Plant–pollinator networks in grassland working landscapes reveal seasonal shifts in network structure and composition

Abstract

Declines in native bee populations can limit pollination services that support native plant communities and global food production. Mitigating the impacts on pollinators and ecosystems requires conservation actions that promote biodiversity and remain practical for producers. We investigated plantpollinator interaction networks in working grassland landscapes, managed for cattle production and biodiversity, to advance conservation of pollinators in grazed systems. We compared and plotted interactions at the network level. We then used a regression framework to evaluate the influence of floristic availability on pollinator abundance in our system. Overall, we detected seasonal shifts at the network level, with increased specialization between flowers and bees occurring at the end of the sampling season. Furthermore, the response to floristic resources differed between honey bees (Apis mellifera) and native bees. While honey bee abundance increased with exotic floral abundance, native bee abundance showed no relationship with floral abundance and instead was positively associated with floral richness in our system. These findings could be an indication of seasonal shifts in bee activity and interactions with plants or a response to the subset of available resources in grazed systems. These interpretations, along with the detected difference in resource use between honey bees and native bees, suggest foraging preferences differ between these two groups and could influence conservation and management strategies. Furthermore, it demonstrates a need to consider how management practices could influence bee communities differentially across the growing season and suggests conservation actions should promote native floristic resources to benefit native bees.

Weed management for landscape scale restoration of global temperate grasslands

“…These biomes are naturally species‐rich (Faber‐Langendoen, Shicheng, Yang, & Meijiao, 2018), providing habitat for many plants, animals and soil biota. In addition, these grasslands offer valuable ecosystem services such as high‐quality forage for herbivores (Boval & Dixon, 2012), habitat for pollinators for crops and native species (Bendel, Kral‐O'Brien, Hovick, Limb, & Harmon, 2019), significant levels of carbon sequestration (Eze, Palmer, & Chapman, 2018), and places for many recreational and cultural activities (Gomez‐Limon & de Lucio, 1995). They also afford many other environment stabilising services, such as soil erosion control and mitigation of flood waters (Sankaran & Anderson, 2009).…”

Do the Quality and Quantity of Honey Bee-Collected Pollen Vary Across an Agricultural Land-Use Gradient?

“…This agricultural intensification in the NGP is particularly problematic for bees, as the NGP supports ca. 38-40% of honey-producing colonies in the United States (Otto et al 2016) and recent research has documented substantial native bee diversity across the region (e.g., Evans et al 2018, Brendel et al 2019, Vickruck et al 2019. Despite this importance of the NGP to managed and native bees, research suggests loss of grasslands to agriculture in this region is negatively impacting both groups of pollinators (Smart et al 2016a(Smart et al ,b, 2018bKoh et al 2016;Otto et al 2016).…”

Molecular sequencing and morphological identification reveal similar patterns in native bee communities across public and private grasslands of eastern North Dakota

“…Prior to European settlement, the Prairie Pothole Region was a mosaic of depressional wetlands with tall-grass prairie in the east to short-grass prairie in the west [16]. While limited research on native bee communities exists in this region, recent work suggests remnant patches of grasslands provide valuable habitat for native bees [17][18][19]. The Prairie Pothole Region is likely the most important region in the country for supporting managed honey bees [20].…”