Posts about South America

Fungus-gardening Ant Species Has Given Up Sex Completely

The complete asexuality of a widespread fungus-gardening ant, the only ant species in the world known to have dispensed with males entirely, has been confirmed by a team of Texas and Brazilian researchers.

photo of christian rabeling excavating ants in BrazilGraduate student Christian Rabeling excavating fungus-farming ant nests in Brasilia.

Most social insects—the wasps, ants and bees—are relatively used to daily life without males. Their colonies are well run by swarms of sterile sisters lorded over by an egg-laying queen. But, eventually, all social insect species have the ability to produce a crop of males who go forth in the world to fertilize new queens and propagate.

Queens of the ant Mycocepurus smithii reproduce without fertilization and males appear to be completely absent, report Christian Rabeling, Ulrich Mueller and their Brazilian colleagues in open access journal PLoS ONE this week.

“Animals that are completely asexual are relatively rare, which makes this is a very interesting ant,” says Rabeling, an ecology, evolution and behavior graduate student at The University of Texas at Austin. “Asexual species don’t mix their genes through recombination, so you expect harmful mutations to accumulate over time and for the species to go extinct more quickly than others. They don’t generally persist for very long over evolutionary time.”

Previous studies of the ants from Puerto Rico and Panama have pointed toward the ants being completely asexual. One study in particular, by Mueller and former graduate student Anna Himler (now at Arizona State University), showed that the ants reproduced in the lab without males, and that no amount of stress induced the production of males.

Scientists believed that specimens of male ants previously collected in Brazil in the 1960s could be males of M. smithii. If males of the species existed, it would suggest that—at least from time to time—the ants reproduce sexually.

Rabeling analyzed the males in question and discovered that they belonged to another closely related (sexually reproducing) species of fungus-farmer, Mycocepurus obsoletus, thus establishing that no males are known to exist for M. smithii. He also dissected reproducing M. smithii queens from Brazil and found that their sperm storage organs were empty.

Taken together with the previous studies of the ants, Rabeling and his colleagues have concluded that the species is very likely to be totally asexual across its entire range, from Northern Mexico through Central America to Brazil, including some Caribbean islands.

As for the age of the species, the scientists estimate the ants could have first evolved within the last one to two million years, a very young species given that the fungus-farming ants evolved 50 million years ago.

Rabeling says he is using genetic markers to study the evolution and systematics of the fungus-gardening ants and this will help determine the date of the appearance and genetic mechanism of asexual reproduction more precisely in the near future.

Full press release

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Anthropologists Find New Type of Urbanism in Amazon Jungles

Anthropologists Find New Type of Urbanism in Amazon Jungles

Recently-discovered Amazonian settlements could be a new type of metropolis, unseen elsewhere in the world and hidden until recently in the Kuikuro jungle, say anthropologists.

Revealed by overgrown earthworks, the 100 square-mile urban units consist of clusters of interconnected villages ranging from 50-150 acres in size. The town-nodes were arranged along a highly-regular pattern of roads built around a central plaza about 500 feet across. The cities appear to have been at their height between the 13th and 17th centuries.

“No single Xingu settlement merits the term ‘city.’ But what do you do with a core of five settlements are few kilometers away from each other?” Michael Heckenberger, a University of Florida anthropologist currently in Brazil, told Science. “A fast walk from one to another would take you 15 minutes, maximum.”

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Using Cameras Monitoring To Aid Conservation Efforts

photo of Jaguar

How Hidden Cameras Aid Conservation Efforts for Jaguars and Other Rare Animals

Tobler and his fellow authors write that “despite years of research throughout the Amazon, there are few complete mammal inventories and our knowledge of the distributions of rare and elusive species is still poor.” They explain further that traditional techniques for inventorying which animals are present in a given ecosystem, such as identification of tracks and scat, direct observations, and trapping of animals often do not account for species of animals that are rare and/or low in their numbers in a certain area. For these reasons, they wanted to test out how well cameras could document animals in the rainforest, where cover is dense and many species are hard to observe.

Over the two years of the study, some of the more photographed animals included the Lowland tapir, which was caught on camera 102 times and also the White-lipped Peccary (seen 210 times). Among cat species, jaguars were photographed 51 times, ocelots 46 times, pumas 25 times, margays 15 times, and jaguarundis proved the most elusive, only being photographed twice.

The four species of animals that were not photographed included the pacarana, the grison, the Southern naked-tailed armadillo, and the Bush dog.

