Diversity and abundance of a pollinator group: hawkmoths (Lepidoptera: Sphingidae) in forests and surrounding farmlands, East Usambara Mountains, Tanzania

"Pollinators are now facing a drastic biodiversity fall in various parts of our world. In Africa data to measure and monitor their biodiversity trend is still inadequate and concentrated more on some insect pollinator groups, especially bees and butterflies. In this study, hawkmoth diversity and abundance in East Usambara Mountains were assessed. Data collection was conducted from three different habitat types that included thick vegetation assemblage with canopy cover, edges of the forest, and farmlands between 2017 and 2019. Hawkmoths were captured using a UV-light trap 250W mercury bulb in 12 sampling sites. A total of 35 hawkmoth species and 991 individuals belonging to the family Sphingidae were identified. The highest hawkmoth abundance was recorded from forest edges (p < 0.05). Canopy cover and farmlands showed lower hawkmoth abundance. Accordingly, higher Shannon Weiner diversity indices were recorded from canopy cover and forest edges (p < 0.05). Farmlands had the lowest Shannon Weiner diversity index. Differences in diversity and abundance of hawkmoths among three habitat types suggest that accelerating anthropogenic factors has led to the destruction of natural habitats. Meanwhile, natural habitat destruction has often been found to exert adverse effects on biodiversity. Moreover, the decline in biodiversity of pollinator insects like hawkmoths hinders the vital pollination service to both crops and wild flora. East Usambara Mountains are still an important refuge for many species that become restricted to different environments due to climate change and anthropogenic pressure, hence calling for regular pollinator conservation and monitoring. This study will provide the baseline data on hawkmoth species richness, abundances and diversity for potential conservation and monitoring programs."