Earth’s inner core is solid, 'J waves' suggest

View of Earth from space, showing North Africa, Europe and the Middle East. Elements of this image furnished by NASA.

A new study by researchers at The Australian National University (ANU) could help us understand how our planet was formed.

Associate Professor Hrvoje Tkalčić and PhD Scholar Than-Son Phạm are confident they now have direct proof that Earth's inner core is solid.

They came up with a way to detect shear waves, or "J waves" in the inner core -- a type of wave which can only travel through solid objects.

"We found the inner core is indeed solid, but we also found that it's softer than previously thought," Associate Professor Tkalčić said.

"It turns out -- if our results are correct -- the inner core shares some similar elastic properties with gold and platinum. The inner core is like a time capsule, if we understand it we'll understand how the planet was formed, and how it evolves."

Inner core shear waves are so tiny and feeble they can't be observed directly. In fact, detecting them has been considered the "Holy Grail" of global seismology since scientists first predicted the inner core was solid in the 1930s and 40s.

So the researchers had to come up with a creative approach.

Their so-called correlation wavefield method looks at the similarities between the signals at two receivers after a major earthquake, rather than the direct wave arrivals. A similar technique has been used by the same team to measure the thickness of the ice in Antarctica.

"We're throwing away the first three hours of the seismogram and what we're looking at is between three and 10 hours after a large earthquake happens. We want to get rid of the big signals," Dr Tkalčic said.

"Using a global network of stations, we take every single receiver pair and every single large earthquake -- that's many combinations -- and we measure the similarity between the seismograms. That's called cross correlation, or the measure of similarity. From those similarities we construct a global correlogram -- a sort of fingerprint of the Earth."

The study shows these results can then be used to demonstrate the existence of J waves and infer the shear wave speed in the inner core.

While this specific information about shear waves is important, Dr Tkalčić says what this research tells us about the inner core is even more exciting.

"For instance we don't know yet what the exact temperature of the inner core is, what the age of the inner core is, or how quickly it solidifies, but with these new advances in global seismology, we are slowly getting there.

Read more at Science Daily

Genomic evidence of rapid adaptation of invasive Burmese pythons in Florida

These are researchers holding pythons.

Det var ett tag sedan jag skrev här i bloggen. Detta beror mest på det att jag har gjort väldigt mycket research om militärhistoria och då inkluderar det I12 i Skillingaryd. Anledningen till att jag forskar om det är att jag just nu skriver en bok om min morfars far Gerhard. Boken går långsamt framåt då jag vill att allting ska vara så nära sanningen som möjligt även att jag får hitta på ett och annat själv som kanske inte riktigt stämmer men som ändå ligger inom felmarginalen. Även konversationerna i boken vid vissa tillfällen ska ligga så nära som möjligt till vad som brukade sägas och sådant kräver väldigt mycket research. Jag skrev på facebook för ett tag sedan att jag skulle lägga ut första kapitlet av boken här i bloggen och ni som väntar på det får faktiskt vänta lite till tyvär!

När man sitte och gör research som jag gör så går det åt väldigt många timmar till just det. Eftersom att det inte finns några knektar längre så blir det ju lite svårt att intervjua några sådana, så man måste försöka att få tag på skrivna källor och det är inte alltid det lättaste alla gångerFlorida has become a haven for invasive species in the United States, but perhaps the most well-known of the State's alien residents is the Burmese python. These giant snakes, native to Southeast Asia, have become well-established over the past few decades and even flourish in their new environment.

"In Burmese pythons, we observed the rapid establishment and expansion of an invasive population in Florida, which is quite ecologically distinct from Southeast Asia and likely imposes significant ecological selection on the invasive Burmese python population," said Todd Castoe, biology professor at the University of Texas at Arlington and director of the Castoe Lab. "This situation had all of the hallmarks of a system where rapid adaptation could occur, so we were excited to test for this possibility using cutting-edge genomic approaches."

The researchers originally set out to determine whether pythons could have adapted to an extreme Florida freeze event in 2010. They generated data for dozens of samples before and after the freeze event. By scanning regions of the Burmese python genome, they identified parts of the genome that changed significantly between the two time periods, providing clear evidence of evolution occurring over a very short time scale in this population.

"The 2010 Florida freeze event led to a 40 percent to 90 percent documented field mortality in invasive Burmese pythons, so if evolution and adaptation were to be occurring, we knew we should see it over this time period that imposed a very strong bottleneck of selection," Castoe said.

"We employed a technique commonly referred to as a genome scan, which identifies regions of the genome that appear to be under strong natural selection, which could contain genes important in adaptation that may have allowed a subset of this population to survive these freeze events," he added.

The researchers expected to find genes in these regions that are important for potential adaptation to cold, but as they further scrutinized the data, a different signal began to emerge that told a more broad story about adaptation in this invasive population.

"We kept seeing evidence of adaptation in genes related to cell division, organ growth, and tissue development, which admittedly puzzled us at first. However, it eventually occurred to us that there was a connection with a parallel project in the lab that uses Burmese pythons as a model system for understanding regenerative organ growth, where tissues are downregulated when fasting and then regenerated in cyclical patterns corresponding with feeding cycles of most pythons. We began to wonder whether the signal we were seeing in the genome of Florida Burmese pythons was linked to adaptation in how they regenerated organ systems based on their feeding ecology," said Daren Card, a recently graduated Ph.D. student in the Castoe lab who worked on this project for his dissertation.

Armed with a working hypothesis that invasive Burmese pythons may be adapting to more regular feeding opportunity in Florida, the researchers gathered further ecological, functional genomic, and morphological data to understand the frequency at which pythons are feeding and whether there are physiological changes consistent with more regular feeding.

"These additional analyses showed that Burmese pythons in Florida are constantly feeding and that tissue morphological and gene expression patterns support a more up-regulated physiological state in fasted pythons -- Florida pythons appear to have adapted to regulating their digestive physiology to more efficiently eat prey constantly. This is alarming because these snakes have already been shown to have major negative impacts on endemic mammalian and bird populations in South Florida, including Everglades National Park, and our data was suggesting that, through rapid adaptation, they are only 'getting better' at being an effective invasive predator," Card added.

UTA biology chair Clay Clark congratulated the team on this work, which provides tangible evidence that evolution can occur extremely rapidly in natural populations, and that such rapid evolution can result in major changes in very complex traits that impact the physiology and ecology of vertebrates.

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Piranha-like specimen, 150 million years old, is earliest known flesh-eating fish

This image shows a new piranha-like fish from Jurassic seas with sharp, pointed teeth that probably fed on the fins of other fishes. From the time of dinosaurs and from the same deposits that contained Archaeopteryx, scientists recovered both this flesh-tearing fish and its scarred prey.

Researchers reporting in Current Biology on October 18 have described a remarkable new species of fish that lived in the sea about 150 million years ago in the time of the dinosaurs. The new species of bony fish had teeth like a piranha, which the researchers suggest they used as piranhas do: to bite off chunks of flesh from other fish.

As further support for that notion, the researchers also found the victims: other fish that had apparently been nibbled on in the same limestone deposits in South Germany (the quarry of Ettling in the Solnhofen region) where this piranha-like fish was found.

"We have other fish from the same locality with chunks missing from their fins," says David Bellwood of James Cook University, Australia. "This is an amazing parallel with modern piranhas, which feed predominantly not on flesh but the fins of other fishes. It's a remarkably smart move as fins regrow, a neat renewable resource. Feed on a fish and it is dead; nibble its fins and you have food for the future."

The newly described fish is part of the world famous collections in the Jura-Museum in Eichstätt. It comes from the same limestone deposits that contained Archaeopteryx.

Careful study of the fossilized specimen's well-preserved jaws revealed long, pointed teeth on the exterior of the vomer, a bone forming the roof of the mouth, and at the front of both upper and lower jaws. Additionally, there are triangular teeth with serrated cutting edges on the prearticular bones that lie along the side of the lower jaw.

The tooth pattern and shape, jaw morphology, and mechanics suggest a mouth equipped to slice flesh or fins, the international team of researchers report. The evidence points to the possibility that the early piranha-like fish may have exploited aggressive mimicry in a striking parallel to the feeding patterns of modern piranha.

