Thursday, January 17, 2013

"Social chromosome" found in fire ants

 Fire ant mounds are common on Texas lawns 
Here in Houston, we think twice about laying down in the grass.

Such reckless behavior, which quickly identifies one as being "not from around these parts," would be an invitation for pain. That's because most of our lawns are patrolled by armies of fire ants (Solenopsis invicta), quick to defend their nests with their small but potent stings.

We try our best to kill them with poison baits, toxic chemical sprays, and (for the more ecologically minded) pots of boiling water. But they always seem to return, like Medusa's heads, in even greater numbers.

Why are fire ants so hard to kill?

As many people are aware, to kill an ant colony you must kill the queen. And the trouble with most of the fire ants here in Texas and in other parts of the South is that they often have more than one queen. Many, in fact.

Among ants, this is a fairly uncommon characteristic, but it comes with a number of interesting "side effects" that have been noted by biologists. Colonies with multiple queens (known as "polygyne" colonies) tend to be smaller and more numerous in a given patch of land, like a lawn. The queens are also smaller, on average, and don't fly away to mate like their single-queen cousins.

Instead, when queens decide to leave home to start their own colony, they leave the nest on foot and bring a few workers with them. They might even join forces with other queens, setting up the new nest together. It's no problem if the new nest happens to be near an established ant mound, even the one they came from-- unlike in single-queen colonies, polygyne workers are tolerant of their fellow fire ant neighbors.

Red imported fire ant workers surround a winged queen

Researchers have known for a decade or so that there is a genetic difference between  queens in polygyne colonies and those in single-queen colonies. A single gene, called Gp-9, was identified by Laurent Keller and Kenneth Ross in 1998 that determines the social form (polygyne or not) of a fire ant queen. What couldn't be explained is how this single gene, which codes for a pheromone-binding protein, could be responsible for so many different physical traits and behaviors as observed between single-queen and polygyne colonies.

Today, a study published by John Wang and colleagues in the journal Nature explains the answer. Gp-9, it turns out, is just one of many genes that are located on what the authors call a "social chromosome" in fire ants.

In much the same way that multiple genes are packaged together on the Y chromosome in human males, and are together responsible for the many physical traits and behaviors that distinguish men from women, so too do these genes synergistically create the polygyne syndrome in fire ants.

The social chromosome even shares similarities with the human Y chromosome (and the sex chromosomes of animals), such as not recombining with other chromosomes the way most genes do. Such recombination, which shuffles genes around to create new and sometimes useful combinations, would not work well with sex-related traits since the traits need to stay associated with a particular sex. So strategies have evolved that prevent  this from happening in sex chromosomes, and similar mechanisms appear to exist in the social chromosome of fire ants.

Highly social organisms like ants have always fascinated us, and researchers have been interested for decades in the genetic basis for sociality in its various forms. This study is the first to document the existence of a social chromosome, but it is not likely to be the last.

It seems we may be on the verge of deciphering the fascinating secrets behind the social lives of insects, which will have the potential to help us finally understand the evolutionary basis of complex behaviors. It may even help us control pest species like fire ants, whose success is due in large part to their unusual ability to cooperate.

For now, though, I'd stay off the lawn.

Photos by Alex Wild (http://www.alexanderwild.com)

Wednesday, December 12, 2012

"A Great Smile"

Science news sites this week are covering an article published on Monday in the journal Proceedings of the National Academies of Science, but the headlines are a little surprising given the subject of the research.

Authors Nicholas Longrich and colleagues explain that recent re-examinations of fossil snakes and lizards from just before and just after the event that caused the extinction of the dinosaurs (likely a meteor impact) suggests that these animals were more affected by the event than was previously recognized.

Whereas researchers had concluded that most snake and lizard species survived the event, Longrich et al. argue that as many as 83% of squamates (as the group that consists of both snakes and lizards are known) went extinct during this time, about 65 million years ago.

Most news sources, however, picked up on the fact that one of the two newly described species of lizards included in the report is named Obamadon gracilis.

That's right-- "Obamadon," a new genus name, is a tribute to our president, who Longrich claims, "has these tall, straight incisors and a great smile."

Apparently, so did the lizard.

The fossil jaw of Obamadon gracilis, whose teeth are said to resemble the President's (from Figure 1 in Longrich et al. (2012) http://www.pnas.org/content/early/2012/12/07/1211526)

The carnivorous lizard Palaeosaniwa stalks a pair of hatchling Edmontosaurus as the snake Cerberophis and the lizard Obamadon look on.
A reconstruction of Obamadon (the small lizard on the bottom left)


Monday, November 12, 2012

Another sign of the apocalypse

Apparently, climate change is threatening coffee (Coffea arabica) with extinction. Sure, we may have to get used to epic droughts, catastrophic floods, and rising coastlines-- but no coffee??!!!

Monday, February 21, 2011

Texas leafcutter ants adapt to cold winters


A study that I was involved in will be published this week in the Proceedings of the National Academy of Sciences! Click here to read the Rice University press release summarizing our findings.

Photo of Atta texana workers tending their fungus garden, by Alexander Mikheyev

Wednesday, February 09, 2011

Visualizing deep history

A student in my Introductory Biology class shared this website with me.

It has a fun animation summarizing the history of the Universe, including the history of the Earth. It's interactive, so you can take your time, go backwards, or forwards, and get a sense of when some of the major events (e.g. origin of life, first land animals, etc.) took place.

I've seen many similar tools, but what I like about this one is that it goes back beyond the origin of the Earth, giving you a sense of how new, relatively speaking, our entire planet is. Not to mention its "intelligent" inhabitants...

Wednesday, February 02, 2011

Not bad for a blob

Check out a piece I wrote for Slate Magazine about some research by my Rice colleagues on the evolution of primitive farming by a social amoeba-- aka "slime mold."

A variety of other places have covered the story, which is great publicity for their cool discovery. Some photos that I took of the social amoeba got picked up by several places, including The New York Times and a magazine in Sweden that plans to publish a full page version of this photo:



Here are a few more photos I took of the lovely Dicty farmers, as well as their discoverer, Debbie Brock, in her natural habitat.







Ants navigate with an internal compass



Research on the South American ant species Pachycondyla marginata shows that worker ants navigate by means of a magnetic compass housed within their antennae.

Photo by Alex Wild

Monday, July 05, 2010

It's time to tidy up the colony!


Please excuse the long break from new posts. I am in the process of restructuring this blog. Please check back soon for an update...





Image from: http://www.shelleyandjoshua.com/power_point_&_video.htm