Differences in plant community composition along socioeconomic gradients in Baltimore, MD and Washington, DC: Implications for Aedes albopictus and Culex pipiens mosquitoes

Background/Question/Methods

Aedes albopictus and Culex pipiens are two of the most abundant urban mosquito species in the eastern United States and can vector numerous arboviruses, including chikungunya, Zika, and West Nile viruses. Previous research has shown that adult mosquitoes are larger, more abundant, and have higher infection rates in lower-income neighborhoods, creating a disproportionate and unjust risk of disease for their residents. The abundance, distribution, and vectorial capacity of A. albopictus and C. pipiens are mostly determined by developmental ecology in water-filled container habitats, which usually includes strong resource competition for allochthonous organic detritus and associated microbes. Past studies suggest that non-native plant detritus supports mosquito population growth better than native plant detritus, and that more non-native biomass can alleviate pressure of larval competition. We sought to determine whether differences in the composition of urban vegetation distributed along an income gradient are associated with observed patterns of mosquito composition and abundance in Baltimore, MD and Washington, DC, and also examined differences between occupied and abandoned residential parcels in Baltimore. In summer 2020, we surveyed the composition and abundance of standing vegetation (e.g. canopy and ground cover) around potential juvenile mosquito habitat across 18 socioeconomically diverse neighborhoods.

Results/Conclusions

Non-metric multidimensional scaling revealed that both canopy and ground community composition were distinct between Baltimore and Washington, DC. Additionally, occupied properties on Baltimore blocks with 40% or more abandonment had distinctly different canopy composition compared to occupied properties on blocks with little to no abandonment. This is likely due to the intermixing of abandoned and occupied parcels, creating opportunity for tree crowns and climbing vines on abandoned lots to cross property lines and influence community composition on occupied parcels. In Baltimore, mean canopy cover was greater on abandoned (43%) vs. occupied (25%) lots, creating potential for more allochthonous detritus input to mosquito habitats. The canopy species that appeared most frequently in low-income neighborhoods were largely non-native, including Ailanthus altissima and Paulownia tomentosa, while canopies in high-income neighborhoods frequently contained native species like Acer rubrum and Ulmus americana. These differences in canopy cover and native status may help explain variation in mosquito community characteristics and composition through the alteration of available plant detritus quantity and quality. These results will inform future competition experiments between A. albopictus and C. pipiens. Understanding the associations between mosquitoes and plants across socioeconomic gradients can help us better predict mosquito infestations and manage inequitable disease risks.