Urban ecosystems are widely hypothesized to be more ecologically homogeneous than natural ecosystems. We argue that urban plant communities assemble from a complex mix of horticultural and regional species pools, and evaluate the homogenization hypothesis by comparing cultivated and spontaneously occurring urban vegetation to natural area vegetation across seven major U.S. cities. There was limited support for homogenization of urban diversity, as the cultivated and spontaneous yard flora had greater numbers of species than natural areas, and cultivated phylogenetic diversity was also greater. However, urban yards showed evidence of homogenization of composition and structure. Yards were compositionally more similar across regions than were natural areas, and tree density was less variable in yards than in comparable natural areas. This homogenization of biodiversity likely reflects similar horticultural source pools, homeowner preferences, and management practices across U.S. cities.
Bibliographical noteFunding Information:
Funding for this research came from the National Science Foundation MacroSystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate and Long Term Ecological Research Program. The “Ecological Homogenization of Urban America” project was supported by a series of collaborative grants from the Macrosystems program (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320). The work arose from research funded by grants from the NSF Long Term Ecological Research Program supporting work in Baltimore (DEB-0423476), Phoenix (BCS-1026865, DEB-0423704, and DEB-9714833), Plum Island (Boston; OCE-1058747 and 1238212), Cedar Creek (Minneapolis–St. Paul; DEB-0620652), and Florida Coastal Everglades (Miami; DBI-0620409). We are grateful to the botanical field teams involved in yard sampling and data organization: BAL—Charlie Davis, Dan Dillon, Erin Mellenthin, Charlie Nicholson, Hannah Saunders, and Avery Uslaner; BOS—Emma Dixon, Roberta Lom-bardiy, Pamela Polloni, Jehane Semaha, Elisabeth Ward, and Megan Wheeler; LA—Aprille Curtis and La’Shaye Ervin; MIA–Bianca Bonilla, Stephen Hodges, Lawrence Lopez, and Gabriel Sone; MSP—Chris Buyarksi, Emily Loberg, Alison Slaats, and Kelsey Thurow; PHX—Erin Barton and Miguel Morgan; and SL—Moumita Kundu.
- ecosystem services
- functional traits
- phylogenetic diversity
- urban ecology