Epigeic macrofaunal assemblages vary among landscape positions along a tropical semiarid mountain catena

Pitfall traps reveal variation in ground-active arthropod assemblages, but their captures reflect both organism abundance and surface activity. We examined epigeic macrofauna along a tropical semiarid mountain catena at Pico do Jabre, northeastern Brazil, using 30 pitfall traps (ten each at summit, midslope and footslope) exposed for 48 h during campaigns on 13–15 January and 15–17 October 2021. The 12-group dataset comprised 2,339 individuals. The October (dry-season) campaign yielded 2,127 captures, including 1,609 ants (Formicidae; 75.65%); the January (rainy-season) campaign yielded 212 captures, including one ant (0.47%). Shannon diversity was lower in October than in January (H′ = 0.802 versus 1.905), and excluding ants increased October H′ to 1.013 but scarcely changed January H′ (1.884). Composition also varied along the catena: ants dominated all three October positions, whereas Dermaptera dominated the January summit and Coleoptera the January footslope. Trap-level coefficients of variation revealed substantial within-position heterogeneity (129.4–154.1% in October; 58.8–127.9% in January). Rainfall observations from the regional reference station showed 632.7 mm in 2021, but no precipitation or soil-moisture measurements were made at individual traps. Accordingly, these patterns describe campaign-specific activity-density and within-position dispersion; they neither establish population changes nor identify a causal rainfall mechanism. The catena provides a spatially explicit framework for soil-fauna monitoring while retaining the limitations of a single hillslope and one campaign per season.