Remnant Prairies and Organic Gardens Provide Complementary Habitat for Native Bees Within a Midwestern Urban Matrix

Evidence indicates native bees are in decline across North America, with several species rare or absent in parts of their historical range (Grixti et al. 2008, Cameron et al. 2011, Vanbergen 2013). Declines in pollinator diversity can interrupt pollinator links and impact ecosystem services such as fruit and seed production, resulting in reduced agricultural yields and food supply (Winfree et al. 2008, Rogers et al. 2014). With multiple threats to native pollinators, research has increasingly focused on managing pollinator habitats across a range of natural and anthropogenic environments (Reed 1995a, Kremen and M’Gonigle 2015, Tonietto and Larkin 2017, Denning and Foster 2018, Handel 2019). Within this context, urban landscapes can be important for pollinator conservation and even small spaces, when well-managed, can support diverse and unique insect communities (Reed 1995b, McFrederick and LeBuhn 2006, Hernandez et al. 2009, Matteson and Langellotto 2010, Threlfall 2015, Kaluza et al. 2016). Here, we report an assessment of native bee abundance and diversity in habitat remnants and organic gardens embedded in the midwestern metropolitan area of Kansas City, Missouri.

Historically dominated by prairie-oak transition transected by wetlands, rivers, and streams, Kansas City is largely urbanized with a population of over two million. Jackson County, where this study was conducted, covers 1595 km² including the urban core, and is home to approximately 700,307 people. Scattered across the metropolitan area are prairie and woodland remnants connected by occasional public greenways and power line transects, as well as residential areas, parks, and urban gardens. Kansas City Parks and Recreation (KC Parks), the Missouri Department of Conservation (MDC), and the volunteer organization Bridging the Gap/Kansas City Wildlands (KC Wildlands) manage several conservation sites within this matrix. As in much of the United States, native bees have not been well documented in the area. The historical existence of a patchwork of habitats may have set the stage for a unique urban refuge, with native bees potentially pre-adapted to exploit fragmented landscapes. In 2018, we conducted surveys to document the presence and abundance of bee species utilizing remnant prairies and organic gardens. The results of these surveys are reported here. This work represents baseline data for a developing project that will 1) establish long-term monitoring of wild bees in the Greater Kansas City Metropolitan Area, 2) investigate the ecology and natural history of species of interest, and 3) identify practices to better support wild bees in managed habitats.

Because prairie remnants are likely to have abundant food and nesting resources (Kearns and Oliveras 2009, Denning and Foster 2018), we predicted greater abundance and diversity of wild bees in remnant prairies compared to urban gardens. Previous studies have also shown that different urban habitats can favor different guilds of bees (McFrederick and LeBuhn 2006, Hernandez et al. 2009, Kearns and Oliveras 2009, Matteson and Langellotto 2010, Lowenstein et al. 2015, Threlfall et al. 2015). For example, ground nesters and floral specialists are thought to do better in open areas while cavity nesters may persist in built environments that have sufficient floral resources (Hernandez et al. 2009). We therefore expected different guilds to be represented in remnant prairies compared to urban gardens with a handful of generalist bee species exploiting both habitats.

We conducted field work for the survey from April to September of 2018. Remnant prairie sites were in south Kansas City at Jerry Smith Park, which encompasses approximately 145 hectares (h) including a 1.2 h pond. Of this, about 16 h are managed tall grass prairie divided into two sectors, Jerry Smith East (JSE) and Jerry Smith West (JSW). The sectors are not contiguous but separated by approximately 1.3 km of woodland corridor, a pond, and meadows within the park. Both JSE and JSW are categorized as remnant prairie, although they have distinct management histories. JSE appears to have experienced little woody encroachment prior to the park’s establishment in 1975 and is managed through regular prescribed burns and occasional removal of woody plants. JSW was recently restored to grassland as a...