Posts tagged CU
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 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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Dinwiddie, CU Men Rally To Defeat Beavers
Feb 11th
By B.G. Brooks, CUBuffs.com Contributing Editor
CORVALLIS, Ore. – Nothing came easy for the Colorado Buffaloes in Oregon, but they might like it that way – especially Spencer Dinwiddie.
On a night marked by his perfection, the Buffs rallied behind their stellar sophomore guard here Sunday to beat Oregon State 72-68 and sweep their two-game trip in the Northwest.
Dinwiddie’s long-range shooting and free throw accuracy brought CU back from a seven-point second-half deficit and kept the Buffs in prime position for a February ascent in the Pac-12 Conference.
Spencer Dinwiddie
The difference Sunday night in OSU’s antiquated Gill Coliseum, said CU coach Tad Boyle: “We had Spencer Dinwiddie and they didn’t.”
Dinwiddie scored 17 of his 24 points in the second half, helping CU to go above .500 (6-5, 16-7 overall) for the first time this season in Pac-12 play.
Dinwiddie turned in a night of perfect shooting. He hit four-of-four from beyond the three-point arc (six-of-six overall from the field) and eight-of-eight from the free throw line in the final 20 minutes, including six-of-six in the last 1:41.
“I can’t remember if I’ve ever shot like that before,” Dinwiddie said. “But every shot you take you think you’re going to make. It was one of those nights.”
CU also got double-figure scoring from freshman Josh Scott (17) and senior Sabatino Chen (10).
Oregon State (2-9, 12-12) was led by Roberto Nelson with 21 points. Teammate Ahmad Starks had 20, 17 of them in the first half before CU tightened its defense on him.
The Buffs return to the Coors Events Center this week. On Thursday they face No. 7 Arizona (8 p.m., Pac-12 Network), with Arizona State visiting on Saturday (7 p.m., ESPNU).
CU started with a feverish pace, hitting its first six shots before finally missing and going up by 13 points (19-6) on a pair of free throws by Askia Booker. But the Buffs hot hands didn’t remain that way.
A 13-4 run pulled the Beavers to within 27-25 and Starks took over from there, hitting consecutive treys to tie the score at 31-31 then adding a third to give Oregon its first lead, 34-33.
The half ended that way, and whatever early momentum the Buffs had was swept away.
Starks finished the half with 17 points, hitting five of his nine three-point attempts. And it wasn’t like the Buffs hadn’t been warned: Their scouting report on Starks said he was most dangerous going to his left off the dribble – and that’s what he did on four of his five first-half treys.
In the second half, said Boyle, CU wanted to deny him the ball – and Booker helped answer that challenge. Overall, Boyle said his team didn’t play its best game – just as it didn’t in a 48-47 win on Thursday night at Oregon.
“But you’re seeing this team grow up before your eyes,” he added. “When you don’t play your best in two road games and still win, it shows you something about your players.”
Added junior forward Andre Roberson, who finished with a career-best five steals to go with his 10 rebounds and seven points: “We’ve got heart. It showed in Oregon and it showed here tonight.”
Andre Roberson
CU didn’t have a player in double figures in the first 20 minutes and was outrebounded 21-17 – 39-30 for the game. The Buffs shot 41.4 percent from the field, the Beavers 45.6. But CU got 21 points off of that many OSU turnovers while committing only nine. The Buffs also had 13 second-chance points to the Beavers’ seven.
Nelson, tied for the conference scoring lead at 18.4 points a game, had only four first-half points. But he opened the second half with a long trey from the right wing, giving the Beavers a 37-33 advantage.
The Buffs caught and passed them with a 6-0 run, going ahead 39-37 on a pair of Dinwiddie free throws with 17:51 to play. From there, it was back and forth for the next 3 minutes, with neither team able to take more than three-point lead until Joe Burton converted a three-point play with 14:22 left to send the Beavers ahead 51-47 – their largest lead of the night.
And it got larger. When Starks drained another triple from just left of the top of the key, Oregon was up 56-49 – and with 12:50 remaining the Buffs were entering dangerous territory. No matter; they had been there before and survived.
CU crept to within two (56-54) on a three-pointer by Dinwiddie over Oregon’s 2-3 zone and a transition basket by Scott. Just under 3 minutes later, Dinwiddie got another triple and the Buffs suddenly were down just a point (58-57).
Then a short shootout began.
After Oregon freshman Olaf Schaftenaar answered with a trey, restoring the Beavers’ four-point lead, Dinwiddie struck again from beyond the arc and pulled the Buffs to within 63-62. Roberson made one of two free throws with 3:23 showing to tie the score at 63-63.
CU freshman Xavier Johnson’s tip-dunk at the 2:20 mark put CU ahead (65-63) for the first time in nearly 14 minutes, and the Buffs might have been flashing back to their final-minute win (48-47) in Eugene on Thursday night.
Dinwiddie made both ends of a one-and-one with 1:41 left, giving CU a 67-63 lead. But on the other end, he fouled Nelson beyond the arc, and Nelson’s three free throws cut the Buffs’ lead to 67-66.
At 1:10, Boyle called a timeout. With 3 seconds showing on the shot clock and 52.9 on the game clock, Dinwiddie was fouled and hit both ends of his one-and-one for a 69-66 lead.
Oregon missed, Roberson rebounded and Booker was fouled with 29.1 seconds to play. Making one of two foul shots, he put CU ahead 70-66, but Nelson scored in the lane to pull Oregon to within 70-68 with 16.7 seconds left.
Fouled by Nelson on the inbounds pass, Dinwiddie hit both free throws and the Buffs were up 72-68 with 14.2 seconds showing. Oregon’s Eric Moreland missed at point blank range, Roberson rebounded and was tied up.
The possession arrow favored the Buffs – and this one was done.
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