Social then solitary – then social again?
Last week BeeCon 2020, the annual bee research symposium hosted by the good people at York University, happened via Zoom. The presentations were varied, interesting and (I mean this as a compliment) nerdy. But one in particular grabbed my attention: an investigation by Lyllian Corbin, a masters student at Brock University in the Brock Bee Lab, into the social behavior of Lasioglossum ellisiae. Is this bee solitary or eusocial?
L. ellisiae is part of a group of sweat bee species who vary in their sociality, but who are all descended from a 20 million year-old common ancestor that we confidently presume was eusocial. Many of the species in this group remain undescribed in their social habits, and L. ellsiae is one of those – was one of those – question-mark species.
By using standard methods of collection and dissection, and relying on a robust existing collection of specimens, Corbin was able to gather the clues and data needed to deductively conclude that L. ellisiae is a solitary bee (based on ovary measurements) who has retained the traits of a eusocial bee (producing two broods in the same season and females differing in size between those broods). So it’s a bee that straddles the sociality fence, apparently?
“Sweat bees are a very confusing bunch, and often we get interesting results we didn’t expect to find,” says Corbin. “I think that it certainly adds to their charm and it’s one of the reasons they are so interesting to study.”
These results definitely raise some interesting questions, such as: Might this mixing of social traits be an indication of social polymorphism in L. ellisiae? Like, for example, Lasioglossum calceatum, another sweat bee, who is known to be solitary in cooler climates and eusocial in warmer ones.
“Based on the findings that we have, it follows the patterns that we’d expect to find in a solitary bee,” says Corbin of L. ellsiae. The ovary measurements are especially compelling because all the females – from both the first and second broods – show they are capable of reproducing; it doesn’t appear that later females are relegated to worker status. “But that size difference is really throwing me off.”
Another set of questions is: What environmental conditions and fitness benefits pushed L. ellisiae’s differentiation from the original ancestor in the first place? And what conditions might continue to push this species further in one social direction or the other? Interestingly, an important factor could could very well be temperature.
“We believe that eusociality arose during a time of global warming,” says Corbin. This change from a solitary way of life for bees is thought have occurred millions of years ago when the Earth was a much hotter place. When seasons are warmer for longer periods of time, multiple broods can be produced and fully develop. In the millennia that followed, the Earth’s temperatures cooled, creating the conditions that could make it beneficial to become solitary again. Which might be what we’re seeing in L. ellisiae: a modern descendant who is solitary but retaining eusocial traits.
But with the current state of man-made climate change, with temperatures rising rapidly, could L. ellisiae move back to eusociality?
It’s possible, says Corbin. L. calceatum certainly gives us a solid example of how and why this could occur over time. But Corbin also says there’s isn’t one linear path to sociality. And how species adapt and change is, of course, never as simple as a single factor.
Corbin’s work has definitely given us even more questions than we had before, but it’s also given us greater insight into some of the many bees who have been overlooked for too long. Her work is also a reminder that bees don’t fit into the tidy little boxes we might want to put them in – and why our nerdy conversations are so important.
Conservation
Australia’s Wild Pollinator Count begins in November
(Twitter, Dr Manu Saunders @ManuSaunders) “It’s spring! And that means #WildPollinatorCount time. Our next count is on between 8-15 November. Find out how to participate on our website”
Science
Bark beetle outbreaks benefit wild bee populations, habitat
(Colorado State University) When southern Rocky Mountain forests are viewed from a distance these days, it may not look like much is left. Large swaths of dead, standing Engelmann spruce trees tell the tale of a severe regional spruce beetle epidemic in its waning stages. But new research suggests that spruce beetle outbreaks may help create habitat for pollinator communities in wilderness settings. The research team found significant increases in floral abundance and wild bee diversity in outbreak-affected forests, compared to similar, undisturbed forest.
How can bees tell friend from foe?
(Washington University in St. Louis) For a honey bee, few things are more important than recognizing your nest mates. Being able to tell a nest mate from an invader could mean the difference between a honey-stocked hive and a long, lean winter. New research shows that honey bees rely on chemical cues related to their shared gut microbial communities, instead of genetic relatedness, to identify members of their colony.
Migrating bumble bees: an overlooked phenomenon?
(Twitter, Thijs Fijen @ThijsFijen) “Mass-migration of bumblebees might mean that bumblebee populations in intensive agricultural landscapes are continuously supplemented by bumblebee queens from far-away natural areas.” Here’s the original paper.
Current Chernobyl-level radiation harmful to bees
(Phys.org) Bumble bees exposed to levels of radiation found within the Chernobyl exclusion zone suffered a “significant” drop in reproduction. The authors of the study said if their findings could be generalized “they suggest insects suffer significant negative consequences at dose rates previously thought safe” and called for revisions to the international framework for radiological protection of the environment.
Genome sequencing shows climate barrier to spread of Africanized bees
(ScienceDaily, University of California, Davis) Since the 1950s, ‘Africanized’ honeybees have spread north and south across the Americas until apparently coming to a halt in California and northern Argentina. Now genome sequencing of hundreds of bees from the northern and southern limits shows a gradual decline in African ancestry across hundreds of miles, rather than an abrupt shift.
Society/Culture
Xerces Society annual report available
(Xerces Society) “Our annual report for 2019 - 2020 is available. Find out what we have achieved with your donations and support. Thank you to all of our project partners, collaborators, and donors!”
Why Nature supports Joe Biden for U.S president
(Nature) “Trump has not grown into his position as president, and has demonstrated that he can neither lead nor unite the United States. Joe Biden, by contrast, has a history in the Senate as a politician who has reached across to his political opponents and worked with them to achieve bipartisan support for legislation — a skill that will be needed now more than at any time in the recent past, because he will inherit a nation that is even more divided than it was four years ago. He has shown that he respects the values of research, and has vowed to work to restore the United States’ fractured global relationships. For these reasons, Nature is endorsing Biden and urging voters to cast a ballot for him on 3 November.”
One More Thing…
Nature journals rock. “Ivy Bees Colletes hederae, only females flying still and battling against a strong wind to bring pollen loads to their nest burrows Branscombe Devon”. From John Walters @JWentomologist via Twitter.