Invertebrate diversity in peri-urban community gardens and possible mechanisms of community assemblage

Urban gardening is becoming increasingly popular in the U.S., in metro and nonmetro communities alike, to address rapid urbanization and food insecurity. Urban gardens are incredibly diverse systems, and likely have equally diverse invertebrate communities. To support this growing trend, more information is needed on invertebrate communities that impact crop production. The primary objective of this study was to describe invertebrate community composition at 10 urban community gardens across two counties in Indiana. We also aimed to identify possible mechanisms that determine community assemblages, such as garden size, surrounding land use, ground cover management, and crop diversity. Using pitfall traps, sticky cards, and in-situ visual assessments, we determined that herbivores represent the dominant feeding guild at community gardens, and herbivore counts were highest on zucchini and tomato. However, sentinel prey releases suggested that predators and parasitoids are important regulators of pest populations. Overall, the assemblage of feeding guilds was similar across sites, suggesting a common metapopulation present in the surrounding landscape. On-farm practices that had the greatest influence on insect diversity were crop diversity, the presence of floral resources, and ground cover management. Insect diversity was positively correlated with crop diversity, and pollination activity was associated with flowering crops, namely dill. Parasitoid counts on sticky cards were often associated with sites that had more ground cover, such as straw mulch. This study provides useful insights on the dominant invertebrate groups present at urban community gardens in Indiana and accessible on-farm practices to improve farm biodiversity.

Automated summary

Urban gardening is gaining popularity in the U.S. to address urbanization and food insecurity. This study investigated the invertebrate community composition at urban community gardens in Indiana and found that herbivores were dominant, but predators and parasitoids played a key role in controlling pest populations. Farm practices such as crop diversity, floral resources, and ground cover management were found to influence insect diversity.