"We were stunned that this fish had piranha-like teeth," says Martina Kölbl-Ebert of Jura-Museum Eichstätt (JME-SNSB). "It comes from a group of fishes (the pycnodontids) that are famous for their crushing teeth. It is like finding a sheep with a snarl like a wolf. But what was even more remarkable is that it was from the Jurassic. Fish as we know them, bony fishes, just did not bite flesh of other fishes at that time. Sharks have been able to bite out chunks of flesh but throughout history bony fishes have either fed on invertebrates or largely swallowed their prey whole. Biting chunks of flesh or fins was something that came much later."

Or, so it had seemed.

"The new finding represents the earliest record of a bony fish that bit bits off other fishes, and what's more it was doing it in the sea," Bellwood says, noting that today's piranhas all live in freshwater. "So when dinosaurs were walking the earth and small dinosaurs were trying to fly with the pterosaurs, fish were swimming around their feet tearing the fins or flesh off each other."

Read more at Science Daily

Working lands play a key role in protecting biodiversity

California wine country with a trees nestled on the hillside.

With a body the size of a fist and wings that span more than a foot, the big brown bat must gorge on 6,000 to 8,000 bugs a night to maintain its stature. This mighty appetite can be a boon to farmers battling crop-eating pests.

But few types of bats live on American farms. That's because the current practice of monoculture -- dedicating large swathes of land to a single crop -- doesn't give the bats many places to land or to nest.

Diversifying working lands -- including farmland, rangeland and forests -- may be key to preserving biodiversity in the face of climate change, says a new review paper published this week in Science by conservation biologists at the University of California, Berkeley.

Diversification could be as simple as adding trees or hedgerows along the edges of fields, giving animals like birds, bats and insects places to live, or as complex as incorporating a patchwork of fields, orchards, pasture and flowers into a single working farm.

These changes could extend the habitat of critters like bats, but also much larger creatures like bears, elk and other wildlife, outside the boundaries of parks and other protected areas, while creating more sustainable, and potentially more productive, working lands.

"Protected areas are extremely important, but we can't rely on those on their own to prevent the pending sixth mass extinction," said study co-author Adina Merenlender, a Cooperative Extension Specialist in the Department of Environmental Science, Policy and Management at UC Berkeley. "This is even more true in the face of climate change, because species will need to move around to adapt to shifts in temperature and climate."

Maintaining even small pieces of the original landscape -- even a single tree- can help conserve the original diversity of species, Merenlender said.

Clearing oak woodlands and shrublands to establish large vineyards hits many native species hard. Animals that are well adapted to urban and agricultural areas, such as mockingbirds, house finches and free-tail bats, continue to flourish, while animals that are more sensitive to disturbance, like acorn woodpeckers, orange-crowned warblers and big brown bats, begin to drop away.

"If you can leave shrubs, trees and flowering plants, the habitat suitability -- not just for sensitive birds but also for other vertebrates -- goes way up," Merenlender said. This is true not only in California's vineyards, but on working lands around the world.

Incorporating natural vegetation makes the farm more hospitable to more creatures, while reducing the use of environmentally degrading chemicals like herbicides, pesticides and human-made fertilizer.

The ideal farming landscape includes woodland pastures and vegetable plots bumping up against orchards and small fields, said Claire Kremen, a professor in the Department of Environmental Science, Policy and Management.

Integrating livestock produces manure which can fertilize the crops, while those same crops produce feed for livestock. Birds and bats provide pest control, and bees boost crop production by pollinating plants.

"It is possible for these working landscapes to support biodiversity but also be productive and profitable," Kremen said. "And ultimately, this is where we have to go. We just can't keep mining our soils for their fertility and polluting our streams -- in the end, this will diminish our capacity to continue producing the food that we need. Instead, we must pay attention to the species, from microbes to mammals, that supply us with critical services, like pollination, pest control and nutrient cycling"

Read more at Science Daily

Superflares from young red dwarf stars imperil planets

Violent outbursts of seething gas from young red dwarf stars may make conditions uninhabitable on fledgling planets. In this artist's rendering, an active, young red dwarf (right) is stripping the atmosphere from an orbiting planet (left). Scientists found that flares from the youngest red dwarfs they surveyed -- approximately 40 million years old -- are 100 to 1,000 times more energetic than when the stars are older. They also detected one of the most intense stellar flares ever observed in ultraviolet light -- more energetic than the most powerful flare ever recorded from our Sun.

The word "HAZMAT" describes substances that pose a risk to the environment, or even to life itself. Imagine the term being applied to entire planets, where violent flares from the host star may make worlds uninhabitable by affecting their atmospheres.

NASA's Hubble Space Telescope is observing such stars through a large program called HAZMAT -- Habitable Zones and M dwarf Activity across Time.

"M dwarf" is the astronomical term for a red dwarf star -- the smallest, most abundant and longest-lived type of star in our galaxy. The HAZMAT program is an ultraviolet survey of red dwarfs at three different ages: young, intermediate, and old.

Stellar flares from red dwarfs are particularly bright in ultraviolet wavelengths, compared with Sun-like stars. Hubble's ultraviolet sensitivity makes the telescope very valuable for observing these flares. The flares are believed to be powered by intense magnetic fields that get tangled by the roiling motions of the stellar atmosphere. When the tangling gets too intense, the fields break and reconnect, unleashing tremendous amounts of energy.

The team has found that the flares from the youngest red dwarfs they surveyed -- just about 40 million years old -- are 100 to 1,000 times more energetic than when the stars are older. This younger age is when terrestrial planets are forming around their stars.

Approximately three-quarters of the stars in our galaxy are red dwarfs. Most of the galaxy's "habitable-zone" planets -- planets orbiting their stars at a distance where temperatures are moderate enough for liquid water to exist on their surface -- likely orbit red dwarfs. In fact, the nearest star to our Sun, a red dwarf named Proxima Centauri, has an Earth-size planet in its habitable zone.

However, young red dwarfs are active stars, producing ultraviolet flares that blast out so much energy that they could influence atmospheric chemistry and possibly strip off the atmospheres of these fledgling planets.

"The goal of the HAZMAT program is to help understand the habitability of planets around low-mass stars," explained Arizona State University's Evgenya Shkolnik, the program's principal investigator. "These low-mass stars are critically important in understanding planetary atmospheres."

The results of the first part of this Hubble program are being published in The Astrophysical Journal. This study examines the flare frequency of 12 young red dwarfs. "Getting these data on the young stars has been especially important, because the difference in their flare activity is quite large as compared to older stars," said Arizona State University's Parke Loyd, the first author on this paper.

The observing program detected one of the most intense stellar flares ever observed in ultraviolet light. Dubbed the "Hazflare," this event was more energetic than the most powerful flare from our Sun ever recorded.

"With the Sun, we have a hundred years of good observations," Loyd said. "And in that time, we've seen one, maybe two, flares that have an energy approaching that of the Hazflare. In a little less than a day's worth of Hubble observations of these young stars, we caught the Hazflare, which means that we're looking at superflares happening every day or even a few times a day."

Could super-flares of such frequency and intensity bathe young planets in so much ultraviolet radiation that they forever doom chances of habitability? According to Loyd, "Flares like we observed have the capacity to strip away the atmosphere from a planet. But that doesn't necessarily mean doom and gloom for life on the planet. It just might be different life than we imagine. Or there might be other processes that could replenish the atmosphere of the planet. It's certainly a harsh environment, but I would hesitate to say that it is a sterile environment."

Read more at Science Daily

Electrical properties of dendrites help explain our brain's unique computing power

MIT neuroscientists can now record electrical activity from the dendrites of human neurons.

Neurons in the human brain receive electrical signals from thousands of other cells, and long neural extensions called dendrites play a critical role in incorporating all of that information so the cells can respond appropriately.

Using hard-to-obtain samples of human brain tissue, MIT neuroscientists have now discovered that human dendrites have different electrical properties from those of other species. Their studies reveal that electrical signals weaken more as they flow along human dendrites, resulting in a higher degree of electrical compartmentalization, meaning that small sections of dendrites can behave independently from the rest of the neuron.

These differences may contribute to the enhanced computing power of the human brain, the researchers say.

"It's not just that humans are smart because we have more neurons and a larger cortex. From the bottom up, neurons behave differently," says Mark Harnett, the Fred and Carole Middleton Career Development Assistant Professor of Brain and Cognitive Sciences. "In human neurons, there is more electrical compartmentalization, and that allows these units to be a little bit more independent, potentially leading to increased computational capabilities of single neurons."

