Diversity assessment of Western Indian Ocean whiprays (Himantura spp.) through a molecular species delimitation approach

Abstract

Abstract The Himantura species complex consists of large demersal whiprays vulnerable to coastal fisheries, yet unresolved taxonomy within the genus hinders conservation efforts, making molecular assessments crucial for effective fishery management. This study clarified genetic relationships among Himantura species in the Western Indian Ocean (WIO) using species delimitation techniques. Tissue samples from South Africa ( n = 27), Mozambique ( n = 30), Tanzania ( n = 28), Saudi Arabia ( n = 7), and Qatar ( n = 1) were analysed alongside publicly available sequences from the greater Indian Ocean and Indo-West Pacific (Bay of Bengal to the South China Sea). Genetic distance- and tree-based methods identified molecular operational taxonomic units (MOTUs) using three mitochondrial markers: cytochrome c oxidase subunit 1 ( COI ), cytochrome b ( cytb ) and NADH dehydrogenase subunit 2 ( ND2 ). Analyses revealed multiple MOTUs, with WIO specimens falling into two units separated by deep divergence. One MOTU occurred in Tanzania, Mozambique and the Saudi Arabian Red Sea, while the other was found in South Africa, Mozambique and the Saudi Arabian Red Sea. Based on available evidence, the Tanzania–Mozambique–Saudi Arabia MOTU is provisionally assigned to Himantura uarnak Gmelin, 1789, and the South Africa–Mozambique–Saudi Arabia MOTU to H. leoparda Manjaji-Matsumoto and Last, 2008. However, definitive assignments are complicated by limited sequenced type material and ongoing debate over the H. uarnak neotype and require further investigation. These results confirm at least two genetically distinct Himantura species in the WIO; until taxonomy is formally resolved and reliable field identification is feasible, they should be managed as a single conservation unit.