Assembleia de borboletas frugívoras (Lepidoptera, Nymphalidae) em diferentes estratos florestais ao longo de um gradiente topográfico na Amazônia Central

The Amazon harbors a vast diversity of ecosystems, particularly terra firme forests, which account for approximately 84% of the region’s forest cover. Although they may appear homogeneous, these forests exhibit significant topographic variation. Higher, well-drained areas (plateaus) provide distinct microclimatic conditions compared to lower, more humid areas (valleys) near streams. This variation in moisture and related factors can affect organisms that exploit different forest strata. Regardless of topography, the forest canopy presents conditions that contrast sharply with those of the understory. The main goal of the present study was to investigate how fruit-feeding butterfly assemblages are structured across different forest strata along a topographic gradient in central Amazonia. Sampling was conducted between June and September 2024 in the Adolpho Ducke Forest Reserve (Manaus – AM), across 30 plots spaced 1 km apart. In each plot, we installed eight Van Someren-Rydon bait traps, placed in pairs in the understory and canopy (four per stratum), which remained active for six days, totaling 1,440 trap-days of sampling effort. We sampled 90 individuals belonging to 29 species of fruit-feeding butterflies. The most abundant species was Bia actorion, with 15 individuals collected. Satyrinae was the most abundant subfamily overall, representing 45.56% of the total individuals, followed by Charaxinae (30%), Biblidinae (12.2%), and Nymphalinae (12.2%). In the understory, 21 species and 65 individuals were collected, with Satyrinae as the most abundant subfamily. In the canopy, 25 individuals representing 15 species were recorded, and Charaxinae was the most abundant subfamily. The rarefaction curve did not reach an asymptote in either stratum, but the understory was relatively better sampled, with 80% sample completeness compared to 60% in the canopy. In the understory, abundance was negatively related to altitude (p = 0.039). In contrast, in the canopy, richness and abundance increased with altitude (p = 0.037) and sand content (p = 0.027). Species composition differed between strata (p = 0.001). However, only in the understory was composition influenced by altitude (p = 0.015; R² = 0.072) and slope (p = 0.043; R² = 0.072). The vertical stratification of the forest plays a central role in structuring butterfly assemblages, whereas topography shows subtle, stratum-dependent effects. However, the analyzed variables explained only a small portion of the observed variation, with relatively low R² values in the regressions (Altitude: R² = 0.072; Slope: R² = 0.072), indicating that results should be extrapolated with caution.