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Image right: These ancient corn cobs date roughly from 6,500-4,000 years ago. A is Proto-Confite Morocho race; B, Confite Chavinense maize race; and C is Proto-Alazan maize race.. (Photo by Tom Dillehay)

Some of the oldest known corncobs, husks, stalks and tassels, dating from 6,700 to 3,000 years ago were found at Paredones and Huaca Prieta, two mound sites on Peru’s arid northern coast. The research group, led by Tom Dillehay from Vanderbilt University and Duccio Bonavia from Peru’s Academia Nacional de la Historia, also found corn microfossils: starch grains and phytoliths. Characteristics of the cobs—the earliest ever discovered in South America—indicate that the sites’ ancient inhabitants ate corn several ways, including popcorn and flour corn. However, corn was still not an important part of their diet.

Image left: Wild forms of Zea mays are called ‘teosinte’. Over time, selective breeding modifies teosinte’s few fruitcases (left) into modern corn’s rows of exposed kernels (right). (Photo courtesy John Doebley.).

“Corn was first domesticated in Mexico nearly 9,000 years ago from a wild grass called teosinte,” Piperno says. “Our results show that only a few thousand years later corn arrived in South America where its evolution into different varieties that are now common in the Andean region began. This evidence further indicates that in many areas corn arrived before pots did and that early experimentation with corn as a food was not dependent on the presence of pottery.”

Understanding the subtle transformations in the characteristics of cobs and kernels that led to the hundreds of maize races known today, as well as where and when each of them developed, is a challenge. Corncobs and kernels were not well preserved in the humid tropical forests between Central and South America, including Panama—the primary dispersal routes for the crop after it first left Mexico about 8,000 years ago.

“These new and unique races of corn may have developed quickly in South America, where there was no chance that they would continue to be pollinated by wild teosinte,” Piperno says. “Because there is so little data available from other places for this time period, the wealth of morphological information about the cobs and other corn remains at this early date is very important for understanding how corn became the crop we know today.”

“Preceramic corn from Pardones and Huaca Prieta, Peru,” Grobman, A., Bonavia, D., Dillehay, T.D., Piperno, D.R., Iriarte, J., Holst, I. 2012. . PNAS early online edition, week of Jan. 16, 2012.

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Small monkey groups may win territorial disputes against larger groups because some members of the larger, invading groups avoid aggressive encounters. In a new report published in Proceedings of the National Academy of Sciences, Margaret Crofoot and Ian Gilby of the Smithsonian Tropical Research Institute in Panama and the Max Planck Institute of Ornithology show that individual monkeys that don’t participate in conflicts prevent large groups from achieving their competitive potential.

Image above: Is this monkey a wimp? A new study by Margaret Crofoot and Ian Gilby carried out at a research station run by the Smithsonian on an island in the Panama Canal shows that the answer may depend on the size of the group it belongs to. (Photo by Marcos Guerra)

The authors used recorded vocalizations to simulate territorial invasions into the ranges of wild white-faced capuchin monkey groups at the Smithsonian reasearch station on Barro Colorado Island in Panama. Monkeys responded more vigorously to territorial challenges near the center of their territories and were more likely to flee in encounters near the borders.

Defection by members of larger groups was more common than defection by members of smaller groups. Groups that outnumbered their opponents could convert their numerical superiority to a competitive advantage when defending the center of their own range against neighboring intruders, but failed to do so when they attempted to invade the ranges of their neighbors, because more individuals in large groups chose not to participate. According to the authors, these behavior patterns even the balance of power among groups and create a ‘home-field advantage’ which may explain how large and small groups are able to coexist.

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Image right: Common basilisk lizard female, Basiliscus basiliscus. (Photo by Steven Johnson)

In a study recently published in the journal Diseases of Aquatic Organisms, scientists took skin swabs from individuals of 13 different species of lizards and 8 different species of snakes caught in western and central Panama. DNA analysis of the swabs revealed that 16 percent of the lizards and 38 percent of the snakes carried the chytrid fungus on their skin. None of the reptiles that tested positive for the disease showed signs of infection or sickness comparable to what is observed in amphibians stricken with the disease.

