Seasonal and Spatial Shapes of Leafroller Moth Diversity in Tropical Forests of Laos

1. Predicting how insect diversity responds to spatial and temporal variation is key to understanding biodiversity dynamics under environmental change. In tropical forests, herbivorous insects such as leafroller moths (Lepidoptera: Tortricidae) play critical roles in ecosystem functioning but remain poorly studied in Southeast Asia, particularly in Laos.2. We examined how seasonality and forest degraded shape leafroller moth diversity and community structure across three National Protected Areas (NPAs) in Laos, representing a gradient from old-growth to selectively degraded and logged forests. Standardized light-trap surveys were conducted across wet and dry seasons over five years.3. A total of 2,879 individuals belonging to 35 species and 19 genera were recorded. Diversity and abundance were significantly higher in the rainy season, which also exhibited lower compositional heterogeneity. Old-growth forest (Hin Nam No) supported the greatest richness and the highest number of indicator species, while degraded and logged forests showed reduced diversity and community turnover. Seasonality explained ~19% of the variation in community composition, compared with ~12% for spatial differences among NPAs. Seven species showed strong fidelity to old-growth forest and 17 to rainy-season conditions, indicating their potential as indicator taxa.4. Our results demonstrate that leafroller moth assemblages in tropical Laos are jointly structured by seasonal resource pulses and habitat integrity. These patterns highlight the importance of maintaining intact forest structure and incorporating temporal variability into biodiversity monitoring and conservation strategies for tropical invertebrates.5. Protecting old-growth forests and maintaining seasonal ecological processes will be key to sustaining insect diversity and associated ecosystem functions in tropical Southeast Asia.