Given the recent lowering of costs and improvements in camera technology, hopefully their example and those of others will help other conservationists around the world to better understand the location of important and rare animals in their respective ecosystems. Given the large range of jaguars and their need for connected habitat, this study gives us hope to think that little hidden cameras might help us better understand where these charismatic cats and other rare animals roam, and consequently give us better information with which to help protect them.

Photo Credit: purplegrum at Flickr under a Creative Commons attribution license

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Aztec Math

Aztec Math Decoded, Reveals Woes of Ancient Tax Time

By reading Aztec records from the city-state of Tepetlaoztoc, a pair of scientists recently figured out the complicated equations and fractions that officials once used to determine the size of land on which tributes were paid. Two ancient codices, written from A.D. 1540 to 1544, survive from Tepetlaoztoc. They record each household and its number of members, the amount of land owned, and soil types such as stony, sandy, or “yellow earth.”

“The ancient texts were extremely detailed and well organized, because landowners often had to pay tribute according to the value of their holdings,” said co-author Maria del Carmen Jorge y Jorge at the National Autonomous University in Mexico City, Mexico. The Aztecs recorded only the total area of each parcel and the length of the four sides of its perimeter, Jorge y Jorge explained. Officials calculated the size of each parcel using a series of five algorithms—including one also employed by the ancient Sumerians—she added.

Aztec math finally adds up

That meant that some of the unknown symbols had to represent fractions of a rod, she said. By trial and error, she decoded the system. A hand equaled 3/5 of a rod, an arrow was 1/2 , a heart was 2/5 , an arm was 1/3 , and a bone was 1/5 .

A set of at least five formulas emerged showing how the Aztec surveyors determined the areas of irregular shapes. In some cases, the Aztecs averaged opposite sides and then multiplied. In others, they bisected the fields into triangles.

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Ethanol Scam

The Clean Energy Scam

The Amazon was the chic eco-cause of the 1990s, revered as an incomparable storehouse of biodiversity. It’s been overshadowed lately by global warming, but the Amazon rain forest happens also to be an incomparable storehouse of carbon, the very carbon that heats up the planet when it’s released into the atmosphere. Brazil now ranks fourth in the world in carbon emissions, and most of its emissions come from deforestation.

Meanwhile, by diverting grain and oilseed crops from dinner plates to fuel tanks, biofuels are jacking up world food prices and endangering the hungry. The grain it takes to fill an SUV tank with ethanol could feed a person for a year. Harvests are being plucked to fuel our cars instead of ourselves. The U.N.’s World Food Program says it needs $500 million in additional funding and supplies, calling the rising costs for food nothing less than a global emergency. Soaring corn prices have sparked tortilla riots in Mexico City, and skyrocketing flour prices have destabilized Pakistan, which wasn’t exactly tranquil when flour was affordable.

One groundbreaking new study in Science concluded that when this deforestation effect is taken into account, corn ethanol and soy biodiesel produce about twice the emissions of gasoline. Sugarcane ethanol is much cleaner, and biofuels created from waste products that don’t gobble up land have real potential, but even cellulosic ethanol increases overall emissions when its plant source is grown on good cropland. “People don’t want to believe renewable fuels could be bad,” says the lead author, Tim Searchinger, a Princeton scholar and former Environmental Defense attorney. “But when you realize we’re tearing down rain forests that store loads of carbon to grow crops that store much less carbon, it becomes obvious.”

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Peru Meteorite Provides Puzzles

Peru meteorite may rewrite rules

Usually, only meteorites made of metal survive the passage through Earth’s atmosphere sufficiently intact to scoop out a crater. But the object which came down in the Puno region of Peru was a relatively fragile stony meteorite. During the fiery descent through Earth’s atmosphere, these are thought to fragment into smaller pieces which then scatter over a wide area.

Yet pieces of the estimated 1m-wide meteorite are thought to have stayed together during entry, hitting the ground as one.

Peter Schultz told the conference that the meteorite was travelling at about 24,000km/h (15,000mph) at the moment of impact – much faster than would be expected. “This just isn’t what we expected,” said Professor Schultz, from Brown University in Providence, US. “It was to the point that many thought this was fake. It was completely inconsistent with our understanding of how stony meteorites act.”

At the velocity it was travelling, fragments could not escape the “shock-wave” barrier which accompanies the meteorite’s passage through the atmosphere. Instead, the fragments may have reconstituted themselves into another shape, which made them more aerodynamic. Consequently, they encountered less friction during their plunge to Earth, holding together until they reached the ground. “Although [the meteorite] is quickly broken up, it is behaving like a solid mass,” Professor Schultz told the conference.

Excellent article. First it is just interesting. Also it shows how scientists have to learn from what they observe and try to understand what explains the results they see.

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