Search

Hybridization Hybridization between species has long been seen as an accidental contributor to evolution in some cases and as a dead end in others. New evidence is emerging, however, that hybridization may have played important, and nonrandom, roles in adaptation. Chen and Pfennig describe just such a case where female Plains spadefoot toads preferentially choose males from another toad species, the Mexican spadefoot, as mates, but only under certain environmental conditions (see the Perspective by Zuk). The offspring of this preferred hybrid mating event have higher fitness than nonhybrids in the same environment. Thus, not only do hybrids have an advantage, but females of one species are exerting a selective influence on the other species. Science , this issue p. [1377][1]; see also p. [1304][2] [1]: /lookup/doi/10.1126/science.aaz5109 [2]: /lookup/doi/10.1126/science.abb2398

For 15 years, researchers have accumulated hints that the "sterile neutrino"—a more-elusive cousin of the nearly undetectable neutrinos—might be out there. But most physicists have found the evidence unconvincing, as most of the results pointing toward sterile neutrinos are of marginal statistical significance. Recently, however, the case for sterile neutrinos has grown stronger, bolstered by a new analysis of data from nuclear reactors. So last month 60 physicists from around the world gathered to hash out the arguments for and against the existence of sterile neutrinos and to try to decide whether it9s worth staging a dedicated experiment to settle the matter. Performing such an experiment won9t be easy. The hypothetical neutrinos are called sterile because they do not interact at all with known particles. Still, physicists say, it9s time to figure out what it will take to discover or rule out sterile neutrinos once and for all.

The first birds arose from dinosaur ancestors about 150 million years ago, but what happened after that has not been clear. The earliest known bird, Archaeopteryx, was probably a poor flier and an evolutionary dead end. But spectacular finds of early birds from northeastern China over the past 15 years or so have started to fill in some of the gaps. These fossils had shown that by 125 million years ago, birds had split into two main groups: one that led to modern birds and another that went extinct at the end of the Cretaceous period 66 million years ago—along with all other dinosaurs. This week, researchers from China report in Nature Communications the discovery of the earliest known relative of modern birds, a 130-million-year-old species they have named Archaeornithura meemannae. These two very well preserved fossils—including the feathers—provide important new insights into how modern birds arose, because the details of their skeletons show that they were waders like today9s plovers. This strongly suggests that modern birds evolved in an aquatic environment. Archaeornithura also appears to have been a very able flier, indicating that this key feature behind the success of the modern bird lineage arose very early. The finds push the origins of modern birds back more than just 5 million years, however, because they were already so specialized for wading that these features—including the ability to engage in skillful, wing-powered flight—must have evolved millions of years earlier.

ANTHROPOLOGYIn a technical tour de force, scientists from Germany and the United States for the first time extracted and analyzed DNA from a Neandertal. The mitochondrial DNA sequence they found offers a new kind of evidence for the view that Neandertals were not our ancestors, but an evolutionary dead end.

Polyploidy, the doubling of genomic content, is a widespread feature, especially among plants, yet its macroevolutionary impacts are contentious. Traditionally, polyploidy has been considered an evolutionary dead end, whereas recent genomic studies suggest that polyploidy has been a key driver of macroevolutionary success. We examined the consequences of polyploidy on the time scale of genera across a diverse set of vascular plants, encompassing hundreds of inferred polyploidization events. Likelihood-based analyses indicate that polyploids generally exhibit lower speciation rates and higher extinction rates than diploids, providing the first quantitative corroboration of the dead-end hypothesis. The increased speciation rates of diploids can, in part, be ascribed to their capacity to speciate via polyploidy. Only particularly fit lineages of polyploids may persist to enjoy longer-term evolutionary success.

The stormy debate over a potential cause of chronic fatigue syndrome (CFS) is nearing hurricane force. Last month, it prompted headlines suggesting that researchers have reached a dead end, scores of blog posts from disappointed patients, and accusations that scientists had gone beyond their data. The 14-month-old row intensified when four papers appeared in Retrovirology suggesting that reports linking the virus XMRV to CFS were based on false positives. * With reporting by Martin Enserink.

Apoptosis is a simple concept with complex underpinnings--damaged cells are prompted to self-destruct through a series of molecular events, like dominos toppling over one by one. Unraveling the mechanisms underlying apoptosis is akin to determining the role each individual domino plays in a falling cascade--one strategically placed tile can trigger a cascade of several lines, and one misplaced tile can mean a dead end in the chain reaction. Techniques that pick apart this intricate process have been rapidly advancing, now offering more than the ability to look at a single event with high throughput, multiplexing capabilities, and in vivo imaging. Future technologies aim to help scientists visualize human cellular processes in vivo to aid researchers in tailoring and monitoring treatment for a variety of diseases, especially cancer.

From a food-web perspective, jellyfish are typically considered a dead end. Few organisms are thought to eat them, so they tend to sink to the ocean bottom, where they slowly decay, their carbon and energy wasted. But off the coast of southwest Africa, researchers have discovered that a small fish called the bearded goby feasts on jellies, and in doing so, helps to sustain seabirds, mammals, and larger fish in that ecosystem. On page 333 of this week9s issue of Science , they describe this fish9s unusual lifestyle, which includes hiding out on the muddy sea floor in water toxic to other fish.

Phenotypic Evolution A Reaction Norm Perspective. Carl D. Schlichting and Massimo Pigliucci. Sinauer Associates, Sunderland, MA, 1998. 400 pp. Paper, $38.95. ISBN 0-87893-799-4. Schlichting and Pigliucci argue for the evolutionary importance of the "developmental reaction norm," a concept that combines adaptive plasticity, development, and allometry.

KOREASEOUL, KOREA-- Korean planners and economists believe that the nation's reliance on a few large conglomerates, the so-called chaebol that include such familiar names as Samsung, Hyundai, and Daewoo, has reached a dead end. That's why Sunyoung Kim, a molecular biologist at Seoul National University, has suddenly found himself not only the founder of a company to commercialize a new gene-therapy technique but also a role model for Korean entrepreneurs and the recipient of front-page newspaper and television coverage, admiring letters from high schoolers, and envious phone calls from friends.

Evolutionary BiologyPaleontologists have long debated whether the bizarre Ediacara—blobs of living matter that inhabited Earth before the Cambrian Period's explosion of new species some 540 million years ago—were an evolutionary dead end or ancestors of later species. New dates for Ediacaran fossils, reported in this issue of Science ([p. 598][1]), lend support to the ancestral camp. The Ediacara didn'tdie out in the Precambrian, as many supposed, but persisted at least up to the beginning of the Cambrian. [1]: /lookup/doi/10.1126/science.270.5236.598