Despite extensive genomic exchange within adjacent Himalayan rivers
High-altitude environments present extreme physiological challenges for aquatic organisms, including low oxygen availability, cold temperatures, and increased UV radiation . The snowtrout (Schizothorax spp.) represents an excellent model system for studying adaptation to these conditions due to their distribution across steep altitudinal gradients in the Himalayan region .
Snowtrout are tetraploid cyprinids, providing a unique genomic architecture for studying adaptation . Their duplicated genome may facilitate rapid evolutionary responses to environmental challenges.
The Himalayan region offers natural laboratories with elevation gradients exceeding 4000 meters, creating distinct selective pressures across relatively short geographical distances .
Individuals Sequenced
River Systems
Elevation Range
Snowtrout specimens were collected from multiple locations across seven Himalayan river systems, spanning elevations from 2500 to 4500 meters above sea level .
High-coverage whole genome sequencing was performed on 156 individuals using Illumina NovaSeq platform, with an average coverage of 30× .
We employed multiple approaches including PCA, ADMIXTURE, and Fst analyses to characterize population structure and identify genomic regions under selection .
Genome-environment association analyses were conducted to identify loci correlated with altitudinal gradients and other environmental variables .
We integrated population genomic, phylogenomic, and environmental association methods to detect signatures of parallel adaptation across independent river systems while accounting for gene flow and demographic history .
Despite strong population structure along altitudinal gradients, we detected significant gene flow between adjacent populations within river systems . Migration rates estimated using coalescent methods revealed ongoing genetic exchange.
Multiple genomic regions showed consistent signatures of selection across independent river systems, indicating parallel adaptation to altitudinal gradients . These regions were enriched for genes involved in hypoxia response and metabolic processes.
Parallel adaptations to altitude persist despite extensive genomic exchange, suggesting strong selective pressures maintain adaptive divergence in the face of gene flow . This demonstrates the resilience of locally adapted genomic architectures.
The persistence of parallel adaptations despite gene flow highlights the strength of natural selection in maintaining functional genomic differences . This has important implications for understanding evolutionary resilience in changing environments.
Our findings suggest that locally adapted populations may persist despite connectivity, informing conservation strategies for high-altitude freshwater ecosystems facing climate change .
Further research should focus on functional validation of candidate genes and investigation of epigenetic mechanisms that may contribute to rapid adaptation .
This study demonstrates that parallel genetic adaptations to altitudinal gradients can persist in tetraploid snowtrout despite extensive genomic exchange within Himalayan river systems. The findings contribute to our understanding of evolutionary processes in extreme environments and have implications for biodiversity conservation in high-altitude ecosystems.
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