Why animals have evolved to favour one side of the brain

Most left-handers can rattle off a list of their eminent comrades-in-arms: Oprah Winfrey, Albert Einstein, and Barack Obama, just to name three, but they may want to add on cockatoos, "southpaw" squirrels, and some house cats. "Handed-ness" or left-right asymmetry is prevalent throughout the animal kingdom, including in pigeons and zebrafish. But why do people and animals naturally favor one side over the other, and what does it teach us about the brain's inner workings? Researchers explore these questions in a Review published in Neuron.

While small fish (Girardinus falcatus) caught live Artemia, they were observed by a large predatory fish in an
 adjacent tank. Thus, this task required attention sharing between two parallel tasks: prey capture and predator 
vigilance. When comparing lateralized and non-lateralized Girardinus falcatus, lateralized individuals were 
twice as fast as non-lateralized ones at catching prey with their preferred eye for foraging while 
simultaneously monitoring the predator with the other eye [Credit: Oliver Wrobel]

"Studying asymmetry can provide the most basic blueprints for how the brain is organized," says lead author Onur Güntürkün, of the Institute of Cognitive Neuroscience at Ruhr-University Bochum, in Germany. "It gives us an unprecedented window into the wiring of the early, developing brain that ultimately determines the fate of the adult brain." Because asymmetry is not limited to human brains, a number of animal models have emerged that can help unravel both the genetic and epigenetic foundations for the phenomenon of lateralization.

Güntürkün says that brain lateralization serves three purposes. The first of those is perceptual specialization: the more complex a task, the more it helps to have a specialized area for performing that task. For example, in most people, the right side of the brain focuses on recognizing faces, while the left side is responsible for identifying letters and words.

The next area is motor specialization, which brings us to the southpaw. "What you do with your hands is a miracle of biological evolution," he says. "We are the master of our hands, and by funneling this training to one hemisphere of our brains, we can become more proficient at that kind of dexterity." Natural selection likely provided an advantage that resulted in a proportion of the population -- about 10% -- favoring the opposite hand. The thing that connects the two is parallel processing, which enables us to do two things that use different parts of the brain at the same time.

Brain asymmetry is present in many vertebrates and invertebrates. "It is, in fact, an invention of nature, which evolved because many animals have the same needs for specialization that we do," says Güntürkün, who is also currently a visiting fellow at the Stellenbosch Institute for Advanced Study in South Africa. Studies have shown that birds, like chickens, use one eye to distinguish grain from pebbles on the ground while at the same time using the other eye to keep watch for predators overhead.

Research on pigeons has shown that this specialization often is a function of environmental influences. When a pigeon chick develops in the shell, its right eye turns toward the outside, leaving its left eye to face its body. When the right eye is exposed to light coming through the shell, it triggers a series of neuronal changes that allow the two eyes to ultimately have different jobs.

A zebrafish model of lateralization, meanwhile, has enabled researchers to delve into the genetic aspects of asymmetrical development. Studies of important developmental pathways, including the Nodal signaling pathway, are uncovering details about how, very early in an embryo's development, the cilia act to shuffle gene products to one side of the brain or the other. By manipulating the genes in Nodal and other pathways, researchers can study the effects of these developmental changes on zebrafish behaviors.

Güntürkün says that this research can provide insight into the effects of asymmetry on brain conditions in humans. "There are almost no disorders of the human brain that are not linked to brain asymmetries," he says. "If we understand the ontogeny of lateralization, we can make a great leap to see how brain wiring early in the developmental process may go wrong in these pathological cases."

Source: Cell Press [April 19, 2017]

byUnknown

in Biology, Ecosystems, Evolution, Neuroscience

April 19, 2017

Why animals have evolved to favour one side of the brain

Most left-handers can rattle off a list of their eminent comrades-in-arms: Oprah Winfrey, Albert Einstein, and Barack Obama, just to name th...

Read More

Birds vs. bees: Study helps explain how flowers evolved to get pollinators to specialize

Ecologists who study flowering plants have long believed that flowers evolved with particular sets of characteristics -- unique combinations of colors, shapes, and orientations, for example -- as a means of attracting specific pollinators. But a recent paper in the journal Ecology suggests that flowers that are visited almost exclusively by hummingbirds are actually designed not to lure birds, but to deter bumblebees and their wasteful visits.

Work by Robert J. Gegear at Worcester Polytechnic Institute (WPI) shows that flowers that were thought 
to have evolved to lure hummingbirds, actually have combinations of traits that discourage wasteful 
visits by bumblebees [Credit: WPI]

The paper, "'Hummingbird' floral traits interact synergistically to discourage visitation by bumble bee foragers," demonstrates that traits of so-called "hummingbird flowers" work together to confuse bees and cost them precious time as they move from flower to flower. This extra cost leads most bees to seek nectar rewards from floral alternatives that they can more easily exploit, thus enabling the plants to more effectively attract more efficient hummingbird pollinators.

Most hummingbird-pollinated flowers evolved from bee-pollinated ancestors, according to lead author Robert J. Gegear, assistant professor of biology and biotechnology at Worcester Polytechnic Institute (WPI). While the "bee" floral variants tend to be upright and have blue or purple coloration, the "bird" variants have a horizontal orientation and red or orange coloration. Also, bee flowers typically contain small amounts of concentrated nectar, while bird flowers have larger amounts of dilute nectar.

While it has long been thought that the characteristics of bird flowers operate independently to make it difficult for bees to access their nectar (or in the case of the red coloration, to even see the flowers), Gegear's research shows that, in fact, the traits interact synergistically to encourage bees to look elsewhere for nectar rewards.

