Protection status and environmental gradients shape butterfly assemblages in an East African tropical ecosystem

Although butterflies are abundant in tropical and subtropical grassland, savanna and shrubland biomes in sub-Saharan Africa, they are often overlooked in land-use planning in the tropics and rarely assessed for their responses to conservation interventions. We compared butterfly diversity patterns across a protection gradient in the Katavi-Rukwa Ecosystem (KRE), western Tanzania. We surveyed 105 randomly selected sites spanning national park (NP), game reserve (GR), game-controlled areas (GCA), forest reserve (FR) and unprotected areas (UA) during the 2021 dry season. Species were classified by habitat specialization, larval host–plant specialization and wingspan. Environmental variables were derived from remote sensing and spatial datasets. We analysed butterfly richness, abundance, functional composition and assemblage structure, and evaluated the influence of environmental conditions, habitat type and protection status using generalized linear models, multivariate ordination, PERMANOVA and additive diversity partitioning. We recorded the highest butterfly richness and abundance in GR, while NP supported comparatively lower richness and abundance. Vegetation productivity (EVI), percent bare soil cover and human population density were significant drivers of assemblage structure. Through regression analysis, EVI and human population density emerged as key predictors of species richness, with higher productivity supporting greater richness and higher human population density associated with reduced species richness. Additive partitioning analysis revealed that β-diversity, particularly turnover among protection types, was the main contributor to total richness. We recommend conservation strategies in KRE to move beyond formal protection status and consider the role of moderately managed landscapes and environmental conditions in maintaining butterfly diversity.