Do levees support diversity and affect spatial turnover of communities in plant-herbivore systems in an urban landscape?

Abstract

Valuable habitats in various spatial configurations are essential for maintaining biodiversity across highly fragmented urban landscapes. In a large-scale study, we explored the value of human-made structures – river levees – as valuable habitats that support large populations of plants and butterflies and affects the spatial turnover of species within an urban landscape. The most significant environmental variables affecting plant and butterfly populations on levees were also examined. The richness of native plant species was about 25% greater on levee transects than on control grassland transects. However, the richness and abundance of butterflies on levees were the same as on grassland sites. Among environmental factors, urban area cover negatively affected the richness of native plant species. Shrub cover decreases the richness and abundance of butterfly species. In addition, high mowing intensity had a negative influence on abundance. Community dissimilarity of plants on levees was affected by spatial variables. Our study is the first to highlight levees as significant habitats for plant and herbivorous insect persistence, and their potential function for plant dispersal.