Diversity and Species Richness of Lepidopteran Stemborers and Their Host Plants Across Major Vegetation Mosaics of East Africa.

The study was carried out in the major ecological vegetation mosaics of Rwanda, including Afro-alpine mountain mosaics within the Guineo-Congolese region in the north; Akagera sub-humid savanna mosaics in the east; montane forest mosaics in the south; and modified urban wetland and riparian mosaics of Kigali City, within the Sudanian-Guinea-Congo transition zone. At each selected locality, purposive sampling in (i) edges of the cultivated field and adjacent uncultivated lands, (ii) open patches along the forest access roads and pathways, (iii) riparian zones along urban areas, rivers, and streams, (iv) edge of lakes, and (v) swamp ecosystems was conducted to detect stemborer infestations. A total of 6098 larvae belonging to 18 genera representing five families were recovered from 56 wild host plant species. The abundance of stemborers and host plants was higher in modified urban wetlands and its riparian zones (41.7%, N = 2536; 47 host plants) and lower in Afro-alpine mountain mosaics (10.3% of larvae; seven host plants). The Poaceae family hosted 62.5% of all stemborers, with Pennisetum purpureum being the most affected host, accounting for 29.53% (N = 1801). Two major economically important pests in sub-Saharan Africa dominated collections: Busseola fusca (47.11%, N = 2873) and Chilo partellus (17.61%, N = 1074). Additionally, five new stemborer-host plant associations and a fruit-feeder genus of Thaumatotibia were observed associated with stems. These results are preliminary indicators of possible new stemborer species and host use that warrant further investigation. Our findings provide a baseline assessment of lepidopteran stemborer diversity and host plant associations across regional vegetation mosaics, highlighting the importance of natural and semi-natural habitats in supporting stemborer communities. The study also reveals previously undocumented plant associations that warrant further ecological and taxonomic investigation.