In the laboratory, Gegear and his students observed the behavior of foraging bees using arrays of paper flowers that mimicked the blooms of Mimulus lewisii (purple monkey flower), which is pollinated primarily by bumblebees, and a related species, Mimulus cardinalis (scarlet monkey flower), which is pollinated primarily by hummingbirds. They tested three characteristics -- color, orientation, and nectar reward -- in various combinations.

They found that bees readily visited upright flowers, regardless of their color, as well as lavender flowers, regardless of their orientation. However, when red flowers were placed in the horizontal orientation and lavender flowers were placed in a vertical orientation -- mimicking the natural flowers of Mimulus cardinalis and Mimulus lewisii -- visits by foraging bumblebees dropped dramatically. Similar effects were observed when red coloration and dilute nectar were combined, showing that floral display and reward traits also interact to discourage bee visitation.

To understand how floral characteristics can combine to influence the decisions bumblebees make about which flowers to 
visit, Robert Gegear, assistant professor of biology and biotechnology at Worcester Polytechnic Institute (WPI), had bees 
forage on arrays of paper representations of typical "hummingbird flowers" (red coloration, horizontal orientation)
 and "bee flowers" (lavender or blue coloration, upright orientation) [Credit: Robert Gegear, WPI]

Bumblebees, like most pollinators, are not genetically programmed to visit only particular flowers, Gegear says. They are generalists that seek to maximize their rate of reward intake. But the ideal pollinator, from the plant's perspective, is one that adopts a specialist foraging strategy, since that will help assure that each plant receives only pollen from its own species. By combining particular floral characteristics, plants manipulate pollinators to become specialists by making generalization a less economically attractive option.

Gegear says his study shows that at least two floral characteristics had to change for the bird flower Mimulus cardinalis to evolve from the bee flower Mimulus lewisii, and that those changes served to discourage bees. To learn why bees avoid the bird flowers, Gegear set up a different experiment in his lab. He first had bees forage on arrays of paper flowers, all of which were of the same color and orientation. Every flower contained a sugar reward. During these runs each bee learned to associate every color and orientation combination with a reward.

Next, the same bees foraged on mixed arrays in which one color-orientation combination contained nectar and the other combinations contained distilled water. Gegear and his students watched to see how long it took the bees to learn which flowers were worth visiting. Once they were able to make the right choice 80 percent of the time, they observed the next 20 flower visits, noting the time interval between flower visits and the number of times the bees visited non-rewarding flowers.

They found that it was much more difficult for bees to learn and effectively locate bird-trait combinations than bee-trait combinations, a response that was not predicted based on the response observed when each trait was presented in isolation. "These data suggests that the reason bee-to-bird evolutionary transitions are often accompanied by a floral shift to classic 'bird' trait complexes is because bees have a particularly difficult time combining red with other sensory traits, including nectar rewards," he says.

"It takes them longer to learn to seek out these combinations, and once they learn them, it takes them longer to recognize these flowers. Thus, bees avoid bird flowers in mixed floral environments because it makes economic sense for them to do so. When you put all this together, you find that 'bird flowers' are really 'anti-bee flowers' that function by exploiting specific sensory and cognitive limitations."

Gegear says the study offers a new perspective on prevailing theories about how plants evolve to manipulate their animal pollinators. "From an ecological perspective, an ideal pollinator is one that always forages on flowers of the same type so pollen is transferred effectively. In reality, pollinators are generalists and they should simply forage randomly. So the big question has been, how do plants get the pollinators to do what they want?

"The answer lies in floral complexity. Each plant has a flower made up of a unique combination of sensory and structural traits that pollinators must learn and remember in order to effectively locate nectar rewards. However, pollinators are limited in their ability to manage information on more than one unique combination at a time, making generalization a costly foraging strategy. In the case of the two species of Mimulus, the costs associated with bird combinations are much greater than the costs associated with bee combinations, so bees avoid them to increase their foraging efficiency."

Source: Worcester Polytechnic Institute [April 19, 2017]

byUnknown

in Biology, Ecosystems, Evolution

April 19, 2017

Birds vs. bees: Study helps explain how flowers evolved to get pollinators to specialize

Ecologists who study flowering plants have long believed that flowers evolved with particular sets of characteristics -- unique combinations...

Read More

Cave-in: How blind species evolve

Why do animals that live in caves become blind? This question has long intrigued scientists and been the subject of hot debate. Clearly, across the animal kingdom, blindness has evolved repeatedly. There are thousands of underground and cave-dwelling species, from naked mole rats to bats, found throughout nature. Many of these species have lost their sense of sight.

A well-studied blind cavefish (bottom), the Mexican tetra (Astyanax mexicanus), is a small, docile, 
pink-hued fish just a few centimeters long that could easily make its home in an aquarium. 
ASU evolutionary biologist Reed Cartwright chose this Mexican tetra because 
there is also a surface-dwelling form (top) that has retained its sight 
[Credit: Arizona State University]

Charles Darwin originally suggested that eyes could be lost by "disuse" over time. Now, Reed Cartwright, an ASU evolutionary biologist in the School of Life Sciences and researcher at the Biodesign Institute, wants to get to the heart of the matter -- and in a recent publication in the journal BMC Evolutionary Biology, may be proving Darwin wrong.

"We think that blindness in cavefish is indeed Darwinian, but ultimately this disproves Darwin's original hypothesis of 'disuse'," said Cartwright. In new research, Cartwright explains that eyes are not lost by disuse, but rather, demonstrate Darwin's fundamental theory of natural selection at work -- with blindness selected as favorable and the fittest -- for living in a cave.

Go Fish

For their work, his research team choose to model a well-studied blind cavefish, the Mexican tetra (Astyanax mexicanus), a small, docile, pink-hued fish just a few centimeters long that could easily make its home in an aquarium.

