The Benefits of Being a Loner
Whether you're a scientist or not, chances are you've had experience with one of those things that is not like the others. Researchers are finding that loners, or small groups that don't react the way all others of their kind do, may be serving a crucial purpose; the flower that blooms late or early or the herd that misses the migration might actually be ecologically important, suggested associate professor of ecology and evolutionary biology Corina Tarnita. Evolution may actually select for the behavior of loners in some cases, according to a study in PLOS Biology by Tarnita and colleagues.
"Now that we're starting to look for it, we realize that a whole lot of systems are not perfectly synchronized -- and it's tantalizing to think that that there may be something to this imperfect synchronization," Tarnita said. "Individuals that are out of sync with the majority of a population exist in humans, too. We call them misfits or geniuses, contrarians or visionaries, very much depending on how the rest of the society feels about their behavior, but they certainly exist."Unfortunately, Tarnita and other researchers face challenges in the study of collective systems; a locust swarm or wildebeest migration can't be used in an experiment that tests the impact of loners. In this work, however, they were able to find a model organism: the slime mold Dictyostelium discoideum. This enabled the scientists to select for loner behavior, and show that loners can act as a kind of protection that ensures a population stays diverse and will survive.
Slime mold expert John Bonner has shown (video above) that if the resources used by slime mold diminish and starvation is a threat, they aggregate into a tower that can grow upward. That enables spores from the colony to stick to passing insects and spread out into the world, even as the base of the tower is dying. Thus, collective behavior is necessary for survival. But in 2013, Tarnita began to take note of the slime mold cells that didn't take part in this activity."I was at a conference, and a speaker was showing videos of slime molds doing this very complex collective behavior, all determined to reach the center of aggregation," Tarnita said. "All but some, I noticed: Here and there, some scattered cells on the plate just didn't seem to react at all to this aggregation process."While these loners had been dismissed by others as mere mistakes, she wondered about them and began to test them in her studies.Careful studies by graduate candidate and co-first study author Fernando Rossine showed that loners couldn't be eliminated, even in a controlled environment. When he used wild slime molds, up to 30 percent of cells opted to act as loners. He was able to confirm Tarnita's hypothesis that they aren't random errors. If the slime mold population was small, all the cells behaved like loners. Over a certain limit, the tower-building starts, with a fraction avoiding the task.
Once the population got to a certain size, the number of loners leveled off."This was exhilarating because it meant that we had originally been right that the loners were far from boring, but it also meant that, theoretically, we needed to go back to the drawing board," said Tarnita.The collective behavior of a group can have major benefits but also poses some risks, leaving loners as a kind of insurance policy."It's a social bet-hedging," said Rossine. "And a fascinating conclusion that follows from our findings is that, at least for slime molds, the decision not to become part of the collective is, in fact, taken collectively.
All the cells kind of talk to each other chemically: 'Oh, you're going? I guess I'm staying.'
There's communication involved in becoming a loner."
Study Shows Some Worker Ants Don’t Work At All
BY Matt Soniak August 3, 2015
Last summer, researchers at the University of Illinois revealed that most bees aren’t as busy as we give them credit for, and a small group of workers handles the bulk of the labor in a hive. Now, another research team has taken the famously industrious ant down a peg, showing that many ants don’t do their fair share of work—or any work at all.In many types of social insect, entomologists have found workers that really don’t do much. In some cases, researchers report that half or more of the bugs in a colony are inactive and spend their time just hanging around. Daniel Charbonneau and Anna Dornhaus are biologists at the University of Arizona’s Social Insect Lab, where they primarily study Temnothorax rugatulus, a species of ant found throughout the Western U.S. and Canada.
They’ve seen plenty of lazy ants first-hand during their research, but it wasn’t clear whether these ants were consistently inactive or simply taking a break or working in shifts. In a new study, the pair shows that these ants are dedicated to being bums, and that might actually be their job.The scientists collected five colonies of the ants around Tucson and, using a microscope and thin wire, painstakingly marked 250 workers with unique combinations of paint spots so they could be identified and tracked. They let the ants go about their business for three weeks and recorded them on video for a few minutes at regular intervals. They then went through their footage and recorded what each of the tagged ants was doing.They found that around 25 percent of the ants were inactive throughout the study. Differences in rest schedules and work shifts didn’t explain the difference, because no matter what time the videos were taken, the same ants were still standing around. These ants were so consistent at doing nothing, the researchers say, that it looks like some workers “effectively specialize in ‘inactivity’” the same way others specialize in foraging for food or tending to the colony’s larvae.Why do so many ants dedicate themselves to doing so little? Charbonneau and Dornhaus’ study didn’t try to figure that out, but they suggest plenty of ideas that can be tested.
First, they say, the inactive ants may have a job to do that they just didn’t see during their short window of ant-watching, maybe a task that’s only performed at a certain time of year or at a specific point in the ants’ life cycle. These particular ants could have also been too young to start working, or too old to continue working and were living the easy life of insect retirement.They might also be a kind of reserve work force that springs into action when other workers die or the workload in the colony suddenly increases, though other studies testing that idea with different insects found little support for it and showed that when more labor is needed, the ants that are already working just work harder and increase their activity.Another possibility is that the lazy ants are “behaviorally idle” but not “functionally idle,” and have jobs that don’t require much movement or look like work, such as acting as live feeding stations and regurgitating food for other ants when needed, or relaying chemical messages around the nest.Finally, the researchers say these ants might just be selfish, shirking their assigned duties so they can conserve energy and minimize their exposure to danger.“Ultimately, the question of why colonies would produce so many inactive workers, in spite of potentially high production and maintenance costs, is still very much a mystery,” the scientists write, one that will be solved only with more experiments testing all these ideas and others. For now, they urge other ant researchers to not write inactive ants off as inefficient or unimportant just because they don’t do active tasks.
Lazy ants are a distinct group with their own unique set of behaviors and characteristics, they write, and ignoring them and their main “activity” in certain studies may skew our understanding of ants’ social structure and division of labor.