November 14, 2007, 8:52 PM CT

Simple reason helps males evolve more quickly

The observation that males evolve more quickly than females has been around since 19th century biologist Charles Darwin noted the majesty of a peacocks tail feather in comparison with the plainness of the peahens.

No matter the species, males apparently ramp up flashier features and more melodious warbles in an eternal competition to win the best mates, a concept known as sexual selection.

Why males are in evolutionary overdrive even though they have essentially the same genes as females has been a mystery, but an explanation by University of Florida Genetics Institute scientists to appear online in the Proceedings of the National Academy of Sciences this week may shed light on the subject.

Its because males are simpler, said Marta Wayne, an associate professor of zoology in the College of Liberal Arts and Sciences and director of UFs Graduate Program in Genetics and Genomics. The mode of inheritance in males involves simpler genetic architecture that does not include as a number of interactions between genes as could be involved in female inheritance.

The finding may also be useful to researchers studying why diseases may present themselves or respond to therapy differently in men and women.

Scientists examined how gene expression is inherited differently in male and female fruit flies using microarray analysis, which is a way to monitor the activity of thousands of genes simultaneously. The flies were identical genetically, except that females have two X chromosomes and males have a single X and a single Y chromosome......... Posted by: Kelly      Read more         Source

November 13, 2007, 9:58 PM CT

Flying Lemurs Are the Closest Relatives of Primates

While the human species is unquestionably a member of the primate group, the identity of the next closest group to primates within the entire class of living mammals has been hotly debated. Now, new molecular and genomic data gathered by a team including Webb Miller, a professor of biology and computer science and engineering at Penn State, has shown that the colugos -- nicknamed the flying lemurs -- is the closest group to the primates. A paper announcing the results would be reported in the journal Science on Nov. 2. The team was led by William J. Murphy, associate professor in the Department of Veterinary Integrative Biosciences at Texas A & M University.

Debates over which of several mammalian groups is the closest relative to the primates have become more intense in the last 10 years because of new fossil and molecular evidence. Some researchers have suggested that the group Scandentia, which includes the small tree shrews that scamper up and down trees in Asia, deserves the honor. Tree shrews have fluffy tails, long, pointed snouts and a very large brain size for their body size.

Others researchers favor dermopterans, a relatively little-known group that includes two living species of colugos in southeast Asia. Eventhough colugos are colloquially termed "flying lemurs," they are not lemurs and they do not fly. Instead, they have a specialized skin fold, called a patagium, that stretches from the neck to the forelimbs, back to the hindlimbs and finally to the tail. A colugo gliding from tree to tree at dusk uses its patagium for support and resembles nothing so much as a furry kite......... Posted by: Kelly      Read more         Source

November 13, 2007, 8:58 PM CT

"Time-sharing" birds key to evolutionary mystery

Whereas most birds are sole proprietors of their nests, some tropical species "time share" together - a discovery that helps clear up a 150-year-old evolutionary mystery, says Biology professor Vicki Friesen.

The Queen's-led international study confirms one of Charles Darwin's more controversial theories - first put forward in 1859 and since disputed by a number of experts - that different species can arise, unhindered, in the same place. Others think that a geographic barrier such as a mountain or a river is mandatory to produce two separate species. Eventhough focused on how species change over time through natural selection, Darwin's landmark book, The Origin of Species, also speculates that it is possible for different species to develop in the same place.

The team's findings will appear in the international journal, Proceedings of the National Academy of Sciences (PNAS).

With PhD student Andrea Smith and an international team of researchers, Dr. Friesen studied a small seabird called the band-rumped storm petrel, which nests on desert islands in the tropics and sub-tropics. They found that one set of petrels will breed in burrows, raise their chicks, and leave for the winter. Then a different set of birds moves in - similar to a vacation "time share" - and repeats the pattern in the very same burrows. When the season changes again, the first set of birds will return......... Posted by: Kelly      Read more         Source

November 12, 2007, 9:50 PM CT

Human ancestors: more gatherers than hunters?

Chimpanzees crave roots and tubers even when food is plentiful above ground, as per a new study that raises questions about the relative importance of meat for brain evolution.

Appearing online the week of Nov. 12 in the early edition of the Proceedings of the National Academy of Sciences, the study documents a novel use of tools by chimps to dig for tubers and roots in the savanna woodlands of western Tanzania.

