April 13, 2006, 0:06 AM CT

Evolutionary Consequences Of Bluebird Aggression

In findings that may offer insight into how evolution operates, a Duke University evolutionary ecologist reported evidence that aggressive male western bluebirds out-compete less aggressive males for preferred breeding territories. In the process, she found that more-aggressive and milder mannered birds also tended to breed in different settings that favor different body types.

This study, conducted by Renee Duckworth, Ph.D., suggests the birds may play more active roles in their own natural selection than traditional models of evolution would support.

"The traditional view of evolution is that organisms are passive creatures on which natural selection operates," said Duckworth, who just completed her doctoral training at Duke. But her research results, published online on Wednesday, April 12, 2006, in the journal Proceedings of the Royal Society B, suggest a different model, at least among these bluebirds.

"By selecting the environment in which they live, animals can actively affect the natural selection they experience," Duckworth said in an interview. "The main message of this study is that the ability of organisms to choose their environment needs to be made a more explicit part of evolutionary theory."

In her studies, funded by the National Science Foundation, Duckworth followed up on prior findings that adult western bluebirds aggressively defend large breeding territories and also use different foraging strategies in wooded and open habitats.........

Posted by: Kelly      Permalink         Source

April 13, 2006, 0:03 AM CT

Green sturgeon now have a 'threatened' status

The living fossil that still patrols the rivers of the Pacific Coast recently received a boost from the US government, which listed the green sturgeon as "threatened" under the Endangered Species Act, effective April 6th. While the ruling is needed to improve the health and outlook for the species, the new listing--authorized by a final ruling by the National Marine Fisheries Service--only applies to the southern population, and may fail to protect these fish leaving California's Sacramento River System unless stiff measures are applied over a wide geographical range, said the Wildlife Conservation Society (WCS).

"We support the 'threatened' listing of green sturgeon under the ESA; it is based on good science and we feel that this is a step in the right direction," said WCS researcher Dan Erickson, one of the leading experts on the species. "However, managers will have to craft regulations carefully to protect this southern population of green sturgeon, which are highly migratory and thus vulnerable to threats in Oregon and Washington coastal waters, and even impacts in Canada."

Eventhough the northern population of green sturgeon, which spawns in the Klamath River in California and the Rogue River in Oregon, is genetically distinct from this southern population that is now listed as Threatened, individual fish from each separate population most likely frequent the same coastal waters. As per archival-tagging studies conducted by Erickson, green sturgeon travel great distances from their ancestral rivers; individual fish from Oregon's Rogue River were tracked as far north as northern Vancouver Island, Canada, providing support to the theory that both populations likely interact with one another. Understanding the behavior and migratory patterns of these two populations are therefore important considerations for improving current regulatory frameworks for the species.........

Posted by: Kelly      Permalink         Source

April 11, 2006, 11:22 PM CT

Global Warming May Lead To Mass Species Extinctions

The Earth could see massive waves of species extinctions around the world if global warming continues unabated, according to a new study published in the scientific journal Conservation Biology.

Given its potential to damage areas far away from human habitation, the study finds that global warming represents one of the most pervasive threats to our planet's biodiversity - in some areas rivaling and even surpassing deforestation as the main threat to biodiversity.

The study expands on a much-debated 2004 paper published in the journal Nature that suggested a quarter of the world's species would be committed to extinction by 2050 as a result of global warming. This latest study picks up where the Nature paper left off, incorporating critiques and suggestions from other scientists while increasing the global scope of the research to include diverse hotspots around the world. The results reinforce the massive species extinction risks identified in the 2004 study.

"Climate change is rapidly becoming the most serious threats to the planet's biodiversity," said lead author Dr. Jay Malcolm, an assistant forestry professor at the University of Toronto. "This study provides even stronger scientific evidence that global warming will result in catastrophic species loss across the planet".........

Posted by: Kelly      Permalink         Source

April 11, 2006, 11:15 PM CT

Sex-Change Secrets Of The Black Sea Bass

In a former cowshed on the edge of the University of New Hampshire campus, David Berlinsky, assistant professor of zoology, peers into a big blue plastic tub. Inside, black sea bass circle slowly in the dim light. The converted barn is now an aquaculture research facility for the College of Life Sciences and Agriculture, and home to Berlinsky's latest research.

Black sea bass feature prominently on a number of menus, but wild populations of the fish are in decline and their availability is limited. Because of the high demand, they're a good candidate for aquaculture on the east coast. Except, that is, for one problem: they have a tendency to change sex unpredictably in captivity.

