Species richness patterns of brachyuran crabs in the Persian Gulf and the Gulf of Oman

The Persian Gulf is a shallow, semi-enclosed marginal sea basin characterized by a distinct geological history, harsh environmental conditions, and intermittent connection with the Indian Ocean during the Pleistocene glacial periods. Brachyuran crabs constitute a diverse component of the Persian Gulf fauna, distributed unevenly in the various habitats. The biodiversity and regional biogeographic data for the Persian Gulf and Gulf of Oman crab fauna are still poorly understood and rarely incorporated into global biodiversity databases. Here, we have addressed this shortfall by mapping the regional distributions of 262 species of brachyuran crabs in the Persian Gulf and the Gulf of Oman and incorporating the data with open-access biodiversity databases. We used QGIS 3.24.3 and R 4.2.2 packages for mapping and analyzing the distribution records. Our analyses revealed that the Persian Gulf exhibits proportionally higher diversity metrics than the Gulf of Oman for brachyuran crabs. Cluster analysis revealed that the Iranian coasts are relatively differentiated from the Arabian coasts of the Persian Gulf and the Gulf of Oman. The distribution and alpha species richness patterns per hexagonal cells were higher in the Iranian coastal waters, particularly around the Strait of Hormuz and Qeshm Island. Furthermore, the distribution and species richness of the Persian Gulf brachyuran crabs were positively correlated with temperature (°C) and calcite (mol.m-3), while negatively correlated with dissolved oxygen (mol.m-3). Although our analyses did not recognize the Persian Gulf as a center of endemism, but highlighted it as an important peripheral region with significant influences on the present-day diversity and distribution of northwestern Indian Ocean brachyuran crabs. We believe that the present results reveal new insights to be considered in conservation actions to protect marine biodiversity in underrepresented and ecologically unique regions such as the Persian Gulf.