Social competition but not subfertility leads to a division of labour in the facultatively social sweat bee Megalopta genalis (Hymenoptera: Halictidae)

Smith, Adam R.; Kapheim, Karen M.; O’Donnell, Sean; Wcislo, William T.

doi:10.1016/j.anbehav.2009.06.032

Cited by 54 publications

(68 citation statements)

References 43 publications

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“…Social nests were filmed with a camcorder under infrared light during the approximately 2 h a day (1 h each before sunrise and after sunset, respectively) when bees forage (Wcislo et al 2004;Kelber et al 2006). These recordings allowed us to determine which bees were queens and workers (Smith et al 2008(Smith et al , 2009). Solitary and social nesting are distinct behavioural strategies, rather than different points on the same developmental trajectory (Smith et al 2007(Smith et al , 2009).…”

Section: Methodsmentioning

confidence: 99%

“…These recordings allowed us to determine which bees were queens and workers (Smith et al 2008(Smith et al , 2009). Solitary and social nesting are distinct behavioural strategies, rather than different points on the same developmental trajectory (Smith et al 2007(Smith et al , 2009). To distinguish solitary reproductives from social queens waiting for offspring to emerge, we monitored single-bee nests for at least five weeks (the time needed for offspring to complete development) after they were modified.…”

Section: Methodsmentioning

confidence: 99%

“…We photographed the ovaries dorsally at 20Â magnification through a dissecting microscope with a digital camera at 2272 Â 1720 pixels resolution. As a metric of ovary size, we calculated total ovary area from the digital photographs using Adobe PHOTOSHOP 6.0, calibrated with similarly produced digital photographs of a stage micrometer as described in Smith et al (2008Smith et al ( , 2009. We report the mean of the left and right ovary areas as 'ovary size'.…”

Section: Methodsmentioning

confidence: 99%

“…Two of the social nests contained a third young female that did not forage. These females may have been future reproductives that had not yet dispersed (Smith et al 2008(Smith et al , 2009), but we had no knowledge of their behaviour, so we excluded them.…”

Section: Methodsmentioning

confidence: 99%

“…Despite the smallest colony size possible (i.e. two-bee groups), social nests exhibit the same behaviours that characterize eusocial insects: reproductive division of labour such that queens reproduce and rarely leave the nest, while workers forage for pollen and nectar, and tend to have slender, undeveloped ovaries (Wcislo & Gonzalez 2006;Smith et al 2008Smith et al , 2009). All nests are independently founded, so even queens have experience foraging when they are raising their first brood.…”

Section: Introductionmentioning

confidence: 99%

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Socially induced brain development in a facultatively eusocial sweat beeMegalopta genalis(Halictidae)

et al. 2010

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Changes in the relative size of brain regions are often dependent on experience and environmental stimulation, which includes an animal's social environment. Some studies suggest that social interactions are cognitively demanding, and have examined predictions that the evolution of sociality led to the evolution of larger brains. Previous studies have compared species with different social organizations or different groups within obligately social species. Here, we report the first intraspecific study to examine how social experience shapes brain volume using a species with facultatively eusocial or solitary behaviour, the sweat bee Megalopta genalis. Serial histological sections were used to reconstruct and measure the volume of brain areas of bees behaving as social reproductives, social workers, solitary reproductives or 1-day-old bees that are undifferentiated with respect to the social phenotype. Social reproductives showed increased development of the mushroom body (an area of the insect brain associated with sensory integration and learning) relative to social workers and solitary reproductives. The gross neuroanatomy of young bees is developmentally similar to the advanced eusocial species previously studied, despite vast differences in colony size and social organization. Our results suggest that the transition from solitary to social behaviour is associated with modified brain development, and that maintaining dominance, rather than sociality per se, leads to increased mushroom body development, even in the smallest social groups possible (i.e. groups with two bees). Such results suggest that capabilities to navigate the complexities of social life may be a factor shaping brain evolution in some social insects, as for some vertebrates.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Socially induced brain development in a facultatively eusocial sweat beeMegalopta genalis(Halictidae)

et al. 2010

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Queen Dominance May Reduce Worker Mushroom Body Size in a Social Bee

Jaumann

Seid

Simons

et al. 2019

Developmental Neurobiology

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The mushroom body (MB) is an area of the insect brain involved in learning, memory, and sensory integration. Here, we used the sweat bee Megalopta genalis (Halictidae) to test for differences between queens and workers in the volume of the MB calyces. We used confocal microscopy to measure the volume of the whole brain, MB calyces, optic lobes, and antennal lobes of queens and workers. Queens had larger brains, larger MB calyces, and a larger MB calyces:whole brain ratio than workers, suggesting an effect of social dominance in brain development. This could result from social interactions leading to smaller worker MBs, or larger queen MBs. It could also result from other factors, such as differences in age or sensory experience. To test these explanations, we next compared queens and workers to other groups. We compared newly emerged bees, bees reared in isolation for 10 days, bees initiating new observation nests, and bees initiating new natural nests collected from the field to queens and workers. Queens did not differ from these other groups. We suggest that the effects of queen dominance over workers, rather than differences in age, experience, or reproductive status, are responsible for the queen-worker differences we observed. Worker MB development may be affected by queen aggression directly and/or manipulation of larval nutrition, which is provisioned by the queen. We found no consistent differences in the size of antennal lobes or optic lobes associated with differences in age, experience, reproductive status, or social caste.

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Megalopta

Smith

2021

Encyclopedia of Social Insects

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Social competition but not subfertility leads to a division of labour in the facultatively social sweat bee Megalopta genalis (Hymenoptera: Halictidae)

Cited by 54 publications

References 43 publications

Socially induced brain development in a facultatively eusocial sweat beeMegalopta genalis(Halictidae)

Socially induced brain development in a facultatively eusocial sweat beeMegalopta genalis(Halictidae)

Queen Dominance May Reduce Worker Mushroom Body Size in a Social Bee

Megalopta

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