Abstract
Urban landscapes include a mix of biotic and anthropogenic elements that can interact with and influence species occurrence and behaviour. In order to outline the drivers of bee (Hymenoptera: Apoidea) occurrence in tropical urban landscapes, foraging patterns and community characteristics were examined at a common and broadly attractive food resource, Tecoma stans (Bignoniaceae). Bee visitation was monitored at 120 individual resources in three cities from June 2007 to March 2009. Resource characteristics, spatial distribution, and other local and regional landscape variables were assessed and then used to develop descriptive regression models of forager visitation. The results indicated that increased bee abundance and taxon richness consistently correlated with increased floral abundance. Resource distribution was also influential, with more spatially aggregated resources receiving more foragers. Individual bee guilds had differential responses to the variables tested, but the significant impact of increased floral abundance was generally conserved. Smaller bodied bee species responded to floral abundance, resource structure, and proximity to natural habitats, suggesting that size-related dispersal abilities structure occurrence patterns in this guild. Larger bees favoured spatially aggregated resources in addition to increased floral abundance, suggesting an optimization of foraging energetics. The impact of the urban matrix was minimal and was only seen in generalist feeders (African honey bees). The strongly resource-driven foraging dynamics described in this study can be used to inform conservation and management practices in urban landscapes. download Appendix
Highlights
Bees (Hymenoptera: Apoidea) and other pollinators are facing global survival challenges that are attributed in part to local anthropogenic change (NRC 2007)
The importance of characteristically anthropogenic variables was minimal, indicating that bees were generally not influenced by the urban matrix
Similar trends highlighting the greater importance of floral resources are emerging from studies conducted elsewhere (Colla et al 2009; Werrell et al 2009; Matteson & Langellotto 2010), further supporting the idea that the constructed elements of the urban landscape generally do not interfere with the occurrence and foraging of bees
Summary
Bees (Hymenoptera: Apoidea) and other pollinators are facing global survival challenges that are attributed in part to local anthropogenic change (NRC 2007). In the form of agricultural and urban development, has been shown to diminish the nesting and foraging habitats of native bees, resulting in decreases in abundance and changes in pollinator function (Kremen et al 2002; Buchmann & Ascher 2005). Changes in bee community composition that correspond to local fragmentation have already been recorded (Frankie et al 1997) and are evident at the edge of urban development (Frankie et al 2009a). Recent studies focusing on urban bees have documented species occurrences (Owen 1991; Frankie et al 2002), examined community composition with respect to general Investigating how bees respond to urbanization is imperative given the everincreasing rate of landscape conversion and their importance as pollinators to nearly 90% of tropical floral species (Ollerton et al 2011) and over 30% of the crops that make up the human diet (Buchmann & Nabhan 1996).
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