CU News
News from the University of Colorado in Boulder.
CU scientists seek solution to the mystery of ever-increasing frog deformities
Feb 14th
CU-Boulder amphibian study shows how
biodiversity can protect against disease
The richer the assortment of amphibian species living in a pond, the more protection that community of frogs, toads and salamanders has against a parasitic infection that can cause severe deformities, including the growth of extra legs, according to a new study by the University of Colorado Boulder.
The findings, published Feb. 14 in the journal Nature, support the idea that greater biodiversity in larger-scale ecosystems, such as forests or grasslands, may also provide greater protection against diseases, including those that attack humans. For example, a larger number of mammal species in an area may curb cases of Lyme disease, while a larger number of bird species may slow the spread of West Nile virus.
“How biodiversity affects the risk of infectious diseases, including those of humans and wildlife, has become an increasingly important question,” said Pieter Johnson, an assistant professor in the Department of Ecology and Evolutionary Biology and lead author of the study. “But as it turns out, solidly testing these linkages with realistic experiments has proven very challenging in most systems.”
Researchers have struggled to design comprehensive studies that could illuminate the possible connection between disease transmission and the number of species living in complex ecosystems. Part of the problem is simply the enormous number of organisms that may need to be sampled and the vast areas over which those organisms may roam.
The new CU-Boulder study overcomes that problem by studying smaller, easier-to-sample ecosystems. Johnson and his team visited hundreds of ponds in California, recording the types of amphibians living there as well as the number of snails infected by the pathogen Ribeiroia ondatrae. Snails are an intermediate host used by the parasite during part of its life cycle.
“One of the great challenges in studying the diversity-disease link has been collecting data from enough replicate systems to differentiate the influence of diversity from background ‘noise,’ ” Johnson said. “By collecting data from hundreds of ponds and thousands of amphibian hosts, our group was able to provide a rigorous test of this hypothesis, which has relevance to a wide range of disease systems.”
Johnson’s team buttressed its field observations both with laboratory tests designed to measure how prone to infection each amphibian species is and by creating pond replicas outside using large plastic tubs stocked with tadpoles that were exposed to a known number of parasites. All of the experiments told the same story, Johnson said. Greater biodiversity reduced the number of successful amphibian infections and the number of deformed frogs.
A normal and a deformed bullfrog
In all, the CU-Boulder researchers spent three years sampling 345 wetlands and recording malformations — which include missing, misshapen or extra sets of hind legs — caused by parasitic infections in 24,215 amphibians. They also cataloged 17,516 snails. The results showed that ponds with half a dozen amphibian species had a 78 percent reduction in parasite transmission compared to ponds with just one amphibian species. The research team also set up experiments in the lab and outdoors using 40 artificial ponds, each stocked with 60 amphibians and 5,000 parasites.
The reason for the decline in parasitic infections as biodiversity increases is likely related to the fact that ponds add amphibian species in a predictable pattern, with the first species to appear being the most prone to infection and the later species to appear being the least prone. For example, the research team found that in a pond with just one type of amphibian, that amphibian was almost always the Pacific chorus frog, a creature that is able to rapidly reproduce and quickly colonize wetland habitats, but which is also especially vulnerable to infection and parasite-induced deformities.
On the other hand, the California tiger salamander was typically one of the last species to be added to a pond community and also one of the most resistant to parasitic infection. Therefore, in a pond with greater biodiversity, parasites have a higher chance of encountering an amphibian that is resistant to infection, lowering the overall success rate of transmission between infected snails and amphibians.
This same pattern — of less diverse communities being made up of species that are more susceptible to disease infection — may well play out in more complex ecosystems as well, Johnson said. That’s because species that disperse quickly across ecosystems appear to trade off the ability to quickly reproduce with the ability to develop disease resistance.
“This research reaches the surprising conclusion that the entire set of species in a community affects the susceptibility to disease,” said Doug Levey, program director in the National Science Foundation’s Division of Environmental Biology, which helped fund the research. “Biodiversity matters.”
The sheer magnitude of the recent study also reinforces the connection between deformed frogs and parasitic infection, Johnson said. Beginning in the mid-1990s reports of frogs with extra, missing or misshapen legs skyrocketed, attracting widespread attention in the media and motivating scientists to try to figure out the cause. Johnson was among the researchers who found evidence of a link between infection with Ribeiroia and frog deformities, though the apparent rise in reports of deformations, and its underlying cause, remains controversial.
While the new study has implications beyond parasitic infections in amphibians, it does not mean that an increase in biodiversity always results in a decrease in disease, Johnson cautioned. Other factors also affect rates of disease transmission. For example, a large number of mosquitoes hatching in a particular year will increase the risk of contracting West Nile virus, even if there has been an increase in the biodiversity of the bird population. Birds act as “reservoir hosts” for West Nile virus, harboring the pathogen indefinitely with no ill effects and passing the pathogen onto mosquitoes.
