The conservation value of urban green space habitats for Australian native bee communities

Abstract

Networks of urban green space can provide critical resources for wild bees, however it is unclear which attributes of green spaces provide these resources, or how their management can be improved to benefit a diversity of bee species. We examined bee communities in three dominant urban green space habitats: 1) golf courses, 2) public parks and 3) front gardens and streetscapes in residential neighbourhoods in Melbourne, Australia and assessed which local and landscape attributes influenced bee communities. There was a greater abundance and richness of bee species in public parks compared to golf courses and residential neighbourhoods, where the latter habitat was dominated by European Honeybees (Apis mellifera). The occurrence of A. mellifera was positively associated with increases in flowering and native plants. Ground-nesting Homalictus species occurred more frequently in older golf courses and public parks surrounded by low impervious surface cover, and with a low diversity of flowering plants. Cavity nesting, floral specialists within the Colletidae family occurred more often in green space habitats with greater native vegetation, and occurred infrequently in residential neighbourhoods. The lack of appropriate nesting habitat and dominance of exotic flowering plants in residential neighbourhoods appeared to positively impact upon the generalist A. mellifera, but negatively affected cavity and ground nesting floral specialist bee species (e.g. Halictidae and Colletidae). Our results highlight the need to include urban areas in pollinator conservation initiatives, as providing resources critical to diverse bee communities can assist in maintaining these key pollinators in urban landscapes.

City parks vs. natural areas - is it possible to preserve a natural level of bee richness and abundance in a city park?

“…Many researchers report that natural habitats display greater diversity of pollinators compared to urban areas (McIntyre and Hostetler 2001;Eremeeva and Sushchev 2005;Matteson et al 2008;Ahrné et al 2009). At the same time, data provided by other authors show that cities are important habitats for a considerable number of bee species (Saure 1996;Frankie et al 2005;Banaszak-Cibicka and Żmihorski 2012;Frankie et al 2013;Baldock et al 2015;Cariveau and Winfree 2015;Sirohi et al 2015;Threlfall et al 2015;Hall et al 2017;Normandin et al 2017), and urbanization has a lesser effect on bees than on other insects (Deguines et al 2012). For instance, urban parks in San Francisco, USA, support higher mean abundances of bumblebees (Bombus spp.)…”

Landscape and Local Correlates of Bee Abundance and Species Richness in Urban Gardens

“…Many studies describe A. mellifera to be very common in urban garden studies (e.g., Tommasi et al 2004, Matteson et al 2008), and may thrive in urban green spaces as floral generalists (Threlfall et al 2015). In another types of landscapes, A. mellifera responds strongly to landscape scale changes with increased density in less seminatural habitats, thus showing adaptation to more fragmented habitats and patchy resources (Steffan-Dewenter et al 2002), such as in medium intensity developed areas.…”

Variation in Vegetation Structure and Composition across Urban Green Space Types

“…Previous studies of urban golf courses have highlighted their role in urban biodiversity conservation (Hodgkison et al, 2007;Colding and Folke, 2009;Threlfall et al, 2015). Patches of remnant vegetation (RE) and out-of-play areas of golf courses (GC) were similar in vegetation structure and similarly possessed large trees and standing dead trees.…”

“…In light of the existing research highlighting the importance of vegetation structure as opposed to plant composition for many animal species, this finding suggests that that when green spaces dominated by exotic plants are managed in an appropriate way they may provide important habitat structure for a variety of taxa. However, there will also continue to be situations where strong co-evolution means this isn't the case, such as short-tongued Colletid bees in Australia which are reliant on plants that provide nectar in shallow open cups such as those found within the Myrtaceae plant family (Threlfall et al, 2015). Identifying which species respond to structural habitat characteristics, and which species are sensitive to the identity of the plant species will be an important area for future research to ensure that the habitat requirements of both groups are maintained and enhanced in urban landscapes.…”

“…The fauna biodiversity that residential neighborhoods support is likely to reflect the available habitat resources. As such, residential neighborhoods are likely to support generalist species, rather than species that require specialized habitat attributes such as bare soil, leaf litter, large trees, dead trees, and complex understorey vegetation or those dependent of particular plant species or genera (Threlfall et al, 2015).…”