It's inhabited caves for 2-3 million years, giving it 5 million generations worth of time to evolve blindness. Cartwright's group chose this Mexican tetra because there is also a surface-dwelling form that has retained its sight. And for scientists, this built-in comparative power makes it a good choice for further exploration. They have two populations to study that can interbreed and are polar opposites for physical traits.

So Cartwright's group decided to use computational power to investigate how multiple evolutionary mechanisms interact to shape the fish that live in caves.

"The problem we have in these caves is that they are connected to the surface, and fish that can see immigrate into the cave and bring genes for sight with them," said Cartwright. "Under these conditions, we don't typically expect to find such a difference in traits between surface and cave populations. Unless selection was really, really, strong."

How strong? In their model, the selection for blindness would need to be about 48 times stronger than the immigration rate for Mexican tetras to evolve blindness in caves. Cartwright's group estimates that a measure of fitness for blindness, called the selection coefficient, in the tetra is between 0.5 percent and 50 percent.

These coefficients are high enough that laboratory experiments should have detected a difference between surface and cave forms of the fish; however, none have to date.

Blinded by the light

Cartwright's team turned to a hypothesis going all the way back to a letter to the editor of Nature in 1925 by E. Ray Lankester, that essentially stated that the reason you have blindness in caves is because the fish that can see simply leave.

"If sighted fish swim towards the light, the only fish that stay in the cave are blind fish. They aren't trying to get to the light anymore because they can't see it. Which actually is a form of selection, and thus, Darwinian evolution in action," said Cartwright.

According to Cartwright, explaining a fitness difference as big as 10 percent between sighted and blind fish may be difficult, "Iosing eyes might not give you 10 percent more offspring. However, if 10 percent of your seeing eye fish leave the cave, the migration rate is reasonably low, and that could be enough."

If over time, enough of the seeing eye fish are systematically being removed, they will also be removed from the gene pool, and that could be enough to drive the evolutionary process.

It could be this sort of habitat preference that maintains the local blind fish population and the fish that can see are preferentially moving out of the cave. "We found that even a low level of preferential emigration, e.g. two percent, would provide a significant boost to local adaptation and the evolution of blindness in caves."

Cartwright's team hopes that field biologists begin to consider Lankester's 90-year old hypothesis when studying cavefish. "It would be great if someone could develop a study to test Lankester's hypothesis and whether it is driving the evolution of blindness in caves. That would really help answer one of the questions that have intrigued biologists for over a century."

Source: Arizona State University [April 17, 2017]

byUnknown

in Biology, Ecosystems, Evolution

April 17, 2017

Cave-in: How blind species evolve

Why do animals that live in caves become blind? This question has long intrigued scientists and been the subject of hot debate. Clearly, acr...

Read More

Retreating Yukon glacier caused a river to disappear

The massive Kaskawulsh Glacier in northern Canada has retreated about a mile up its valley over the past century.

A Sept. 2, 2016 aerial photo shows the meltwater stream along the toe of Kaskawulsh Glacier, seen on the left, that is 
diverting fresh water from one river to the other [Credit: Dan Shugar/University of Washington Tacoma]

Last spring, its retreat triggered a geologic event at relatively breakneck speed. The toe of ice that was sending meltwater toward the Slims River and then north to the Bering Sea retreated so far that the water changed course, joining the Kaskawulsh River and flowing south toward the Gulf of Alaska.

This capture of one river's flow by another, documented in a study led by the University of Washington Tacoma and published in Nature Geoscience, is the first known case of "river piracy" in modern times. "Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes," said lead author Dan Shugar, a geoscientist at the University of Washington Tacoma. "People had looked at the geological record -- thousands or millions of years ago -- not the 21st century, where it's happening under our noses."

River piracy, also known as stream capture, can happen due to tectonic motion of Earth's crust, landslides, erosion or, in this case, changes in a glacial dam. The new study documents one of the less-anticipated shifts that can occur in a changing climate.

Shugar and co-authors Jim Best at the University of Illinois and John Clague at Canada's Simon Fraser University had planned fieldwork last summer on the Slims River, a geologically active system that feeds Kluane Lake in the Yukon. When they arrived in August, the river was not flowing. River gauges show an abrupt drop over four days from May 26 to 29, 2016.

By late summer, "there was barely any flow whatsoever. It was essentially a long, skinny lake," Shugar said. "The water was somewhat treacherous to approach, because you're walking on these old river sediments that were really goopy and would suck you in. And day by day we could see the water level dropping."

Images captured by the European Space Agency’s Sentinel2 satellite in 2015 and 2016 show a dramatic drop in the Slims 
River’s flow. The receding toe of Kaskawulsh Glacier is seen at the bottom. Kluane Lake can be seen at the top of the 
2016 image. Water now flows east and then south via the Kaskawulsh River [Credit: European Space Agency]

The research team puzzled about what to do next. They got permission to use their mapping drone to create a detailed elevation model of the glacier tongue and headwater region. The resulting paper is a geological postmortem of the river's disappearance.

"For the last 300 years, Slims River flowed out to the Bering Sea, and the smaller Kaskawulsh River flowed to the Gulf of Alaska. What we found was the glacial lake that fed Slims River had actually changed its outlet," Shugar said. "A 30-meter (100-foot) canyon had been carved through the terminus of the glacier. Meltwater was flowing through that canyon from one lake into another glacial lake, almost like when you see champagne poured into glasses that are stacked in a pyramid."

That second lake drains via the Kaskawulsh River in a different direction than the first. The situation is fairly unique, Shugar said, since the glacier's toe was sitting on a geologic divide.

Clague began studying this glacier years ago for the Geological Survey of Canada. He observed that Kluane Lake, which is Yukon's largest lake, had changed its water level by about 40 feet (12 meters) a few centuries ago. He concluded that the Slims River that feeds it had appeared as the glacier advanced, and a decade ago predicted the river would disappear again as the glacier retreated.

