EAGER: The role of native and nonnative plants in structuring food webs in urban ecosystems

Cities contain a mixture of native and nonnative plants that are often unusually diverse when compared with nearby natural areas. The high diversity of plants in cities suggests urban areas can potentially support a diverse mixture of feeding insects as well as birds that eat those insects. However, given that many plants in cities are not native to the region, it is unclear whether they provide the same conditions and benefits to local insects and wildlife.

In this study, a team of researchers from California State University Los Angeles will assess the role of native and nonnative trees in supporting food webs composed of insects and birds. The research will focus on oak trees (genus, Quercus) as oaks are renowned for harboring high levels of insect diversity and supporting bird populations. It is not known if birds, which generally are abundant in oaks, can control the insects on those oak trees.

Both native and nonnative oaks are planted throughout the Los Angeles study area thus offering an opportunity to compare the accumulation of insects on trees and the use of trees by birds. This project, which involves planting 200 oak trees in sets that include native and non-native species across a range of urban settings, is designed to provide clues about whether native versus nonnative trees support the most diverse and abundant collection of insects, and in turn, whether birds are attracted to feeding on those insects or to using native versus non-native oak trees differentially.

The field locations for this project will be set in highly visible areas throughout Los Angeles, and thus public outreach and education will happen organically throughout the project. Further, the study will engage and employ students from underrepresented groups, with a focus on students from East Los Angeles, where California State University Los Angeles is located.

Overall, this research will provide novel and unique outcomes for discerning how to better landscape and design cities to promote native biodiversity.

The goal of this study is to critically evaluate the role of native and nonnative trees, in structuring urban food webs, composed of plants, insects, and birds, in Los Angeles, CA (L.A), USA. While these questions have been addressed in non-urban settings, almost no work has experimentally evaluated the potential influence of tree species on birds and insects in an urban setting.

This research will address the question, are nonnative oak trees functionally similar to native trees in structuring urban food webs. The influence of birds will be inferred by surveys of bird usage and time spent in the different trees. The project will erect a large-scale field experiment, involving the planting of 200 native and nonnative oak trees (Quercus spp.) and a reference species, the Southern Magnolia, Magnolia grandiflora, at 10 locations throughout L.A.

The study will include undergraduate students and a graduate student, plus project collaborators, to collect field data on plant growth, herbivory, insect and avian communities, and bird feeding behavior, on the native and nonnative trees at experimental sites. Further, the study will use sophisticated statistical analyses and laboratory methodologies, including leaf-trait analyses and DNA metabarcoding of insect communities on plants to elucidate food web networks/connections among trophic levels.

The work will engage the broader community of Los Angeles through outreach displays and scheduled activities at experimental sites (ten institutions with high visitation rates of students and the public). Outreach events will focus on the importance of native plants, local biodiversity, and urban food webs. Further, the project will influence the ecology of the city as the research team will work to integrate research findings with the management of biodiversity in the urbanized region.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.