Leaf litter characteristic of low-income urban blocks improves population performance of Aedes albopictus (Diptera: Culicidae) and Culex pipiens mosquitoes

Abstract

Mosquito larvae feed on microbes growing on decomposing organic matter, which in cities is often limited to a finite amount of allochthonous leaf litter in artificial container habitats. Curiously, field surveys in US cities consistently document a mismatch between blocks with the greatest mosquito infestations and blocks where their plant resources are most plentiful, with variation shaped by socioeconomic factors. We gathered leaves characteristic of socioeconomically diverse blocks in Baltimore, Maryland, and Washington, DC, to create lab mesocosms for two common mosquito species, Aedes albopictus (Skuse) and Culex pipiens (Linnaeus). We reared mosquitoes at varying densities to assess the effects of leaf litter composition on survival, development time, and body size, from which we calculated population performance and effects on competition. We also investigated traits of the leaf litter and aquatic environment. Leaf litter containing at least one non-native species, including the mix common on low-income blocks (nonnative trees Ailanthus altissima and Paulownia tomentosa) and the mix common across the region (native tree Juglans nigra and nonnative tree Morus alba) improved mosquito outcomes compared to the native leaf litter common on high-income blocks (native trees Acer rubrum and Ulmus americana) and also alleviated competitive effects on development time, perhaps making coexistence more likely. The three litter types showed significant differences in C:N ratio, decay rate, and tannin/lignin concentration but not in microbial abundance. These results offer a mechanistic explanation for previously observed socioeconomic patterns in urban mosquito populations and point toward novel strategies for mosquito control through vegetation management.