September 20, 2006, 9:59 PM CT

Sea Squirts Problem Persisting

Researchers have just completed a field survey of the invasive sea squirt colony on the Georges Bank, first discovered in 2003. A wider area was searched for the sea squirt this year, and it was mapped over about twice the area observed in 2004. Results show that the species is present in two adjacent areas totaling 88 square miles in U.S. waters near the U.S.-Canada boundary. The very large mat-like colonies observed in 2004 have been replaced by fewer smaller ones. The Georges Bank occurrence is the largest known infestation of colonial sea squirts in a major offshore fishing ground.

For the fourth consecutive year, federal and university scientists have surveyed two areas on Georges Bank where an invasive colonial sea squirt continues to thrive on the gravel bottom. The colonies are denser than in 2005 over the 88 square-mile area observed. But researchers found no colonies in nearby Canadian waters, indicating they have not spread eastward. The Georges Bank squirts are a species of the genus Didemnum.

"The area of seabed covered by the colonies has doubled at 75 percent of the sites we observed in both 2005 and 2006," said Dr. Page Valentine of the U.S. Geological Survey, who tracks occurrences of the species off the northeastern U.S., and elsewhere in the world. Greater density of colonies observed during the survey is evidence that the infestation is persistent, and not a short-lived phenomenon.........

Posted by: Ashley      Permalink         Source

September 19, 2006, 9:24 PM CT

Evolution at fast pace In The Island

The restricted scale, isolation, and sharp boundaries of islands create unique selective pressures, often to dramatic effect. Following what's known as the "island rule," small animals evolve into outsize versions of their continental counterparts while large animals shrink.

Giant tortoises and iguanas still inhabit the Galápagos and a few other remote islands today, but only fossils remain of the dwarf hippopotami, elephants, and deer that once lived on islands in Indonesia, the Mediterranean, and the Pacific Ocean. The fossil record suggests that these size changes occur rapidly after species become isolated on islands, but this long standing assumption has never been empirically examined in a systematic manner. Now, in a new study published in PLoS Biology, Virginie Millien confirms that island species undergo accelerated evolutionary changes over relatively short time frames, between decades and several thousand years.

Millien collected data from text, figures, and tables in an extensive survey of the published literature. From these datasets, she calculated a total of 826 evolutionary rates for 170 populations representing 88 species. Rates of evolutionary change, she found, decreased over time for both island and mainland species, with a slower rate of decrease for island species. The differences in evolutionary rates between island and mainland pairs also decreased over time, becoming statistically insignificant for intervals over 45,000 years. Overall, island species evolved faster than mainland species--a phenomenon that was most pronounced for intervals between 21 years through 20,000 years.........

Posted by: Ashley      Permalink         Source

September 18, 2006, 10:32 PM CT

Bird Moms Manipulate Birth Order To Protect Sons

Protecting her kids from peril is the job of every good mom.

When marauding mites turn up in a house finch's nest, she shelters her sons from the blood-suckers by laying male eggs later than those containing their sturdier sisters, according to new research.

Making sure the vulnerable baby boys are exposed to mites for a shorter period allows both the sons and the daughters to survive long enough to leave the nest.

"Sons are more sensitive to the mites than daughters," said Alexander V. Badyaev of The University of Arizona in Tucson. "Mothers minimize sons' exposure to mites by laying male eggs later than female eggs. As a result, the males are in the nest fewer days".

Even so, the male chicks that grow up during mite season end up just as big as ones from the mite-free time of the year.

It's all mom's doing, Badyaev said.

Once breeding female finches are exposed to mites, their bodies make hormonal changes that affect the order of egg laying and accelerates the development of their sons while they're still in the egg.

"We've found a mechanism by which duration of growth can be adjusted to a changing risk of mortality," said Badyaev, a UA assistant professor of ecology and evolutionary biology. He added that this is the first documentation that maternal manipulation of both ovulation and growth influences the duration of development in birds.........

