CU News
News from the University of Colorado in Boulder.
CU researchers find hyper evolution in walking stick insects
Oct 21st
Poorly camouflaged insects can kick
off a cascade of ecological impacts,
new CU-Boulder study finds
off a cascade of ecological impacts,
new CU-Boulder study finds
A California walking stick insect that has evolved to produce individuals with two distinct appearances—an all-green form that camouflages well with broader leaves and a form with a white stripe running down its back that blends better with needle-like leaves—can markedly affect its broader ecological community when the appearance of the bug is mismatched with the plant it’s living on.
The new findings, based on research carried out at the University of Colorado Boulder, illustrate the ability of rapid evolution to cause a cascade of ecological impacts.
Can you find the camouflaged insect?
The scientists found that a walking stick insect that is not well camouflaged is more likely to be eaten by birds, and in turn, those birds are then also more likely to feast on the spiders, caterpillars, plant hoppers, ants and other arthropods living on the same plant. The resulting overall reduction in bugs living on the plant also means that the plant itself was less likely to be attacked by sap-feeding insects.
“Our study shows that the evolution of poor camouflage in one species can affect all the other species living there and affect the plant as well,” said Tim Farkas, lead author of the study published in the journal Current Biology. “It’s intuitive, but also really surprising.”
Farkas led the study as an ecology and evolutionary biology doctoral student in Assistant Professor Patrik Nosil’s lab at CU-Boulder. Nosil and CU-Boulder doctoral student Aaron Comeault are also study co-authors. All three have since moved to the University of Sheffield in England.
Evolution is often thought of as a process that unfolds slowly over centuries if not millennia, as individuals with genetic advantages have a greater chance of surviving to pass down their genes to the next generation.
But scientists are increasingly identifying instances when evolution works on a much shorter time scale. An oft-cited example of rapid evolution is the peppered moth. The light-colored moths were historically able to camouflage themselves against lichen-covered tree bark in England. A darker variant of the moth existed but was more rare, since birds were able to easily spot the dark moth against the light trees. But during the industrial revolution, when soot blackened the trees, natural selection favored a darker variation of the moth, which began to flourish while the light-colored variant became less common.
Evolution on such a rapid scale opens up the possibility that the process could have ecological effects in the short term, impacting population sizes or changing the community makeup, for example.
Researchers have begun to compile examples of these “eco-evolutionary dynamics.” The new study offers some of the most comprehensive evidence yet that evolution can drive ecological change.
“We have combined both experimental and observational data with mathematical modeling to show that evolution causes ecological effects and that it does so under natural conditions,” Farkas said. “We also focused simultaneously on multiple evolutionary processes—including natural selection and gene flow—rather than just one, which affords us some unique insights.”
Farkas and his colleagues—including Ilkka Hanski and Tommi Mononen, both of the University of Helsinki in Finland—focused their attention on the walking stick Timema cristinae, which lives in Southern California. The flightless insect lives primarily on two shrubs: chamise, which has narrow, needle-like leaves; and greenbark ceanothus, which has broad, oval-shaped leaves. The variant of the walking sticks that have a white stripe down their backs are better camouflaged on the chamise, while the solid-green walking sticks are better camouflaged on the greenbark ceanothus.
The research team began by cataloguing the walking sticks living on the two types of shrubs in 186 research patches, and determined that the striped walking sticks were indeed more common on chamise and vice versa.
Maybe this one should be tagged a walking {twig).
In a second experiment, the researchers artificially stocked the needle-like chamise with the different variants of walking sticks. A month later, they sampled the shrubs and found that more striped walking sticks survived than un-striped walking sticks. They also found that chamise stocked with striped walking sticks were home to a greater number of arthropods as well as a greater variety of arthropods than shrubs stocked with un-striped walking sticks. Finally, there were more leaves damaged by hungry insects on chamise stocked with striped walking sticks.
The scientists surmised that the differences were caused by scrub jays and other birds that feed on walking sticks. A group of easy-to-spot walking sticks could attract birds, which might then feed on other arthropods as well. To test their idea, the researchers repeated the experiment, but in this case, they caged some of the shrubs to keep the birds from feeding. As they expected, the caged chamise stocked with un-striped walking sticks did not have the same drop in numbers as they did when the bushes were not caged.
“Studies of how rapid evolution can affect the ecology of populations, communities and ecosystems are difficult to accomplish and therefore rare,” Farkas said. “We’re hoping our research helps biologists to appreciate the extent of dynamic interplay between ecology and evolution, and that it can be used by applied scientists to combat emerging threats to biodiversity, ecosystem services, and food security.”
Funding for the study was provided by CU-Boulder, the European Research Council and the Academy of Finland.
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Boulder High, CU grad astronaut Scott Carpenter dies at 88
Oct 11th
Scott Carpenter, a University of Colorado Boulder alumnus and a famed NASA Mercury astronaut who became only the second American to orbit Earth, died Thursday.