Image left: The anolis lizard Anolis humilis. (Photo by Shawn Mallan)

“Lizards and snakes will harbor Batrachochytrium dedrobatidis at non-pathological levels,” the researchers write, and infection in reptiles is highly plausible. “By potentially maintaining the pathogen in the environment without succumbing to the disease, these reptiles may be important vectors or reservoir hosts for Batrachochytrium dedrobatidis… and may allow virulent strains of it to spread.”

While the study presents no evidence that chytridiomycosis is lethal to reptiles, its presence on the skin of reptiles in areas that have witnessed the decline of both amphibians and reptiles in recent years is cause for concern, the scientists say.

Image right: The tropical snake Imantodes cenchoa. (Photo by Geoff Gallice)

“Reptiles as potential vectors and hosts of the amphibian pathogen Batrachochytrium dendrobatidis in Panama,” by Vanessa Kilburn and David Green of McGill University and Roberto Ibanez of the Smithsonian Tropical Research Institute, was published in December in the journal Diseases of Aquatic Organisms.

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Image right: The Red-eyed treefrog (Agalychnis callidryas) is one of the species the team will be examining in Panama. (Photo by Brian Gratwicke)

Belden is leading a team of researchers who will study the microbial communities living on the skins of frogs that are surviving the fungal scourge. The effort is one of 11 new Dimensions of Biodiversity projects funded by the National Science Foundation with the aim of transforming, by 2020, how scientists describe and understand the scope and role of life on earth. Additional members of the $2 million research project are Virginia Tech’s Leanna House, assistant professor of statistics, and Roderick Jensen, professor of biological sciences; Brian Gratwicke, a research biologist at the Smithsonian Conservation Biology Institute, and Roberto Ibáñez, a scientist at the Smithsonian Tropical Research Institute in Panama; Reid Harris, professor of biology at James Madison University; and Kevin Minbiole, assistant professor of organic and natural products chemistry at Villanova University;

The goals of the research team will be achieved through hands on work in Panama, where the spread of chytrid fungus has been extensively documented. Researchers will swab the skin of frogs in areas with and without chytrid to collect samples of the microbes that live there. They will then release the frogs and assess the microbial community, both in terms of what microbes are there and what they are doing functionally on the frogs’ skin. To see what microbes are there, researchers will examine the microbe DNA. To see what the microbes are doing, researchers will examine how well they inhibit the growth of the chytrid fungus, and also assess what chemical metabolites are being produced by the microbes.

As leaders of the Panama Amphibian Rescue and Conservation Project the Smithsonian’s Brian Gratwicke and Roberto Ibáñez are maintaining captive colonies of endangered Panamanian frogs that are highly susceptible to the chytrid fungus. The hope is that the use of probiotics will someday allow release some of these species back into nature.

The research team is interested in whether microbial communities on the skin of frogs have a role in disease resistance, in particular to the devastating chytrid fungus. And if there is such immunity, does it rely on the same mechanism from one frog to another, on different species of frogs, and in different locations?

“Our long-term goal is to try to develop probiotics” – to share the biochemistry employed by beneficial microbes with frogs who need it,” Belden said.–Source: Virginia Tech

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Image right: The Smithsonian’s Barro Colorado Island was the site of the first large-scale, long-term forest dyanmics plots. Now there are 42 forest dynamics plots worldwide that use the same methodology, the Smithsonian Institution Global Earth Observatory system managed by the Center for Tropical Forest Science. (Photo by Marcos Guerra)

“Air pollution is fertilizing tropical forests with one of the most important nutrients for growth,” said S. Joseph Wright, staff scientist at the Smithsonian Tropical Research Institute in Panama. “We compared nitrogen in leaves from dried specimens collected in 1968 with nitrogen in samples of new leaves collected in 2007. Leaf nitrogen concentration and the proportion of heavy to light nitrogen isotopes increased in the last 40 years, just as they did in another experiment when we applied fertilizer to the forest floor.”

