Climate-driven vegetation characteristics shape phytophagous and carnivorous insect diversity in South African savannahs

Despite the recognized importance of insects in savannah ecosystems, the drivers of their diversity patterns remain poorly understood, particularly in the Afrotropical region. This study addresses this gap by investigating the impacts of climate, habitat, disturbance, and vegetation variables on the diversity of phytophagous moths (Lepidoptera) and carnivorous mantises (Mantodea) across 60 plots in Kruger National Park, South Africa. Based on an extensive dataset of 65,593 moth individuals representing 817 morphospecies and 3,511 mantis individuals representing 38 morphospecies, our results revealed plant communities as the fundamental driver of diversity for both insect groups. The effects of vegetation on insect diversity were indirectly influenced by climate, particularly mean temperature (negatively correlated with precipitation), through its impact on plant species richness. Additionally, a complex interplay among bedrock type, water availability, and disturbances from large herbivores and fire further shaped insect diversity. Our findings highlight the region's vulnerability to climate change, as decreasing precipitation and increasing temperatures were shown to alter vegetation composition and biomass, consequently affecting insect communities. Overall, our results emphasize the necessity of managing large herbivores and regulating fire regimes to maintain diverse vegetation, which is crucial for supporting insect diversity. Effective conservation strategies should prioritize balancing water availability and disturbance intensity, particularly in maintaining the health of seasonal rivers, to mitigate the adverse effects of climate change on these ecosystems.