Carpenter, a Boulder native, entered CU-Boulder’s astronautical engineering program in 1945, eventually earning a bachelor of science degree. He orbited Earth three times on May 24, 1962, in NASA’s Aurora 7 capsule before splashing down in the Atlantic Ocean.
Carpenter was the first of 18 CU-Boulder astronaut affiliates to have flown in space. As one of the first NASA astronauts, Carpenter and his colleagues were celebrated in the Tom Wolfe book, “The Right Stuff,” which told the story of early military test pilots and the original Mercury 7 astronauts.
Born in Boulder on May 1, 1925, Carpenter and graduated from Boulder High School in 1943. He then entered the Navy’s V12a flight training program at Colorado College in Colorado Springs. He spent the next year training in California and Iowa, returning to Boulder in 1945 to study at CU-Boulder.
“In his two-decades long career as a Naval aviator, astronaut and aquanaut, Scott Carpenter brought honor and distinction to CU-Boulder while embodying the adventurous spirit of our nation,” said CU-Boulder Chancellor Philip P. DiStefano. “Our space program, and all space and ocean researchers everywhere, owe him a debt of gratitude. He will be sorely missed.”
In 1965 Carpenter took a leave of absence from NASA to participate in the Navy’s Man-in-the Sea Project as an aquanaut in the SEALAB II project off the coast of La Jolla, Calif. where he spent 30 days living and working on the ocean floor at a depth of more than 200 feet. Because of his groundbreaking deep-sea diving experiences with the Navy, Carpenter is hailed by many to be the first person to conquer both outer and inner space.
“My colleagues and I are deeply saddened by the passing of Astronaut Scott Carpenter,” said CU-Boulder aerospace engineering sciences Chair Penina Axelrad. “He has long been a member of the CU family and a tremendous inspiration for our aerospace faculty and students.”
In a 2012 interview with CU’s alumni magazine, the Coloradan, Carpenter spoke about his historic space journey. “I still remember what a thrill it was being up there — I liked the feeling of weightlessness, and the view I had of Earth.”
Carpenter and the other Mercury 7 astronauts created the Astronaut Scholarship Foundation in 1984. The foundation now involves more than 80 astronauts, awards 28 $10,000 scholarships annually and has dispersed more than $3 million to promising students in science and engineering since 1986.
As one of the original Mercury 7 astronauts, Carpenter followed Alan Shepard, Gus Grissom and Glenn into space and was followed by Wally Schirra, Gordon Cooper and Deke Slayton.
Carpenter was commissioned in the U.S. Navy in 1949 and flew a variety of missions during the Korean War. He attended Navy Test Pilot School in Maryland in 1954 and was assigned as an Air Intelligence Officer on the USS Hornet aircraft carrier. In April of 1959 he was selected by NASA to be an astronaut.
Although he was one course requirement short of graduating with a bachelor’s degree in aeronautical engineering when he left CU in 1949, the university awarded him his degree in 1962 following the successful Aurora 7 flight. When presenting the degree to Carpenter, then-CU President Quigg Newton noted that “his subsequent training as an astronaut has more than made up for his deficiency in the subject of heat transfer.”
In 1967 he became the Navy’s director of aquanaut operations during the SEALAB III experiment. After retiring from the Navy in 1969, he founded and became CEO of Sea Sciences Inc., a venture capital corporation that developed programs aimed at enhanced use of ocean resources and improved health of the planet. He worked closely with noted diver and scientist Jacques Cousteau and members of his Calypso team, and subsequently dove in most of the world’s oceans, including under Arctic ice.
Carpenter later became a consultant to industry and the private sector and has lectured around the world, narrated TV documentaries and written several books, including the 2002 New York Times best-seller, “For Spacious Skies: The Uncommon Journey of a Mercury Astronaut” co-authored with his daughter, Kris Stoever.
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CU study: Spruce beetle infestation in N. Colo. tied to drought
Oct 10th
A new University of Colorado Boulder study indicates drought high in the northern Colorado mountains is the primary trigger of a massive spruce beetle outbreak that is tied to long-term changes in sea-surface temperatures from the Northern Atlantic Ocean, a trend that is expected to continue for decades.
The new study is important because it shows that drought is a better predictor of spruce beetle outbreaks in northern Colorado than temperature alone, said lead study author Sarah Hart, a CU-Boulder doctoral student in geography. Drought conditions appear to decrease host tree defenses against spruce beetles, which attack the inner layers of bark, feeding and breeding in the phloem, a soft inner bark tissue, which impedes tree growth and eventually kills vast swaths of forest.
This spruce forest hit with a double whammy– Spruce bark beetles killed the trees then a forest fire burned it.
Spruce beetles, like their close relatives, mountain pine beetles, are attacking large areas of coniferous forests across the West. While the mountain pine beetle outbreak in the Southern Rocky Mountains is the best known and appears to be the worst in the historical record, the lesser known spruce beetle infestation has the potential to be equally or even more devastating in Colorado, said Hart, lead author on the new study.
