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October 31, 2007, 9:10 PM CT

Why do so many species live in tropical forests and coral reefs?

Why do so many species live in tropical forests and coral reefs?
An adult male parrotfish.

Credit: University of Exeter
The latest development in a major debate over a controversial hypothesis of biodiversity and species abundance is the subject of a paper would be reported in the 1 November 2007 issue of the journal Nature. The authors report good agreement between the species richness of two of the world's most vulnerable ecosystems -- tropical forests and coral reefs -- and a simple mathematical model building on the so-called "neutral theory of biodiversity." "We're helping to refine and improve this theory because it might have important implications for the effort to protect terrestrial biodiversity from climate change and urban development," says Jayanth Banavar of the Department of Physics at Penn State, a member of the research team.

The Nature paper is based on a counterintuitive assumption of neutral theory: that one can largely ignore interactions between species in modeling patterns of species abundance. The authors are physicists Igor Volkov and Jayanth Banavar of Penn State University, plant biologist Stephen Hubbell of UCLA (formerly of the University of Georgia), and physicist Amos Maritan of the University of Padua in Italy.

Among ecological theorists, neutral theory has sparked a six-year quarrel over the fundamental assumptions of their discipline. The Nature paper counters another scientific team's claim in 2006 that coral-reef diversity "refutes" the neutral theory. At the same time, the paper by Volkov et al., would be published on 1 November 2007, modifies the classical version of neutral theory that appeared in a 2001 book by Hubbell. (Graham Bell of McGill University also developed a neutral theory independently of Hubbell.) Banavar, Maritan, Volkov, and their collaborators have been active in the development of a mathematical framework for understanding ecosystems that builds on and clarifies Hubbell's neutral theory.........

Posted by: Kelly      Read more         Source


October 31, 2007, 9:05 PM CT

Tangled web of the insect, plant and parasite arms race

Tangled web of the insect, plant and parasite arms race
New insights into the evolutionary relationship between plant-dwelling insects and their parasites are revealed in the online open access journal BMC Biology. Scientists shed light on how sawflies evolved to escape their parasites and gain themselves an 'enemy-free space' for millions of years.

Tommi Nyman of the University of Joensuu in Finland together with colleagues from Sweden and Gera number of uncovered a food web involving willow trees, sawflies, and the parasites feeding on sawfly larvae. Sawflies (a group of insects correlation to bees and wasps) lay their larvae in willows creating galls, which are protruding growths of plant tissue. Nyman's group used data from galls collected from willows over an 18-year period. They classified 43 sawfly species using genetic analysis and assessed the degree of parasitism to which these insects had been subjected by 72 different parasites.

Their statistical analysis showed that parasitism promotes the insects' ecological divergence in a co-evolutionary arms race. The sawflies develop new gall-types and, in doing so, can escape the attentions of the parasites without having to switch host plant. Some parasites, however, have in turn adapted to the divergence in gall-types, driving further speciation. These processes partly explain the unusual diversity of herbivorous insects and their parasitoids.........

Posted by: Kelly      Read more         Source


October 31, 2007, 9:04 PM CT

Coral reefs will be permanently damaged

Coral reefs will be permanently damaged
Coral reefs could be damaged beyond repair, unless we change the way we manage the marine environment. New research by the Universities of Exeter and California Davis, published recently (1 November 2007) in Nature, shows how damaged Caribbean reefs will continue to decline over the next 50 years.

Coral reefs conjure up images of rich, colourful ecosystems yet an increasing number of reefs are becoming unhealthy and overrun by seaweed. The research team wanted to test whether reefs that are overgrown with algae could return to good health if the original causes of the problem, such as fishing or pollution, were addressed. This could mean, for example, reducing fishing or introducing better sewage management. The study revealed that the answer is no because coral reefs can become permanently unhealthy.

In the 1980s, reefs in the Caribbean were hit by the devastating impact of the near-extinction of the herbivorous urchin, Diadema antillarum, with devastating results. Along with parrotfish, this grazing urchin kept seaweed levels down, creating space for coral to grow. Parrotfish are now the sole grazers of seaweed on a number of Caribbean reefs, but fishing has limited their numbers. With insufficient parrotfish grazing, corals are unable to recover after major disturbances like hurricanes and become much less healthy as a result. The team discovered this result by creating and testing a computer model that simulates the effects of a number of factors on the health of Caribbean reefs.........

