Evolution: Genetic relatedness doesn't matter much in forming society

October 3, 2018, Hokkaido University
Lasioglossum baleicum, commonly known as the sweat bee, used in the study. Credit: Norihiro Yagi

Genetics isn't as important as once thought for the evolution of altruistic social behavior in some organisms, according to a new insight into a decade-long debate. This is the first empirical evidence that suggests social behavior in eusocial species—organisms that are highly organized, with divisions of infertile workers—is only mildly attributed to how related these organisms are to each other.

In evolutionary biology, fitness refers to an organism's reproductive success and propagation of its genes. When researchers at Hokkaido University studied the foraging and nesting behaviors of the eusocial species Lasioglossum baleicum, commonly known as the sweat bee, they found that the fitness was more a result of the bees' cooperative behaviour than it was a result of their genetic similarity.

This evidence is contrary to earlier theories that attributed altruistic selfless behavior in eusocial species to genetic relatedness and a want to ensure the propagation of their genes. In some insect species, genetic similarity is higher between sisters than between a sister and its own offspring, and this has been considered the key driver to the formation of a eusociety.

Evolutionary biologist Eisuke Hasegawa and his colleagues studied five aggregations of sweat bee nests in various areas on the island of Hokkaido in Japan. In each aggregation, there were two types of nests: those in which multiple worked together to take care of the offspring of a single queen, and those in which a mother bee took care of her offspring on her own.

Queen bees lay several eggs at a time. They hatch as predominantly infertile females, who grow to become workers. The team marked all the adult bees in the nests so they could identify them, then studied how often and for how long each adult female left the to forage over a 12-hour period.

They found that the females working in the cooperative nests foraged more often than the females from the solitary nests. In addition, solitary nests were devoid of adult females much more often than social nests, leaving the nests more vulnerable to predators.

Ants are the main predator of . A female sweat bee protects the offspring in her nest from scout ants, which can recruit many other ants to attack, by plugging the nest opening with her head. This is why solitary adult females can only leave their nests for short periods of time. Cooperative nests, on the other hand, are more efficiently defended.

Individual females in social nests are known to have higher fitness than solitary females, meaning that social bees are more successful in propagating their genes. The team has found that 92 percent of the increase in fitness can be attributed to the benefit of grouping—efficient foraging and defense—while the rest is due to the genetic similarity between the individuals

The findings indicate that, contrary to previous theories, the main contributing aspect of fitness in a social nest comes from the benefit of grouping. "There has been a decade-long debate among scientists as to whether or the benefit of grouping is the primary drive of sociality. Our study could help reveal some of the factors behind the of cooperation, including among humans, by quantifying how much cooperative behavior contributes to the increased of altruistic individuals in a group," says Hasegawa.

The study is published in Science Advances.

Explore further: How unrelated wasps succeed by helping others breed

More information: "The benefits of grouping as a main driver of social evolution in a halictine bee" Science Advances, advances.sciencemag.org/content/4/10/e1700741

Related Stories

Predator pressures maintain bees' social life

December 21, 2007

The complex organisation of some insect societies is thought to have developed to such a level that these animals can no longer survive on their own. Research published in the online open access journal BMC Evolutionary Biology ...

Swarm-like behavior of red mason solitary bees

May 5, 2011

Have you seen what looks like a bee swarm in your garden recently? Well, if you think you have, it is more likely to be a gathering of harmless red mason bees than a swarm of aggressive bees.

Male wasps help to defend the nest

April 27, 2011

Male wasps are not exactly famous for their contributions to domestic life. Most do precious little, leaving the nest's maintenance chores to the females. Now a group of researchers has shown that when push comes to shove, ...

Recommended for you

Study links genes to social behaviors, including autism

October 18, 2018

Those pesky bees that come buzzing around on a muggy summer day are helping researchers reveal the genes responsible for social behaviors. A new study published this week found that the social lives of sweat bees—named ...

Bioceramics power the mantis shrimp's famous punch

October 18, 2018

Researchers in Singapore can now explain what gives the mantis shrimp, a marine crustacean that hunts by battering its prey with its club-like appendages, the most powerful punch in the animal kingdom. In a paper publishing ...

Expanding the optogenetics toolkit

October 18, 2018

Controlling individual brain cells using light-sensitive proteins has proven to be a powerful tool for probing the brain's complexities. As this branch of neuroscience has expanded, so has the demand for a diverse palette ...

Staying a step ahead of the game

October 18, 2018

Trypanosoma brucei, which causes sleeping sickness, evades the immune system by repeatedly altering the structure of its surface coat. Sequencing of its genome and studies of its 3-D genome architecture have now revealed ...

Elucidating cuttlefish camouflage

October 18, 2018

The unique ability of cuttlefish, squid and octopuses to hide by imitating the colors and texture of their environment has fascinated natural scientists since the time of Aristotle. Uniquely among all animals, these mollusks ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

torbjorn_b_g_larsson
not rated yet Oct 04, 2018
I find the article problematic. They speculate in fitness differences, but do not attempt to uncover a genetic template which invalidates their model. On the contrary they observe that the socially polymorphic bee makes situational social choices, which trait may have evolved for any reason including drift. I do not know if phylogenies uncover it as a putative heritable trait, but it is possible since the data suggesting population wide mechanisms is meager and not tested against a random null hypothesis: they note "36.4% of eusocial colonies contain at least one unrelated adult female (23)".

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.