Comparative study on the potential distribution of <i>Simulium equinum</i> (Diptera: Simuliidae) on the Tibetan Plateau under climate change based on predictive ecological models

Simulium equinum is a notorious blood-sucking insect acting as a potential vector for various human and animal pathogens. In this study, we employed a single-species ecological niche model and an ensemble model to compare the potential distribution of S. equinum in northeastern regions of the Tibetan Plateau under paleoclimatic, current, and future climate scenarios. The accuracy metrics derived from Kuenm and ENMeval packages, two optimization methods of MaxEnt model calibration and evaluation, all exceeded 0.8, with no statistically significant differences among them. Temperature, precipitation, and elevation were identified as the primary environmental factors influencing the distribution of S. equinum, with the total contribution rate and permutation importance both exceeding 95%. Under current climate scenarios, both MaxEnt and BIOMOD2 models predicted similar distribution patterns, with potential distribution mainly concentrated in the northeastern Tibetan Plateau. The potential distribution area was significantly positively correlated with human activity intensity and ecosystem quality. Under paleoclimatic scenarios, model predictions diverged: MaxEnt identified high-suitability zones primarily in the Hengduan Mountains in the southern Tibetan Plateau, while the BIOMOD2 model predicted broader distributions across the eastern and southern Tibetan Plateau. The distribution center of this species shifted northward from the Hengduan Mountains to the Qilian Mountains over time, supporting the glacial refugium hypothesis for the Hengduan region. Under future climate scenarios, both models predicted similar potential distribution in the northeastern Tibetan Plateau. These all provide a theoretical basis for understanding the ecological dynamics of S. equinum, delineating control zones, and evaluating freshwater ecosystems in the Tibetan Plateau.