The chimps eagerness for buried treats offers new insights in an ongoing debate about the role of meat versus potato-like foods in the diet of our hominid ancestors, said first author Adriana Hernandez-Aguilar, who collected the field data for her doctoral research at the University of Southern California.

The debate centers on the diet followed by early hominids as their brain and body size slowly increased towards a human level. Was it meat-and-potatoes, or potatoes-and-meat".

Some scientists have suggested that what made us human was actually the tubers, Hernandez-Aguilar said.

Anthropologists had speculated that roots and tubers were mere fallback foods for hominids trying to survive the harsh dry season in the savanna 3.5 million years ago and later (hominids are known to have consumed meat at least as early as 2.5 million years ago)......... Posted by: Kelly      Read more         Source

November 12, 2007, 9:45 PM CT

Repellents between dusk and bedtime

Using insect repellent in addition to insecticide treated bednets (ITNs) has been shown to provide greater protection against malaria in areas where mosquitoes feed in the early evening.

The findings of a study carried out by the team based at the London School of Hygiene & Tropical Medicine and working in collaboration with the National Bureau of Malaria Control at the Ministry of Health in La Paz, Bolivia, are published recently in the British Medical Journal.

36% of the population of the Americas live in areas with a risk of malaria. This includes 293 million people in 21 endemic countries. Of the 1.14 million cases of malaria published in the Americas during 2000, 87% were recorded in the Amazonian subregion of South America.

The primary malaria vector in the Amazon in anopheles Darlingi. Its peak biting activity is between 8 and 10pm, and more than 80% of feeding occurs before most local people to go bed, where they can be protected by an insecticide treated bednet. Tourists visiting the area are already advised to use repellents as well as bed nets. The scientists sought to determine whether this advice was justified, and whether the combination of repellents and ITNs is indeed more effective in reducing malaria than using ITNs alone.

4008 individuals, based in 860 households in rural villages and peri-urban districts in the Bolivian Amazon, were divided into two groups; all participants already slept under ITNs, but one group also used a plant-based insect repellent, and the second a placebo......... Posted by: Kelly      Read more         Source

November 8, 2007, 9:44 PM CT

Fruit Fly Gives Clues To Genetic Adaptation

Cornell scientists have played a major role in an international scientific team that has compared the complete set of genes of 12 closely related fruit fly species. As well has having implications for human health -- from genetic adaptation to evolving immune systems -- the analysis paves the way for better understanding the evolution of each species.

From the results of the research, the Cornell researchers coordinated one of the two papers published this week in the journal Nature. The team, known as the Drosophila 12 Genomes Consortium, represented 16 countries and was supported by the U.S. National Institutes of Health National Human Genome Research Institute.

"By looking at a wider number of species, we had much greater power to detect genes and regulatory elements from the way the sequences diverged between species, and to test models of what evolutionary pressures those genes and regulatory elements must have faced," said Andrew Clark, Cornell professor of population genetics and one of the paper's co-authors.

Drosophila (fruit flies) are one of most studied and most important model organisms used in genetics research. A number of fruit fly genes are also found in humans and control the same biological functions. As a result, fruit fly research has led to discoveries correlation to the influence of genes on diseases, animal development, population genetics, cell biology, neurobiology, behavior, physiology and evolution......... Posted by: Kelly      Read more         Source

November 7, 2007, 8:18 PM CT

Biologists Assemble Fly mtDNA for Landmark Genome Project

Brown University biologist David Rand and members of his lab have made a major contribution to a groundbreaking genome sequencing project - single-handedly assembling the mitochondrial DNA sequences of seven species of fruit fly.

The work, appearing in Nature, is part of an international research effort to catalogue the DNA sequences of 12 species of Drosophila, or fruit fly, a critical and common laboratory model used to study human development, genetics, and evolution. Results of the "Drosophila Dozen" project are the complete sequences of both nuclear and mitochondrial DNA from the 12 species of fly - a data set that gives researchers the unprecedented ability to compare related species and how they changed over time.

About 150 researchers from around the world, collectively known as the Drosophila 12 Genomes Consortium, came together to sequence, assemble and analyze the genomes, all from closely related species that range from Drosophila yakuba, a red-eyed variety found on the African savannah, to Drosophila mojavensis, a cactus-dweller from the Sonoran desert.

