Moth Diversity Increases along a Continent-Wide Gradient of Environmental Productivity in South African Savannahs

SIMPLE SUMMARY: Environmental productivity is considered among the key factors responsible for the uneven distribution of biodiversity on the globe, despite the lack of comprehensive studies for many groups of organisms and regions. We partly filled this gap by this study of moth diversity along the unique continent-wide gradient of environmental productivity across southern African savannahs. We revealed a significantly positive relationship of the moth species richness and environmental productivity, which we did not observe for moth abundance. We hypothesize the effects of water availability, habitat complexity, and plant diversity drive the described relationships. ABSTRACT: Environmental productivity, i.e., the amount of biomass produced by primary producers, belongs among the key factors for the biodiversity patterns. Although the relationship of diversity to environmental productivity differs among studied taxa, detailed data are largely missing for most groups, including insects. Here, we present a study of moth diversity patterns at local and regional scales along a continent-wide gradient of environmental productivity in southern African savannah ecosystems. We sampled diversity of moths (Lepidoptera: Heterocera) at 120 local plots along a gradient of normalized difference vegetation index (NDVI) from the Namib Desert to woodland savannahs along the Zambezi River. By standardized light trapping, we collected 12,372 specimens belonging to 487 moth species. The relationship between species richness for most analyzed moth groups and environmental productivity was significantly positively linear at the local and regional scales. The absence of a significant relationship of most moth groups’ abundance to environmental productivity did not support the role of the number of individuals in the diversity–productivity relationship for south African moths. We hypothesize the effects of water availability, habitat complexity, and plant diversity drive the observed moth diversity patterns.