Global distribution and biodiversity of brachyuran crabs in the Persian Gulf

Abstract The tropical Indo-West Pacific (IWP) is one of the species-rich and high endemicity hotspots around the East Indies Triangle. However, recent research demonstrates that peripheral regions may act as evolutionary incubators, sharing unique genetic lineages with other regions of the IWP. The Persian Gulf is a shallow semi-enclosed marginal sea basin characterized by geological history, stressful environmental conditions, and intermittent connection with the Indian Ocean during the Pleistocene glacial periods. Understanding the global distribution and importance of environmental variables in shaping species richness patterns of brachyuran crabs in this region is necessary for comprehending evolutionary and ecological processes, as well as conservation priorities. We merged our own distribution dataset of 261 species of brachyuran crabs in the Persian Gulf and Gulf of Oman with the GBIF and OBIS open-access biodiversity datasets, which lack the data from this region. QGIS 3.24.3 and R 4.2.2 packages were used for data analysis and visualization of the distribution records. The highest sampling effort (1,955), species richness (225 spp.) and ES50 (expected number of species) (40.94), along with 21 endemic species of brachyuran crabs were observed in the Persian Gulf. Distribution and species richness of brachyuran crabs significantly increased with temperature (°C) and calcite (mol.m-3), and decreased with dissolved oxygen (mol.m-3), and nitrate (mol.m-3), the focus of this study. This study suggested that the Persian Gulf, as a peripheral region, may play a role in shaping brachyuran diversity and current species distribution. This highlights the importance of prioritizing marine protected areas and establishing species management in this economically and ecologically important region.