Harnett, who is also a member of MIT's McGovern Institute for Brain Research, and Sydney Cash, an assistant professor of neurology at Harvard Medical School and Massachusetts General Hospital, are the senior authors of the study, which appears in the Oct. 18 issue of Cell. The paper's lead author is Lou Beaulieu-Laroche, a graduate student in MIT's Department of Brain and Cognitive Sciences.

Neural computation

Dendrites can be thought of as analogous to transistors in a computer, performing simple operations using electrical signals. Dendrites receive input from many other neurons and carry those signals to the cell body. If stimulated enough, a neuron fires an action potential -- an electrical impulse that then stimulates other neurons. Large networks of these neurons communicate with each other to generate thoughts and behavior.

The structure of a single neuron often resembles a tree, with many branches bringing in information that arrives far from the cell body. Previous research has found that the strength of electrical signals arriving at the cell body depends, in part, on how far they travel along the dendrite to get there. As the signals propagate, they become weaker, so a signal that arrives far from the cell body has less of an impact than one that arrives near the cell body.

Dendrites in the cortex of the human brain are much longer than those in rats and most other species, because the human cortex has evolved to be much thicker than that of other species. In humans, the cortex makes up about 75 percent of the total brain volume, compared to about 30 percent in the rat brain.

Although the human cortex is two to three times thicker than that of rats, it maintains the same overall organization, consisting of six distinctive layers of neurons. Neurons from layer 5 have dendrites long enough to reach all the way to layer 1, meaning that human dendrites have had to elongate as the human brain has evolved, and electrical signals have to travel that much farther.

In the new study, the MIT team wanted to investigate how these length differences might affect dendrites' electrical properties. They were able to compare electrical activity in rat and human dendrites, using small pieces of brain tissue removed from epilepsy patients undergoing surgical removal of part of the temporal lobe. In order to reach the diseased part of the brain, surgeons also have to take out a small chunk of the anterior temporal lobe.

With the help of MGH collaborators Cash, Matthew Frosch, Ziv Williams, and Emad Eskandar, Harnett's lab was able to obtain samples of the anterior temporal lobe, each about the size of a fingernail.

Evidence suggests that the anterior temporal lobe is not affected by epilepsy, and the tissue appears normal when examined with neuropathological techniques, Harnett says. This part of the brain appears to be involved in a variety of functions, including language and visual processing, but is not critical to any one function; patients are able to function normally after it is removed.

Once the tissue was removed, the researchers placed it in a solution very similar to cerebrospinal fluid, with oxygen flowing through it. This allowed them to keep the tissue alive for up to 48 hours. During that time, they used a technique known as patch-clamp electrophysiology to measure how electrical signals travel along dendrites of pyramidal neurons, which are the most common type of excitatory neurons in the cortex.

These experiments were performed primarily by Beaulieu-Laroche. Harnett's lab (and others) have previously done this kind of experiment in rodent dendrites, but his team is the first to analyze electrical properties of human dendrites.

Unique features

The researchers found that because human dendrites cover longer distances, a signal flowing along a human dendrite from layer 1 to the cell body in layer 5 is much weaker when it arrives than a signal flowing along a rat dendrite from layer 1 to layer 5.

They also showed that human and rat dendrites have the same number of ion channels, which regulate the current flow, but these channels occur at a lower density in human dendrites as a result of the dendrite elongation. They also developed a detailed biophysical model that shows that this density change can account for some of the differences in electrical activity seen between human and rat dendrites, Harnett says.

The question remains, how do these differences affect human brainpower? Harnett's hypothesis is that because of these differences, which allow more regions of a dendrite to influence the strength of an incoming signal, individual neurons can perform more complex computations on the information.

"If you have a cortical column that has a chunk of human or rodent cortex, you're going to be able to accomplish more computations faster with the human architecture versus the rodent architecture," he says.

There are many other differences between human neurons and those of other species, Harnett adds, making it difficult to tease out the effects of dendritic electrical properties. In future studies, he hopes to explore further the precise impact of these electrical properties, and how they interact with other unique features of human neurons to produce more computing power.

Read more at Science Daily

Double dust ring test could spot migrating planets

Dust density rendered simulation image of the disc -- white circle is inner dust ring.

New research by a team led by an astrophysicist at the University of Warwick has a way of finally telling whether newly forming planets are migrating within the disc of dust and gas that typically surrounds stars or whether they are simply staying put in the same orbit around the star.

Finding real evidence that a planet is migrating (usually inwards) within such discs would help solve a number of problems that have emerged as astronomers are able to see more and more detail within protoplanetary discs. In particular it might provide a simple explanation for a range of strange patterns and disturbances that astronomers are beginning to identify within these discs.

Planet migration is a process that astronomers have known the theory about for 40 years but it's only now that they have been able to find a way of observationally testing if it really occurs. This new research from a team led by the University of Warwick, along with Cambridge, provides two new observational signatures in young solar system's dust rings that would be evidence of a migrating planet. That research will be published in the Monthly Notices of the Royal Astronomical Society.

The lead author, Dr Farzana Meru of the University of Warwick's Astronomy and Astrophysics Group in the Department of Physics, on the paper said:

"Planet migration in protoplanetary discs plays an important role in the longer term evolution of planetary systems, yet we currently have no direct observational test to determine if a planet is migrating in its gaseous disc. However the technology now available to us in the Atacama Large Millimeter/submillimeter Array (ALMA), is able to look deep into these discs, and even see detailed structures within the discs such as rings, gaps, spiral arms, crescents and clumps. ALMA can also use different millimetre frequencies to seek out concentrations of different particle sizes so we can also use it to explore the make up of individual dust rings within the disc"

"Our latest research has found a way to use this new technology to spot what we think will be a clear signature within these dust rings that the planet closest to them is actually migrating within that very young solar system."

The University of Warwick led research team have concluded that if ALMA looks at the two dust rings nearest the orbit of a planet a simple measurement of the typical particle size in each ring will reveal the answer.

If ALMA finds that the interior dust ring (i.e. between the planet's orbit and the star) is typically made up of smaller sized particles, and that the exterior dust ring (immediately outside of the planet's orbit) is typically made up of larger particles, then that will be clear evidence that the planet is migrating within the system's protoplanetary disc. The size of the particles would differ for each disc but in a case where the planet is located 30 astronomical units from the star and is 30 times the mass of the Earth, the smaller particles in the inner ring would typically be less than a millimetre in size, whereas those in the outer ring would be a little over a millimetre.

ALMA will be able to observe this because the wavelength at which it observes roughly correlates with the dust particle size. This means that as observers look at the disc with ALMA at increasing wavelengths, the interior dust ring is expected to fade, while the exterior ring would become brighter.

The reason for this pattern is twofold. Firstly the researchers' model shows that the exterior dust ring will contain more large dust particles because they move at a higher velocity (than the smaller particles) and are fast enough to keep up with the planet as it orbits inwards. This will result in a ring exterior to the planet's orbit that is mostly made up of large particles.

Secondly, the inner ring consists of small particles because they move inwards more slowly than the planet. Consequently they are unable to get out of the way of the inwardly migrating planet and so accumulate in a ring just inwards of the planet. This time the fast-moving large dust moves rapidly towards the star leaving an interior dust ring of small-sized particles.

The research team will continue to simulate what such ALMA observations would look like and astronomers can now use this method in their own ALMA observations to look for this two ring signature.

Read more at Science Daily

Bee social or buzz off: Study links genes to social behaviors, including autism

Fields of yellow flowers provide habitat for sweat bees.

Those pesky bees that come buzzing around on a muggy summer day are helping researchers reveal the genes responsible for social behaviors. A new study published this week found that the social lives of sweat bees -- named for their attraction to perspiration -- are linked to patterns of activity in specific genes, including ones linked to autism.

"Bees have complex social behaviors, and with this species of bee, we can directly compare individuals that live in social groups to those that don't live in social groups," said Sarah Kocher, an assistant professor of ecology and evolutionary biology and the Lewis-Sigler Institute for Integrative Genomics at Princeton University, who led the research. "We can ask: 'What are the fundamental differences between a social and nonsocial animal?'"

The researchers found that one of these differences involves the gene syntaxin 1a, which governs the release of chemical messengers in the brain. In all, the study found nearly 200 gene variations that were linked to social behavior, with 21 clustered in or nearby six genes implicated in human autism. The study was published in the journal Nature Communications.