"In the wild, black sea bass are born as females and turn into males at around two to five years old," Berlinsky explains. "When you bring them into captivity, they change into males more quickly." Some captive-born fish emerge as males even before reaching adulthood, devoting energy toward reproductive development and away from growth. Such problems make breeding and growing the fish in captivity a tricky proposition.

"Black sea bass is a wonderful fish to culture and to eat," says George Nardi, vice president and director of GreatBay Aquaculture, a commercial fish farm in Newington, NH. But the sex change problem must be tackled if fish farmers are to bring a high-quality fish to market. "We invest in our brood stocks, the parents of the young fish, much as a thoroughbred horse farm invests in mares and stallions," he says. "It doesn't do us much good if we always have to go out and get new females".........

Posted by: Kelly      Permalink         Source

April 11, 2006, 11:03 PM CT

Dead Zone" Summer Killed Billions of Ocean State Mussels

Fish kills, foul odors and closed beaches hit Rhode Island's Narragansett Bay during the summer of 2001. The culprit was hypoxia, or oxygen depletion, which literally suffocates sea life. While some evidence of this "dead zone" could be seen on the bay's surface, Brown University ecologists went underwater and discovered a massive mussel die-off.

In a survey of nine mussel reefs located in the central bay, scientists found one reef completely wiped out. Of the remaining eight, seven were severely depleted. The ecologists estimate that the number of mussels that died was roughly 4.5 billion, or about 80 percent of the reefs' population.

Just one month before hypoxia hit, scientists surveyed the same reefs and saw acres of healthy, densely packed mussels blanketing the estuary floor.

"What we saw was a local extinction," said Andrew Altieri, a new Ph.D. graduate from Brown University's Department of Ecology and Evolutionary Biology. "The mussel population was devastated. If the magnitude of this die-off was visible from the surface, there would've been public alarm".

Altieri conducted the surveys with Jon Witman, a marine ecologist and an associate professor in the Department of Ecology and Evolutionary Biology. In a report on their research, published in Ecology, Altieri and Witman show that mussel die-off had a lasting effect.........

Posted by: Kelly      Permalink         Source

April 11, 2006, 10:40 PM CT

Environmental Toxins Effect Hearing In Mammals

Yale School of Medicine scientists have new data showing chloride ions are critical to hearing in mammals, which builds on prior research showing a chemical used to keep barnacles off boats might disrupt the balance of these ions in ear cells.

"Our data are the first to directly show that chloride ions are crucial for our exquisite sense of hearing," said Joseph Santos-Sacchi, professor in the Departments of Surgery and Neurobiology and first author of the study in the Journal of Neuroscience. "These data also indicate that the hearing in marine and other mammals could be affected by environmental toxins, such as TBT (tributyl tin), because they appear to alter the balance of chloride ions in the outer hair cell."

Sensitive hearing in mammals relies on cochlear amplification resulting from the motor activity of outer hair cells. They are the only group of animals that have outer hair cells. Additionally, TBT is known to damage the immune and hormonal systems of marine mammals.

In this study on guinea pigs, Santos-Sacchi tested whether TBT or salicylate, which is a chemical that occurs naturally in plants and is a component of aspirin, interfered with the guinea pigs' ability to hear. He found that TBT, salicylate, or otherwise altering the extracellular chloride levels in the cochleas, interfered with the balance of chloride in the outer hair cells and caused profound changes in sound amplification in the inner ear.........

Posted by: Kelly      Permalink         Source

April 10, 2006, 7:00 PM CT

Restoring Seagrass Beds

Eventhough most people consider bird droppings a nuisance, researchers at the Dauphin Island Sea Lab see them as a rich source of phosphorus, a natural fertilizer for grassbeds which have been destroyed by boat propellers. Over the next couple of months, Sea Lab researchers Dr. Ken Heck and Dr. John Dindo will be setting out bird stakes in an effort to revive scarred grassbeds around the popular recreational spot of Robinson Island in Orange Beach, Alabama.

Robinson Island is a favored spot in the summer, with constant boat traffic in its shallow waters. Its underwater shoal grassbeds, however, have been much impacted by propeller damage; and much of the terrestrial vegetation on the island itself was destroyed by Hurricane Ivan in 2004. Drs. Heck and Dindo received a grant from the Gulf of Mexico Program to restore both the dune habitation and the prop-scarred grassbeds of this popular location.

Dune restoration will begin on Tuesday, April 11, from 10am to 1pm as Dr. Dindo and volunteers from AmeriCorps plant 1,000 sea oats on the beaches of Robinson Island.