“It was interesting that drought was a better predictor for spruce beetle outbreaks than temperature,” said Hart of the geography department. “The study suggests that spruce beetle outbreaks occur when warm and dry conditions cause stress in the host trees.”
A paper on the subject was published online in the journal Ecology. Co-authors include CU-Boulder geography Professor Thomas Veblen; former CU-Boulder graduate student Karen Eisenhart, now at Edinboro University of Pennsylvania; and former CU-Boulder students Daniel Jarvis and Dominik Kulakowski, now at Clark University in Worcester, Mass. The National Science Foundation and the National Geographic Society funded the study.
The new study also puts to rest false claims that fire suppression in the West is the trigger for spruce beetle outbreaks, said Veblen.
Spruce beetles range from Alaska to Arizona and live in forests of Engelmann spruce and subalpine fir trees in Colorado. The CU-Boulder study area included sites in the White River, Routt, Arapaho, Roosevelt and Grand Mesa national forests as well as in Rocky Mountain National Park.
The CU-Boulder team assembled a long-term record of spruce beetle outbreaks from the northern Front Range to the Grand Mesa in western Colorado using a combination of historical documents and tree ring data from 1650 to 2011. Broad-scale outbreaks were charted by the team from 1843-1860, 1882-1889, 1931-1957 and 2004 to 2010.
The researchers used a variety of statistical methods to tease out causes for variations in the dataset at 18 sites in Colorado. “The extent to which we could distinguish between the warming signals and the drought signals was surprising,” said Veblen. “These are two things that easily can get mixed together in most tree ring analyses.”
European Spruce bark beetle
There are several lines of evidence that drought is the main driver of the spruce beetle outbreak. The new study showed when northwest Colorado was in a warm, wet climate period from 1976 to 1998, for example, both spruce beetle reproduction and tree defenses like “pitching” beetles out of tree interiors with resin were likely high. But during that period of warming, outbreak was minimal.
The strongest climate correlation to spruce beetle outbreaks was above average annual values for the Atlantic Multi-decadal Oscillation, or AMO, a long-term phenomenon that changes sea-surface temperatures in the North Atlantic. Believed to shift from cool to warm phases roughly every 60 years, positive AMO conditions are linked to warmer and drier conditions over much of North America, including the West.
Veblen said the AMO shifted from its cool to warm phase in the 1990s, meaning the climate phenomenon could be contributing to drought conditions in the West into the middle of this century. A 2006 tree-ring study involving Veblen, his former student, Thomas Kitzberger and researchers from several other institutions concluded that the warm phase of AMO also was correlated to increased wildfires in the West.
In addition to AMO, the researchers looked at two other ocean-atmosphere oscillations — the El Nino Southern Oscillation and the Pacific Decadal Oscillation — as well as past temperatures, precipitation and aridity to better understand the spruce beetle outbreaks. The team found that another effective predictor of drought conditions was summer “vapor pressure deficit,” a measurement of atmospheric dryness, said Veblen.
In the new study, the researchers were particularly interested in “radial growth” rates of tree rings from sub-canopy trees of various species in the study areas that thrived following outbreaks. One hallmark of spruce beetle outbreaks is that slow radial growth rates in such areas are followed by extremely rapid radial growth rates, an indication smaller trees flourish in the absence of the larger spruce trees because of decreased competition for water and increased opportunities for photosynthesis, said Hart.
The area of high-elevation forests affected by spruce beetles is growing in the West, Hart said. “In 2012, U.S. Forest Service surveys indicated that more area was under attack by spruce beetles than mountain pine beetles in the Southern Rocky Mountains, which includes southern Wyoming, Colorado and northern New Mexico,” she said. “The drought conditions that promote spruce beetle outbreak are expected to continue.”
Spruce beetles have even hit Alaska.
One big concern about spruce beetle outbreaks is their effects on headwater streams that are important for water resources, said Veblen. “In the short term, trees killed by spruce beetles will lead to less water use by trees and more water discharge into streams. But in the long term, the absence of the trees killed by beetles may lead to less persistence of snow and earlier runoff.”
Veblen said it might seem counterintuitive to some that spruce-fir subalpine forests in Colorado are larger by area than lodgepole/ponderosa pine forests. “It is probably because spruce and subalpine forests are found in more remote areas not as visible to most people,” he said. “But potentially, the current spruce beetle outbreak could affect a larger area than the mountain pine beetle outbreak.”
The study had its beginnings in 1986, when Veblen and his students began compiling spruce and subalpine fir tree rings from various study sites in the Colorado mountains. Tree rings from individual trees — which carry information about weather, climate and even events like volcanic eruptions — can be matched up and read with rings from other trees, much like the pages of a book, from year to year and even from season to season.
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