Sweat bees are ideal for studying the genes underlying social behavior, Kocher said, because some are naturally social while others are solitary, even though both types belong to the Halictidae family. Both types nest in the ground, but the social bees live in a hierarchal society consisting of a queen and workers, like their honey bee relatives, while nonsocial sweat bees live alone.

Until Kocher began studying sweat bees, not many scientists had looked at the mechanisms underlying their behavior. One of the few scientists to have studied the bees was Cecile Plateaux-Quenu, an entomologist who in the 1960s documented sweat bee populations -- and their social habits -- in sites around France.

In 2010, Kocher located the retired scientist and eventually traveled to France to meet her. Plateaux-Quenu helped the younger scientist learn to identify the bees, find their nests, and net the insects as they traveled among the dandelions, asters and daisies.

Kocher, who was then a postdoctoral researcher at Harvard University, brought the bees back to the laboratory to analyze their genes. She sequenced the genomes of hundreds of bees of the species Lasioglossum albipes, known from locations that Plateaux-Quenu had classified decades earlier as home to either social or solitary bees. Next, the researchers looked through the genetic data to detect correlations between patterns of gene activity and social behavior.

The findings suggest that variations in several genes play a role in causing or contributing to the social behavior of these bees. Many of the variations detected were found in sections of the genetic code that are not genes themselves but rather regulate other genes by enhancing their activity.

Social behavior is complex and is determined by multiple genes rather than a single gene. Genes are important for brain development -- they orchestrate connections between neurons and pruning of those connections during development and childhood.

Another study conducted last year on honey bees also found a link between bee genes and autism genes. One of the differences between that study and this new one, Kocher said, is that honey bees are by nature social, whereas sweat bees can be either social or nonsocial.

Read more at Science Daily

Biological invisibility cloak: Elucidating cuttlefish camouflage

A common cuttlefish (Sepia officinalis).

The unique ability of cuttlefish, squid and octopuses to hide by imitating the colors and texture of their environment has fascinated natural scientists since the time of Aristotle. Uniquely among all animals, these mollusks control their appearance by the direct action of neurons onto expandable pixels, numbered in millions, located in their skin. Scientists at the Max Planck Institute for Brain Research and the Frankfurt Institute for Advanced Studies/Goethe University used this neuron-pixel correspondence to peer into the brain of cuttlefish, inferring the putative structure of control networks through analysis of skin pattern dynamics.

Cuttlefish, squid and octopus are a group of marine mollusks called coleoid cephalopods that once included ammonites, today only known as spiral fossils of the Cretaceous era. Modern coleoid cephalopods lost their external shells about 150 million years ago and took up an increasingly active predatory lifestyle. This development was accompanied by a massive increase in the size of their brains: modern cuttlefish and octopus have the largest brains (relative to body size) among invertebrates with a size comparable to that of reptiles and some mammals. They use these large brains to perform a range of intelligent behaviors, including the singular ability to change their skin pattern to camouflage, or hide, in their surroundings.

Cephalopods control camouflage by the direct action of their brain onto specialized skin cells called chromatophores, that act as biological color "pixels" on a soft skin display. Cuttlefish possess up to millions of chromatophores, each of which can be expanded and contracted to produce local changes in skin contrast. By controlling these chromatophores, cuttlefish can transform their appearance in a fraction of a second. They use camouflage to hunt, to avoid predators, but also to communicate.

To camouflage, cuttlefish do not match their local environment pixel by pixel. Instead, they seem to extract, through vision, a statistical approximation of their environment, and use these heuristics to select an adaptive camouflage out of a presumed large but finite repertoire of likely patterns, selected by evolution. The biological solutions to this statistical-matching problem are unknown. But because cuttlefish can solve it as soon as they hatch out of their egg, their solutions are probably innate, embedded in the cuttlefish brain and relatively simple. A team of scientists at the Max Planck Institute for Brain Research and at the Frankfurt Institute for Advanced Studies (FIAS)/Goethe University, led by MPI Director Gilles Laurent, developed techniques that begin to reveal those solutions.

Cuttlefish chromatophores are specialized cells containing an elastic sack of colored pigment granules. Each chromatophore is attached to minute radial muscles, themselves controlled by small numbers of motor neurons in the brain. When these motor neurons are activated, they cause the muscles to contract, expanding the chromatophore and displaying the pigment. When neural activity ceases, the muscles relax, the elastic pigment sack shrinks back, and the reflective underlying skin is revealed. Because single chromatophores receive input from small numbers of motor neurons, the expansion state of a chromatophore could provide an indirect measurement of motor neuron activity.

"We set out to measure the output of the brain simply and indirectly by imaging the pixels on the animal's skin" says Laurent. Indeed, monitoring cuttlefish behavior with chromatophore resolution provided a unique opportunity to indirectly 'image' very large populations of neurons in freely behaving animals. Postdoc Sam Reiter from the Laurent Lab, the first author of this study, and his coauthors inferred motor neuron activity by analyzing the details of chromatophore co-fluctuations. In turn, by analyzing the co-variations of these inferred motor neurons, they could predict the structure of yet higher levels of control, 'imaging' increasingly more deeply into the cuttlefish brain through detailed statistical analysis of its chromatophore output.

Getting there took many years of hard work, some good insights and a few lucky breaks. A key requirement for success was to manage to track tens of thousands of individual chromatophores in parallel at 60 high-resolution images per second and to track every chromatophore from one image to the next, from one pattern to the next, from one week to the next, as the animal breathed, moved, changed appearance and grew, constantly inserting new chromatophores. One key insight was "realizing that the physical arrangement of chromatophores on the skin is irregular enough that it is locally unique, thus providing local fingerprints for image stitching" says Matthias Kaschube of FIAS/GU. By iterative and piecewise image comparison, it became possible to warp images such that all the chromatophores were properly aligned and trackable, even when their individual sizes differed -- as occurs when skin patterns change -- and even when new chromatophores had appeared -- as happens from one day to the next as the animal grows.

With insights such as this one, and aided by multiple supercomputers, Laurent's team managed to meet their goal and with this, started peering into the brain of the animal and its camouflage control system. Along the way, they also made unexpected observations. For example, when an animal changes appearance, it changes in a very specific manner through a sequence of precisely determined intermediate patterns. This observation is important because it suggests internal constraints on pattern generation, thus revealing hidden aspects of the neural control circuits. They also found that chromatophores systematically change colors over time, and that the time necessary for this change is matched to the rate of production of new chromatophores as the animal grows, such that the relative fraction of each color remains constant. Finally, from observing this development they derived minimal rules that may explain skin morphogenesis in this and possibly all other species of coleoid cephalopods.

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Massive organism is crashing on our watch

Pando Grove in fall foliage at Dr. Creek Campground, Utah

Utah State University researchers Paul Rogers and Darren McAvoy have conducted the first complete assessment of the Pando aspen clone and the results show continuing deterioration of this 'forest of one tree.' While a portion of the famed grove is recovery nicely as a result of previous restoration, the majority of Pando (Latin for "I Spread") is diminishing by attrition.

Rogers and McAvoy, in a PLOS ONE publication released 17 October, 2018, show Pando, Utah's massive, yet imperiled, aspen clone, is in grave need of forest triage. Early protection from fencing showed great promise in abating browser impacts, which have nearly eliminated recruitment of young aspen stems for decades now. However, follow-up fencing of a larger area (in combination with about half of Pando remaining unprotected by fencing) is currently failing according to this study. "After significant investment in protecting the iconic Pando clone, we were disappointed in this result. In particular, mule deer appear to be finding ways to enter through weak points in the fence or by jumping over the eight-foot barrier," says Rogers, Director of the Western Aspen Alliance and Adjunct Faculty member in USU's Wildland Resources Department. He further adds, "While Pando has likely existed for thousands of years -- we have no method of firmly fixing its' age -- it is now collapsing on our watch. One clear lesson emerges here: we cannot independently manage wildlife and forests."

In addition to presenting the first comprehensive analysis of forest conditions, the study offers a unique 72-year historical aerial photo sequence the visually chronicles the a steady thinning of the forest, past clear-cuts that remain deforested today, and continual intrusion of human development. Taken as a whole, objective analysis and the subjective photo chronology reveal a modern tragedy: the "trembling giant" that has lasted millennia may not survive a half-century of human meddling.

