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A rapidly warming climate is driving changes in biodiversity worldwide, and its impact on insect communities is critical given their outsized role in ecosystem function and services. We use a long‐term dataset of North American bumble bee species occurrences to determine whether the community temperature index (CTI), a measure of the balance of warm‐ and cool‐adapted species in a community, has increased given warming temperatures. CTI has increased by an average of 0.99°C in strong association with warming maximum summer temperatures over the last 30 years with the areas exhibiting the largest increases including mid‐ to high latitudes as well as low and high elevations—areas relatively shielded from other intensive global changes. CTI shifts have been driven by the decline of cold‐adapted species and increases in warm‐adapted species within bumble bee communities. Our results show the pervasive impacts and ecological implications warming temperatures pose to insects. [ABSTRACT FROM AUTHOR]

Agricultural practices and intensification during the past two centuries have dramatically altered the abundance and temporal continuity of floral resources that support pollinating insects such as bumble bees. Long‐term trends among bumble bees within agricultural regions suggest that intensive agricultural conditions have created inhospitable conditions for some species, while other species have maintained their relative abundances despite landscape‐level changes in flower availability. Bumble bee responses to spatiotemporal resource heterogeneity have been explored at the colony and behavioral level, but we have yet to understand whether these conditions drive community structure and ultimately explain the diverging patterns in long‐term species trends. To explore the relationship between landscape‐level floral resource continuity and the likelihood of bumble bee occurrence, we mapped the relative spatial and temporal availability of floral resources within an intensive agricultural region in the US Upper Midwest and related this resource availability with bumble bee species relative abundance. Across the bee community, we found that relative bumble bee occurrence increases in landscapes containing more abundant and more temporally continuous floral resources. Declining species, such as Bombus terricola, exhibited the strongest, positive responses to resource abundance and continuity whereas common, stable species, such as Bombus impatiens, showed no statistical relationship to either. Together with existing experimental evidence, this work suggests that efforts to increase spatiotemporal flower availability, along with overall flower abundance at landscape scales may have positive effects on bumble bee communities in the US Upper Midwest. [ABSTRACT FROM AUTHOR]

Centuries of landscape changes associated with agriculture have dramatically reduced the amount and increased the temporal variability of the floral resources that support key pollinating insects such as bumble bees. Adapting to these novel resource conditions is important to ensure the persistence of bumble bee species. While several species appear to be in decline in modern agricultural landscapes, others have thrived, suggesting adaptation to exploit highly variable floral resources. Bombus impatiens, the common eastern bumble bee, is a prime example of such a species.We designed an experiment to compare how free‐foraging colonies of B. impatiens performed adjacent to areas with either temporally continuous or variable (pulsed) patches of purple tansy (Phacelia tanacetifolia) plantings.We found that colonies in Phacelia landscapes grew faster, had gained more mass, and produced more gynes than did colonies in reference landscapes with no Phacelia.Comparing colony responses between pulsed and continuous flowering resources showed that total mass gain at the end of the experiment was greater with continuous flowering resources. In contrast, colony growth rate and total gyne production were comparable for colonies adjacent to Phacelia plantings that were continuous versus pulsed.While low in statistical replication, given the scale of the experimental manipulation, our experiment shows that although B. impatiens colonies can exploit periods of resource discontinuity and gain mass, these continuously available floral resources appear important for colony growth and benefit gyne production. [ABSTRACT FROM AUTHOR]

1. Resource pulses, narrow periods of high resource availability, can elicit strong behavioural responses across diverse taxa. Mass‐flowering agricultural crops are an example of a resource pulse that insect pollinators exploit. However, the underlying mechanism behind changes in pollinator behaviour associated with mass‐flowering crops is still relatively unexplored. 2. The present study quantified the behavioural response of bumble bees, an important wild pollinator, to commercial cranberry bloom, an important mass‐flowering crop in Wisconsin, U.S.A. Over a 2‐year period, foraging trip duration was measured using radio frequency identification at 14 farms situated across landscape contexts, ranging from high to low natural area (woodland amount). Using transect surveys, floral resource abundance at a landscape scale was estimated. 3. It was found that bumble bees were highly sensitive to temporal changes in landscape‐level resource abundance associated with the onset of cranberry bloom, during which they decreased foraging trip duration by 22% and increased the number of foraging trips during bloom by 24% on average relative to the period before and after bloom. This phenomenon was consistent across colonies, individual bees, and landscape contexts, despite a higher abundance of flowers in low woodland landscapes. Bumble bee colonies growing in low‐ and high‐woodland landscapes exhibited a similar performance. 4. As mass‐flowering crops are probably a factor influencing bumble bee foraging behaviour in agricultural regions, investigations should continue into how variable resource landscapes, particularly those offering resource pulses, affect wild pollinators and the pollination services they provide. [ABSTRACT FROM AUTHOR]