Biodiversity and genetic connectivity of Brachyura and Anomura (Decapoda) from artificial reefs in the Gulf of Mexico

Artificial reefs act as islands of biodiversity that provide substrate where sessile organisms can settle and mobile invertebrates and fishes can find shelter and food. Though these structures are common and widespread in the Gulf of Mexico, their community composition is not well understood. We aimed to ameliorate understanding of the invertebrate communities living on artificial reefs in the northeastern Gulf of Mexico by using molecular techniques and morphological examination to describe the biodiversity and genetic connectivity of crabs (Infraorders Anomura and Brachyura) living on and among artificial reefs near Pensacola, FL, USA. Specimens (N = 1,241) were collected from six artificial reefs using Autonomous Reef Monitoring Structures (ARMS) after four, six, and ten months of submergence, respectively, and were identified using DNA barcoding and morphological examination. Spatial and temporal trends in biodiversity were examined by comparing Hill-Shannon and Hill-Simpson diversities, richness, and canonical correspondence analysis. Population genetic analyses were performed on the two most commonly recovered species, Pseudomedaeus agassizii (A. Milne-Edwards, 1880) and Hexapanopeus paulensis (Rathbun, 1930). A total of 11 taxa were identified, and artificial reef shape was found to be influential in shaping spatial patterns of biodiversity. Species turnover was common across the ten months of sampling, and richness peaked at the ten-month mark. Population genetics revealed that there is high gene flow between the six sampling locations. This study is the first to describe the biodiversity of crab communities on artificial reefs in the northeastern Gulf of Mexico.