"The event is a bit idiosyncratic, given the peculiar geographic situation in which it happened, but in a broader sense it highlights the huge changes that glaciers are undergoing around the world due to climate change," Clague said.

A close-up view of the ice-walled canyon at the terminus of the Kaskawulsh Glacier, with recently collapsed ice blocks. 
This canyon now carries almost all meltwater from the toe of the glacier down the Kaskawulsh Valley 
and toward the Gulf of Alaska [Credit: Jim Best/University of Illinois]

The geologic event has redrawn the local landscape. Slims River crosses the Alaska Highway, and its banks were a popular hiking route. Now that the riverbed is exposed, Dall sheep from Kluane National Park are making their way down to eat the fresh vegetation, venturing into territory where they can legally be hunted. With less water flowing in, Kluane Lake did not refill last spring, and by summer 2016 was about 3 feet (1 meter) lower than ever recorded for that time of year. Waterfront land, which includes the small communities of Burwash Landing and Destruction Bay, is now farther from shore. As the lake level continues to drop researchers expect this will become an isolated lake cut off from any outflow.

On the other hand, the Alsek River, a popular whitewater rafting river that is a UNESCO world heritage site, was running higher last summer due to the addition of the Slims River's water.

Shifts in sediment transport, lake chemistry, fish populations, wildlife behavior and other factors will continue to occur as the ecosystem adjusts to the new reality, Shugar said.

"So far, a lot of the scientific work surrounding glaciers and climate change has been focused on sea-level rise," Shugar said. "Our study shows there may be other underappreciated, unanticipated effects of glacial retreat."

The Kaskawulsh Glacier is retreating up the valley because of both readjustment after a cold period centuries ago, known as the Little Ice Age, and warming due to greenhouse gases. A technique published in 2016 by UW co-author Gerard Roe shows a 99.5 percent probability that this glacier's retreat is showing the effects of modern climate change.

"I always point out to climate-change skeptics that Earth's glaciers are becoming markedly smaller, and that can only happen in a warming climate," Clague said.

Source: University of Washington [April 17, 2017]

byUnknown

in Canada, Climate Change, Ecosystems, Natural Heritage, North America

April 17, 2017

Retreating Yukon glacier caused a river to disappear

The massive Kaskawulsh Glacier in northern Canada has retreated about a mile up its valley over the past century. A Sept. 2, 2016 aerial pho...

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Distantly related fish find same evolutionary solution to dark water

Changes in a single color-vision gene demonstrate convergent evolutionary adaptations in widely separated species and across vastly different time scales, according to a study in the open access journal PLOS Biology by David Marques of the University of Victoria, British Columbia, and colleagues. The study, which combined genetic analysis with a 19-year-long selection experiment, supports the idea that the mechanisms of adaptive evolution may be more predictable than previously suspected.

Threespine sticklebacks on Haida Gwaii have repeatedly colonized tannin-stained blackwater lakes with a strongly 
red-shifted light spectrum. Here a male is near its nest at Drizzle lake [Credit: Thomas E. Reimchen]

Over the past 12,000 years or more, species of three-spined stickleback fish have colonized hundreds of freshwater lakes in the Haida Gwaii archipelago off the coast of British Columbia, forming independently evolving populations. The lakes can be broadly classified as "clearwater," in which full-spectrum light passes relatively unimpeded, or "blackwater," in which most of the visible light is absorbed by dissolved tannins, creating an almost nocturnal environment with only dim, red-shifted light filtering in from above.

Cone cells responsible for color vision in the stickleback retina contain SWS2, an opsin protein sensitive to blue light. Amino acid changes in SWS2 have been previously shown to "tune" this opsin to make it more sensitive to either the blue or red end of the spectrum. In the current study, the authors compared genetic sequences of SWS2 from marine, clearwater, and blackwater sticklebacks, including a group of blackwater fish that they had transplanted to an empty clearwater lake 19 years previously and left there to evolve.

The researchers found that the pattern of genetic changes in SWS2 seen in blackwater sticklebacks implied there had been very strong selection for red-shift tuning, maximizing the opsin's sensitivity in the dark water; no such pattern was seen in clearwater sticklebacks. In blackwater fish transplanted to a clearwater lake, after only 13 generations, many members of the population contained alternative versions of SWS2 that were more sensitive to the more abundant blue light of their new habitat, demonstrating the rapid effect of this selective pressure.

Next, the authors compared their stickleback results to previously published opsin genes in two related species of fish (bluefin killifish and black bream), separated from sticklebacks by millions of years, that had also adapted to blackwater and clearwater habitats. These fish have two distinct copies of the SWS2 gene -- SWS2A and SWS2B, which arose from an ancient gene duplication event 198 million years ago in the ancestor of all spiny-finned fish. Remarkably, two of the same genetic changes seen in stickleback SWS2 also distinguish SWS2A (red-shifted) and SWS2B (blue-shifted) of these fish species, with whom they last shared a common ancestor many million years ago. Since the same genetic changes arose separately in their ancestor and in the sticklebacks, they demonstrate convergent evolution, but over vastly different time scales.

"These data support the emerging view in evolutionary biology that mechanisms underlying adaptive evolution are often highly repeatable and thus may be predictable," said Marques. "They show that evolutionary 'tinkering' with a limited set of tools can lead to convergent 'solutions' to common problems both within species and between widely separated groups."

Source: PLOS [April 11, 2017]

byUnknown

in Biology, Ecosystems, Evolution, Genetics

April 11, 2017

Distantly related fish find same evolutionary solution to dark water

Changes in a single color-vision gene demonstrate convergent evolutionary adaptations in widely separated species and across vastly differen...