Over the next two months, Drs. Heck and Dindo will also plant birdstakes in the damaged grassbeds, hoping to attract seabirds to use the stakes as a resting area where they can "do their business" and fertilize the shoal grass beneath them.........

Posted by: Kelly      Permalink         Source

April 9, 2006, 8:20 PM CT

Ants Arose 140-168 Million Years Ago

Ants are considerably older than previously believed, having originated 140 to 168 million years ago, as per new research on the cover of this week's issue of the journal Science.

But these resilient insects, now found in terrestrial ecosystems the world over, apparently began to diversify only about 100 million years ago in concert with the flowering plants, the researchers say.

"This study integrates numerous fossil records and a large molecular data set to infer the evolutionary radiation of ants, which have deeper roots than we thought," said Chuck Lydeard, program director in NSF's Division of Environmental Biology, which funded the research.

The study was also supported by the Green Fund.

Led by biologists Corrie Moreau and Naomi Pierce of Harvard University, the scientists reconstructed the ant family tree using DNA sequencing of six genes from 139 representative ant genera, encompassing 19 of 20 ant subfamilies around the world.

"Ants are a dominant feature of nearly all terrestrial ecosystems, and yet we know surprisingly little about their evolutionary history: the major groupings of ants, how they are correlation to each other, and when and how they arose," said Moreau. "We now have a clear picture of how this extraordinarily dominant - in ecological terms - and successful - in evolutionary terms - group of insects originated and diversified."........

Posted by: Kelly      Permalink         Source

April 6, 2006, 11:11 PM CT

Nanopore To Revolutionize Genome Sequencing

A team led by physicists at the University of California, San Diego has shown the feasibility of a fast, inexpensive technique to sequence DNA as it passes through tiny pores. The advance brings personalized, genome-based medicine closer to reality.

The paper, reported in the recent issue of the journal Nano Letters, describes a method to sequence a human genome in a matter of hours at a potentially low cost, by measuring the electrical perturbations generated by a single strand of DNA as it passes through a pore more than a thousand times smaller than the diameter of a human hair. Because sequencing a person's genome would take several months and millions of dollars with current DNA sequencing technology, the scientists say that the new method has the potential to usher in a revolution in medicine.

"Current DNA sequencing methods are too slow and expensive for it to be realistic to sequence people's genomes to tailor medical therapys for each individual," said Massimiliano Di Ventra, an associate professor of physics at UCSD who directed the project. "The practical implementation of our approach could make the dream of personalizing medicine as per a person's unique genetic makeup a reality".

The physicists used mathematical calculations and computer modeling of the motions and electrical fluctuations of DNA molecules to determine how to distinguish each of the four different bases (A, G, C, T) that constitute a strand of DNA. They based their calculations on a pore about a nanometer in diameter made from silicon nitride-a material that is easy to work with and usually used in nanostructures-surrounded by two pairs of tiny gold electrodes. The electrodes would record the electrical current perpendicular to the DNA strand as the DNA passed through the pore. Because each DNA base is structurally and chemically different, each base creates its own distinct electronic signature.........

Posted by: Kelly      Permalink         Source

April 6, 2006, 10:55 PM CT

War between the sexes influences evolution

Competition and conflict between males and females start inside the egg in some species, say scientists.

Birds, butterflies, and snakes have a genetic war between the sexes that influences the way they evolve, as per a new theory reported in the April 7 issue of the journal Science.

"Genetic conflict is of great interest in evolutionary biology," explained first author Paige M. Miller. Miller is a postdoctoral fellow in the Department of Ecology, Evolution and Marine Biology (EEMB) at the University of California, Santa Barbara.

The recent publication of the chicken genome has sparked new interest in ZW species, explained William R. Rice, co-author and professor in the Department of EEMB at UC Santa Barbara.

Chickens serve as model organisms in a number of areas of research. Unlike mammals, the females are heterozygous; they have two different sex chromosomes, Z and W. In the human female, the sex chromosomes are XX; they are homozygous. Butterflies, birds and snakes are ZW species.

The authors explain that maternal-effect genes are those that are expressed in the mother, are packaged in the egg, and influence the development of offspring.

"We believe that the maternal-effect genes are a new arena for conflict in ZW species," said Rice. "The mathematical models support this conclusion. 'Son killers' are predicted to accumulate on the W chromosome and 'daughter killers' to accumulate on the Z."........

Posted by: Kelly      Permalink         Source