Pando is widely considered the world's largest single organism weighing in at an estimated 13 million lbs. (5.9 million kg). Covering some 106 acres (43 ha) in south-central Utah's Fishlake National Forest, the clonal colony consists of more than 47,000 genetically identical above-ground stems or "ramets" originating from a single underground parent clone. Quaking aspen, Pando's iconic species, was named Utah's State Tree in 2014 and, among numerous values, is considered a staple of scenic montane landscapes in the American West. Rogers sees trends found at Pando occurring across the western states, thus the Western Aspen Alliance serves as a clearinghouse of contemporary aspen sciences for professionals, scientists, and policymakers.

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World Heritage Sites threatened by rising sea levels

The UNESCO World Heritage Site of Venice and its lagoon is one of the most endangered World Heritage Sites in the Mediterranean region, due to storm surges and coastal erosion. In the course of this century, the ongoing rise in sea levels will further aggravate this danger.

In the Mediterranean region, there are numerous UNESCO World Heritage Sites in low-lying coastal areas. These include, for example, the Venetian Lagoon, the Old City of Dubrovnik and the ruins of Carthage. In the course of the 21st century, these sites will increasingly be at risk by storm surges and increasing coastal erosion due to sea-level rise. This is the conclusion of one of the first large-scale studies, carried out by doctoral researcher Lena Reimann from the Department of Geography at Kiel University (CAU), together with Professor Athanasios Vafeidis and international partners. The team published their results in the current issue (Tuesday 16 October) of the journal Nature Communications.

Already today, a large number of the altogether 49 World Heritage Sites investigated are at risk due to rising sea levels. Up to 37 of these sites are at risk from a so-called 100-year storm surge, which has a 1 percent chance of being exceeded in any given year. 42 of the 49 sites are at risk from coastal erosion. If sea levels continue rising further, "in the Mediterranean region, the risk posed by storm surges, which are 100-year storm surges under today's conditions, may increase by up to 50 percent on average, and that from coastal erosion by up to 13 percent -- and all of this by the end of the 21st century under high-end sea-level rise. Individual World Heritage Sites could even be affected much more due to their exposed location," said Lena Reimann to explain the study results.

In order to be able to evaluate the potential risks, the research team created a spatial database of all UNESCO World Heritage Sites in low-lying coastal areas of the Mediterranean region. In addition to the location and form of the sites, the study also included the heritage type, the distance from the coastline, and its location in urban or rural surroundings. "Using this database and model simulations of flooding, taking into account various scenarios of sea-level rise, we were able to develop indices: the index for flood risk and for erosion risk," said Reimann. The flood risk index takes into account the potentially-flooded area and the maximum flood depth of each World Heritage Site. The erosion risk index is based on the distance of each site from the coastline and the physical properties of the coast, which largely determine the degree of erosion. These include, among others, the material properties of the coast, from sandy through to rocky, and the availability of new sediment.

The increase in flood risk of up to 50 percent and erosion risk of up to 13 percent are based on an assumed average sea-level rise in the Mediterranean region of 1.46 meters by the year 2100. This increase could occur with a five percent probability (95th percentile) under a high-end climate change scenario (RCP8.5). "Even if such a high sea-level rise has a low probability of occurring by the year 2100, this scenario cannot be ruled out, due to the high uncertainties in relation to the melting of the ice sheets," said Professor Vafeidis. "In addition, such a scenario is quite relevant from a risk management perspective, since a 5% probability in this context is not low."

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Dandelion seeds reveal newly discovered form of natural flight

When dandelion seeds fly, a ring-shaped air bubble forms as air moves through the bristles, enhancing the drag that slows their descent.

The extraordinary flying ability of dandelion seeds is possible thanks to a form of flight that has not been seen before in nature, research has revealed.

The discovery, which confirms the common plant among the natural world's best fliers, shows that movement of air around and within its parachute-shaped bundle of bristles enables seeds to travel great distances -- often a kilometre or more, kept afloat entirely by wind power.

Researchers from the University of Edinburgh carried out experiments to better understand why dandelion seeds fly so well, despite their parachute structure being largely made up of empty space.

Their study revealed that a ring-shaped air bubble forms as air moves through the bristles, enhancing the drag that slows each seed's descent to the ground.

This newly found form of air bubble -- which the scientists have named the separated vortex ring -- is physically detached from the bristles and is stabilised by air flowing through it.

The amount of air flowing through, which is critical for keeping the bubble stable and directly above the seed in flight, is precisely controlled by the spacing of the bristles.

This flight mechanism of the bristly parachute underpins the seeds' steady flight. It is four times more efficient than what is possible with conventional parachute design, according to the research.

Researchers suggest that the dandelion's porous parachute might inspire the development of small-scale drones that require little or no power consumption. Such drones could be useful for remote sensing or air pollution monitoring.

The study, published in Nature, was funded by the Leverhulme Trust and the Royal Society.

Dr Cathal Cummins, of the University of Edinburgh's Schools of Biological Sciences and Engineering, who led the study, said: "Taking a closer look at the ingenious structures in nature -- like the dandelion's parachute -- can reveal novel insights. We found a natural solution for flight that minimises the material and energy costs, which can be applied to engineering of sustainable technology."

From Science Daily

Astronomers find a cosmic Titan in the early universe

An international team of astronomers has discovered a titanic structure in the early Universe, just two billion years after the Big Bang. This galaxy proto-supercluster, nicknamed Hyperion, is the largest and most massive structure yet found at such a remote time and distance. It has a mass estimated at a million billion Suns.

An international team of astronomers has discovered a titanic structure in the early Universe, just two billion years after the Big Bang. This galaxy proto-supercluster, nicknamed Hyperion, is the largest and most massive structure yet found at such a remote time and distance.

The team that made the discovery was led by Olga Cucciati of Istituto Nazionale di Astrofisica (INAF) Bologna, Italy and project scientist Brian Lemaux in the Department of Physics, College of Letters and Science at the University of California, Davis, and included Lori Lubin, professor of physics at UC Davis. They used the VIMOSinstrument on ESO's Very Large Telescope in Paranal, Chile to identify a gigantic proto-supercluster of galaxies forming in the early Universe, just 2.3 billion years after the Big Bang.

Hyperion is the largest and most massive structure to be found so early in the formation of the Universe, with a calculated mass more than one million billion times that of the Sun. This enormous mass is similar to that of the largest structures observed in the Universe today, but finding such a massive object in the early Universe surprised astronomers.

"This is the first time that such a large structure has been identified at such a high redshift, just over 2 billion years after the Big Bang," Cucciati said. "Normally these kinds of structures are known at lower redshifts, which means when the Universe has had much more time to evolve and construct such huge things. It was a surprise to see something this evolved when the Universe was relatively young."

Supercluster mapped in three dimensions

Located in the constellation of Sextans (The Sextant), Hyperion was identified by a novel technique developed at UC Davis to analyze the vast amount of data obtained from the VIMOS Ultra-Deep Survey led by Olivier Le Fèvre from Laboratoire d'Astrophysique de Marseille, Centre National de la Recherche Scientifique and Centre National d'Etudes Spatiales. The VIMOS instrument can measure the distance to hundreds of galaxies at the same time, making it possible to map the position of galaxies within the forming supercluster in three dimensions.

The team found that Hyperion has a very complex structure, containing at least seven high-density regions connected by filaments of galaxies, and its size is comparable to superclusters closer to Earth, though it has a very different structure.

"Superclusters closer to Earth tend to a much more concentrated distribution of mass with clear structural features," Lemaux said. "But in Hyperion, the mass is distributed much more uniformly in a series of connected blobs, populated by loose associations of galaxies."

The researchers are comparing the Hyperion findings with results from the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey, led by Lubin. The ORELSE survey uses telescopes at the W.M. Keck Observatory in Hawaii to study superclusters closer to Earth. Lubin and Lemaux are also using the Keck observatory to map out Hyperion and similar structures more completely.

The contrast between Hyperion and less distant superclusters is most likely due to the fact that nearby superclusters have had billions of years for gravity to gather matter together into denser regions -- a process that has been acting for far less time in the much younger Hyperion.

Given its size so early in the history of the Universe, Hyperion is expected to evolve into something similar to the immense structures in the local Universe such as the superclusters making up the Sloan Great Wall or the Virgo Supercluster that contains our own galaxy, the Milky Way.

