Regional Temperature and Apple Snail Pomacea canaliculata Shape Aquatic Macroinvertebrate Community Structure in Rice Paddies of South Korea

Rice paddies function as temporary wetlands that provide important habitats for diverse aquatic macroinvertebrates. However, the relative roles of regional climatic conditions and invasive species in shaping macroinvertebrate communities remain insufficiently understood. This study investigated the effects of regional temperature variation and the invasive apple snail Pomacea canaliculata on aquatic macroinvertebrate communities in rice paddies across South Korea. Aquatic macroinvertebrates were surveyed annually from 2021 to 2024 in five regions distributed along a latitudinal gradient, and additional local-scale comparisons were conducted between rice paddies with and without P. canaliculata. A total of 42 species comprising 24,524 individuals were recorded. Community composition differed significantly among regions and variation partitioning indicated that regional temperature explained 17.5% of the community variation in paddies containing P. canaliculata, whereas the snail explained 2.3%. Several dominant aquatic insect species exhibited distinct temperature-associated distribution patterns, with Rhantus suturalis and Hydrochara affinis showing negative relationships with temperature and Sternolophus rufipes showing a positive relationship. In contrast, P. canaliculata had little influence on aquatic insects but reduced overall macroinvertebrate diversity through its negative effects on native gastropod assemblages. These findings demonstrate that regional temperature and P. canaliculata influence rice-paddy macroinvertebrate communities through different ecological pathways. Regional temperature primarily affects the distribution of several dominant aquatic insect species, whereas P. canaliculata alters community diversity by reducing native gastropod populations. This study provides ecological evidence for predicting the combined impacts of climate warming and biological invasion on rice-paddy ecosystems.