Nav: Home

Ant study sheds light on the evolution of workers and queens

July 26, 2018

Worker ants, despite their diligence, seldom encounter opportunities for social mobility. In many species, individuals adhere to strict caste roles: queens lay eggs and workers take care of almost everything else, including offspring.

In a new study, published in Science, Rockefeller scientists describe the molecular mechanisms controlling this division of labor. "We wanted to know: what makes the queens lay eggs and the workers sterile?" says Daniel Kronauer, the Stanley S. and Sydney R. Shuman Associate Professor. Kronauer and colleagues report that a gene coding for an insulin-like peptide, ILP2, is instrumental in promoting and suppressing reproduction--a finding that illuminates a possible trajectory for the evolution of specialized castes.

A different kind of insulin injection

Working with graduate fellow Vikram Chandra and postdoctoral associate Ingrid Fetter-Pruneda, Kronauer first searched for differences in gene expression between reproducing and non-reproducing ants from a variety of species. They discovered that a single gene, which codes for the peptide ILP2, is consistently upregulated in reproducers. ILP2 is the ant version of insulin and, like human insulin, probably regulates metabolism. According to Kronauer, there is a direct link between reproduction and food intake: "If the nutritional state is really low, you can't afford to produce offspring," he says.

Next, the researchers studied the role of insulin in the clonal raider ant Ooceraea biroi. This species lacks distinct queens and workers; all ants simultaneously enter a reproductive phase, followed by a brood care phase in which the insects nurture their young. Transitions between phases are regulated by the presence of larvae: when newborns are around, the ants stop reproducing and shift into caretaking mode.

When Kronauer's group removed larvae during the brood care phase, adult insulin production increased substantially; and when they introduced larvae during the reproductive phase, insulin production decreased. These results indicate that the presence of larvae suppresses the production of insulin; and without sufficient levels of this peptide, the ants cannot reproduce.

In another experiment, the researchers injected ants with synthetic insulin during brood care, which resulted in ovary activation--even when larvae were nearby. This outcome suggests that ants with heightened insulin can override larval cues and reproduce at any time.

"In the brood care phase, the presence of larvae typically reduces insulin in adults--so their ovaries switch off and they go care for the larvae," says Chandra. "But if you experimentally inject insulin, you can break this cycle."

Yes, queen

This research offers clues about how ants evolved from solitary organisms to social species with specialized castes. Kronauer proposes that, first, insulin signaling became responsive to the presence of larvae, resulting in reproductive cycles reminiscent of those observed in O. biroi. Such an adaption makes good sense, as ants caring for offspring must prioritize food finding over egg laying--and both behaviors are known to be regulated by insulin.

Following this evolutionary stage, says Kronauer, the question becomes: "How do ants break out of this cycle?" He proposes that, due to individual variation, some ants would have naturally high levels of insulin, and others would have low levels. Notably, the researchers observed exactly this kind of variation in O. biroi. Kronauer posits that high-insulin individuals, like his insulin-injected ants, would be able to override larval cues and reproduce continuously, whereas low-insulin individuals would be very sensitive to the presence of larvae and thus more likely to focus on brood care.

"Once you have that kind of asymmetry in a colony, and the colony performs well, selection will drive insulin levels further apart," says Kronauer. "The eventual result would be two castes of ants--workers and queens."

Rockefeller University

Related Evolution Articles:

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.
Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.
A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.
Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?
Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.
Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.
Evolution of aesthetic dentistry
One of the main goals of dental treatment is to mimic teeth and design smiles in the most natural and aesthetic manner, based on the individual and specific needs of the patient.
An evolution in the understanding of evolution
In an open-source research paper, a UVA Engineering professor and her former Ph.D. student share a new, more accurate method for modeling evolutionary change.
Chemical evolution -- One-pot wonder
Before life, there was RNA: Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich show how the four different letters of this genetic alphabet could be created from simple precursor molecules on early Earth -- under the same environmental conditions.
Catching evolution in the act
Researchers have produced some of the first evidence that shows that artificial selection and natural selection act on the same genes, a hypothesis predicted by Charles Darwin in 1859.
More Evolution News and Evolution Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.