Modern lacustrine cladocera and their controlling factors in Western Yunnan, SW China

Plankton is crucial for lake ecosystem health. However, large-scale studies linking zooplankton communities, particularly cladocerans, to environmental factors remain scarce in China and worldwide. As one of the five lake regions in China, Yunnan is a key region for understanding past and present global lake plankton patterns and their relationships with environmental factors. This study presents an initial systematic investigation of modern cladoceran assemblages from 67 lakes in western Yunnan to reveal the pattern of modern cladoceran communities and their controlling factors. Modern cladoceran communities are primarily composed of planktonic taxa dominated by Bosmina. Their composition and abundance show a three-group pattern, i.e., cladoceran communities of groups I and II, dominated by planktonic taxa, are mainly from medium-deep lakes, whereas cladoceran communities of group III, dominated by littoral taxa such as Alona, are principally from shallow lakes. Community groups I and II are both dominated by Bosmina, but Group I is characterized by a dominance of Bosmina longirostris, whereas Group II is dominated by Bosmina longispina. Our study shows that water depth is the primary factor controlling this pattern, explaining 10.0% of the variation, while temperature acts as a secondary factor, explaining 4.2%; the water depth of ca. 8 m is a threshold to distinguish modern cladoceran communities dominated by planktonic taxa from ones dominated by littoral taxa, implying that modern cladoceran communities are associated with the availability of littoral habitats and thermal gradients. Our results highlight the critical roles of water depth and temperature in shaping zooplankton species composition and abundance patterns, providing a foundation for interpreting modern and fossil cladoceran assemblages in the context of environmental and climatic changes.