Comparing the effectiveness of different monitoring methods on butterfly richness and abundance (Lepidoptera: Rhopalocera) in Serbia

Butterflies are essential for ecosystem stability, offering various ecosystem services, with pollination standing out as particularly important. The ongoing global decline in their richness and abundance highlights the critical need for focused conservation actions, and the first step towards their protection is understanding their richness. On a European scale, the European Pollinator Monitoring Scheme (EUPoMS), created as part of the STING project, is tackling this issue. Based on the EUPoMS, the SPAS project (Serbian Pollinator Advice Strategy – for the next normal) was initiated in Serbia, focusing on the monitoring of wild bees, butterflies, hoverflies, and the plants they visit. Within SPAS, several sampling methods were implemented, with line transects and pan traps (in blue, yellow, and white) as the primary techniques. Butterfly monitoring was conducted across 30 locations in Serbia, three times per year (spring, summer, autumn) from 2022 to 2024. This study evaluated the efficiency of these methods in assessing butterfly richness and abundance. Our findings revealed that line transects recorded a higher species richness and abundance compared to pan traps. However, pan traps detected certain species not observed during transect sampling, suggesting their complementary role in monitoring. Among the trap colors, blue pan traps captured the highest richness and abundance of butterflies, reflecting a possible preference for blue-colored flowers. These results emphasize the importance of employing diverse sampling techniques to achieve a comprehensive understanding of butterfly diversity. They also emphasize the importance of understanding pollinator preferences to enable better decision making and improve strategies for their conservation.