Altitude-driven variations in chrysophycean stomatocyst assemblages: Implications for climate reconstructions in the Three Parallel Rivers of Yunnan Protected Area, China

• Biodiversity of Chrysophyceans stomatocysts is high in low-latitude and high-altitude mountain lakes. • Altitude, a proxy of temperature change, is the most important predictor of chrysophycean. stomatocyst assemblages. • Chrysophycean cysts have a great potential as a powerful tool for temperature reconstructions in alpine regions of the Hengduan Mountains. The Three Parallel Rivers of Yunnan Protected Area (TPRYPA) is in the core area of the Hengduan Mountains, characterized by paralleling alternately high mountains and canyons that led to significant vertical temperature variation. Developing a climate transfer function for this region is crucial for both biodiversity protection and enhancing our understanding of feedback mechanisms between low-latitude and high-altitude areas in the context of global climate change. We investigated the chrysophycean stomatocyst assemblages from surface sediments of 46 high mountain lakes (altitude: 3244 to 5043 m) in the TPRYPA to assess the suitability of cysts in prediction of climate variability in high mountains. A total of 194 morphotypes were identified. Gradient forest (GF) model identified that altitude is the key environmental gradient with relation to cyst assemblages and cyst assemblages changed the composition substantially at altitude of 3200 and 4400 m, respectively. Cyst-based inference model for altitude using weighted-averaging method resulted in cross-validated jack-knifed-R 2 of 0.60. The cyst-altitude transfer functions suggest that chrysophycean stomatocysts have a great potential as a powerful tool for climate reconstructions in alpine regions of the Hengduan Mountains.