Cooperative Living May Speed Up Ant Evolution

At its core, evolution is about pressure. Previously, researchers thought that organisms in mutualist relationships—in which two or more organisms benefit one another—would be quite comfortable and therefore evolve slower than others. But new research published in the journal Nature Communications finds the opposite might be true.   

Ants and their plant buddies are some of the most successful mutualists on Earth. The plants provide a safe place for the ants to live, while the ants keep the plants safe from herbivorous insects. 

Ants’ successful setups don’t always catch on with their relatives. The genus Pseudomyrmex comprises three families of ants: one group of mutualists that make their homes in the enemy-deterring thorns of acacia trees, and two non-mutualist groups that live on their own in related plants.

Mutualist ants on acacia thorns. Image credit: Alexandra Westrich, The Field Museum

The difference in their lifestyles is apparent in their behavior. Mutualist ants are so confident in their safety that they leave the nest and form patrols in order to hunt down plant-eaters and other invaders. Generalists, on the other hand, seem to live in terror, fleeing from any aggressor, even when that means abandoning their nests. 

Biologists were curious to see how some ants became mutualists while their cousins did not. They analyzed the genomes of seven Pseudomyrmex species—three mutualists and four generalists. Because the generalist species live in such stressful conditions, the scientists expected that they would have evolved more rapidly than their gutsy, cushy-living cousins. But the reverse seemed true. The three mutualist species had evolved much faster than their generalist kin. 

Why would anyone in a happy relationship—ant, plant, or otherwise—keep changing? The scientists aren’t totally sure, but they have a theory. 

"Just like all organisms, mutualists need to constantly adapt to their environments to ensure survival,” says co-author and Field Museum curator Carrie Moreau. “However, they also have the additional task of evolving in relation to one another. Many species flip between mutualism and parasitism over time. Even mutualism is a costly relationship that evolution will select against if it is no longer advantageous. All of this likely factors into the accelerated rate of evolution among these species."

Let this be a reminder to us all: Even the best relationships need work.

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Watch How a Bioluminescence Expert Catches a Giant Squid

Giant squid have been the object of fascination for millennia; they may have even provided the origin for the legendary Nordic sea monsters known as the Kraken. But no one had captured them in their natural environment on video until 2012, when marine biologist and bioluminescence expert Edith Widder snagged the first-ever images off Japan's Ogasawara Islands [PDF]. Widder figured out that previous dives—which tended to bring down a ton of gear and bright lights—were scaring all the creatures away. (Slate compares it to "the equivalent of coming into a darkened theater and shining a spotlight at the audience.")

In this clip from BBC Earth Unplugged, Widder explains how the innovative camera-and-lure combo she devised, known as the Eye-in-the-Sea, finally accomplished the job by using red lights (which most deep-sea creatures can't see) and an electronic jellyfish (called the e-jelly) with a flashy light show just right to lure in predators like Architeuthis dux. "I've tried a bunch of different things over the years to try to be able to talk to the animals," Widder says in the video, "and with the e-jelly, I feel like I'm finally making some progress."

[h/t The Kid Should See This]

Big Questions
Why Are There No Snakes in Ireland?

Legend tells of St. Patrick using the power of his faith to drive all of Ireland’s snakes into the sea. It’s an impressive image, but there’s no way it could have happened.

There never were any snakes in Ireland, partly for the same reason that there are no snakes in Hawaii, Iceland, New Zealand, Greenland, or Antarctica: the Emerald Isle is, well, an island.

Eightofnine via Wikimedia Commons // Public Domain

Once upon a time, Ireland was connected to a larger landmass. But that time was an ice age that kept the land far too chilly for cold-blooded reptiles. As the ice age ended around 10,000 years ago, glaciers melted, pouring even more cold water into the now-impassable expanse between Ireland and its neighbors.

Other animals, like wild boars, lynx, and brown bears, managed to make it across—as did a single reptile: the common lizard. Snakes, however, missed their chance.

The country’s serpent-free reputation has, somewhat perversely, turned snake ownership into a status symbol. There have been numerous reports of large pet snakes escaping or being released. As of yet, no species has managed to take hold in the wild—a small miracle in itself.

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