May 25, 2006, 10:45 PM CT

Colorado River Streamflows Reconstructed

A new tree-ring-based reconstruction of 508 years of Colorado River streamflow confirms that droughts more severe than the 2000-2004 drought occurred before stream gages were installed on the river.

The new research also confirms that using stream gage records alone may overestimate the average amount of water in the river because the last 100-year period was wetter than the average for the last five centuries.

"This work updates the original landmark Colorado River reconstruction that was done at The University of Arizona's Laboratory of Tree-Ring Research," said David M. Meko, a UA associate research professor of dendrochronology, the science of tree-ring dating.

"The main points of the 1976 research hold up. Droughts more severe and intense than we've seen in the gaged record occurred in the past, and the long-term mean flow is lower than the gaged mean flow."

Connie A. Woodhouse said, "The updated reconstruction for Lee's Ferry indicates that as a number of as eight droughts similar in severity, in terms of average flow, to the 5-year 2000-2004 drought have occurred since 1500."

Woodhouse, who led the research team, is a physical scientist at the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center Paleoclimatogy Branch in Boulder, Colo.........

Posted by: Tyler      Permalink         Source

May 21, 2006, 8:34 AM CT

Reconstructing Extinct Species

Reconstruction of genomic DNA sequence of extinct species is a daunting task. Scientists who were trying to achieve this goal had faced various difficulties. U.S. Department of Energy (DOE) Joint Genome Institute (JGI) researchers overcame a number of of the difficulties normally associated with recovery of DNA from old samples. Samples of DNA would start degrading at death of the animals and is flooded by various microorganisms. These microbes attack the decaying carcass to utilize the nutrients present in the dead organism as an energy source. What remains and confounds the efforts to sequence and characterize these artifacts is an overabundance of microbial contaminants along with the occasional DNA fingerprints contributed unwittingly by the modern fossil hunters or lab workers.

The genomic DNA sequencing of an extinct Pleistocene cave bear species has been logged into scientific literature thanks to researchers from the U.S. Department of Energy (DOE) Joint Genome Institute (JGI). This study, reported in the latest issue of online edition of the journal Science, has set the research community's sights on traveling back in time through the vehicle of DNA sequencing to reveal the story of other extinct species, including our nearest relatives, the Neanderthals.........

Posted by: William      Permalink

May 18, 2006, 11:00 PM CT

Linking Climate Change Across Time Scales

What do month-to-month changes in temperature have to do with century-to-century changes in temperature? At first it might seem like not much. But in a report published in this week's Nature, researchers from the Woods Hole Oceanographic Institution (WHOI) have found some unifying themes in the global variations of temperature at time scales ranging from a single season to hundreds of thousands of years. These findings help place climate observed at individual places and times into a larger global and temporal context.

"Much of the work went into assembling the different types of records needed to study such diverse time scales", said Peter Huybers, a paleoclimatologist in the Geology and Geophysics Department at WHOI and lead author on the study. "Data from instruments from around the world are available for recent periods, but it is not so easy for earlier times. We have few instrumental records before the 19th century, so we have to use measurements in corals, ice cores, and sediment cores to estimate past temperatures".

These measurements and data compilations were made by researchers at WHOI and other research institutions. "While none of the measurements we use are new," Huybers said, "putting them together told us more than we could learn from any single record".........

Posted by: William      Permalink         Source

May 18, 2006, 9:19 PM CT

Mystery Of Flowering Plants

Scientists from the Floral Genome Project at Penn State University, with an international team of collaborators, have proposed an answer to Charles Darwin's "abominable mystery:" the inexplicably rapid evolution of flowering plants immediately after their first appearance some 140 million years ago. By developing new statistical methods to analyze incomplete DNA sequences from thirteen strategically selected plant species, the scientists uncovered a previously hidden "paleopolyploidy" event, an ancient whole-genome duplication that preceded the appearance of the ancestral flowering plant.

