Rainforests in Central Amazonia.  Full image

A research team of U.S. and Brazilian scientists led by William Laurance of the Smithsonian Tropical Research Institute, has shown that undisturbed, old-growth rainforests in central Amazonia are experiencing striking changes in dynamics and species composition. Although the cause of these changes is uncertain, a leading explanation is that they are being driven by rising levels of carbon dioxide in the atmosphere.

Plants use carbon dioxide from the air for photosynthesis. In the last 200 years, carbon dioxide levels have risen by 30 percent as a result of industrial emissions, automobiles, and rapid forest burning, especially in the tropics; much of this increase has occurred since 1960.

For the past two decades, the research team studied the fate of nearly 14,000 trees in the central Amazon, scattered across a landscape of 120 square miles. During the study, most species of trees began growing faster. The forests also became more dynamic, with existing trees dying faster and being replaced by young new trees. Even more important is that the species composition of the forest is changing. In general, large, fast-growing trees are winning at the expense of smaller, slower-growing trees that live in the forest understory.

“The decline of many small trees is intriguing because they tend to be so specialized,” said Henrique Nascimento, a Brazilian researcher at the Smithsonian Tropical Research Institute. “They live in the dark interior of the forest, and are the only trees that can flower and reproduce in deep shade.” The most likely reason for these changes, say the researchers, is that rising carbon dioxide levels are fertilizing the forests, leading to faster growth and more competition among trees for light, water, and soil nutrients. “Sadly, this could be a signal that the forest’s ecology is changing in fundamental ways,” noted team leader William Laurance. “Tropical rainforests are renowned for having lots of highly specialized species. If you change the tree communities, then other species—especially the animals that feed on and pollinate the trees—will undoubtedly change as well.”

“This appears to be yet another signal of the effects on nature of increasing greenhouse gas concentrations and associated climate change,” said Thomas Lovejoy of the Heinz Center for Science, Economics and Environment in Washington, DC, who helped to establish the tree study. “We really need more research to see if these remarkable changes are also happening in other tropical forests around the world. If they are, then it’s likely that even the world’s remotest forests are now being altered by human activities.”  The research results appear in the March issue of Nature.

Amber specimens, wing reconstruction and systematic...  Full image Amber specimens, wing reconstruction and systematic...  Full image

National Museum of Natural History researcher's Jason Hall, Robert Robbins, and Donald Harvey recently discovered five females of an extinct metalmark butterfly (Voltinia dramba) fossilized in amber in the Dominican Republic. This is the first butterfly to be taxonomically described from amber, and the first adult riodinid fossil of any kind. The series of five specimens represents probably the best-preserved fossil record for any lepidopterous insect, including wing pattern and microscopic features, such as “hairs” used for tasting. 

Amber from the Dominican Republic and Chiapas, Mexico, is unique among ambers of the world for its clarity, and is renowned for its systematically wide array of fossil inclusions. A grant from the Smithsonian Women’s Committee enabled the acquisition of three amber pieces from the Dominican Republic, each of which contains the same extinct metalmark butterfly, Voltinia dramba.

One of the amber fossil butterfly speciman is on display for a limited time in the National Museum of Natural History Insect Zoo. The wings, head, and body of the butterfly fossils are so exquisitely preserved, it is difficult to comprehend that the butterflies alighted on forest trees and became entombed in the sticky resins 15–25 million years ago. Geological evidence suggests that the amber butterfly diverged from its closest relative—today restricted to northwestern Mexico—40–50 million years ago. As this speciation date is contemporaneous with the oldest known butterfly rock fossils, this discovery provides tantalizing evidence that butterflies are older than previously thought.

A multiply mated queen of the leaf-cutting ant Acromyrmex echinatior (below) and its singly...  Full image

Multiple mating (polyandry) is widespread among animal groups, particularly insects. But the factors that maintain it and underlie its evolution are difficult to verify because benefits and costs are not easily quantified and tend to be similar in related species.

In the March 4 issue of Nature, Smithsonian Tropical Research Institute postdoctoral fellow Seirian Sumner and collaborators compare the mating strategies of the leaf-cutting ant Acromyrmex echinatior and its recently derived social parasite Acromyrmex insinuator, which is also its closest relative. They found that although the host queens mate with up to a dozen different males, the social parasite mates only singly. This rapid and surprising reversion to single mating in a socially parasitic ant indicates that the costs of polyandry are probably specific to a free-living lifestyle.

Removal of paint from original transparent nose cone of missile nears completion. Guided by...  Full image

Led by organic chemist Walter Hopwood and paintings conservator Jia-sun Tsang, Smithsonian Center for Materials Research and Education (SCMRE) staff recently assisted National Air and Space Museum conservators in the recovery of a unique guided missile’s materials and appearance.

The Gorgon II-A is the United States’ first liquid-fueled, rocket-powered, guided air-to-air missile. One of 21 missiles of this type built during 1943–46, it is a rare surviving example. The pilot in the cockpit of the plane from which the missile was launched controlled the missile by using radio signals. The missile had the additional feedback of a camera positioned in its nose, which could locate a target in mid-air within 18 miles. This very likely is the first example of the incorporation of television into missile technology. Unfortunately, the early technology, poor equipment resolution, and lack of control at high speeds resulted in inadequate operational performance.

The original transparent tip of the missile was later overpainted, obscuring the important design innovation. The goal of the analysis and treatment was to restore the original appearance of the missile. The first step in removing the overpaint without affecting the original transparent plastic under layer was to identify the paint materials. Fourier Transform Infrared Analysis (FTIR) identified the under layer as acrylic resin, and showed paint to be alkyd, an early synthetic oil paint. SCMRE’s new portable X-ray fluorescence spectrometer showed the paint contained a lead pigment. Removing alkyd paint with organic solvents could have been disastrous to the clear acrylic nose. Paint solubility testing revealed that 30 percent aqueous potassium hydroxide could remove the alkyd without affecting the acrylic. Using these analyses and treatment guidelines, the staff successfully restored the missile to its original appearance.

Hall, J.; Robbins, R.; Harvey, D. 2004. "Extinction and Biogeography in the Caribbean: New Evidence from a Fossil Riodinid Butterfly in Domincan Amber,"  Proceedings of the Royal Society of London, March 16.

Laurance, W.; Oliveira, A.; Laurance, S.; Condit, R.;Nascimento, H.; Sanchez-Thorin, A.; Lovejoy, T.; Andrade, A.; D'Angelo, S.; Ribeiro, J.; Dick, C. 2004. "Pervasive Alteration of  Tree Communities in Undisturbed Amazonian Forests," Nature, 428: 171-175.

Sumner, S.; Hughes, W.O.H.; Pedersen, J.S.; Boomsma, J.J. 2004.  “Ant Parasite Queens Revert to Mating Single,” Nature, 428: 3536.