Vegetation determinants on butterfly diversity and composition in Arabuko-Sokoke coastal forest, a tropical biodiversity hotspot, Kenya

Aims: The Arabuko Sokoke Forest (ASF) is the largest remaining coastal forest fragment in Kenya and Eastern Africa, known for its rich biodiversity and endemic species. This study aims to investigate the relationship between butterfly and woody plants species diversity across different vegetation types in ASF. Methods: We conducted butterfly and woody plant surveys during the dry season across four distinct vegetation types in ASF: Cynometra forest, Brachystegia woodland, mixed forest, and the forest edge. Butterfly populations were sampled using transects measuring 10 m x 100 m, and woody plant species were surveyed along overlapping transects. Results: A total of 6,050 butterfly individuals were recorded, representing 86 species across 38 genera and 5 families. The woody vegetation comprised of 178 species, belonging to 78 genera and 34 families. Significant differences in butterfly species abundance were observed across the vegetation types, though no significant differences were found in species richness. Butterfly species diversity showed a strong correlation with plant species diversity. Key environmental drivers of butterfly diversity included rainfall during the warmest quarter, temperature during the warmest month, altitude, and proximity to the coast. Additionally, butterfly wingspan size varied significantly among vegetation types. Conclusion: Our findings underscore the critical role of plant diversity in sustaining butterfly diversity and emphasize the synergistic ecological functions of both forest edges and mixed forest types as key habitats. These habitat types support a wide range of butterfly species by providing diverse host plants, nectar sources, and microhabitats. Implications for Insect Conservation: These results highlight conservation efforts should focus on preserving high plant diversity and incorporating ecological corridors to connect fragmented vegetation habitats. Such strategies will enhance butterfly diversity and contribute to effective conservation in fragmented forests and especially in Arabuko Sokoke forest.