The effects of natural and anthropogenic habitats on pollinator communities in oak-savannah fragments on Vancouver Island, British Columbia

Fragmentation of natural habitat can lead to loss of species but landscapes surrounding habitat fragments may provide resources and so promote species diversity. I examined the role of the surrounding landscape – Douglas-fir forest and urban residential areas – on pollinator communities in oak-savannah fragments. Bees in fragments surrounded by forest were larger, and body size increased with increased availability of early-blooming, native flowering plants. Small-bodied, mid to late-season bees were more abundant in fragments surrounded by urban landscapes. We propose these late-season generalist pollinators were supported by floral resources in the gardens of urban habitats. In contrast, early-flying species were unique to oak-savannah fragments and some bumble bees may rely on nesting resources found only in forested landscapes. Although urban residential lawns and gardens supported a high richness and abundance of pollinator species, conservation of these oak savannah- and forest-associated species will depend on maintaining and restoring oak-savannah habitats.