Nitrogen is an element created in stars under high temperatures and pressures. Under normal conditions, it is a colorless, odorless gas that does not readily react with other substances. Air consists of more than 75% nitrogen. But nitrogen also plays a big role in life as an essential component of proteins. When nitrogen gas is zapped by lightning, or absorbed by soil bacteria called “nitrogen fixers,” it is converted into other “active” forms that can be used by animals and plants. Humans fix nitrogen by the Haber process, which converts nitrogen gas into ammonia—now a principal ingredient in fertilizers. Today, nitrogen fixation by humans has approximately doubled the amount of reactive nitrogen emitted.

Image left: The Smithsonian’s Barro Colorado Island was the site of the first large-scale, long-term forest dyanmics plots. Now there are 42 forest dynamics plots worldwide that use the same methodology, the Smithsonian Institution Global Earth Observatory system managed by the Center for Tropical Forest Science. (Photo by Marcos Guerra)

Nitrogen comes in two forms or isotopes: atoms that have the same number of protons but different numbers of neutrons. In the case of nitrogen, the isotopes are ¹⁴N and ¹⁵N, although only about one in 300 nitrogen atoms is the heavier form. Imagine nitrogen in the ecosystem like a bowl of popcorn. Normally the ratio of popped (light) to unpopped (heavy) kernels stays the same, but when someone starts to eat the popcorn, the lighter, popped kernels get used up first, increasing the ratio of heavy to light kernels (or ¹⁵N/¹⁴N in the case of the ecosystem). Light nitrogen is lost through nitrate leaching and as gases such as N2, and various forms of nitrous oxides or “noxides,” some of which can be important greenhouse gases. In the fertilization study in Panama, mentioned earlier, N₂O emissions were tripled.

“Tree rings provide a handy timeline for measuring changes in wood nitrogen content,” said Peter Hietz from the Institute of Botany at the University of Natural Resources and Life Sciences in Vienna, who faced down a tiger when sampling trees in a monsoon forest on the Thailand-Myanmar border. “We find that over the last century, there’s an increase in the heavier form of nitrogen over the lighter form, which tells us that there is more nitrogen going into this system and higher losses. We also got the same result in an earlier study of tree rings in Brazilian rainforests, so it looks like nitrogen fixed by humans now affects some of the most remote areas in the world.”

“The results have a number of important implications,” said Ben Turner, staff scientist at STRI. “The most obvious is for trees in the bean family (Fabaceae), a major group in tropical forests that fix their own nitrogen in association with soil bacteria. Increased nitrogen from outside could take away their competitive advantage and make them less common, changing the composition of tree communities.”

“There are also implications for global change models, which are beginning to include nitrogen availability as a factor affecting the response of plants to increasing atmospheric carbon dioxide concentrations,” said Turner. “Most models assume that higher nitrogen equals more plant growth, which would remove carbon from the atmosphere and offset future warming. However a challenge for the models is that there is no evidence that trees are growing faster in Panama, despite the long-term increases in nitrogen deposition and atmospheric carbon dioxide.”

Decades of atmospheric nitrogen deposition have caused major changes in the plants and soils of temperate forests in the U.S. and Europe. Whether tropical forests will face similar consequences is an important question for future research.

The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Website: www.stri.org.

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Adding wings to a robotic bug helped it run faster and better, but was it enough to achieve takeoff?