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Antarctic ice shelf 'sings' as winds whip across its surface

Winds blowing across snow dunes on Antarctica's Ross Ice Shelf cause the massive ice slab's surface to vibrate, producing a near-constant drumroll of seismic 'tones' scientists could potentially use to monitor changes in the ice shelf from afar, according to new research. The ice shelf's 'song' is too low in frequency to be heard by human ears, but it has been made audible here by geophysicist and mathematician Julien Chaput, who sped up a 2015 recording of the ice shelf's vibrations about 1,200 times.

Winds blowing across snow dunes on Antarctica's Ross Ice Shelf cause the massive ice slab's surface to vibrate, producing a near-constant set of seismic "tones" scientists could potentially use to monitor changes in the ice shelf from afar, according to new research.

The Ross Ice Shelf is Antarctica's largest ice shelf, a Texas-sized plate of glacial ice fed from the icy continent's interior that floats atop the Southern Ocean. The ice shelf buttresses adjacent ice sheets on Antarctica's mainland, impeding ice flow from land into water, like a cork in a bottle.

When ice shelves collapse, ice can flow faster from land into the sea, which can raise sea levels. Ice shelves all over Antarctica have been thinning, and in some cases breaking up or retreating, due to rising ocean and air temperatures. Prior observations have shown that Antarctic ice shelves can collapse suddenly and without obvious warning signs, which happened when the Larsen B ice shelf on the Antarctic Peninsula abruptly collapsed in 2002.

To better understand the physical properties of the Ross Ice Shelf, researchers buried 34 extremely sensitive seismic sensors under its snowy surface. The sensors allowed the researchers to monitor the ice shelf's vibrations and study its structure and movements for over two years, from late 2014 to early 2017.

Ice shelves are covered in thick blankets of snow, often several meters deep, that are topped with massive snow dunes, like sand dunes in a desert. This snow layer acts like a fur coat for the underlying ice, insulating the ice below from heating and even melting when temperatures rise.

When the researchers started analyzing seismic data on the Ross Ice Shelf, they noticed something odd: Its fur coat was almost constantly vibrating.

When they looked closer at the data, they discovered winds whipping across the massive snow dunes caused the ice sheet's snow covering to rumble, like the pounding of a colossal drum (see: https://youtu.be/w56RxaX9THY).

They also noticed the pitch of this seismic hum changed when weather conditions altered the snow layer's surface. They found the ice vibrated at different frequencies when strong storms rearranged the snow dunes or when the air temperatures at the surface went up or down, which changed how fast seismic waves traveled through the snow.

"It's kind of like you're blowing a flute, constantly, on the ice shelf," said Julien Chaput, a geophysicist and mathematician at Colorado State University in Fort Collins and lead author of the new study published today in Geophysical Research Letters, a journal of the American Geophysical Union.

Just like musicians can change the pitch of a note on a flute by altering which holes air flows through or how fast it flows, weather conditions on the ice shelf can change the frequency of its vibration by altering its dune-like topography, according to Chaput.

"Either you change the velocity of the snow by heating or cooling it, or you change where you blow on the flute, by adding or destroying dunes," he said. "And that's essentially the two forcing effects we can observe."

The hum is too low in frequency to be audible to human ears, but the new findings suggest scientists could use seismic stations to continuously monitor the conditions on ice shelves in near real-time. Studying the vibrations of an ice shelf's insulating snow jacket could give scientists a sense of how it is responding to changing climate conditions, according to Douglas MacAyeal, a glaciologist at the University of Chicago who was not connected to the new study but wrote a commentary about the findings also published today in Geophysical Research Letters.

Changes to the ice shelf's seismic hum could indicate whether melt ponds or cracks in the ice are forming that might indicate whether the ice shelf is susceptible to breaking up.

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All in the family: Kin of gravitational wave source discovered

This image provides three different perspectives on GRB150101B, the first known cosmic analogue of GW170817, the gravitational wave event discovered in 2017. At center, an image from the Hubble Space Telescope shows the galaxy where GRB150101B took place. At top right, two X-ray images from NASA's Chandra X-ray observatory show the event as it appeared on January 9, 2015 (left), with a jet visible below and to the left; and a month later, on February 10, 2015 (right), as the jet faded away. The bright X-ray spot is the galaxy's nucleus.

On October 16, 2017, an international group of astronomers and physicists excitedly reported the first simultaneous detection of light and gravitational waves from the same source -- a merger of two neutron stars. Now, a team that includes several University of Maryland astronomers has identified a direct relative of that historic event.

The newly described object, named GRB150101B, was reported as a gamma-ray burst localized by NASA's Neil Gehrels Swift Observatory in 2015. Follow-up observations by NASA's Chandra X-ray Observatory, the Hubble Space Telescope (HST) and the Discovery Channel Telescope (DCT) suggest that GRB150101B shares remarkable similarities with the neutron star merger, named GW170817, discovered by the Laser Interferometer Gravitational-wave Observatory (LIGO) and observed by multiple light-gathering telescopes in 2017.

A new study suggests that these two separate objects may, in fact, be directly related. The results were published on October 16, 2018 in the journal Nature Communications.

"It's a big step to go from one detected object to two," said study lead author Eleonora Troja, an associate research scientist in the UMD Department of Astronomy with a joint appointment at NASA's Goddard Space Flight Center. "Our discovery tells us that events like GW170817 and GRB150101B could represent a whole new class of erupting objects that turn on and off -- and might actually be relatively common."

Troja and her colleagues suspect that both GRB150101B and GW170817 were produced by the same type of event: a merger of two neutron stars. These catastrophic coalescences each generated a narrow jet, or beam, of high-energy particles. The jets each produced a short, intense gamma-ray burst (GRB) -- a powerful flash that lasts only a few seconds. GW170817 also created ripples in space-time called gravitational waves, suggesting that this might be a common feature of neutron star mergers.

The apparent match between GRB150101B and GW170817 is striking: both produced an unusually faint and short-lived gamma ray burst and both were a source of bright, blue optical light and long-lasting X-ray emission. The host galaxies are also remarkably similar, based on HST and DCT observations. Both are bright elliptical galaxies with a population of stars a few billion years old that display no evidence of new star formation.

"We have a case of cosmic look-alikes," said study co-author Geoffrey Ryan, a postdoctoral researcher in the UMD Department of Astronomy and a fellow of the Joint Space-Science Institute. "They look the same, act the same and come from similar neighborhoods, so the simplest explanation is that they are from the same family of objects."

In the cases of both GRB150101B and GW170817, the explosion was likely viewed "off-axis," that is, with the jet not pointing directly towards Earth. So far, these events are the only two off-axis short GRBs that astronomers have identified.

The optical emission from GRB150101B is largely in the blue portion of the spectrum, providing an important clue that this event is another kilonova, as seen in GW170817. A kilonova is a luminous flash of radioactive light that produces large quantities of important elements like silver, gold, platinum and uranium.

While there are many commonalities between GRB150101B and GW170817, there are two very important differences. One is their location: GW170817 is relatively close, at about 130 million light years from Earth, while GRB150101B lies about 1.7 billion light years away.

The second important difference is that, unlike GW170817, gravitational wave data does not exist for GRB150101B. Without this information, the team cannot calculate the masses of the two objects that merged. It is possible that the event resulted from the merger of a black hole and a neutron star, rather than two neutron stars.

"Surely it's only a matter of time before another event like GW170817 will provide both gravitational wave data and electromagnetic imagery. If the next such observation reveals a merger between a neutron star and a black hole, that would be truly groundbreaking," said study co-author Alexander Kutyrev, an associate research scientist in the UMD Department of Astronomy with a joint appointment at NASA's Goddard Space Flight Center. "Our latest observations give us renewed hope that we'll see such an event before too long."

It is possible that a few mergers like the ones seen in GW170817 and GRB150101B have been detected previously, but were not properly identified using complementary observations in different wavelengths of light, according to the researchers. Without such detections -- in particular, at longer wavelengths such as X-rays or optical light -- it is very difficult to determine the precise location of events that produce gamma-ray bursts.

In the case of GRB150101B, astronomers first thought that the event might coincide with an X-ray source detected by Swift in the center of the galaxy. The most likely explanation for such a source would be a supermassive black hole devouring gas and dust. However, follow-up observations with Chandra placed the event further away from the center of the host galaxy.

