Microsatellite and mtDNA-based exploration of inter-generic hybridization and patterns of genetic diversity in major carps of Punjab, Pakistan

Over the past two decades, there has been a growing alarm about the role of unintended hybridization in shaping the current biodiversity. Major carps (Labeo rohita, Catla catla, and Cirrhina mrigala) are commercially important freshwater fish for aquaculture and are also found exclusively in the riverine ecosystems of Punjab, Pakistan. One of the main concerns is the genetic integrity of major carps. In this study, we employed both nuclear and mitochondrial DNA markers to determine the potential hybridization and patterns of genetic variation in major carps. Association tests of both nuclear and mtDNA markers provide evidence of recent hybridization, and patterns of genetic variations were also found consistent with observed pattern of admixture in major carps. In all hybridization events, L. rohita is detected to hybridize with C. catla and C. mrigala, whereas C. catla and C. mrigala are established to hybridize with L. rohita. Overall, two levels of hybridization; F1 hybrids reported in hatchery-reared stocks and few backcrosses individuals in wild populations suggest that anthropogenic or demographic dynamics accelerate inter-generic gene flow. Moreover, the disparity in amplified mtDNA COI subunit shows strong directional bias towards Labeo–Catla first-generation hybrids (100%) containing L. rohita maternal lineage while Labeo-Cirrhina hybrids (75%) exhibit C. mrigala maternal lineage. The results of this study endorse that culture-based fish farming and restocking activities of major carps in riverine ecosystems demand regular genetic monitoring of these species. The current genetic evidence and proclamation of practical information should encourage management and conservation efforts to strictly limit the genetic integrity of these species.