Video: A six-legged, 25 g robot has been fitted with flapping wings in order to gain an insight into the evolution of early birds and insects. Published, 18 October, in IOP Publishing’s journal Bioinspiration & Biomimetics, the study showed that although flapping wings significantly increased the speed of running robots, the origin of wings may lie in animals that dwelled in trees rather than on the ground. “A wing assisted running robot and implications for avian flight evolution” (K Peterson, P Birkmeyer, R Dudley and R S Fearing 2011 Bioinspir. Biomim. 6 046008)

Even though the wings significantly improved the running performance of the 10-centimeter-long robot – called DASH, short for Dynamic Autonomous Sprawled Hexapod – they found that the extra boost would not have generated enough speed to launch the critter from the ground. The wing flapping also enhanced the aerial performance of the robot, consistent with the hypothesis that flight originated in gliding tree-dwellers.

The research team, led by Ron Fearing, professor of electrical engineering and head of the Biomimetic Millisystems Lab at U.C. Berkeley, reports its conclusions online Tuesday, Oct. 18, in the journal Bioinspiration and Biomimetics.

Using robot models could play a useful role in studying the origins of flight, particularly since fossil evidence is so limited, the researchers noted.

First unveiled by Fearing and graduate student Paul Birkmeyer in 2009, DASH is a lightweight, speedy robot made of inexpensive, off-the-shelf materials, including compliant fiber board with legs driven by a battery-powered motor. Its small size makes it a candidate for deployment in areas too cramped or dangerous for humans to enter, such as collapsed buildings.

Image right: DASH+Wings showed the possibility of using robotic models to provide insight into biological performance. (Image by Kevin Peterson, Biomimetic Millisystems Lab)

A robot gets its wings

But compared with its biological inspiration, the cockroach, DASH had certain limitations as to where it could scamper. Remaining stable while going over obstacles is fairly tricky for small robots, so the researchers affixed DASH with lateral and tail wings borrowed from a store-bought toy to see if that would help.

The researchers ran tests on four different configurations of the robotic roach, now called DASH+Wings. The test robots included one with a tail only and another that just had the wing’s frames, to determine how the wings impacted locomotion.

With its motorized flapping wings, DASH+Wings’ running speed nearly doubled, going from from 0.68 meters per second with legs alone to 1.29 meters per second. The robot could also take on steeper hills, going from an incline angle of 5.6 degrees to 16.9 degrees.

“With wings, we saw improvements in performance almost immediately,” said study lead author Kevin Peterson, a Ph.D. student in Fearing’s lab. “Not only did the wings make the robot faster and better at steeper inclines, it could now keep itself upright when descending.”

The flapping wings improved the lift-drag ratio, helping DASH+Wings land on its feet instead of just plummeting uncontrolled. Once it hit the ground, the robot was able to continue on its way.

Tree-dwellers vs. ground-runners

The engineering team’s work caught the attention of animal flight expert Robert Dudley, a UC Berkeley professor of integrative biology and researcher at the Smithsonian’s Tropical Research Institute, who noted that the most dominant theories on flight evolution have been primarily derived from scant fossil records and theoretical modeling.

He referenced previous computer models suggesting that ground-dwellers, given the right conditions, would need only to triple their running speed in order to build up enough thrust for takeoff. The fact that DASH+Wings could maximally muster a doubling of its running speed suggests that wings do not provide enough of a boost to launch an animal from the ground. This finding is consistent with the theory that flight arose from animals that glided downwards from some height.

“The fossil evidence we do have suggests that the precursors to early birds had long feathers on all four limbs, and a long tail similarly endowed with a lot of feathers, which would mechanically be more beneficial for tree-dwelling gliders than for runners on the ground,” Dudley says.

The winged version of DASH is not a perfect model for proto-birds – it has six legs instead of two, and its wings use a sheet of plastic rather than feathers – and thus cannot provide a slam-dunk answer to the question of how flight evolved, Dudley explained.

“What the experiments did do was to demonstrate the feasibility of using robot models to test hypotheses of flight origins,” he said. “It’s the proof of concept that we can actually learn something useful about biological performance through systematic testing of a physical model.”—Source: University of California, Berkeley

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