According to the researchers, even if LIGO had been operational in early 2015, it would very likely not have detected gravitational waves from GRB150101B because of the event's greater distance from Earth. All the same, every new event observed with both LIGO and multiple light-gathering telescopes will add important new pieces to the puzzle.

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A selfish gene makes mice into migrants

House mice carrying a specific selfish supergene move from one population to another much more frequently than their peers. This finding of a University of Zurich study shows for the first time that a gene of this type can influence animal migratory behavior. It could help in dealing with invasive plagues transmitted by mice.

Usually the cooperation of genes helps an organism to grow and flourish. But some genes are pursuing a different agenda: Their aim is to propagate themselves by eliminating other genes. One of these selfish supergenes is called the t haplotype. It's a complex of various inherited genes that occurs naturally in house mice. "When it comes to heredity, this supergene gains an unfair advantage over other genes," explains Jan-Niklas Runge, first author of the study and a doctoral candidate in evolutionary biology at the University of Zurich. Any gene should actually have a fifty-fifty chance of being transferred to offspring. But sperm that carry the supergene poison rival sperm of the same animal to increase their probability of fertilization to 90 percent. Similar mechanisms can be found in other organisms such as fruit flies and corn.

Supergene carriers emigrate

The researchers have now conducted a long-term study to find out how this supergene affects the migratory behavior of house mice. This involved keeping precise records of comings and goings in four groups of free-ranging wild house mice in a barn near Zurich. With the help of genetic analyses, radio transmitters and regular headcounts, they were able to demonstrate that carriers of the t haplotype were more likely to switch between groups or leave the barn completely. The probability of migration of this sort was almost 50 percent higher than with normal animals. The study focused on young individuals representing the typical age group for house mice when they migrate.

Self-preservation

The scientists believe that the supergene manipulates the mice's behavior in this way to enable it to propagate further and further. Moreover, this migration probably also ensures that the t haplotype is preserved in the house mice's gene pool: If the supergene gets the upper hand in a population, it can lead to its own eradication. For example, mice that receive two copies of the supergene (from their father and their mother) are no longer viable. Apart from this, supergene sperm have trouble asserting themselves in competition with normal sperm if a female mates with several males during the same ovarian cycle. "This means that large populations with a lot of competition for females that are ready to mate, and populations with a high percentage of t haplotype carriers, are fairly bad for the supergene," explains Runge. "This is probably why carriers of the supergene emigrate and join populations where they have a better chance of propagation." This hunch is confirmed by the study findings: The larger the population, the more pronounced the migratory behavior observed. This would also explain why despite all the handicaps, the supergene has managed to survive in the mice's genetic material for some two million years. The UZH researchers are now working on computer simulations and additional experiments to verify this hypothesis.

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Scientists find missing piece in glacier melt predictions

Meltwater accumulation within 160 feet of the surface causes these bright, white reflections to dim to grey from June to early August before stabilizing in late August.

Stanford scientists have revealed the presence of water stored within a glacier in Greenland, where the rapidly changing ice sheet is a major contributor to the sea-level rise North America will experience in the next 100 years. This observation -- which came out of a new way of looking at existing data -- has been a missing component for models aiming to predict how melting glaciers will impact the planet.

The group made the discovery looking at data intended to reveal the changing shape of Store Glacier in West Greenland. But graduate student Alexander Kendrick figured out that the same data could measure something much more difficult to observe: its capacity to store water. The resulting study, published in Geophysical Research Letters, presents evidence of glacier meltwater from the surface being stored within damaged, solid ice. While ice melting at the surface has been well documented, little is known about what happens below glacier surfaces, and this observation of liquid water stored within solid ice may explain the complex flow behavior of some Greenland glaciers.

"Things like this don't always come along, but when they do, that is the real 'joy of the discovery' component of Earth science," said co-author Dustin Schroeder, an assistant professor of geophysics at Stanford University's School of Earth, Energy & Environmental Sciences (Stanford Earth). "This paper not only highlights this component's existence, but gives you a way to observe it in time."

Surface meltwater plays an important role in Greenland by lubricating the bottoms of ice sheets and impacting how retreating glaciers are affected by the ocean. The process of how the glaciers melt and where the water flows contributes to their behavior in a changing climate, as these factors could alter glaciers' response to melting or impact the timeline for sea-level rise. Knowing that some liquid is intercepted within glaciers after melting on the surface may help scientists more accurately predict oceanic changes and help people prepare for the future, Schroeder said.

"All of our predictions of sea-level rise are missing this meltwater component," Schroeder said. "I think we're only just realizing how important it is to understand at a fundamental physical scale what glacier meltwater does on its way from the surface to the bed."

A different perspective

The researchers analyzed data from a high-resolution, low-power radio-echo sounder (ApRES) collected hourly from May to November 2014. Behaving like an ultrasound for ice, the radar sends an electronic wave that bounces off variations in ice density to create an image of ice structure that shows how quickly the ice melts or moves over time.

When the team plotted the radar data, it looked suspicious, said Kendrick, who was lead author on the paper. They tested ideas such as temperature variations and battery fluctuations to account for what they saw, then wondered if water within the ice was causing the peculiarity. By looking at a different aspect of the data, Kendrick noticed that the idiosyncrasies coming from deep within the glacier correlated with information from a nearby weather station indicating that the glacier had been melting at the time the data was collected. That finding backed up the idea that they were detecting water that had melted on the surface and then trickled down into the glacier, where it got trapped.

"This is a new way you could use these instruments to answer scientific questions -- instead of just looking at changes in the ice thickness, we're also looking at changes in the ice properties itself," said co-author Winnie Chu, a postdoctoral researcher in Schroeder's lab. "Alex set up the groundwork for trying to understand how this meltwater storage changes through time."

The study reveals a significant amount of meltwater produced from the local area surrounding the radar is being intercepted and stored within the ice in a region extending between 15 to 148 feet below the surface during the summer, then released or refrozen during winter.

"The water system of Greenland is critical for understanding what's happening on the planet," said Schroeder, who is also a fellow at the Stanford Woods Institute for the Environment. "This component Alex has discovered shows that there is a piece of this glacier in particular -- and maybe the entire Greenland hydrologic system in general -- that we just were not modeling or thinking about in this way."

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Why tropical forests are so ecologically diverse

In this photo of the tropical rain forest canopy in Panama, Handroanthus guayacan, the focus of a new Brown/UCLA study, blooms in yellow while Jacaranda copaia has blue flowers and Cavanillesia plantanifolia has pink fruit. Taking advantage of regular annual changes, like flowering and fruiting, allowed Brown ecologist Jim Kellner to track individual trees through time and map distributions of some species throughout a large area.

Working with high-resolution satellite imaging technology, researchers from Brown University and the University of California, Los Angeles have uncovered new clues in an age-old question about why tropical forests are so ecologically diverse.

In studying Handroanthus guayacan,a common tropical tree species, over a 10-year period, they found that the tree population increased mainly in locations where the tree is rare, rather than in locations where it is common.

"There are more tree species living in an area not much larger than a few football fields in Panama than in all of North America north of Mexico combined," said Jim Kellner, first author on the paper and an assistant professor of ecology and evolutionary biology at Brown. "How this diversity originated, and why it persists over time is a paradox that has challenged naturalists for more than a century."

Until now.

"The take-home of the study is that there is a 'negative feedback' on population growth," Kellner said, which puts the brakes on population growth in locations where the species is common.

The findings confirm a prediction from the 1970s, which posited that tropical forests are diverse because natural enemies keep populations in check. An enemy could be a seed eater, an herbivore or a pathogen, said Kellner, who is affiliated with the Institute at Brown for Environment and Society.

For example, consider an oak tree and a squirrel. The squirrel eats acorns and prefers to forage where oak trees are abundant. A lone acorn in the middle of a grove of maples is likely to go unnoticed by a squirrel, whereas many acorns in an oak grove will be eaten. If this kind of behavior is widespread in tropical rainforests, it could keep species from becoming too common, Kellner said.

Earlier studies have shown that this negative feedback phenomenon holds true among young trees -- seeds, seedlings and saplings -- but ecologists hadn't been able to determine whether it influences adult trees, the reproductive portion of populations, he said.

"It takes decades for trees to become reproductive in tropical forests, and the problem is compounded by how rare each species is," Kellner said. "We found that for this species, you would have to search about 250 acres to find one new adult tree every year."

