Intraspecific Variation in Worker Body Size Makes North American Bumble Bees (<i>Bombus</i>spp.) Less Susceptible to Decline

Austin, Matthew W.; Dunlap, Aimee S.

doi:10.1086/704280

Cited by 23 publications

(16 citation statements)

References 85 publications

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“…A decrease in body size variation in workers could enhance the recruitment inside the nest to tasks such as fanning or could be a result of a trade‐off of resource distribution between the number and the size variation of colony individuals. These results are in agreement with Austin and Dunlap (2019), where they find that variation in body size is a key feature to resist the impact of altered environments and important for the maintenance of bumblebee populations.…”

Section: Discussionsupporting

confidence: 92%

Interactions among global change pressures act in a non‐additive way on bumblebee individuals and colonies

et al. 2020

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Insect‐mediated pollination is fundamental for terrestrial ecosystems as well as for crop production. However, bee populations are declining as a consequence of different global change pressures. Even though these pressures do not act in isolation, their interactive effects have received less attention. Through a cross‐treatment field experiment with Bombus terrestris colonies, we analysed the joint effect of climate warming, exposure to pesticides and landscape transformation on bumblebee development variables related to individual and colony fitness. Our results show that an average increase of 1.62°C in the presence of high resource availability in the landscape increases the number of individuals of all colony castes. However, temperature increase is only favourable when foraging resources are not limiting. This is partly because under elevated temperatures, colonies can develop faster but also need to invest more in wax and silk material to protect the offspring and to cool the colony. We also found a decrease in the number of male production with exposure to pesticides. At the individual level, colonies exposed to increased temperatures produced larger queens and workers, and at the same time, all castes presented less variability in body size. In addition, we observed a reduction in queen size with increasing resource availability. Our experiment indicates that the interaction between global change pressures can be non‐additive and that colony‐level emergent properties of social species could buffer some of the individual impacts of these pressures. Hence, it is necessary to consider not only the joint effects of global change pressures but also the plasticity of the organisms' responses. This would help us to predict how populations will respond to these stressors in a complex real world and how species life‐history traits could modulate their adverse effects through complex phenotypic plastic responses. A free Plain Language Summary can be found within the Supporting Information of this article.

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Section: Discussionsupporting

confidence: 92%

Interactions among global change pressures act in a non‐additive way on bumblebee individuals and colonies

et al. 2020

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“…The continual supply of floral resources is generally thought to be important for developing social bee colonies (Kaluza et al, 2018; Roulston & Goodell, 2011; Vieli et al, 2016). Mounting evidence, however, suggests that some species may be better suited for periods of resource dearth (Austin & Dunlap, 2019; Hemberger et al, 2020; Schmid‐Hempel & Schmid‐Hempel, 1998). We found that free‐foraging colonies of B. impatiens in agricultural landscapes with adjacent Phacelia plantings grew at a greater rate and gained more mass overall than colonies in reference landscapes that were not enhanced with Phacelia flowers.…”

Section: Discussionmentioning

confidence: 99%

Floral resource continuity boosts bumble bee colony performance relative to variable floral resources

Hemberger

Witynski

Gratton

2022

Ecological Entomology

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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.

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“…Anthropogenic changes in climate and land-use patterns may lead to resource scarcity and increased competition, decreasing bee size within and between species. Historical exploration of Bombus specimens has revealed a reduction in body size within species (Austin and Dunlap 2019), and landscape simplification has led to smaller bees (Persson and Smith 2011). Change in body size may also have consequences for disease transmission; pathogen intensity may increase if hosts are smaller and more susceptible, but prevalence may decrease if transmission is reduced.…”

Section: )mentioning

confidence: 99%

Big bees spread disease: body size mediates transmission of a bumble bee pathogen

Wyk

Amponsah

et al. 2021

Ecology

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Trait variation can have important consequences for the outcomes of species interactions. Even though some traits vary as much within species as across related species, models and empirical studies typically do not consider the role of intraspecific trait variation for processes such as disease transmission. For example, many pollinator species are in decline because of a variety of stressors including pathogens, but the role of intraspecific trait variation in mediating disease dynamics is rarely considered. For example, pollinator body size could affect pathogen transmission via differences in resistance, foraging behavior and physiology. We tested effects of body size on pollinator pathogen transmission using the common eastern bumble bee Bombus impatiens in field tents, introducing an infected "donor" microcolony of large or small workers with an uninfected average-sized "recipient" microcolony and allowing bees to forage for 9-16 d. Small donor bees had nearly 50% higher infection intensity (cells/ 0.02 μL) than large donor bees, but large donor bees were twice as likely to transmit Crithidia bombi to recipient bees. Both behavioral and physiological mechanisms may underlie this apparent paradox. Compared to small bees, large bees foraged more and produced more feces; simulations showed that foraging and defecation rates together had stronger effects on transmission than did donor infection intensity. Thus, effects of bee size on contact rates and pathogen supply may play significant roles in disease transmission, demonstrating the multifaceted impacts of traits on transmission dynamics.

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Intraspecific Variation in Worker Body Size Makes North American Bumble Bees (Bombusspp.) Less Susceptible to Decline

Cited by 23 publications

References 85 publications

Interactions among global change pressures act in a non‐additive way on bumblebee individuals and colonies

Interactions among global change pressures act in a non‐additive way on bumblebee individuals and colonies

Floral resource continuity boosts bumble bee colony performance relative to variable floral resources

Big bees spread disease: body size mediates transmission of a bumble bee pathogen

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