Claude dePamphilis, associate professor of biology at Penn State, is the principal investigator of the Floral Genome Project and the senior author of the paper. "We found a concentration of duplicated genes that suggests a whole-genome duplication event in the earliest flowering plants," he says. "A polyploidy event early in the history of flowering plants could explain their sudden evolution." The results appear in a recent issue of Genome Research.

One unexpected observation from the study is the relatively slow accumulation of mutations in primitive flowering plants like the yellow water lily (Nuphar). "We can view these basal angiosperms like the Hubble Space Telescope, which helps us get a deeper look into the early history of the universe--these plants allow us to take a deeper look into genomic history".........

Posted by: Jessica      Permalink         Source

May 17, 2006, 11:51 PM CT

Ancient Tomb Sheds New Light On Egyptian Colonialism

In approximately 1550 B.C., Egypt conquered its southern neighbor, ancient Nubia, and secured control of valuable trade routes. But rather than excluding the colonized people from management of the region, new evidence from an archaeological site on the Nile reveals that Egyptian immigrants shared administrative responsibilities for ruling this large province with native Nubians.

"The study of culture contact in the past has conventionally used ideas of unidirectional change and modification of a subordinate population by a socially dominant group. The idea that authoritarian European powers forced changes in submissive native cultures dominated this work," explains Michele R. Buzon (University of Alberta). "However, more recent research has reevaluated these traditional notions and suggests that this model might not be appropriate for all situations of culture contact."

Through an examination of the archaeological site of Tombos, a strategic point of control in Egyptian-controlled Nubia, Buzon sought to determine whether the people buried in a colonial cemetery were immigrants from Egypt or Nubians who had adopted Egyptian practices. Comparing skull measurements with other revealing features such as tomb architecture, grave objects, and burial position, Buzon founds that the imperial officials who were buried in symbolically-marked tombs were of both Egyptian and Nubian descent. Egyptians were generally laid to rest on their backs in small tombs or pyramids, while Nubians were buried in fetal position on a bed or cow's skin.........

Posted by: William      Permalink         Source

May 16, 2006, 11:00 PM CT

Small Molecule Interactions Were Central To The Origin Of Life

In an important new paper forthcoming in the recent issue of The Quarterly Review of Biology, Robert Shapiro (New York University) argues against the widely held theory that the origin of life began with the spontaneous appearance of a large, replicating molecule such as RNA. Instead, Shapiro raises an alternative that does not depend on a "stupendously improbable accident," presenting the more plausible idea that life began within a mixture of simple organic molecules, multiplied through catalyzed reaction cycles and an external source of available energy.

"The diversity of organic chemistry, with its harvest of competing, interconnected reactions, becomes an asset rather than a liability in the case of the energy-driven system," explains Shapiro. "The existence of side reaction paths can provide the network with the capacity of reacting to circumstances."

Shapiro outlines how replicator theories, though they have been supported by "prebiotic" syntheses carried out by chemists using modern apparatus and purified reagents, are highly unlikely. The creation of a molecule that can self-replicate requires the combination of diverse chemicals in a long sequence of reactions in a specific order, interspersed by complicated separations, purifications, and changes in locale.........

Posted by: Ashley      Permalink         Source

May 14, 2006, 3:49 PM CT

How did cactuses evolve?

In a groundbreaking new study in the recent issue of American Naturalist, Erika J. Edwards (Yale University and University of California, Santa Barbara) and Michael J. Donoghue (Yale University) explore how leafy, "normal" plants evolved into the leafless succulent cactus.

"The cactus form is often heralded as a striking example of the tight relationship between form and function in plants," write the authors. "A succulent, long-lived photosynthetic system allows cacti to survive periods of extreme drought while maintaining well-hydrated tissues."

Recent molecular phylogenetic work has confirmed that Pereskia, a genus that consists of 17 species of leafy shrubs and trees, is where the earliest cactus lineages began. Using field studies and environmental modeling, Edwards and Donoghue found that the Pereskia species already showed water use patterns that are similar to the leafless, stem-succulent cacti.

"[Our] analyses suggest that several key elements of cactus ecological function were established previous to the evolution of the cactus life form," explain the authors. "Such a sequence may be common in evolution, but it has rarely been documented as few studies have incorporated physiological, ecological, anatomical, and phylogenetic data."........