Read More

Antarctic penguin colony repeatedly decimated by volcanic eruptions

One of the largest colonies of gentoo penguins in Antarctica was decimated by volcanic eruptions several times during the last 7,000 years according to a new study. An international team of researchers, led by British Antarctic Survey (BAS), studied ancient penguin guano and found the colony came close to extinction several times due to ash fall from the nearby Deception Island volcano. Their results are published in Nature Communications.

Gentoo penguins climbing slopes to the nesting colony on Ardley Island 
[Credit: Stephen Roberts]

Ardley Island, near the Antarctic Peninsula, is currently home to a population of around 5,000 pairs of gentoo penguins. Using new chemical analyses of penguin guano extracted in sediment cores from a lake on the island, the researchers unraveled the history of the penguin colony.

Climate conditions around Ardley Island have been generally favourable for penguins over the last 7,000 years and the team had expected the local population to show minor fluctuations in response to changes in climate or sea ice. The surprising result was that the nearby Deception Island volcano had a far greater impact than originally anticipated.

Lead author Dr Steve Roberts from BAS says: "When we first examined the sediment cores we were struck by the intense smell of the guano in some layers and we could also clearly see the volcanic ash layers from nearby Deception Island. By measuring the sediment chemistry, we were able to estimate the population numbers throughout the period and see how penguins were affected by the eruptions.

Volcanic ash layers in lake sediment cores extracted from Kiteschee Lake on Fildes Peninsula. The ash layers shown are 
associated with comparatively small eruptions from Deception Island in the last c. 2000-3000 years. The largest 
eruptions preserved in our lake sediment records from Fildes Peninsula and Ardley Island occurred at c. 7,000 years 
ago and c. 5,500-4,500 years ago and deposited over a metre of airfall and reworked ash in some lake sediment cores 
[Credit: Stephen Roberts and Emma Pearson]

On at least three occasions during the past 7,000 years, the penguin population was similar in magnitude to today, but was almost completely wiped out locally after each of three large volcanic eruptions. It took, on average, between 400 and 800 years for it to re-establish itself sustainably."

Dr Claire Waluda, penguin ecologist from BAS says: "This study reveals the severe impact volcanic eruptions can have on penguins, and just how difficult it can be for a colony to fully recover. An eruption can bury penguin chicks in abrasive and toxic ash, and whilst the adults can swim away, the chicks may be too young to survive in the freezing waters. Suitable nesting sites can also be buried, and may remain uninhabitable for hundreds of years."

The techniques developed in this study will help scientists to reconstruct past changes in colony size and potentially predict how other penguin populations may be affected elsewhere. For example, the chinstrap penguins on Zavodovski Island, which were disturbed by eruptions from the Mt Curry volcano in 2016.

Waluda continues: "Changes in penguin populations on the Antarctic Peninsula have been linked to climate variability and sea-ice changes, but the potentially devastating long-term impact of volcanic activity has not previously been considered."

Source: British Antarctic Survey [April 11, 2017]

byUnknown

in Antarctic, Earth Science, Ecosystems, Natural Heritage, Wildlife

April 11, 2017

Antarctic penguin colony repeatedly decimated by volcanic eruptions

One of the largest colonies of gentoo penguins in Antarctica was decimated by volcanic eruptions several times during the last 7,000 years a...

Read More

Food webs entangle humans in complex relationships with animals, crops and the environment

Reconstructed food webs from the Ancestral Puebloan southwestern United States show the complexity and interconnectedness of humans, other animals, crops and the environment, in an area of uncertain climate and resources, according to researchers, who think climate change and human decisions then, may shed light on future human choices.

Square Tower House in Mesa Verde National Park [Credit: Nate Crabtree]

"As southwestern archaeologists, we know that Ancestral Puebloan people were intrinsically connected to the environment," said Stefani Crabtree, postdoctoral fellow in human behavioral ecology in the Department of Anthropology, Penn State. "But, most food webs have omitted humans."

Traditionally, food webs, while they map the interaction of all the animals and plants in an area, usually do not emphasize the human component. Crabtree and colleagues created a digital food web that captures all categories of consumers and consumed, can be defined for specific time periods and can also represent food webs after major food sources or predators disappear from the area. If an area suddenly becomes devoid of deer or humans or corn, for example, a food web of that situation can show where predators went to find prey, or which prey thrived for lack of a predator.

These knockout food webs -- webs missing a specific predator or prey -- show the changes and pressures on the food sources substituted for the missing ones, or the changes that occur when pressure is removed by removing a major consumer. The researchers report the results of their study in the Journal of Archaeological Science.

"When people show up in the area around A.D. 600 they bring corn," said Crabtree. "It takes a while for critters to get used to it, but eventually, everything that eats vegetation, eats corn and prefers it."

Humans bringing corn into an area is a major disruption of the existing food web. Planting corn means clearing fields to displace whatever plants and animals were there, creating a high-energy plant source of food and switching plant eaters to the preferred higher-calorie food source.

In the American Southwest, the Ancestral Puebloan people eventually preyed on their deer population enough so that they deer were no longer a reliable source of food. To compensate for this, they began to domesticate turkeys for food. Turkeys need to be fed corn if they are captive and that competes with corn for human consumption. At this time, corn made up 70 to 80 percent of Ancestral Puebloans' food and so feeding turkeys altered the food web.

A sample food web with red nodes representing primary producers, orange nodes primary consumers, yellow-orange 
nodes omnivores, true-yellow nodes are true carnivores. This draft food web was created with the program 
Network3D from foodwebs.org [Credit: Stefani Crabtree, Penn State]

To create the food web, the team identified all the common, noninvasive species in the area. They then added species that were found in archaeological sites, but were absent from the modern lists. In some food webs, components are identified by their function, so all humming birds are considered flying pollinators, but in this case each type of humming bird received its own place in the web, linked to what it ate and what, if anything, ate it. This produced a very complicated web, but supplied exceptional redundancy.

