allozyme variation and contradictory to findings of limited gene flow reported for sequence variation at the mitochondrial DNA COI region.