Climate change drives rapid and asymmetric niche divergence in high-altitude freshwater fishes: Insights from niche3D

Climate change poses significant risks to freshwater biodiversity, particularly in climate-sensitive regions like the Tibetan Plateau. This study introduces niche3D, a novel Python package designed to quantify climate-driven niche divergence, demonstrated through a case study of two sympatric cyprinid fishes at the highest elevations. The results indicate that habitat suitability similarity between the two species decreased by approximately 23.21% under the highest-emission scenarios for 2070. Barycenter analyses revealed that the cold-adapted species (Heizensteinia microcephalus) shifted significantly upward in elevation, while the warm-adapted species (Ptychobarbus kaznakovi) showed more stability in its habitat distribution. Additionally, 3D environmental risk detection indicated that the cold-adapted species faces significant risks of habitat loss, particularly at lower elevations, while the warm-adapted species exhibited more stable or even expanding niche occupancy. These findings highlight the vulnerability of cold-water freshwater fish to climate change, with potential disruptions to ecosystem dynamics, species competition, and habitat fragmentation. The niche3D framework provides a powerful tool for understanding and quantifying these shifts, offering valuable insights for biodiversity conservation in climate-sensitive ecosystems.