Posted by: Ashley      Permalink         Source

September 18, 2006, 5:38 PM CT

Remote Island Provides Clues On Population Growth

Halfway between South America and New Zealand, in the remote South Pacific, is Rapa. This horseshoe-shaped, 13.5 square-mile island of volcanic origin, located essentially in the middle of nowhere, is "a microcosm of the world's situation," says a University of Oregon archaeologist.

Until only recently, little was known about the French Polynesian Island, where the current population is less than 500. Archaeological, linguistic and genetic data suggest that the island, like much of East Polynesia, was inhabited in a final pulse of colonization by seafaring travelers who originated from Island Southeast Asia. New research, led by the University of Oregon's Douglas Kennett, has shed fresh new light on Rapa, particularly on what life may have been like for as a number of as 1,500 to 2,000 people who lived there before the arrival of European explorers.

Kennett's team, which included scientists from three institutions, published in the recent issue of the journal Antiquity that Polynesians arrived on the island around A.D. 1200, much later than long assumed. The settlers spread across the island, splintering from a shoreline-based society into competing groups that built and likely defended a growing number of spectacular fortifications carved from mountaintops in the years before English explorer George Vancouver sailed by in 1791, ushering in European contact.........

Posted by: Ashley      Permalink         Source

September 15, 2006, 1:41 PM CT

Genome Compaction In Spores And Sperm

In higher order animals, genetic information is passed from parents to offspring via sperm or eggs, also known as gametes. In some single-celled organisms, such as yeast, the genes can be passed to the next generation in spores. In both reproductive strategies, major physical changes occur in the genetic material after it has been duplicated and then halved on the way to the production of mature gametes or spores. Near the end of the process, the material called chromatin, the substructure of chromosomes becomes dramatically compacted, reduced in volume to as little as five percent of its original volume.

Researchers at The Wistar Institute, studying the mechanisms that control how the genetic material is managed during gamete production, have now identified a single molecule whose presence is required for genome compaction. Their experiments showed that the molecule "marks" the chromatin just prior to compaction and that its presence is mandatory for successful compaction. Additionally, after first noting the molecule's activity during the production of yeast spores, the scientists saw the same activity during the creation of sperm in fruit flies and mice, suggesting that the mechanisms governing genome compaction are evolutionarily ancient, highly conserved in species whose lineages diverged long ago. A report on the new study appears in the September 15 issue of Genes & Development. A "Perspectives" review in the same issue expands on the significance of the findings.........

Posted by: Ashley      Permalink         Source

September 14, 2006, 8:43 PM CT

MIT Team Describes Unique Cloud Forest

Trees that live in an odd desert forest in Oman have found an unusual way to water themselves by extracting moisture from low-lying clouds, MIT researchers report.

In an area that is characterized mostly by desert, the trees have preserved an ecological niche because they exploit a wispy-thin source of water that only occurs seasonally, said Elfatih A.B. Eltahir, professor of civil and environmental engineering, and former MIT graduate student Anke Hildebrandt.

After studying the Oman site, they also expressed concern that the unusual forest could be driven into extinction if hungry camels continue eating too much of the foliage. As the greenery disappears it's possible the trees will lose the ability to pull water from the mist and recharge underground reservoirs.

A report on their research was published in a recent issue of Geophysical Research Letters. They are also advising the Omani government on handling the problem.

The forest is particularly unique, said Eltahir and Hildebrandt, because it "is a water-limited seasonal cloud forest" that is kept alive by water droplets gathered from passing clouds -- ground fog. The water dribbles into the ground and sustains the trees later when the weather is dry. The MIT work suggests the trees actually get more of their water through contact with clouds than via rainfall.........

Posted by: Tyler      Permalink         Source

September 14, 2006, 7:05 PM CT

Senecio Rowleyanus

The longest running plant sale at the garden occurs today and tomorrow: the 29th Annual Indoor Plant Sale. I had a grand time yesterday trying to photograph a few of the plants available, since I don't often get the opportunity to work with indoor plants.