"In the insect world it is harder to get at the data," said Crabtree. "We have not been able to get at good databases so we aggregate at the functional level -- pollinators or bloodsuckers for example."

The exception to individual web entries then are invertebrates -- insects, spiders, snails, etc. -- that were classified by their function. Invertebrates are organized to the level of order and then grouped by function. With insects, for example, the researchers would group butterflies and moths that pollinated and sipped nectar, together in one group.

The overall food web had 334 nodes representing species or order-level functional groups with 11,344 links between predator and prey.

The researchers realize that there are differences in the environment between now and the Ancestral Puebloan period, but many things, such as pinon-juniper woodlands and sage flats are the same. Enough similarity exists for this approach to work.

The team did not produce just one overall food web, but also food webs corresponding to three archaeological locations and three time periods of Ancestral Pueblo occupation in the area -- Grass Mesa Pueblo for Pueblo I, Albert Porter Pueblo for Pueblo II and Sand Canyon Pueblo for Pueblo III. They began with using archaeological assemblages from these sites incorporating all human prey and all human predators into the food web. Then they included the prey of the primary prey of humans and then predators of these human-prey species. Prey, in this case, includes animals, insects and plants.

A coyote preying on an entire clutch of baby rabbits in Boulder County, CO. [Credit: Mindy Wilkinson]

When creating knockout food webs, the researchers included only those species that were found in reasonable quantities in the archaeological assemblages at those times.

"Knockout food webs are one of the best ways to understand how people interact with the environment," said Crabtree. "Because we can remove something, predator or prey, and see what would happen."

When major changes in climate variables such as drought, heat and lack of snowpack are factored in, the balance in the food web may become unstable. When food becomes scarce, most mobile creatures, animals and insects move to another location. During the time of the Ancestral Puebloans, this was possible and eventually, these people moved to the area of the Rio Grande in New Mexico and other places in New Mexico and Arizona.

"We didn't have a long-term plan during the 600 years of Ancestral Pueblo habitation in the Mesa Verde region," said Crabtree. "We don't have a long-term plan today either. We don't even have a four-year plan. Some people are pushing us to look closely at climate change."

In the past, people migrated, said Crabtree. Unless we figure out better strategies, where are we going to migrate out to? We do not have a place to go, she said.

What people plant and eat has a great effect on the environment and on ecosystems. In the end, those choices will impact human survival, according to the researchers.

This work is part of a collaboration of researchers creating resolved food webs from a variety of places. Crabtree believes that she can compare this project to others that include humans in other geographical areas to help understand ecosystems with humans in them.

Author: A'ndrea Elyse Messer | Source: Penn State University [April 10, 2017]

byUnknown

in Americas, Archaeology, Climate Change, Ecosystems, Environment, North America, USA, Wildlife

April 10, 2017

Food webs entangle humans in complex relationships with animals, crops and the environment

Reconstructed food webs from the Ancestral Puebloan southwestern United States show the complexity and interconnectedness of humans, other a...

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Putting a price tag on biodiversity

Talk to just about any biologist long enough and the conversation will steer toward the benefits of biodiversity. Although the ecological benefits of biodiversity are well documented, those benefits have rarely been expressed in dollars and cents. A team of economists and ecologists, including University of Illinois professor of environmental economics Amy Ando, has developed one of the first models to assign a dollar value to the loss or gain of species in an ecosystem. This new work offers an economic argument for preserving biodiversity.

The Cedar Creek Biodiversity Experiment: Each plot has 1, 2, 4, 8 or 16 different species of perennial prairie plants. 
Planted in 1994, this long-term experiment has shown that greater biodiversity leads to greater ecosystem
 productivity and carbon storage [Credit: G. David Tilman]

"Biodiversity has value in its own right, as people marvel at the beauty and variety of the many faces of nature," says Ando. "But those intrinsic values can be hard to quantify. In this study, we pinned down the monetary value of one particular practical service that biodiversity provides to people: carbon storage." The research team was led by Bruce Hungate, director of the Center for Ecosystem Science and Society at Northern Arizona University. The findings are published in Science Advances.

To build the model, the researchers first had to identify some measurable service of biodiversity that society has priced. Although biodiversity provides many valuable services, concern about climate change has led economists to put a dollar value on the abatement of climate-warming carbon emissions (ranging between roughly $40 and $400 per metric ton). And now there's a $175 billion global carbon market that pays for activities that remove carbon from the atmosphere.

Biodiversity could enter the game through a 4-billion-year-old form of carbon storage that plants provide: photosynthesis. Plants absorb carbon dioxide for energy and growth, storing the carbon in their leaves, stems, and roots, and later transferring it to the soil through decay. The key is to link biodiversity and carbon storage in a quantitative way. So researchers asked: Will changing the number of plant species in an ecosystem affect the amount of carbon it stores over time?

The National Socio-Environmental Synthesis Center (SESYNC) convened the team of scientists, which analyzed data from two long-term experiments in Minnesota grasslands that measured how plant and soil carbon changed with the number of plant species in a plot. Modeling results over 50 years, they estimated the "marginal" increase in carbon storage, or how much additional carbon is stored for every species added to the mix.

Each additional species in a grassland plot increased the plot's overall carbon storage, on average. One reason for this gain may be that new species can fill new niches, yielding more overall growth.

With more species came diminishing returns in cumulative carbon storage. A change from five to six species stored almost 10 times more carbon than a change from 15 to 16 species, showing that the biggest benefit came from adding species to the least diverse plots.

