Conservation insights for the Critically Endangered Black Softshell Turtle (Nilssonia nigricans) through integrative ecological and genetic approaches in South Asia

The conservation status of the Black Softshell Turtle, Nilssonia nigricans was recently revised from 'Extinct in the Wild' to 'Critically Endangered' on the IUCN Red List, based on integrative taxonomic assessments incorporating morphological and genetic evidence. However, prior to this study, no comprehensive population genetic or ecological assessments had been conducted on this imperiled species. With the growing application of advanced molecular and ecological tools in biodiversity research, the integration of such multidisciplinary approaches has emerged as a more robust and globally recommended strategy for informed conservation planning and management. Hence, this study integrates mitochondrial DNA-based population structure analysis with species distribution modeling (SDM) to identify regions of habitat suitability with high genetic diversity for N. nigricans under both current and projected climatic scenarios. The genetic analyses revealed low intraspecific divergence (0.3–0.5%) but relatively high haplotypic diversity, with nine and 11 haplotypes identified in the Cytochrome c oxidase I ( COI ) and Cytochrome b ( Cytb ) markers, respectively, indicating the presence of geographically structured or isolated populations. Furthermore, the SDM results indicated that only 8.84% (10,124 km²) of the IUCN-defined range is currently suitable for N. nigricans , with merely 4,984 km² representing areas of both high habitat suitability and significant genetic diversity. While future projections suggest an overall expansion in habitat suitability, the area that maintains both high habitat suitability and genetic uniqueness is expected to contract. Furthermore, the priority conservation areas were delineated in the Brahmaputra basin and select districts across Assam, West Bengal, and northeastern Bangladesh. This study presents a novel framework that integrates genetic and ecological data to identify priority areas for the conservation and captive breeding of N. nigricans , thereby facilitating adaptive management strategies in the face of current and projected climate change.