Early spring floral foraging resources for pollinators in wet heathlands in Belgium

Abstract

In temperate regions, foraging resources for pollinating insects are particularly important in early spring, especially for social insects like bumblebees that are initiating colonies. Heathlands, protected open habitats under EU law, provide floral resources (pollen and nectar) for a range of pollinating insects. In early spring, in Belgian heathlands, only two floral resources are available: willows Salix spp. (Salicaceae) and bilberry Vaccinium myrtillus (Ericaceae). Our objective was to assess whether these two plant species provide quantitative and qualitative resources during early spring. We examined the springtime activity of flower visitors on both S. x multinervis and V. myrtillus flowers in relation to sugar concentration and composition in nectar as well as composition of polypeptides and amino acids in pollen. The chemical composition of pollen differed significantly between the two plant species. Salix x multinervis offered pollen with higher polypeptide and essential amino acid contents than V. myrtillus. However, nectar quantities of V. myrtillus flowers were relatively high compared to S. x multinervis. During the overlapping flowering period of the two plant species, flower visitors seemed to favor high quality and easily accessible pollen of S. x multinervis species and visited V. myrtillus mainly for nectar resources.

Nectar foragers contribute to the pollination of buzz‐pollinated plant species

“…For V. myrtillus , nectar foragers were less effective than pollen foragers but were considerably more abundant and contributed more significantly to pollination than did pollen foragers. The abundant nectar added to the attractiveness of this plant species, increasing pollination success when pollen visitors were scarce or when the pollen was not very attractive (Moquet et al, 2015).…”

“…Observations were performed on each target plant species in at least six of the 10 study sites, depending on the availability of flowering plant individuals. Observations were done using a standardized method, on quadrats of 10 m 2 (for C. vulgaris , quadrats were limited to 1 m 2 because of its high floral density) for 20 min and were repeated every hour between 0900 and 1820 hours (Mayer et al, 2011; Descamps et al, 2015; Moquet et al, 2015). Observation sessions were separated by 40 min.…”

How shrub encroachment under climate change could threaten pollination services for alpine wildflowers: A case study using the alpine skypilot, Polemonium viscosum

“…Proximity to willows had a negligible impact on contamination (distance F = 0.1355, df = 1, p = .71 regardless of site (for site by distance interaction, F = 1.3344, df = 3, p = .2668). for early-season pollinators (Moquet et al, 2015), they attract a variety of insect pollinators including queens of the bumble bee species…”

“…Because willows are important early-season flower resources for pollinators (Formica et al, 2014;Moquet, Mayer, Michez, Wathelet, & Jacquemart, 2015) altitudinal migration of males may also negatively affect pollination regimes of resident alpine wildflower species. At high altitudes and latitudes, Salix acts as a magnet species, drawing pollinators away from the more diminutive floral displays of tundra plants (Lara-Romero et al, 2016;Mosquin & Martin, 1967).…”

Plugging the hunger gap: Organic farming supports more abundant nutritional resources for bees at critical periods

“…For example, spring is often referred to as the pollinator ‘hungry gap’ on farmland (Nowakowski & Pywell 2016), where floral resources can be scarce. Yet, this is a critical time, with adequate floral resources in this period being essential for emerging bees (Moquet et al 2015) and initial colony growth (Williams et al 2012). However, any differences between these early months and later summer months may be lost when analysed together, or inadequately compensated for with general pollinator management schemes.…”