A native of southwestern Africa, "string of beads" grows in arid habitats. The succulent beads are actually the leaves, modified for living through extended periods of drought. Dr. T. Ombrello of Union County College has written an intriguing article on the adaptations of this Senecio and the closely related Senecio herreianus, entitled Senecios, With Windows in Their Leaves. The narrow bands you can see on some of the beads consist of transparent tissue to allow light to penetrate the interior of the bead and increase photosynthesis without increasing water loss.

It might be worth revisiting my comments on diversity within the Asteraceae in the BPotD entry on Raoulia australis. There is simply an amazing amount of diversity of form and structure in this plant family.........

Posted by: Ashley      Permalink         Source

September 14, 2006, 4:30 AM CT

Warming climate might affect polar bear population

Some travel agencies touting Arctic tours have been revving up their recent promotions to tourists about the increased likelihood they will spot polar bears in this region where several populations of polar bears live. As per researchers from NASA and the Canadian Wildlife Service, these increased Arctic polar bear sightings are probably correlation to retreating sea ice triggered by climate warming and not due to population increases as some may believe.

The new research suggests that progressively earlier breakup of the Arctic sea ice, stimulated by climate warming, shortens the spring hunting season for female polar bears in Western Hudson Bay and is likely responsible for the continuing fall in the average weight of these bears. As females become lighter, their ability to reproduce and the survival of their young decline. Also, as the bears become thinner, they are more likely to push into human settlements for food, giving the impression that the population is increasing. The study will be published this week in the recent issue of the Journal Arctic.

Claire Parkinson, a scientist at NASA's Goddard Space Flight Center, Greenbelt, Md., and Ian Stirling, a senior scientist with the Canadian Wildlife Service, Edmonton, Alberta, used NASA satellite observations captured from 1979 to 2004 to show the reduction in sea ice cover in several specific areas where there are known polar bear populations. In most of the areas studied, they observed that ice break-up in these areas has been occurring progressively earlier.........

Posted by: Tyler      Permalink         Source

September 13, 2006, 9:21 PM CT

Cellular Protein Factories

Proteins of all sizes and shapes do most of the work in living cells, and the DNA sequences in genes spell out the instructions for making those proteins. The crucial job of reading the genetic instructions and synthesizing the specified proteins is carried out by ribosomes, tiny protein factories humming away inside the cells of all living things.

Harry Noller, the Sinsheimer Professor of Molecular Biology at the University of California, Santa Cruz, has been studying the ribosome for more than 30 years. His main goal is to understand how the ribosome works and how it evolved, but there are also practical reasons to pursue this research. Many of the most effective antibiotics work by targeting bacterial ribosomes, and findings by Noller and others have led to the development of novel antibiotics that hold promise for use against germs that have developed resistance to current drugs. Drug-resistant staph infections, for example, are a serious problem in hospitals.

Noller's laboratory achieved breakthroughs in 1999 and 2001, producing the first high-resolution images of the molecular structure of a complete ribosome. Now, his team has made another major advance with an even higher-resolution image that enables them to construct an atom-by-atom model of the ribosome.........

Posted by: Ashley      Permalink         Source

September 13, 2006, 5:11 AM CT

Do green markets actually lead to improvements in environmental quality?

Goods and services with environmental benefits are a growing part of many sectors of the economy, and a timely new paper from the current issue of the Journal of Political Economy analyzes how our willingness to pay more for environmentally friendly products actually influences environmental quality and social welfare. Surprisingly, the study finds that under certain reasonable conditions, green markets can actually discourage private support of public environmental entities.

Using a model of impure public goods, Matthew J. Kotchen (University of California, Santa Barbara) analyzes goods that have both private and public components, each of which is available individually. For example, shade-grown coffee is grown not on deforested plantations, but under the canopy of tropical forests. Thus, consumers are not only buying coffee, which is a traditional private good, but also biodiversity conservation. However, consumers also have the option to buy conventional coffee and donate directly to tropical conservation.

"Although green markets are promoted to improve environmental quality and promote social welfare, their actual effects may be detrimental to both," writes Kotchen. "These results, along with the conditions sufficient to rule them out, provide new insight into the potential advantages and disadvantages of green markets as a decentralized mechanism of environmental policy".........

Posted by: Ashley      Permalink         Source