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, and insect behavior. Here, we investigate the stratification of five clades of Lepidoptera: Erebidae-Arctiinae, Geometridae, Hedylidae, Saturniidae and Sphingidae, which differ in many aspects of their ecology and traits. The study was carried out in a tropical rain forest of the Chocó region in NW Ecuador. We used funnel traps equipped with weak UV LED lamps to sample moths simultaneously in the canopy and understory in four forest habitats. We identified species using reference collections and with the aid of DNA barcoding and present a qualitatively unique data set for Neotropical rainforests, with 12,472 individuals of 676 species collected in 48 nightly catches. Species richness was on average 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 and 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 independent of abiotic factors like elevation, temperature, or humidity. Our results allow a comprehensive insight into differences in stratification of five moth clades in a tropical rainforest at high taxonomic resolution with respect to habitat types and influences of environmental factors.