Genetic structure of populations of the mangrove crab Ucides cordatus (Decapoda: Ocypodidae) at local and regional scales

The crab Ucides cordatus (Decapoda: Ocypodidae) is a species of considerable economic and ecological importance in mangrove areas of the Western Atlantic coast. However, habitat loss, overfishing, and a new infectious disease are causing substantial reductions in local stocks of this species, leading to a pressing need to design efficient management strategies. A crucial step in this design in an understanding of how the genetic variability of U. cordatus is distributed among estuaries throughout its range. In this study we assess the degree of spatial structure in the pattern of genetic variation of U. cordatus over local (estuaries located within 100 km from each other) and geographical scales (estuaries located farther than 2700 km from each other). Ninety individuals were collected from nine estuaries and analyzed using PCR-RFLP and RAPD techniques. The percentage of polymorphic bands within populations ranged from 15% to 46% for RFLP markers and from 40% to 70% for RAPD markers. Our results failed to demonstrate significant geographical structure in the pattern of genetic variation, indicating that populations of U. cordatus are capable of extensive gene flow among estuaries. The implications of these results for the management of U. cordatus populations are discussed.