Submitted to: Insect Conservation and Diversity
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/28/2011
Publication Date: 2/16/2012
Citation: Neame, L.A., Griswold, T.L., Elle, E. 2012. Pollinator guilds respond differently to urban habitat fragmentation in a oak-savannah ecosystem. Insect Conservation and Diversity. DOI: 10.1111/j/.1752-4598.2012.00187x. Interpretive Summary: Pollinators provide a vital service in natural and agricultural environments in maintaining plant reproduction and productivity. With increasing habitat modification and fragmentation there comes concern that these changes may jeopardize those vital services. Yet there is little knowledge of how pollinators respond to environmental changes, and in particular, to habitat fragmentation. A study of pollinators was undertaken in a highly-fragmented oak-savannah habitat where habitat fragments ranging from 0.3 to 31 ha were sampled for their pollinators. Surprisingly, the number of species in large fragments was not generally greater than in small fragments. Groups of pollinators with different life-styles responded differently to fragment size and landscapes surrounding these fragments. Ground-nesting bees were more diverse and relatively more abundant when fragments were large and the density of roads surrounding the fragment was low. In contrast, for cavity-nesting bees there was no difference in diversity or relative abundance between small and large fragments. This study, along with similar ones in different habitats can help in making land use decisions that will conserve pollinators and preserve the pollination services they provide.
Technical Abstract: Habitat fragmentation is widely thought to threaten biodiversity. However, response of pollinators to habitat fragmentation is still poorly understood, as pollinator communities are notoriously spatially variable. We investigated pollinator community structure in a highly fragmented oak-savannah ecosystem in south-western British Columbia, Canada. We sampled pollinators in 19 oak-savannah fragments ranging in size from 0.3 ha to 31 ha, and surrounded by a variety of land-use types, including forest, low density suburban and urban neighbourhoods. Pan-trapping and netting surveys captured 4464 bees, flies, and wasps in 140 species and 48 genera. Contrary to predictions that species richness should increase with increasing area, species richness of fragments was not predicted by the size of the fragment. However, guild community composition did respond to fragment characteristics. Ground-nesting species were both more diverse and relatively more abundant in large fragments with lower road density in the surrounding area, but cavity-nesting species showed no response to fragment characteristics. In contrast, syrphid flies decreased in diversity and proportional abundance in larger fragments but were positively influenced by increases in floral resources. Finally, the response of brood cleptoparasites was more complex: cleptoparasite proportional abundance increased in fragments with high road density, but the availability of hosts such as ground-nesters also influenced their diversity and abundance. These responses may reflect nesting requirements; cavity-nesters may find nest sites in fences, gardens, and houses surrounding habitat fragments, but urban land use may be less hospitable for ground-nesting bees. Brood cleptoparasites may be the most sensitive to fragmentation because they are the highest trophic level in this pollinator community. Clarification of the relative importance of site and landscape factors can inform conservation measures for pollinators and pollination services.