Insect Community Assembly in Vacant Lots

What are the primary constraints limiting insect colonization and establishment in urban vacant land?

Loss and fragmentation of natural habitat from urbanization is a primary driver of declines in arthropod biodiversity, including insects that contribute to essential ecosystem services such as pest suppression, decomposition, and nutrient cycling. However, Cleveland, Ohio contains over 1,600 hectares of vacant land with the potential to be re-imagined as conservation spaces to foster insect biodiversity and the services they provide in urban landscapes. To accomplish this, it is imperative to understand the current constraints on insect community abundance and structure in cities. This research program will identify regional and local processes that influence the assembly of ground-dwelling beetles and ants by investigating patterns of functional traits linked to beneficial ecosystem services.

Investigating patterns of community assembly using functional traits of beetles and ants

Local insect communities are assembled from a regional pool of species when individuals disperse to a habitat and interact with the local environment and species that are already present (Figure 1).

Figure 1. Local insect communities are influenced by
regional and local processes of assembly.

Urban landscapes are inherently heterogeneous in composition (the variety and abundance of patch types) and configuration (the spatial arrangement and orientation of patch types). Cities are dominated by impervious paved surfaces and human-built structures with interspersed patches of greenspace. In order for insects to utilize these greenspaces, they must be able to disperse from natural source populations to colonize these areas. I will examine regional processes of community assembly by investigating the relationships between beetle and ant functional traits associated with dispersal ability such as body size, wing type, and leg length and these major landscape-level characteristics (Figure 1, Objective 1). For species that are weak fliers or flightless, dispersal is dependent on walking and running, and greater distances from source habitats may significantly limit dispersal capacity in heterogeneous landscapes. Increased connectivity between existing and future greenspaces may be a targeted management strategy if colonization is limited by dispersal ability.

Once insects colonize a habitat patch, they interact with the local environment and species already present, which may constrain successful establishment. In urban ecosystems, these filters are hypothesized to be strong due to the highly modified nature of these landscapes and thus, generalist species tend to be most successful. I will examine local processes of community assembly by investigating 1) the relationships between beetle and ant functional traits and local environmental conditions associated with plant community characteristics and soil properties, and 2) resource partitioning of predatory beetles by assessing patterns of dietary overlap using gut content analysis (Figure 1, Objective 2). Alternative habitat management strategies may improve colonization and establishment success in urban landscapes, fostering biodiversity in vacant lots.

What impact can this research have?

Management of vacant land to support key ecosystem services hinges on a basic and comprehensive understanding of the regional and local constraints on the assembly of insect communities. This research will lead to applied recommendations for city managers and interest groups on how to achieve economic, ecological, and social benefits of vacant lots through informed greenspace design. Moreover, as vacant land is transformed into community gardens and for-profit farms, the success and sustainability of urban agriculture depends on ecosystem services provided by insects. Although this research focuses on Cleveland, Ohio, our findings will be broadly applicable to other cities with abundant vacant land across the United States.

This project is led by Kayla I Perry, a USDA NIFA Postdoctoral Fellow in the Gardiner Lab. Kayla’s research interests include insect community ecology and disturbance ecology.

This material is based upon work supported by Agriculture and Food Research Initiative Education and Workforce Development (EWD), [grant no. 2018-67012-28011/project accession no. 2017-07182] from the USDA National Institute of Food and Agriculture and the National Science Foundation under Grant No. 1253197.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. Department of Agriculture or National Science Foundation.