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In brief – Research news and discovery WHEN it comes to evolutionary nimbleness, anole lizards are among the most agile of all animals. Their adaptability may be one reason why the Anolis genus has been so successful. Jonathan Losos, a biologist at Harvard University, and his colleagues tracked the fate of individual Anolis sagrei lizards on six small islands in the Bahamas after the team introduced a lizards, which are better climbers. “Natural selection can change direction on the drop of a dime,” says Losos. Anole lizards on control islands without the predator showed no trend toward longer or shorter legs (Science, vol 314, p 1111). The speed with which these lizards respond to changing conditions – faster than any other animal studied that Losos is aware of – may help explain why the genus has exploded into some 400 different species, he says. predatory lizard. Immediately after the predator arrived, longer- legged and therefore faster A. sagrei individuals survived in greater numbers than their slower brethren. Within six months, however, the lizards learned to spend more time up in the branches of shrubs, where their predator could not follow. As a result, natural selection did an about-face to favour short-legged Leggy lizards evolve in fast-forward THE material that revolutionised electronics has been endowed with even greater power: silicon has joined the ranks of the superconductors. In theory, doping silicon with high enough levels of boron atoms should turn it into a superconductor, but getting enough boron into the silicon has been a problem. Now Etienne Bustarret at the French national research agency CNRS in Grenoble and his colleagues have cracked it. They fired a laser pulse at a silicon wafer while passing boron chloride gas over it. The laser melted the silicon, allowing many more boron atoms than normal to enter. When the silicon solidified, the boron atoms were trapped. The team found that the doped silicon superconducted below -272.8 °C (Nature, vol 444, p 465). “We must be able to produce this effect at higher temperatures for it to become widely useful,” Bustarret points out. Silicon goes super THE roof of the world should be covered in trees. Today, Tibet is mainly covered by desert pasture, but it was likely once adorned with cypress forest, which was destroyed by local inhabitants over the past 4600 years. Georg Miehe of the University of Marburg in Germany and colleagues analysed climate data, pollen records and ancient soil samples from around Lhasa. They suggest that not only is the climate, with plenty of rainfall, little permanent frost or snow and good mean temperatures through the growing season, most suited to forest growth, but that people burnt down trees to make way for barley cultivation and grazing animals (Palaeogeography, Palaeoclimatology, Palaeoecology, vol 242, p 54). Tall trees once topped Tibet BRUCE ELY/THE OREGONIAN/CORBIS 18 | NewScientist | 25 November 2006 www.newscientist.com MOUNT St Helens is drumming out a warning beat. Regular, repetitive earthquakes around the volcano are being triggered by the movements of a rock plug, reverberating in the neck of the volcano. In October 2004 a small eruption on Mount St Helens in Washington state was accompanied by a swarm of minor earthquakes, approximately one every half minute. The tremors have continued at the rate of around one every six minutes. By modelling the volcano, Richard Iverson of the Cascades Volcano Observatory in Vancouver, Washington, and his colleagues conclude that the most likely explanation for these unusually regular drumbeat earthquakes is the jerky movements of a giant rock plug, wedged in the throat of the volcano. “Magma pressure in the conduit below the plug pushes it upward,” says team member Daniel Dzurisin. As the plug moves, at the rate of about 3 to 5 metres per day, it triggers tremors in the area surrounding the volcano (Nature, vol 444, p 439). Right now there is no sign that Mount St Helens is about to clear its throat in the spectacular way it did in 1980, but changes in the drumbeat could signal the build- up to some kind of eruption. “We’re making progress, but we don’t have the answers yet,” says Dzurisin. I seem to have something stuck in my throat…
