Flowering phenology and nesting resources influence pollinator community composition in a fragmented ecosystem

Abstract

Introduction Habitat loss is the leading cause of extinctions on the planet. However, negative effects of habitat loss and fragmentation on biodiversity can be reduced if resources in urban or semi-natural areas in the surrounding matrix can be used by wildlife. Methods We investigated the influence of floral and nesting resources in urban-and forest-associated oaksavannah fragments, surrounding urban and forest matrix, and urban areas spatially independent from oak-savannah habitat on pollinator community composition in a fragmented oak-savannah ecosystem. Results Both independent urban and urban matrix sites supported high abundance and richness of plants and pollinators relative to other fragment categories, especially towards the end of the season when plants and pollinators in oak-savannah fragments were scarce. A species of particular conservation concern in our region, Bombus occidentalis, was supported by late-flowering resources in our urban sites. Forestassociated oak-savannah fragments were missing lateseason species while urban-associated fragments supported high abundance and richness of mid-to lateseason pollinators, likely due to supplemental use of floral resources in the urban matrix. Female cavitynesting and ground-nesting bees were not restricted by the availability of natural nesting resources we expected them to require (e.g. small cavities, bare soil). Conclusion These results provide important information on native pollinators in a highly fragmented habitat, and suggest that we should consider matrix quality in conservation planning.

Landscape impacts on pollinator communities in temperate systems: evidence and knowledge gaps

“…Pollinators may also be nest‐site limited in cities (Threlfall et al . ; but see Wray & Elle ) and ‘bee hotels’ and bumblebee nest boxes are widely promoted solutions despite a lack of evidence from urban studies regarding their effectiveness in supporting cavity nesting bees (MacIvor & Packer ) or bumblebees (Gaston et al . ).…”

Local landscapes and microhabitat characteristics are important determinants of urban–suburban forest bee communities

“…, Rhoades et al. ) as well as available nesting substrates and materials (Wray and Elle ), while overall abundance has shown positive correlations with habitat size, connectivity, and composition of the local landscape (Brosi et al. , Proesmans et al.…”

“…The structure of local bee communities is also spatially dependent upon local floral resources (Wray et al 2014, Rhoades et al 2018 as well as available nesting substrates and materials (Wray and Elle 2015), while overall abundance has shown positive correlations with habitat size, connectivity, and composition of the local landscape (Brosi et al 2008, Proesmans et al 2019. Population density similarly increases with connectivity across the landscape (Steffan-Dewenter 2003), depending on the suitability of the forest patches to host bee taxa.…”

Protecting an Ecosystem Service

“…For an insect pollinator, the 887 primary habitat requirements are likely to be: i) floral and other nutritional resources, ii) nest 888 (breeding) sites, and iii) levels of protection (Figure 8; Fortel et al, 2014;Williams and 889 Kremen, 2007;Wray and Elle, 2015). The floral preferences of a large diversity of insect 890 pollinators have been well studied (see section 4.6; Willmer, 2011), and significant advances 891 have been made in understanding how to attract species or communities to engineered or 892 enhanced floral rich habitats (although other predatory or parasitic insects require other 893 available organisms to survive).…”

“…Given the recent policy interest in pollinator 1177 conservation (see section 3), practitioners require information and advice on how to manage 1178 public and private urban land to benefit pollinators. This is challenging, because perhaps 1179 more than any other habitat type, urban areas represent a matrix of different land use types 1180 (Wray and Elle, 2015), from car parks to allotments. Larger areas with more pollinator 1181 friendly habitat, such as nature reserves, parks, allotments and gardens, are connected by 1182 strips of potentially pollinator friendly habitat including roadside verges, hedgerows, river 1183 banks and canal towpaths, railway cuttings and embankments (Figure 11).…”