David Rand, a professor in the Department of Ecology and Evolutionary Biology at Brown, along with postdoctoral research associate Kristi Montooth and laboratory technician Dawn Abt were the only researchers in the consortium to assemble mitochondrial DNA, or mtDNA, sequences. In the sequencing process, DNA is extracted, chopped into bits, then analyzed to determine the order of base pairs. These bits must then be put back together, or assembled, an exacting process that involves piecing together billions of base pairs in proper order using special computer software......... Posted by: Kelly      Read more         Source

November 7, 2007, 7:13 PM CT

Tropical importance in biodiversity

Even a group of shellfish that appear to violate the overarching pattern of global biodiversity actually follows the same biological rules as other marine organisms, confirming a general theory for the spread of life on Earth. The University of Chicago's David Jablonski and colleagues present this finding this week in the advanced online edition of the Proceedings of the National Academy of Sciences.

"There's more of everything in the tropics. More genetic diversity, more diversity in form, more diversity of species," said David Jablonski, the William R. Kenan Jr. Professor in Geophysical Sciences at Chicago. Biologists call this the "latitudinal diversity gradient." They have known about this phenomenon for more than a century, "but there's remarkably little agreement on how it's formed," Jablonski said.

Researchers have offered dozens of different theories to explain the evolutionary underpinnings of the tropics' rich biodiversity. In their Proceedings article, Jablonski, the University of Chicago's Andrew Krug and the University of California, Berkeley's James Valentine present findings that highlight the importance of the tropics in maintaining the entire planet's biodiversity.

Researchers had debated for three decades whether the tropics were a cradle of diversity, where new species originate, or a museum of diversity, where old species persist. Last year Jablonski, Valentine and Kaustuv Roy of the University of California, San Diego, potentially resolved the debate by showing that the tropics is both a cradle and a museum of biodiversity......... Posted by: Kelly      Read more         Source

November 5, 2007, 9:06 PM CT

Worms take the sniff test

Buttery popcorn or fresh green vegetables? Your answer tells a lot about you.

Now, researchers say that the way that thousands of tiny worms have answered that question likely reveals a lot about you and your brain, too.

In the experiment at the University of Rochester Medical Center, worms that are hermaphrodites (with characteristics of both females and males) went for the buttery smell, while the males the other of the two sexes in these worms opted for the scent of fresh vegetables. But when scientists tricked a few nerve cells in hermaphrodites into sensing that they were in a male worm, suddenly they too preferred the smell of fresh vegetables.

While the olfactory likes and dislikes of the tiny roundworm known as C. elegans is the stuff of distinctive cocktail conversation, trivia is the furthest thing on the minds of Rochester researchers who did the study, which is being reported in the Nov. 6 issue of Current Biology.

Geneticist Douglas Portman, Ph.D., and graduate student KyungHwa Lee ultimately hope to understand gender differences in diseases like autism, depression, and attention-deficit disorder. A number of more boys than girls are diagnosed with ADD and autism, and a number of more girls than boys are diagnosed with depression. While proposed explanations abound, few researchers debate the notion that the brains of the sexes are in some ways fundamentally different......... Posted by: Kelly      Read more         Source

November 5, 2007, 8:21 PM CT

Potential to double tiger numbers in South Asia

Scientists at the Wildlife Conservation Society and other institutions declare that improvements in management of existing protected areas in South Asia could double the number of tigers currently existing in the region.

The study appears in the most recent edition of the journal Biological Conservation.

Specifically, the study examined 157 reserves throughout the Indian subcontinentcomprising India, Bangladesh, Bhutan, and Nepal. It observed that 21 of the protected areas meet the criteria needed for large healthy tiger populations. Further, the study noted that these protected areas have the potential to support between 58 percent and 95 percent of the subcontinents potential tiger capacity, estimated to be between 3,500 to 6,500 tigers. In the absence of reliable data to produce a reliable estimate, tiger conservationists say that the big cats may currently number between 1,500 to 4,000 animals in the four countries combined.

The small improvements to increase tiger populations cited in the study include better funding, increasing staff support, restoring tiger habitat, and stepping up enforcement activities that focus on preventing the poaching of tigers and their prey.

We were happy to find that the most important reserves identified in the study already have made tiger conservation a priority, said the lead author Dr. Jai Ranganathan of the National Center for Ecological Analysis and Synthesis......... Posted by: Kelly      Read more         Source