At small scales, about 2.47 acres, going from one to two plant species over a 50-year time period would store an additional 9.1 metric tons of carbon, potentially saving $804 per 2.47 acres based on a mid-range estimate ($137 per metric ton) of the social cost of carbon. At larger scales, cost savings could hypothetically be significant. For example, adding just one species to the approximately 29.5 million acres of cultivated lands restored to grasslands by USDA's Conservation Reserve Program could save over $700 million. The biggest cost savings come from restoring the most degraded, species-poor lands.

These numbers underestimate the total value of increased biodiversity because biodiversity confers economic value in many ways beyond storing carbon. "Biodiversity means products like wood, food, and fuel, and services like recreation, water purification, and flood protection, all of which could be quantified using our approach," says Hungate. "Money is a language that speaks, and showing the economic value of biodiversity underscores the importance of conservation and the policies that support it."

Although the value of biodiversity is more complex than just one economic measure, this new research takes a bold step toward understanding the value of nature.

Author: Debra Levey Larson | Source: University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES) [April 06, 2017]

byUnknown

in Biodiversity, Ecosystems, Environment, Natural Heritage

April 06, 2017

Putting a price tag on biodiversity

Talk to just about any biologist long enough and the conversation will steer toward the benefits of biodiversity. Although the ecological be...

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First world survey finds 9,600 tree species risk extinction

The first ever global database of trees on Wednesday revealed that 9,600 tree species are threatened with extinction and identified a total of 60,065 in existence.

Brazil is the country with the most diverse tree population, with 8,715 species, according to the Botanic Gardens 
Conservation International (BGCI) group [Credit: AFP]

Brazil is the country with the most diverse tree population, with 8,715 species, according to the Botanic Gardens Conservation International (BGCI) group.

It also has the largest number of tree species—4,333—that only exist there.

In total 58 percent of trees are so-called single country endemics, with 2,991 species only found in Madagascar and 2,584 only found in Australia.

After Brazil, Colombia is the second most diverse country, with 5,776 different tree species, followed by Indonesia, with 5,142.

The London-based BGCI, which represents an estimated 2,500 botanic gardens around the world, used data from more than 500 published sources to create the list.

Of the 60,065 tree species, only around 20,000 have been assessed for their conservation status—of which 9,600 are threatened with extinction.

"BGCI's main reason for publishing the list is to provide a tool for people trying to conserve rare and threatened tree species," the organisation said in a statement.

"Currently, around 10,000 tree species are known to be threatened with extinction, largely by deforestation and over-exploitation.

"This number includes over 300 species that are critically endangered with fewer than 50 individuals remaining in the wild."

Aside from the Arctic and the Antarctic where there are no trees, the Nearctic region—comprising most of North America—has the lowest diversity, with less than 1,400 tree species.

The database will be continually updated, as around 2,000 new plants are discovered and described each year.

Source: AFP [April 05, 2017]

byUnknown

in Brazil, Ecosystems, Endangered Species, Environment, Natural Heritage, Rainforests

April 05, 2017

First world survey finds 9,600 tree species risk extinction

The first ever global database of trees on Wednesday revealed that 9,600 tree species are threatened with extinction and identified a total ...

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Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to the Earth's carbon cycle, a finding that has global implications as the bulk of Earth's glaciers shrink in response to a warming climate.

The Cotton Glacier stream in the McMurdo Dry Valleys region of Antarctica, where MSU researchers 
Heidi Smith and Christine Foreman sampled glacier runoff in 2012, in shown in this aerial photo 
[Credit: Christine Foreman]

Heidi Smith, a postdoctoral researcher, and Christine Foreman, associate professor of chemical and biological engineering, both of the Center for Biofilm Engineering in MSU's College of Engineering, were co-authors of a paper published in the prestigious journal Nature Geoscience.

Titled "Microbial formation of labile organic carbon in Antarctic glacial environments," the article was co-authored by researchers at the University of Colorado at Boulder, the U.S. Geological Survey, Stockholm University in Sweden and the Max Planck Institute for Marine Microbiology in Germany.

The paper challenges the prevailing theory that microorganisms found in glacial meltwater primarily consume ancient organic carbon that was once deposited on glacial surfaces and incorporated into ice as glaciers formed.

"We felt that there was another side to the story," said Smith, the paper's lead author. Smith earned a Ph.D. in ecology and environmental sciences in MSU's Department of Land Resources and Environmental Sciences in 2016, with Foreman as her adviser.

"What we showed for the first time is that a large proportion of the organic carbon is instead coming from photosynthetic bacteria" that are also found in the ice and that become active as the ice melts, Smith said. Like plants, those bacteria absorb carbon dioxide and in turn provide a source of organic matter.

The research team made the discovery after sampling meltwater from a large stream flowing over the surface of a glacier in the McMurdo Dry Valleys region of Antarctica in 2012.

Afterward, Smith spent two months at the Max Planck Institute for Marine Microbiology in Bremen, Germany, with support from the National Science Foundation's flagship interdisciplinary training program, the Integrative Graduate Education and Research Traineeship. There, she worked with colleagues to track how different carbon isotopes moved through the meltwater's ecosystem, allowing the team to determine the carbon's origin and activity.

The researchers ultimately found that the glacial microbes utilized the carbon produced by the photosynthetic bacteria at a greater rate than the older, more complex carbon molecules deposited in the ice, because the bacterial carbon is more "labile," or easily broken down. The labile carbon "is kind of like a Snickers bar," meaning that it's a quick, energizing food source that's most available to the microbes, Smith said.

Moreover, the researchers found that the photosynthetic bacteria produced roughly four times more carbon than was taken up by the microbes, resulting in an excess of organic carbon being flushed downstream. "The ecological impact of this biologically produced organic carbon on downstream ecosystems will be amplified due to its highly labile nature," Foreman said.

