Deterministic and Stochastic Processes Regulate Co‐Occurrence Network Structure and Shape Macroinvertebrate Diversity in Karst Environment

ABSTRACT Biodiversity and ecosystems around the world are consistently threatened by different factors. How deterministic processes and stochastic processes shape biodiversity have become one of the central questions in ecological studies today. The karst region of Southwest China's Yunnan Province is one of the world's biodiversity hotspots and features unique surface and underground riverine landscapes. We studied macroinvertebrate communities in a Cave‐Reservoir‐and‐Stream (CRS) ecotone to assess drivers of macroinvertebrate diversity in the region. Our results demonstrated that in co‐occurrence network, keystone taxa such as Trigomphus (betweenness = 0.303, degree = 0.298) contributed to shape the community assembly and maintain diversity, while modules (subcommunities of closely related taxa) promoted species coexistence and interactions further enhancing taxonomic and functional diversity. The diameter and average path length (APL) of co‐occurrence network of cave, reservoir, and stream were 2.83, 3.98, 8.10 and 1.27, 1.43, 2.82, respectively, with 17.4%, 12.0%, and 5.0% isolated taxa and 5, 4, and 9 modules. Stochastic processes would maintain diversity and community assembly when the environment favored taxa growth, while deterministic processes would become critical under deteriorated environmental condition due to the loss of keystone taxa. Deterministic processes dominate in caves (73.6%), stochastic processes in streams (85.9%), while in lakes the two processes are almost similar. This study provided insights into the significance of riverine connectivity in the karst landscape ecotone for maintenance and conservation of endemic freshwater ecosystem and diversity and contributing to important ecosystem services in southwest China.