Pollen metabarcoding reveals broad and species-specific resource use by urban bees

Abstract

Bee populations are currently undergoing severe global declines driven by the interactive effects of a number of factors. Ongoing urbanisation has the potential to exacerbate bee declines, unless steps are taken to ensure appropriate floral resources are available. Sown wildflower strips are one way in which floral resources can be provided to urban bees. However, the use of these strips by pollinators in urban environments remains little studied. Here, we employ pollen metabarcoding of the rbcL gene to compare the foraging patterns of different bee species observed using urban sown wildflower strips in July 2016, with a goal of identifying which plant species are most important for bees. We also demonstrate the use of a non-destructive method of pollen collection. Bees were found to forage on a wide variety of plant genera and families, including a diverse range of plants from outside the wildflower plots, suggesting that foragers visiting sown wildflower strips also utilize other urban habitats. Particular plants within the wildflower strips dominated metabarcoding data, particularly Papaver rhoeas and Phacelia tanacetifolia. Overall, we demonstrate that pollinators observed in sown wildflower strips use certain sown foodplants as part of a larger urban matrix.

A citizen science supported study on seasonal diversity and monoflorality of pollen collected by honey bees in Austria

“…Figure 7 also depicts the large variations in the diversity of pollen samples within one sampling date. These variations most likely come from a different availability of pollen in different ecological habitats 17,19,25,28 , or in spring from decelerated development and late blooming in elevated mountainous sampling locations. As floral availability in the environment affects colony development and health status of bees 39 , the reasons for the geographic variations in pollen diversity and connection to landscape composition in Austria deserve further analysis in a separate article.…”

“…The majority of these investigations determined botanical origin with palynological light microscopy, though also molecular next generation sequencing or multi-locus metabarcoding methods exist 16–18 . According to the addressed research question, previous investigations of the bees’ pollen spectrum were often temporally and spatially limited to certain habitats like agricultural sites 15,19–25 or urban and suburban areas 17,26 . Other studies compared the pollen availability of different landscapes 27–29 .…”

Development of an environmental DNA metabarcoding assay for aquatic vascular plant communities

“…The Consortium for the Barcode of Life (CBOL) recommended a combination of rbcL and matK as the “best” two‐locus barcode for plants, with the caveat that this combination can distinguish only ~70% of species (CBOL 2009). Plant metabarcoding studies have most commonly been conducted on pollen, and these have typically used rbcL (Macgregor et al., 2019; McFrederick & Rehan, 2019; Potter et al., 2019), ITS1 or ITS2 (Suchan, Talavera, Sáez, Ronikier, & Vila, 2019), or a combination of ITS1, ITS2, and rbcL (Gous, Swanevelder, Eardley, & Willows‐Munro, 2019). Other studies have included additional plastid markers such as trnL and trnH (Richardson et al., 2019).…”

Floral hosts of leaf-cutter bees (Megachilidae) in a biodiversity hotspot revealed by pollen DNA metabarcoding of historic specimens

“…The use of next-generation sequencing (NGS) technology and DNA barcoding in highthroughput identification of plant origins from pollen samples has been on the rise in recent years [1][2][3][4][5][6]. There are many advantages to this method over traditional microscopic palynology, including increased time-efficiency, multiplexing samples to reduce costs, and the relative ease of the process that does not require a trained palynologist [7].…”