Although individual glacial streams export relatively small amounts of organic carbon, the large mass of glaciers, which cover more than 10 percent of the Earth's surface, means that total glacial runoff is an important source of the material. Marine organic carbon underpins wide-ranging ecological processes such as the production of phytoplankton, the foundation of the oceans' food web.

As glaciers increasingly melt and release the organically produced, labile carbon, "we think that marine microbial communities will be most impacted," Smith said. "We hope this generates more discussion."

In a "News and Views" commentary accompanying the article in Nature Geoscience, Elizabeth Kujawinski, a tenured scientist at Woods Hole Oceanographic Institution, called the team's work "an elegant combination" of research methods.

Taken together with another study published in the same issue of Nature Geoscience, about microbial carbon cycling in Greenland, Smith's paper "deflates the notion that glacier surfaces are poor hosts for microbial metabolism," according to Kujawinski. The two studies "have established that microbial carbon cycling on glacier surfaces cannot be ignored," she added.

Source: Montana State University [April 04, 2017]

byUnknown

in Antarctic, Biology, Climate Change, Ecosystems, Environment, Natural Heritage

April 04, 2017

Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to...

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New species evolve faster as mountains form

Mountains, like rainforests, are hotbeds of biodiversity. But scientists aren't sure why. For years, they've thought that it might be related to the new environments that arise when mountains form— as plants and animals adapt to the new micro-habitats and their populations become isolated by increasingly rugged terrain, they divide into new species at a faster rate than usual. However, there was little hard proof that this hypothesis was correct.

Plants in the Hengduan Mountains [Credit: Jian Huang]

In a new paper in the Proceedings of the National Academy of Sciences, a team has put forth compelling quantitative evidence in favor of the hypothesis, analyzing thousands of plant species from China's Hengduan Mountains and adjacent regions. They found that as the Hengduan Mountains were forming, the plants there evolved into new species at a faster rate than in the nearby Himalayas, which are older.

"Essentially, this paper is about why there are so many species in mountains and how they came to be there," says corresponding author Rick Ree, Associate Curator of Botany at Chicago's Field Museum. "There are two main ways species can get to a place—either they emigrated from another place, or they evolved from an earlier species that was already there. Our research provides the strongest evidence yet that when mountains form, new species evolve and diversify at an increased rate."

The mountain range that Ree and his co-author Yaowu Xing studied, the Hengduan Mountains region in western China, is directly to the east of the Himalayas. It formed recently (in Earth-time, at least), eight million years ago, the result of colliding tectonic plates. Among global biodiversity hotspots, it's unusual in not having a tropical or Mediterranean climate.

"The Hengduan Mountains are temperate, with cold winters and short wet summers. They have conifer forests, glaciers, alpine meadows—you could be tricked into thinking you were in the Rockies or the Alps, until you looked around and saw that there was ten times the biodiversity you see in those places," says Ree.

That incredible biodiversity, Ree and Xing suspected, was the result of uplift-driven diversification. According to this hypothesis, when mountains are formed by tectonic forces, the new distinct environments forming along the mountainsides allow the species already there to split and branch into new species that are specially adapted to those new environments. "As mountains form, you get different elevations, different substrates exposed, different soil chemistries, different climates. They create lots of little micro-habitats along which species can adapt to local conditions," explains Ree. "These changes mean more opportunities for species to diversity and fill new niches."

To test this hypothesis, the scientists examined the plants growing in the Hengduan Mountains, which are relatively young in geological time, and compared them to plants that live nearby on the Qinghai-Tibetan Plateau and Himalayas, which are much older. "We were able to use the differences in age as a natural experiment, with controlled comparisons of how species accumulated in the different regions, says Ree. "The fact that these mountains are next to each other but have different ages allows us to compare their histories in terms of how the species got there."

Ree and Xing performed phylogenetic analyses of thousands of plants, using DNA sequences to put together family trees showing how the species are related to one another. Then they used fossil plants to give their findings a time scale. "By looking at fossils, we were able to tell when different groups appeared and when ancestral species branched apart," says Ree. "The combination of modern plant DNA and ancient plant fossils gave us a historical framework that allowed us to reconstruct where and when species moved and diversified."

The team found that new species were formed at an increased rate within the Hengduan Mountains as they were forming, compared to species formation rates in the surrounding regions—evidence that species form faster as mountains are uplifted. But those revelations only became clear when Ree and Xing looked at the data set as a whole. "On their own, many of the plant groups don't show a strong pattern of increased diversity as the mountains uplifted, but when you look at them collectively, the pattern emerges quite clearly," says Ree.

This discovery is especially important in that it provides support for a hypothesis that largely lacked quantitative evidence until now. "The uplift-driven diversification hypothesis is popular, but this study provides the strongest empirical evidence so far," says Ree. "What sets this study apart is the way that we included lots of different plant groups, performed controlled natural comparions of these regions at different ages, and measured the rates of these processes over time. It's the first study that brings evidence from lots of different groups to bear on this question in a quantitative framework."

While Ree's main interest remains the Hengduan Mountains, he notes that the comparative approach employed in this study could be applied to other biodiversity hotspots and other organisms, including animals. "Ever since Darwin, we've wanted to know the what, where, and how of species' origins," says Ree. "How do species come to live where they do? Why are there more species here than there? Our study sheds a little light on those questions."

Source: Field Museum [April 03, 2017]

byUnknown

in Biodiversity, Biology, China, Ecosystems, Evolution

April 03, 2017

New species evolve faster as mountains form

Mountains, like rainforests, are hotbeds of biodiversity. But scientists aren't sure why. For years, they've thought that it might b...

Read More