Posted by: Janet      Read more         Source


October 31, 2007, 8:56 PM CT

Domestic cat genome sequenced

Domestic cat genome sequenced
A report that appears in the scientific journal Genome Research (www.genome.org) details the first assembly, annotation, and comparative analysis of the domestic cat genome (Felis catus).

The DNA of a 4-year-old Abyssinian cat named Cinnamon, whose well-documented lineage can be traced back several generations to Sweden, has been sequenced. Cinnamon is one of several mammals that are currently being analyzed using light (two hundred percent) genome sequence coverage. To make sense of Cinnamons raw sequence data, a multi-center collaboration of researchers leveraged information from previously sequenced mammalian genomes as well as prior gene-mapping studies in the cat. In doing so, they observed that Cinnamons sequences spanned about 65% of the euchromatic (gene-containing) regions of the feline genome.

The similarity between the cat genome and six recently completed mammalian genomes (human, chimpanzee, mouse, rat, dog, and cow) allowed the researchers to identify 20,285 putative genes in the cat genome. The comparison also revealed hundreds of chromosomal rearrangements that have occurred among the different lineages of mammals since they diverged from a diminutive ancestor that roamed the earth among the dinosaurs some 100 million years ago.........

Posted by: Janet      Read more         Source


October 31, 2007, 8:08 PM CT

Go nano, natural and green

Go nano, natural and green
In 2002, U.S. farmers harvested 2.7 billion bushels of soybeans. Last year in Missouri, farmers harvested 194 million bushels of soybeans worth about $1.2 billion. Now, a team of scientists at the University of Missouri-Columbia is turning those soybeans into gold, with nothing more than a little water.

MU scientists Kattesh Katti, Raghuraman Kannan, and Kavita Katti led a team of researchers that have discovered how to make gold nanoparticles using gold salts, soybeans and water. No other chemicals are used in the process, which means this new process could have major environmental implications for the future.

Typically, a producer must use a variety of synthetic or man-made chemicals to produce gold nanoparticles, said Katti, professor of radiology and physics in MUs School of Medicine, senior research scientist at MURR, and College of Arts and Science, and director of the University of Missouri Cancer Nanotechnology Platform. In addition, to make the chemicals necessary for production, you need to have other artificial chemicals produced, creating an even larger, negative environmental impact. Our new process only takes what nature has made available to us and uses that to produce a technology that has already proven to have far-reaching impacts in technology and medicine.........

Posted by: Erica      Read more         Source


October 31, 2007, 7:17 PM CT

Genes Behind Alcohol Sensitivity in Fruit Flies

Genes Behind Alcohol Sensitivity in Fruit Flies
Drs. Robert Anholt and Trudy Mackay watch drunk and sober fruit flies in the inebriometer. Photo by Roger Winstead.
Some fruit flies can drink others under the table.

Now, researchers at North Carolina State University have a few more genetic clues behind why some flies are more sensitive to alcohol than others. And the results might lead to more knowledge about alcoholism in humans.

After genetically modifying fruit flies to be either extremely sensitive or extremely resistant to alcohol - lightweights or lushes - the NC State researchers observed that many fruit fly genes undergo changes when sensitivity to alcohol changes.

Many these genes, the scientists report, are similar to genes found in humans, suggesting that they may be good targets to study human predisposal to alcoholism.

The research is reported in the November edition of Genome Biology, which is available online at http://genomebiology.com.

The research team - Dr. Tatiana Morozova, a post-doctoral researcher in zoology; Dr. Trudy Mackay, William Neal Reynolds Professor of Genetics; and Dr. Robert Anholt, professor of zoology and genetics - used a unique approach in the study.

Rather than examining gene changes after exposure to alcohol and the development of tolerance to it, the NC State study first artificially selected flies for alcohol sensitivity - creating the lushes and the lightweights - and then, in a "whole-genome" approach, examined the entire genome, or set of all genes, to find genes that had consistent changes in expression as a response to the artificial selection.........

Posted by: Janet      Read more         Source


October 30, 2007, 10:27 PM CT

Origin of life on primitive Earth?

Origin of life on primitive Earth?
Experiments show that simple molecules can combine chemically rather than biologically to form the building blocks of DNA, the key component of all life forms. These processes might have taken place on primitive earth, but how they occur is an unsolved puzzle.

Chemists at the University of Georgia have now proposed the first detailed, feasible mechanism to explain how adenine, one of the four building blocks of DNA, might be built up from the combination of five cyanide molecules. The investigation is based on extensive quantum chemical computations over several years.