“Our results indicate that higher diversity reduces the success of pathogens in moving between hosts,” Johnson said. “Nonetheless, if infection pressure is high, for instance in a year with high abundance of vectors, there will still be a significant risk of disease; biodiversity will simply function to dampen transmission success.”
CU-Boulder graduate students Dan Preston and Katie Richgels co-authored the study along with Jason Hoverman, a former postdoctoral researcher in Johnson’s lab who is now an assistant professor at Purdue. The research was funded by NSF, the National Geographic Society and the David and Lucile Packard Foundation.
To view photos and a video about the research, visit http://freshwatersillustrated.org/link/AmphibianDeformities.
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CU’s anti-violence production of ‘The Tempest’ to tour Colorado schools
Feb 12th
The Colorado Shakespeare Festival’s highly praised school anti-violence tour continues in spring 2013 with a new program based on “The Tempest” that focuses on themes of vengeance and forgiveness.
Created in conjunction with the Center for the Study and Prevention of Violence at the University of Colorado Boulder, CSF’s “Twelfth Night” anti-bullying tour has now been seen by more than 22,000 Colorado schoolchildren. That inaugural program examined the problem of bullying through the character Malvolio.
The new program explores the character of Prospero, who conjures a mighty tempest to shipwreck his enemies of old on his remote island domain. But even as he plots his revenge on those who wronged him years before, he ponders his actions and at the last moment turns to forgiveness instead.
“The rarer action is in virtue rather than vengeance,” Prospero says, renouncing all his schemes for payback.
“This is really about how to relate to other people and deal with conflict in your life. This performance and the workshops that follow focus on the importance of reconciliation and forgiveness as a tool for ending the cycle of violence,” says CSF Literary Manager Amanda Giguere, who co-created the program with Timothy Orr, interim producing artistic director.
During the program, four professional actors perform an abbreviated version of the play. The actors then lead the students in small-group exercises exploring alternatives to violence that are based on the latest research from CU-Boulder’s Center for the Study and Prevention of Violence.
The play emphasizes that there is always a choice between continuing the “cycles of revenge” and choosing not to retaliate, says Beverly Kingston, director of the center. She notes that 33 percent of American high school students had been in at least one physical fight in the preceding 12 months, according to the 2011 national youth risk behavior survey.
“You can see that in every one of those fights, someone had to make a decision to retaliate for some reason,” Kingston says. “Violence really begins with a decision and we all have a choice how we respond to difficult circumstances in our lives. That’s the message of this play.”
The new play makes use of Japanese bunraku-style puppets to represent some of the characters, including Prospero and his spirit servant Ariel.
In actor and stage manager Caroline Barry’s hands and animated by her voice, Ariel’s sea-blue face and colorful trailing veils seem almost to swim across the stage. With a few simple gestures — a thoughtful nod and touching foreheads with his spirit companion — the puppet Prospero becomes a fully-fledged character.
“We really want you to start imagining the actors’ expressions on the puppets,” says actor Crystal Eisele.
The new program debuts Feb. 12 at the Cole Arts and Sciences Academy in Denver. There are more than 40 schools on the spring schedule — and for the first time, a senior center — and Giguere expects to add more.
CSF’s innovative anti-violence school programs have received tens of thousands of dollars in grant funding and been featured prominently in print, online and television media across Colorado.
CSF’s anti-violence production of “The Tempest” is available for booking. For more information email csfedout@colorado.edu, call 303-492-1973 or visit .
CSF in the Schools: “The Tempest,” spring 2013 scheduled performances
February 12 (AM) Cole Arts & Sciences Academy – Denver
February 12 (PM) Denver Montclair International – Denver
February 13 (AM) Whittier Elementary School – Boulder
February 13 (PM) Angevine Middle School – Lafayette
February 14 (AM) Eagle Ridge Academy – Brighton
February 15 (PM) Flagstaff Charter School – Longmont
February 19 (AM) Westminster High School – Westminster
February 20 (AM) High Point Academy – Aurora
February 20 (PM) Clyde Miller P-8 – Aurora
February 21 (AM) Sunset Middle School – Longmont
February 22 (AM) Archuleta Elementary School – Denver
February 22 (PM) McGlone Elementary – Denver
February 26 (PM) Platte River Charter Academy – Highlands Ranch
February 27 (AM) The Academy of Charter Schools – Westminster
February 28 (AM) Douglass Elementary School – Boulder
February 28 (PM) Friends’ School – Boulder
March 1 (PM) Asbury Elementary School – Denver
March 5 (AM) Boulder Explore – Boulder
March 5 (PM) Gold Hill Elementary School – Gold Hill
March 6 (PM) Spangler Elementary – Longmont
March 8 (PM) Sacred Heart of Jesus – Boulder
March 13 (AM/PM) Timberview Middle School – Colorado Springs
March 15 (AM) Coal Ridge Middle School – Firestone
March 20 (AM) Thornton High School – Thornton
March 20 (PM) North High School – Denver
April 2 (AM) Escuela Tlatelolco Charter School – Denver
April 2 (PM) Force Elementary School – Denver
April 3 (AM) SOAR Green Valley Ranch – Denver
April 4 (AM) Woodlin School – Woodrow
April 4 (PM) Arickaree School – Anton
April 5 (AM) Dunstan Middle School – Lakewood
April 5 (PM) Bryant Webster Elementary – Denver
April 9 (AM) Northeast Elementary School – Parker
April 9 (PM) Henry World School – Denver
April 10 (AM) Lafayette Elementary School – Lafayette
April 10 (PM) Longmont Estates Elementary – Longmont
April 11 (AM) Niwot Elementary School – Niwot
April 11 (PM) Eagle Crest Elementary School – Longmont
April 12 (AM) OLLI West (Senior Center) – Denver
April 12 (PM) Horizon Community Middle – Aurora
CU study: Southwest regional warming likely cause of pinyon pine cone decline
Feb 12th
Creeping climate change in the Southwest appears to be having a negative effect on pinyon pine reproduction, a finding with implications for wildlife species sharing the same woodland ecosystems, says a University of Colorado Boulder-led study.
