Bumble bee colony growth and reproduction depend on local flower dominance and natural habitat area in the surrounding landscape

Abstract

Conservation measures for bees often focus on increasing the diversity and abundance of floral resources. But it has not been clear if observed benefits of floral enhancements result from greater population growth, which is critical for the long-term success of conservation, or from mobile foragers aggregating in high-resource locations. Experimental evidence is only beginning to emerge in favor of the former mechanism and it is not well-established how different aspects of floral resources affect population growth. For example, bumble bee colonies may benefit from greater overall floral abundance, richness, or relative dominance of resource species. Because bumble bees are highly mobile, resource variability in the surrounding landscape is also important for colonies and may mediate local-scale effects. We experimentally assessed the growth and reproduction of bumble bee colonies (Bombus impatiens) deployed in grasslands in different local-and landscape-scale resource environments. We found that floral dominance, rather than the overall abundance or richness of floral resources, was the most important local factor for colony growth and reproduction. This may reflect more efficient foraging on a few numerically dominant and abundant resource species. Local-and landscape-scale predictor variables had interacting effects on colony growth and reproduction, suggesting that foraging distance depends on where in the landscape efficiently used resources are located. Our results provide further evidence that conservation strategies aimed at enhancing floral resources can increase bumble bee population growth. However, the most effective form of floral enhancement may vary among bee species.

Grassland harvesting alters ant community trophic structure: An isotopic study in tallgrass prairies

“…Furthermore, understanding how disturbance affects both the consumer and resource isotopic signatures can offer insight into the mechanisms by which disturbances affect communities and important ecological functions including seed dispersal and predation, aphid tending, top-down control of insect herbivores, and decomposition and nutrient cycling (Agosti, Majer, Alonso, & Schultz, 2000;Blomqvist, Olff, Blaauw, Bongers, & Putten, 2000;Culver & Beattie, 1980;Dostál, 2005). In our previous work in tallgrass prairies, we document changes in both plant and ant diversity following biomass removal (Kim, Bartel, Wills, Landis, & Gratton, 2018;Kim et al, 2017;Spiesman, Bennett, Isaacs, & Gratton, 2017), in part to due to greater openness and changes in the competitive interactions of ants following the disturbance (Andersen, 2019). These changes in habitat structure and resource availability could also affect the feeding behavior of ants within these grasslands (Kaspari, Donoso, Lucas, Zumbusch, & Kay, 2012).…”

“…We focus on ants as consumer species because they have diverse diets including plant-derived material such as seeds, nectar, and honeydew from sucking insects, and animal-derived materials including herbivores, predators, and microarthropods such as collembola and springtails. In our previous work in tallgrass prairies, we document changes in both plant and ant diversity following biomass removal (Kim, Bartel, Wills, Landis, & Gratton, 2018;Kim et al, 2017;Spiesman, Bennett, Isaacs, & Gratton, 2017), in part to due to greater openness and changes in the competitive interactions of ants following the disturbance (Andersen, 2019). While there are a few studies that have tested whether disturbance affects trophic structure of ants (e.g., Penick, Savage, & Dunn, 2015;Resasco et al, 2012;Woodcock et al, 2013), these studies did not control for site-level differences in isotopic signatures of baseline resources (i.e., plants) which could also vary with disturbance.…”

Floral resource pulse decreases bumble bee foraging trip duration in central Wisconsin agroecosystem

“…We hypothesise that this response is due to the presence of similar quantities of alternate floral resources across these landscape with highly different land cover types. Indeed, other studies have also found that woodland cover does not necessarily translate to increased resource abundance (Winfree et al, 2007;Mallinger et al, 2015;Spiesman et al, 2017). Additionally, the quality of resources in the surrounding landscape may have been no different from cranberry, making foraging outside of cranberry during crop bloom uneconomical.…”

Disturbance differentially affects alpha and beta diversity of ants in tallgrass prairies

“…Data from this study were a part of a larger study examining the effects of biomass harvest on arthropod communities and arthropod-derived ecosystem services (see Kim et al 2017, Spiesman et al 2017. Data from this study were a part of a larger study examining the effects of biomass harvest on arthropod communities and arthropod-derived ecosystem services (see Kim et al 2017, Spiesman et al 2017.…”

“…This study took place in tallgrass prairies in Wisconsin in 2013-2015 in 20 sites. Data from this study were a part of a larger study examining the effects of biomass harvest on arthropod communities and arthropod-derived ecosystem services (see Kim et al 2017, Spiesman et al 2017. Sites were managed by the US Fish and Wildlife Service (N = 13) and Wisconsin Department of Natural Resources (N = 7) and were at least 2 km away from one another.…”