Moth communities are more diverse in the understory than in the canopy of a tropical lowland rainforest in NW Ecuador

"Tropical rainforests are the most species-rich terrestrial habitats and provide distinct niches for specialization and speciation, in part due to their vertical stratification. Stratification is observed in many insect orders as a result of abiotic factors, resource availability, competition, and behavior. Here, we investigate five clades of Lepidoptera, which differ in many aspects of their ecology and traits. We aim for a better understanding of the stratification patterns of Erebidae-Arctiinae, Geometridae, Hedylidae, Saturniidae, and Sphingidae. The study was carried out in a tropical rainforest of the Chocó region in NW Ecuador in 2021 and 2022. We used funnel traps equipped with weak UV-lamps to sample moths simultaneously in the canopy and understory in four forest habitats. We identified species using reference collections and DNA barcoding and present a qualitatively unique database for Neotropical rainforests, with 12,472 individuals of 676 species collected in 48 nightly catches. Average species richness was higher in the understory (73.54 ± 22.58) than in the canopy (59.09 ± 17.24), and median sample sizes were similar (understory: 217.5 (160.5–336), canopy: 187.5 (138–328.5)). We found taxon-specific patterns: Arctiinae and Sphingidae—the stronger flyers—were more species-rich and abundant in the canopy, and weaker flyers Geometridae and Saturniidae were more species-rich and abundant in the understory. We assume that predation pressure, availability of nectar and host plants shape the vertical distribution of moth assemblages. Communities largely overlapped, were highly nested in each stratum and between habitat types, and differences in composition among habitats were mainly driven by elevation. We found more species in regenerating forests compared to old growth forests, while sample size was only marginally influenced by trap height but independent of elevation, temperature, and humidity."