The bee fauna associated with Pacific Northwest (USA) native plants for gardens

Abstract

Growing public awareness of pollinator declines has led to an increase in gardening for pollinators, particularly bees. In most regions of the United States a better understanding of the plants that support abundant and species rich bee communities will help urban pollinator conservation programs. To address this, we compared the relative attractiveness of 23 native Pacific Northwest plant species to bees. We performed timed bee counts and vacuum-sampled bee communities, weekly, when plots were in peak bloom. Across three field seasons, we found that Douglas' aster (Symphyotrichum subspicatum), California poppy (Eschscholzia californica), varileaf phacelia (Phacelia heterophylla), Canada goldenrod (Solidago canadensis), farewell-to-spring (Clarkia amoena), globe gilia (Gilia capitata), and Oregon sunshine (Eriophyllum lanatum) consistently harbored high bee abundance and species richness, and show great potential for garden pollinator plantings. These findings can be applied to residential and community gardens, municipal parks and other plantings, as well as by restoration professionals and policy makers interested in creating and supporting pollinator habitat.

Native Bee Habitat Restoration- Key Ecological Considerations from Recent Literature

“…Bee habitat restoration in urban settings can be undertaken in backyards, parks, and public or commercial open spaces. While often overlooked, 25-30% of urban land consists of private yards which can yield resources for native pollinators (Tallamy, 2020;Anderson et al, 2022). Multiple studies have found that urban environments can provide habitat for many bee species (Frankie et al, 2009;Hall et al, 2017;Rahimi et al, 2022).…”

“…Multiple studies have found that urban environments can provide habitat for many bee species (Frankie et al, 2009;Hall et al, 2017;Rahimi et al, 2022). In particular, small urban gardens can maintain floral resources better than larger restoration projects because gardens can focus solely on pollinators compared to larger restoration projects with multiple objectives (Anderson et al, 2022;Prendergast et al, 2022;Rahimi et al, 2022). Thus, even on a small scale, restoration efforts can support pollinator communities.…”

Assessing five decades of garden bee studies

“…Many of the specialist bees found in urban gardens, such as bees from the family Andrenidae and bees from the genus Melissodes, also specialize on plants in the Asteraceae (Cameron et al, 1996;Michez et al, 2008). In a study of bee associations with native plants, Douglas' aster (Symphyotrichum subspicatum) was observed to support 19 different bee species, and estimated to support up to 74 bee species (Anderson et al, 2022). Though many bees specialize on Asteraceae, host plant specialization is not limited to this one botanical family (Larkin et al, 2008), suggesting that a broad representation of plant families in a garden may be best suited to supporting oligolectic species.…”

“…Gardens also offer opportunities to engage the general public in bee conservation efforts via science-based planting and management practices (Anderson et al, 2022), unlike vacant lots and other minimally managed urban greenspaces. The management of urban gardens, though, can also vary widely, both within and between individual gardens, including those gardens with vigorous maintenance and frequent mowing (Ayers and Rehan, 2021) and those that use more natural landscaping approaches (McCarthy, 2018).…”

“…Highly bred ornamental plants, with reduced floral rewards of nectar and/or pollen, often dominate garden plant assemblages, which may limit the usefulness of urban gardens for bees (Comba et al, 1999;Corbet et al, 2001;Wenzel et al, 2020). However, gardeners' enthusiasm for bee conservation also has potential to drive plant purchases toward native species (Anderson et al, 2021), which tend to attract more diverse bee assemblages (Williams et al, 2011;Morandin and Kremen, 2013;Pardee and Philpott, 2014;Salisbury et al, 2015;Anderson et al, 2022). Although we have a general sense of the types of management practices that enhance or exclude bee taxa in gardens, we also have an opportunity to look at the types of bees that are relatively abundant or sparse in garden systems.…”