Posted by: Jessica      Permalink         Source

May 12, 2006, 6:56 AM CT

Mobile DNA Part of Evolution's Toolbox

The repeated copying of a small segment of DNA in the genome of a primeval fish may have been crucial to the transition of ancient animals from sea to land, or to later key evolutionary changes in land vertebrates. The discovery is "tantalizing evidence" that copied DNA elements known as retroposons could be an important source of evolutionary innovations, says the director of the research, Howard Hughes Medical Institute investigator David Haussler.

"The big question is whether this is a special case or whether it's the tip of the iceberg," says Haussler, who is at the University of California, Santa Cruz. A report on the research is published in the May 4, 2006, issue of the journal Nature.

Haussler and his colleagues were led to the discovery through their work on what they call "ultraconserved elements"-segments of DNA hundreds of nucleotides long that are almost exactly the same in a wide variety of vertebrate organisms. Haussler and postdoctoral fellow Gill Bejerano discovered the ultraconserved elements in 2003, and since then they have been trying to figure out how they arose and what function they serve.

One ultraconserved element in particular caught their eye. "We were very interested in this sequence, because it had a number of copies elsewhere in the genome," says Bejerano, who is the first author of the study. Close copies of the sequence were ubiquitous in amphibians, birds, and mammals, indicating that it served an important function. "We found it in every species for which we have genomes, from frogs to humans," says Bejerano.........

Posted by: William      Permalink         Source

May 4, 2006, 5:03 PM CT

Man May Have Caused Pre-historic Extinctions

New research shows that pre-historic horses in Alaska may have been hunted into extinction by man, rather than by climate change as previously thought.

The discovery by Andrew Solow of Woods Hole Oceanographic Institute, US, David Roberts of the Royal Botanic Garden, Kew and Karen Robbirt of the University of East Anglia (UEA) is published this week in Proceedings of the National Academy of Sciences (PNAS).

The accepted view had previously been that the wild horses became extinct long before the extinction of mammoths and the arrival of humans from Asia - ruling out the possibility that they were over-hunted by man. One theory had been that a period of climate cooling wiped them out.

However, the scientists have discovered that uncertainties in dating fossil remains and the incompleteness of fossil records mean that the survival of the horse beyond the arrival of humans cannot be ruled out.

The PNAS paper develops a new statistical method to help resolve the inherent problems associated with dating fossils from the Pleistocene period. The aim is to provide a far more accurate timetable for the extinction of caballoid horses and mammoths and, ultimately, the cause.

"This research is exciting because it throws open the debate as to whether climate change or over-hunting may have led to the extinction of pre-historic horses in North America," said UEA's Karen Robbirt.........

Posted by: William      Permalink         Source

May 1, 2006, 11:58 PM CT

The Greenbeards Have Blue Throats

A new study of side-blotched lizards in California has revealed the genetic underpinnings of altruistic behavior in this common lizard species, providing new insights into the long-standing puzzle of how cooperation and altruism can evolve. The study, led by researchers at the University of California, Santa Cruz, offers the first evidence in vertebrates of an important theoretical concept in evolutionary biology known as "greenbeard" altruism.

"This reflects a major breakthrough in our understanding of how cooperative behavior arises from genes," said Barry Sinervo, professor of ecology and evolutionary biology at UCSC and first author of a paper describing the new findings. The paper would be published in the May 9 issue of Proceedings of the National Academy of Sciences (PNAS) and is currently available in the online early edition of PNAS.

The paper describes unrelated male lizards that form cooperative partnerships to protect their territories. These partnerships are often mutually beneficial, enabling both partners to father more offspring than they would on their own. Under some circumstances, however, one male in the pair may have few or no offspring as a result of protecting its partner from the aggressive intrusions of other lizards.

This type of cooperation, in which one individual bears all the costs and another unrelated individual receives the benefits, is called "true altruism." These lizards have an annual life cycle, so this behavior may spell the end of the altruistic male's lineage.........

Posted by: William      Permalink         Source

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