Year-Round Variation in a Butterfly Assemblage in a Subtropical Region Assessed Using Malaise Traps

Understanding the mechanisms driving patterns of alpha and beta-diversity through temporal variation in taxonomic diversity remains a fundamental question in community ecology surveys. Insects represent a species-rich group playing several roles in ecological processes. However, knowledge of their temporal distribution and seasonality remains limited, particularly in subtropical regions. We investigated intra-annual patterns of alpha and beta-diversity of butterflies in Restinga ecosystems of southern Brazil, a subtropical region characterised by marked seasonality. Butterflies were monitored throughout one year using Malaise interception traps, and data were grouped by season. We tested seasonal differences in temperature and humidity and evaluated their association with patterns of richness, abundance, evenness, and species composition. Temperature was the main environmental filter structuring butterfly assemblages compared to humidity. Butterfly richness and abundance peaked in summer, followed by spring, coinciding with higher temperatures, while diversity declined markedly during winter. Although we expected winter assemblages to represent nested subsets of other seasons, beta-diversity analyses revealed high species turnover among seasons. Our findings demonstrate that temperature drove the structure of butterfly assemblages across seasons, highlighting the importance of monitoring to increase knowledge on the temporal dynamics and distribution of insects in the subtropical region.