That challenge isn't feasible on foot, but remote sensing can overcome the challenges of observing large areas.

Kellner and co-author Stephen Hubbell, an ecology professor emeritus at UCLA, used high-resolution satellite images to track individuals on Barro Colorado Island, a six-square-mile island in the middle of the Panama Canal, over 10 years. They looked for Handroanthus guayacan, a tropical rainforest tree that produces bright yellow flowers for a few days a year.

"By timing the satellite image acquisition with seasonal flowering, we were able to identify most of the adults for this species on the island," said Kellner.

They found 1,006 adult trees. Starting in 2012 and looking backward over the 10-year study period, Kellner and Hubbell were able to identify when new trees joined the adult population for the first time. They used advanced statistical methods to make sure that they were in fact identifying new adults and not just trees that had skipped a year of flowering or had flowered early or late.

The researchers found that negative feedback affected the abundance of new adult trees and that it can influence the population of new adult trees in an area of almost 100 football fields. This contrasts with prior studies of juvenile trees, which found the effects of host-specific enemies are usually restricted to small areas, Kellner said.

To confirm the locations of trees from the satellite data, they went to the island and independently found 123 adult trees of the same species. Of these, 89 percent had been detected in the high-resolution images, suggesting that their data are a nearly complete census of the species.

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Mammals cannot evolve fast enough to escape current extinction crisis

An illustration of how the smaller mammals will have to evolve and diversify over the next 3-5 million years to make up for the loss of the large mammals.

We humans are exterminating animal and plant species so quickly that nature's built-in defence mechanism, evolution, cannot keep up. An Aarhus-led research team calculated that if current conservation efforts are not improved, so many mammal species will become extinct during the next five decades that nature will need 3-5 million years to recover.

There have been five upheavals over the past 450 million years when the environment on our planet has changed so dramatically that the majority of Earth's plant and animal species became extinct. After each mass extinction, evolution has slowly filled in the gaps with new species.

The sixth mass extinction is happening now, but this time the extinctions are not being caused by natural disasters; they are the work of humans. A team of researchers from Aarhus University and the University of Gothenburg has calculated that the extinctions are moving too rapidly for evolution to keep up.

If mammals diversify at their normal rates, it will still take them 5-7 million years to restore biodiversity to its level before modern humans evolved, and 3-5 million years just to reach current biodiversity levels, according to the analysis, which was published recently in the scientific journal, PNAS.

Some species are more distinct than others

The researchers used their extensive database of mammals, which includes not only species that still exist, but also the hundreds of species that lived in the recent past and became extinct as Homo sapiens spread across the globe. This meant that the researchers could study the full impact of our species on other mammals.

However, not all species have the same significance. Some extinct animals, such as the Australian leopard-like marsupial lion Thylacoleo, or the strange South American Macrauchenia (imagine a lama with an elephant trunk) were evolutionary distinct lineages and had only few close relatives. When these animals became extinct, they took whole branches of the evolutionary tree of life with them. We not only lost these species, we also lost the unique ecological functions and the millions of years of evolutionary history they represented.

"Large mammals, or megafauna, such as giant sloths and sabre-toothed tigers, which became extinct about 10,000 years ago, were highly evolutionarily distinct. Since they had few close relatives, their extinctions meant that entire branches of Earth's evolutionary tree were chopped off" says palaeontologist Matt Davis from Aarhus University, who led the study. And he adds:

"There are hundreds of species of shrew, so they can weather a few extinctions. There were only four species of sabre-toothed tiger; they all went extinct."

Long waits for replacement rhinos

Regenerating 2.5 billion years of evolutionary history is hard enough, but today's mammals are also facing increasing rates of extinction. Critically endangered species such as the black rhino are at high risk of becoming extinct within the next 50 years. Asian elephants, one of only two surviving species of a once mighty mammalian order that included mammoths and mastodons, have less than a 33 percent chance of surviving past this century.

The researchers incorporated these expected extinctions in their calculations of lost evolutionary history and asked themselves: Can existing mammals naturally regenerate this lost biodiversity?

Using powerful computers, advanced evolutionary simulations and comprehensive data about evolutionary relationships and body sizes of existing and extinct mammals, the researchers were able to quantify how much evolutionary time would be lost from past and potential future extinctions as well as how long recovery would take.

The researchers came up with a best-case scenario of the future, where humans have stopped destroying habitats and eradicating species, reducing extinction rates to the low background levels seen in fossils. However, even with this overly optimistic scenario, it will take mammals 3-5 million years just to diversify enough to regenerate the branches of the evolutionary tree that they are expected to lose over the next 50 years. It will take more than 5 million years to regenerate what was lost from giant Ice Age species.

Prioritizing conservation work

"Although we once lived in a world of giants: giant beavers, giant armadillos, giant deer, etc., we now live in a world that is becoming increasingly impoverished of large wild mammalian species. The few remaining giants, such as rhinos and elephants, are in danger of being wiped out very rapidly," says Professor Jens-Christian Svenning from Aarhus University, who heads a large research program on megafauna, which includes the study.

The research team doesn't have only bad news, however. Their data and methods could be used to quickly identify endangered, evolutionarily distinct species, so that we can prioritise conservation efforts, and focus on avoiding the most serious extinctions.

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Males have greater reproductive success if they spend more time taking care of kids

A gorilla baby.

Males have greater reproductive success if they spend more time taking care of kids -- and not necessarily only their own, according to new research published by anthropologists at Northwestern University.

In a previous study, the researchers found that wild male mountain gorillas living in Rwanda do something that is quite unusual for a mammal -- they help take care of all of the kids that live in their social group, regardless of whether they are the father. The goal of the new study was to figure out why.

"Mountain gorillas and humans are the only great apes in which males regularly develop strong social bonds with kids, so learning about what mountain gorillas do and why helps us understand how human males may have started down the path to our more involved form of fatherhood," said Stacy Rosenbaum, lead author of the study and a post-doctoral fellow in anthropology at Northwestern.

Christopher Kuzawa, a co-author of the study, said the findings run counter to how we typically think of male mountain gorillas -- huge, competitive and with reproduction in the group dominated by a single alpha male.

"Males are spending a lot of time with groups of kids -- and those who groom and rest more with them end up having more reproductive opportunities," said Kuzawa, professor of anthropology at Northwestern and a faculty fellow at the University's Institute for Policy Research. "One likely interpretation is that females are choosing to mate with males based upon these interactions."

Added Rosenbaum: "We've known for a long time that male mountain gorillas compete with one another to gain access to females and mating opportunities, but these new data suggest that they may have a more diverse strategy. Even after multiple controls for dominance ranks, age and the number of reproductive chances they get, males who have these bonds with kids are much more successful."

This research suggests an alternative route by which fathering behaviors might have evolved in our own species, Rosenbaum said.

"We traditionally have believed that male caretaking is reliant on a specific social structure, monogamy, because it helps ensure that males are taking care of their own kids. Our data suggest that there is an alternative pathway by which evolution can generate this behavior, even when males may not know who their offspring are," Rosenbaum said.

This raises the possibility that similar behaviors could have been important in the initial establishment of fathering behaviors in distant human ancestors.

The researchers are currently investigating whether hormones might play a role in helping facilitate these male behaviors, as they do in humans. Seminal work on the hormonal changes that men experience as they become fathers and care for kids has been conducted in the anthropology department at Northwestern.

"In human males, testosterone declines as men become fathers, and this is believed to help focus their attention on the needs of the newborn," said Kuzawa, who co-authored a study on this topic in the journal Proceedings of the National Academy of Sciences in 2011. "Might gorillas that are particularly engaged in infant interaction experience similar declines in testosterone? Because this would probably impede their ability to compete with other males, evidence that testosterone goes down would be a clear indication that they must be gaining some real benefit -- such as attracting mates. Alternatively, if it does not go down, this suggests that high testosterone and caretaking behavior don't have to be mutually exclusive in mountain gorillas."

The researchers look forward to exploring these new questions. "We're working on characterizing these males' hormone profiles across time, to see if events such as the birth of new infants might be related to their testosterone levels," Rosenbaum said. "We're fortunate to have data that span many years of their lives."

The study's senior author, Tara Stoinski of The Dian Fossey Gorilla Fund, added that such work highlights the critical importance of long-term research studies.

Read more at Science Daily