The new study showed that pinyon pine seed cone production declined by an average of about 40 percent at nine study sites in New Mexico and northwestern Oklahoma over the past four decades, said CU-Boulder doctoral student Miranda Redmond, who led the study. The biggest declines in pinyon pine seed cone reproduction were at the higher elevation research sites experiencing more dramatic warming relative to lower elevations, said Redmond of CU’s ecology and evolutionary biology department.
“We are finding significant declines in pinyon pine cone production at many of our study sites,” said Redmond. “The biggest declines in cone production we measured were in areas with greater increases in temperatures over the past several decades during the March to October growing season.”
The cones in which the pinyon seeds are produced are initiated two years prior to seed maturity, and research suggests the environmental stimulus for cone initiation is unseasonably low temperatures during the late summer, said Redmond. Between 1969 and 2009, unseasonably low temperatures in late summer decreased in the study areas, likely inhibiting cone initiation and development.
The study is one of the first to examine the impact of climate change on tree species like pinyon pines that, instead of reproducing annually, shed vast quantities of cones every few years during synchronous, episodic occurrences known as “masting” events. Redmond said such masting in the pinyon pine appears to occur every three to seven years, resulting in massive “bumper crops” of cones covering the ground.
In the new Ecosphere study, the researchers compared two 10-year sequences of time. In addition to showing that total pinyon pine cone production during the 2003-2012 decade had declined from the 1969-1978 decade in the study areas, the team found the production of cones during masting events also declined during that period.
Some scientists believe masting events evolved to produce a big surplus of nut-carrying cones — far too many for wildlife species to consume in a season — making it more likely the nuts eventually will sprout into pinyon pine seedlings, she said. Others have suggested masting events occur during favorable climate conditions and/or to increase pollination efficiency. “Right now we really don’t know what drives them,” Redmond said.
“Across a range of forested ecosystems we are observing widespread mortality events due to stressors such as changing climate, drought, insects and fire,” said CU’s Barger. “This study provides evidence that increasing air temperatures may be influencing the ability of a common and iconic western U.S. tree, pinyon pine, to reproduce. We would predict that declines in pinyon pine cone production may impact the long-term viability of these tree populations.”
Wildlife biologists say pinyon-juniper woodlands are popular with scores of bird and mammal species ranging from black-chinned hummingbirds to black bears. A 2007 study by researchers at the University of Northern Arizona estimated that 150 Clark’s Nutcrackers cached roughly 5 million pinyon pine nuts in a single season, benefiting not only the birds themselves but also the pines whose nuts were distributed more widely for possible germination.
For the new study, Redmond revisited nine pinyon pine study sites scattered throughout New Mexico and Oklahoma that had been studied previously in 1978 by Forcella. Both Forcella and Redmond were able to document pinyon pine masting years by counting small, concave blemishes known as “abscission scars” on individual tree branches that appeared after the cones have been dropped, she said.
Since each year in the life of a pinyon pine tree is marked by a “whorl” — a single circle of branches extending around a tree trunk — the researchers were able to bracket pinyon pine reproductive activity in the nine study areas for the 1969-1978 decade and 2003-2012 decade, which were then compared.
Pinyon pines take three growing seasons, or about 26 months, to produce mature cones from the time of cone initiation. Low elevation conifers including pinyon pines grow in water-limited environments and have been shown to have higher cone output during cool and/or wet summers, said Redmond. In addition to the climate-warming trend under way in the Southwest, the 2002-03 drought caused significant mortality in pinyon pine forests, Redmond said.
“Miranda’s ideas and accompanying results will be of value to ecologists and land managers in the deserts of the Southwest and beyond,” said Forcella, now a research agronomist in the USDA’s Agricultural Research Service. “The work is evidence that the University of Colorado continues to cultivate a cadre of high-caliber graduate students for which it rightfully can take tremendous pride.”
Pinyon nuts, the Southwest’s only commercial source of edible pine seeds today, were dietary staples of indigenous Americans going back millennia.
For more information on CU-Boulder’s ecology and evolutionary biology department visit http://ebio.colorado.edu.
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