Science News - December 2, 2006

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lutionary path, the researchers say in a paper that Science has posted online.

Some new hybrid species arise with an increase in the number of chromosomes. However, the butterfly hybrid has the same number of chromosomes as its parents do, so some other barrier must prevent it from interbreeding with those species.

Not only does the hybrid survive in a different habitat, says Gompert, but the butterflies strongly prefer as host plants a specialized high-altitude Astragalus in the pea family. The parent species rely on other plants, such as alfalfa and lupines.

Moreover, the hybrid females have the unusual quirk of laying eggs on their host plant without glue, although the parent species use glue on their eggs. The eggs without glue quickly tumble off the plant, and that tumble protects the next generation. In winter, alpine gales blast away dried-up plants and any hitchhikers. However, eggs that fell to the ground hatch in spring near emerging shoots.

Botanists have already accepted the idea of this kind of hybrid species, such as some native sunflowers, says insect evolutionary ecologist Mark Scriber of Michigan State University in East Lansing. As zoologists, “we’d been brainwashed into thinking hybrids are dead ends,” he says.

Yet recent research has revealed animal species that seem to have come from hybrids, including the unusual tiger swallowtail butterflies that Scriber studies in the Appalachian Mountains.

Biologists have also recently proposed hybrid speciation to explain a new Rhagoletis fruit-eating fly that has appeared on an invasive honeysuckle shrub. Other teams report that they have re-created a type of Helico-nius butterfly by crossbreeding two related species in the lab (SN: 6/17/06, p. 371).

Hybrid species with the same chromosome number as their parent species “may be more common than we thought possible,” Scriber says. —S. MILIUS

THE STARS NEXT DOOR A pair of red dwarfs, dubbed SCR 0630-7643, shown in this artist’s representation, is one of 20 newfound star systems that lie within 33 light-years of Earth.

within 33 light-years of Earth. All the stars are faint, low-mass objects called red dwarfs, which rank among the most prevalent stars in the Milky Way.

The team discovered the star systems— 2 triplets, 3 pairs, and 15 single stars—using a telescope at the Cerro Tololo Inter-American Observatory near La Serena, Chile. Since 1999, the astronomers have been monitoring hundreds of stars, looking for motions indicating that some might lie close to the solar system.

Todd Henry of Georgia State University in Atlanta and his colleagues describe their findings in the December Astronomical Journal.

The newfound neighbors offer fresh data on the frequency with which stars have partners, notes Henry. The growing census of nearby stars also provides new places to search for extrasolar planets.

“Red dwarf stars … are the closest and most numerous stars to us, so they are the best places to look for planets,” comments theorist Alan Boss of the Carnegie Institution of Washington (D.C.).

Nearby stars reveal their distances from Earth by tracing tiny ellipses in the sky—a consequence of Earth’s orbit around the sun. The greater the apparent motion, the nearer the star. Henry’s team has concentrated on red dwarfs, which range in size from about a tenth to half the mass of the sun. The dwarfs are among the dimmest stars and so have taken a long time to find.

Although astronomers have found several extrasolar planets orbiting red dwarfs, theorists had dismissed the possibility that any such planet could harbor life. Calculations indicated that a body warm enough to hold liquid water would have to lie so close to a red dwarf that the planet would be forced to rotate in sync with the star. One side would always face the star, and the other would face away, creating climates that would be either boiling hot or freezing cold.

But models described by Boss and his colleagues in an upcoming Astrobiology paint a more optimistic picture. For instance, if such a planet were to have a thick atmosphere, it could redistribute heat from the star and possibly make both sides of the planet habitable.

In recent years, Henry’s team has also found several near-Earth white dwarfs, which are old, sunlike stars, and failed stars called brown dwarfs. Henry told Science News that his team plans to report eight nearby star systems not mentioned in the current paper. —R. COWEN

A Toast to
Healthy Hearts
Wine compounds benefit
blood vessels

Howdy,

Neighbors

Long-term study finds a batch of red dwarfs

The galactic neighborhood just got more crowded. Astronomers have found 20 previously unknown star systems that lie

Researchers have identified a class of com- pounds in red wine that might be responsible for much of the beverage’s cardiovascular benefit. These compounds vary in concentration among wines grown in different areas and may explain some regional differences in wine drinkers’ longevities.

Some researchers have suggested that the common practice of drinking red wine at meals could explain why life expectancy in France tops that in many countries where people eat lighter fare. Recent studies have suggested that people who consume a glass or two of red wine each day have healthier cardiovascular systems than those who don’t imbibe.