Butterfly diversity along the urbanization gradient in a densely-built Mediterranean city: Land cover is more decisive than resources in structuring communities

Abstract Urbanization induces rapid landscape and habitat modifications leading to alterations in species distribution patterns and biodiversity loss. As pollinating insects such as butterflies are particularly susceptible to urbanization, it is important to pinpoint the factors that could enhance their diversity in the urban areas in order to design adequate management and conservation actions. Our study aims to investigate the influence of land cover and local habitat characteristics on the butterfly diversity patterns and community structure in a densely built city in the eastern Mediterranean region. We carried out butterfly surveys (line transects) in 45 randomly selected sites, distributed along an urbanization gradient. In each site, we assessed the surrounding landscape by measuring the land cover in a 200-m buffer zone, and the local habitat by estimating the available plant resources along each transect. Overall, 1805 individuals belonging to 41 butterfly species were recorded. Land cover was found to have the strongest influence on butterfly species richness, abundance and community structure. Although plant resources were sufficiently available within the whole study area, the butterfly community was significantly poorer in the more urbanized areas, indicating the potential role of habitat fragmentation and patch isolation. In contrast, butterfly diversity was significantly higher in the peri-urban area, underlying its conservation value for butterflies in the urban landscape. We attribute these findings to the degradation of the more urbanized areas due to long-term inadequate planning and the disorganized expansion of the city.