Wasp genetics study suggests altruism evolved from maternal behavior

Like honey bee workers, wasp workers give up their reproductive capabilities and focus entirely on nurturing their larval siblings, a practice that seems to defy the Darwinian prediction that a successful organism strives, above all else, to reproduce itself. Such behaviors are indicative of a eusocial society, in which some individuals lose, or sacrifice, their reproductive functions and instead work to benefit the larger group.

Behavioral scientists have long noted the similarity between the maternal behaviors of some wasps and the nurturing and provisioning activities of workers. Until now, no study had uncovered a genetic link between the two.

The researchers found that the pattern of behavior-related genes expressed in the brains of worker wasps was most similar to that seen in foundresses, the female wasps who alone build new colonies and devote much of their early lives to maternal tasks.

“These wasps start out as single moms,” said postdoctoral researcher Amy Toth. “They don’t have any workers to help them, so they’re responsible for laying all the eggs and provisioning the developing larvae which then turn into workers.”

The researchers selected this species because it appears to represent an evolutionary transition. Once a foundress has raised a first generation of workers, she turns over the task of nurturing the larvae to the workers and devotes herself entirely to her “queenly” reproductive function.

At this point, the researchers discovered, behavioral gene expression in her brain changes, becoming distinct from that seen during her maternal period.

Toth noted that the P. metricus wasps represent a kind of intermediate stage in the evolution of eusocial behavior. The honey bee colony, in which queens never perform maternal tasks, is considered a more developed form of eusociality.

“In Polistes metricus wasps you have behavior that’s more similar to what you might see in a maternal ancestor,” Toth said. “That was really important for our study.”

The study team included researchers from 454 Life Sciences, a Connecticut-based company that has pioneered a method for sequencing short segments of DNA.

“If you had to do this with a conventional approach it would cost a phenomenal amount of money,” said Michael Egholm, vice president for research and development at the company. A miniaturized operation and streamlined process for sequencing the DNA makes the new approach much more economical, he said.

Rather than focus on the entire wasp genome, which would be costly, the research team focused on those genes that were expressed in wasp brains in high enough quantities to be detected and sequenced using the new approach. They then relied on a team of bioinformaticians in the department of crop sciences to make sense of the data.

This was a challenge, said crop sciences professor Matt Hudson, who specializes in bioinformatics and genomics. The new technique produced DNA fragments that were much shorter than those typically used. Because very little genetic data was available on this species of wasp, Hudson and graduate student Kranthi Varala used a computer algorithm to compare the sequenced gene fragments to sequences from the honey bee genome, which has been fully sequenced. This method allowed them to positively identify in the wasps 32 genes known to be behavior-related in honey bees.

With these data, the researchers were able to compare behavioral gene expression in the brains of foundresses, workers, queens and gynes. (Gynes perform no work within the colony. They start their own colonies the following spring.)

“We’ve pushed the boundaries a lot further than what has been done before,” Hudson said. “It’s been 100 to 150 million years since there was a common ancestor for paper wasps and honey bees, and during that time the DNA has changed a lot.” But the proteins encoded by those genes that are important to the behaviors the researchers studied changed very little, Hudson said. This allowed for robust comparisons between the behavior-related genes in both species, and identification of those genes in the wasps that were important to the study.

“This is very good news for people who study organisms in nature, rather than in the laboratory,” Toth said. “If your organism is closely related to an organism for which you have a sequenced genome, you can use this approach and you can get a lot of information about unknown gene sequences in just a matter of days.”

Entomology professor Gene Robinson, an author on the study, predicts that this study will increase interest in the application of modern genomic approaches to questions related to behavior, ecology and evolutionary biology.

Source: University of Illinois at Urbana-Champaign

Altruism in social insects is a family affair
The contentious debate about why insects evolved to put the interests of the colony over the individual has been reignited by new research from the University of Leeds, showing that they do so to increase the chances that their genes will be passed on.
Predator pressures maintain bees' social life
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 suggests that rather than organisational, genetic, or biological complexity defining a ‘point of no return’ for social living, pressures of predation create advantages to not living alone.
Bees are the new silkworms
Moths and butterflies, particularly silkworms, are well known producers of silk. And we all know spiders use it for their webs. But they are not the only invertebrates who make use of the strength and versatility of silk.
How basil gets its zing
The blend of aromatic essential oils that gives fresh basil leaves their characteristic warm and sweet aroma is well characterized but not much is known about the enzymatic machinery manufacturing the odiferous mix. Researchers at the Salk Institute for Biological Studies and the University of Michigan followed their noses and solved part of the molecular puzzle.
Old developmental pathways spawn revolutionary evolutionary changes
When the larvae of the primitive social insect Polistes metricus, a paper wasp, slips into the quiet pupal stage, she doesn’t know if she’ll arise a worker or gyne (future queen) – unless she consults with Arizona State University’s social insect researcher Gro Amdam.
3-D fruit fly images to benefit brain research
The fragile head and brain of a fly are not easy things to examine but MRC scientists have figured out how to make it a little simpler. And they hope their research will shed light on human disease.
Transgenic maize is more susceptible to aphids
The environmental consequences of transgenic crops are the focus of numerous investigations, such as the one published in the journal PloS ONE, which was carried out by Cristina Faria and her colleagues, under the supervision of Ted Turlings, professor in chemical ecology at the University of Neuchâtel.
Wood ant queen has no egg-laying monopoly
The reproductive monopoly of the ant queen is not as strong as is often thought. Dr. Heikki Helanterä and Prof. Lotta Sundström, biologists working at the University of Helsinki, Finland, investigated worker ovary development and egg laying in nine Northern European wood ant species of the genus Formica, and revealed wide spread reproductive endeavours by workers.

Wasp genetics study suggests altruism evolved from maternal behavior

Related stories:

News discussion: