Optimizing sampling protocols: spider assemblages are robust to pitfall trap spacing in Neotropical savannas

Spiders are a highly diverse group that occupies a wide range of terrestrial microhabitats, from leaf litter to the forest canopy, which has led to the development of numerous collection methods. Yet, there remains a pressing need for standardization in sampling protocols to ensure comparability across spider studies. In this study, we evaluated whether pitfall trap spacing (1 m, 10 m, and 20 m) influences the outcomes of spider sampling campaigns in Neotropical savannas. Pitfall traps were arranged in sets of sixteen, with each set representing one of the three spacing treatments. Nine sampling points were established, each comprising three sets of traps positioned 100 m apart. We collected 2,237 specimens representing 26 families and 76 species or morphospecies. Trap spacing had no significant effect on spider abundance, species richness, or assemblage composition. Community composition was influenced only by vegetation complexity, which explained a modest portion of the variation. Among the most abundant taxa, only Salticidae responded significantly to trap spacing, being more abundant at 20 m, while Leprolochus mucuge showed a weak positive association with vegetation complexity. Together, these findings indicate that spider assemblages in the Cerrado are broadly robust to the trap-spacing distances tested. Based on our results, we suggest practical strategies for standardizing pitfall trap designs. Applying and testing these guidelines across additional biomes will be crucial for refining global standards for arthropod sampling.