Just where these biomolecules originated isnt known, said Paul von Ragu Schleyer, Graham Perdue Professor of Chemistry at the University of Georgia. One can only speculate. They could have formed from smaller molecules present on primitive Earth, either very slowly over millions of years or rapidly before the Earth cooled down. Asteroids may have brought them from outer space, but how did biomolecules form there".

The newly proposed mechanism for the formation of adenine gives a clear picture of how it could have become one of the building blocks essential for the formation of DNA. The research was published recently in the print version of the Proceedings of the National Academies of Science. Schleyers coworkers were Ph. D. candidate Debjani Roy, the first author of the paper, and Katayoun Najafian, his former student from Iran.........

Posted by: Janet      Read more         Source


October 30, 2007, 10:26 PM CT

Speed plays crucial role

Speed plays crucial role
IMAGE / Markus Buehler
This figure from an atomistic model shows a protein in the process of unwinding in response to pressure.
Scientists at MIT studying the architecture of proteins have finally explained why computer models of proteins' behavior under mechanical duress differ dramatically from experimental observations. This work could have vast implications in bioengineering and medical research by advancing our understanding of the relationship between structure and function in these basic building blocks of life.

In a paper published as the cover article of the Oct. 16 issue of the Proceedings of the National Academies of Sciences (PNAS), the scientists, who work with atomistic models-accurate representations of nature that use fundamental laws of atomistic interactions as their basis-show for the first time the basic rupture mechanisms of protein structures when protein strands unfold in response to pressure.

"We have for the first time simulated the behavior of protein structures under conditions that correspond to those in living biological systems," said Markus Buehler, the Esther and Harold E. Edgerton Assistant Professor in MIT's Department of Civil and Environmental Engineering and lead researcher on the team. "All the different types of proteins we studied exhibit two distinct fracture modes that are dependent on the speed at which force is applied. Now we understand that what seemed unrealistic in the earlier computer simulations was actually a consequence of deformation rates and a change in the way hydrogen bonds respond to pressure".........

Posted by: Janet      Read more         Source


October 30, 2007, 10:21 PM CT

Gene that gives dogs black fur

Gene that gives dogs black fur
A discovery about the genetics of coat color in dogs could help explain why humans come in different weights and vary in our abilities to cope with stress, a team led by scientists from the Stanford University School of Medicine reports.

The study, reported in the Nov. 2 issue of Science, answers a longtime mystery: What determines coat color in dogs" While scientists have known since the 1900s that most mammals share the same genetic mechanism to determine coat color, by the 1950s they began to suspect that dogs were different.

Now after swabbing the inner cheeks of hundreds of dogs and analyzing the DNA in the resulting samples, a team led by genetics professor Greg Barsh, MD, PhD, has nailed the gene. To the researchers' surprise, the gene makes a protein that's part of a large and variable family called defensins, thought to fight infections.

What is clear now is that this protein engages the melanocortin pathway, a circuit of molecular interactions that controls the type of melanin and amount of cortisol produced by the body. Barsh's lab has studied this pathway, which determines skin and hair color as well as stress adaptation and weight regulation, for 15 years.

The discovery of a new participant in this pathway opens up new vistas for drug research, said the article's co-first author, Sophie Candille, PhD, a former graduate student in Barsh's lab. Candille visited five Bay Area dog shows over six months to gather hundreds of samples by gently swabbing the inside of the dogs' cheeks with a brush.........

Posted by: Kelly      Read more         Source


October 30, 2007, 10:16 PM CT

Underestimation of frog numbers causes concern

Underestimation of frog numbers causes concern
Frogs are vanishing from all the world's ecosystems with unprecedented speed. It is thought that more than 100 species have died out since 1980 alone.

In a paper reported in the online, open-access journal PLoS ONE, a team of experts, including scientists from the University of Canterbury, says the number of species has been strongly underestimated and they are calling for action.

The scientists from France and New Zealand collected and collated more than 500 DNA sequences, including 60 previously recognised species, occurring in the Guiana Shield, which harbours the largest continuous tract of virgin tropical rainforest.

This region of Amazonia comprises French Guiana, Suriname, Guyana, eastern Venezuela and northern Brazil.

PhD researcher Antoine Fouquet says the samples revealed an astonishing level of cryptic diversity, with the number of species identified potentially two hundred percent greater than previously thought.

Antoine says such underestimation of amphibian diversity has broad implications for the management of biodiversity, and especially that of a number of Neotropical amphibians which are considered highly threatened.

He says frogs are the "canaries in the coal mine" and their current decline is regarded as an indicator of the environmental crisis.........

Posted by: Kelly      Read more         Source

   

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