Posts tagged Western Slope
CU: Rare western bumblebees netted on Colorado’s Front Range
Sep 3rd
A white-rumped bumblebee that has been in steep decline across its native range in the western United States and Canada appears to be making a comeback on the Colorado Front Range.
A survey of bumblebee populations carried out largely by University of Colorado Boulder undergraduates in undisturbed patches of prairieland and in mountain meadows above campus has turned up more than 20 rare western bumblebees, known scientifically as Bombus occidentalis.
This is the fourth summer of a planned five-year survey in Boulder County, led by biologists Carol Kearns and Diana Oliveras, both of whom teach in CU-Boulder’s Baker Residential Academic Program. The survey team, which this summer included five undergraduates along with Oliveras and Kearns, has been hunting bumblebees at nine different locations spanning low, middle and high elevations.
Volunteer Zoe Paggastis checks out a rare whire rump bumblebee found along the Front Range
The first western bumblebee was netted last year at one of the low-elevation plots, located at around 5,000 feet. The same plot also was visited frequently by Kearns and Oliveras during a more general survey of all pollinators between 2001 and 2005.
“For five years we sampled fairly intensely at this one site and never found anything,” Oliveras said. “Then all of a sudden, last year, we found several bees at that one site.”
The surveyors also found western bumblebees last year at a mid-elevation site of around 8,000 feet. In all, the team found nine western bumblebees in 2012: three queens and six workers.
Because insect populations are notoriously variable from year to year, Kearns and Oliveras wanted to find the bumblebees for a second year before announcing that the western bumblebee appeared to be returning to the Front Range. This year, the team has netted more than a dozen western bumblebees at four different locations, including the same low-elevation prairie plot and all three mid-elevation meadows. The distance between the sites means that the bumblebees are likely from separate colonies.
“These are sites that are fairly far away from each other, even as the crow flies,” Oliveras said. “Within a plot, if you’re going to be conservative, you can say that all the Bombus occidentalis arose from a single colony. But between plots, that’s quite a distance for them. They wouldn’t normally be traveling that far.”
The western bumblebee was once ubiquitous across the western portion of the United States and Canada, Oliveras and Kearns said. Its northern range encompassed all of Alaska, the Yukon Territory, British Columbia and western Alberta. Its southern boundaries extended as far south as Arizona and New Mexico. The bumblebee’s range also stretched from the Pacific Ocean eastward through North and South Dakota, Nebraska and Colorado. But beginning in the late 1990s, the western bumblebee became harder and harder to find.
“They have been disappearing rapidly across the West Coast, and there have been only occasional sightings in the Rocky Mountains,” Kearns said. “People have found a few bumblebees on the Western Slope of Colorado, but we were looking for them here and we weren’t finding any.”
Several factors have been implicated in the decline of the western bumblebee, according to Kearns and Oliveras. The biggest suspect is a non-native gut parasite that may have been transmitted from commercially raised bumblebee colonies. While parasites and other diseases can kill bees outright, anything that affects the bumblebees’ food supply or nesting sites also will affect their ability to survive. That means that habitat loss, pesticides, climate change and invasive plants and animals may be contributing to the losses in western bumblebee populations.
Earlier this summer, reports that the western bumblebee had been spotted in the Seattle area were confirmed by local biologists, indicating that the bumblebees could be making a broader comeback.
The wider goal of the ongoing bumblebee survey in Boulder County is to catalog all the types of bumblebees buzzing around the area and their population size. The team has catalogued a number of different species during the last four summers, including the mountain bumblebee, the Nevada bumblebee, the two-form bumblebee and the central bumblebee, among others.
“Our whole interest in bumblebees relates to the fact that pollinators are declining, but there is no abundance data for bumblebees in this area from the past,” Kearns said. “How do you tell if something is declining if there are no abundance data? So we decided we’d get out there and we’d find out what bumblebees are here and how many.”
Each year, Kearns and Oliveras have recruited undergraduate students to help them. This summer, the undergraduate researchers were Benjamin Bruffey, Sam Canter, Sarah Niemeyer, Zoe Praggastis and Cole Steinmetz.
To see a video about CU-Boulder’s bumblebee survey visit http://youtu.be/sKryBKX-nbU. For more information on the Baker Residential Academic Program visit http://bakerrap.colorado.edu/.
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2001-02 drought helped to shift Rocky Mountain pine beetle outbreak into epidemic
Nov 5th
A new University of Colorado Boulder study shows for the first time that episodes of reduced precipitation in the southern Rocky Mountains, especially during the 2001-02 drought, greatly accelerated development of the mountain pine beetle epidemic.
The study, the first ever to chart the evolution of the current pine beetle epidemic in the southern Rocky Mountains, compared patterns of beetle outbreak in the two primary host species, the ponderosa pine and lodgepole pine, said CU-Boulder doctoral student Teresa Chapman. The current mountain pine beetle outbreak in the southern Rockies — which range from southern Wyoming through Colorado and into northern New Mexico –is estimated to have impacted nearly 3,000 square miles of forests, said Chapman, lead study author.
While the 2001-02 drought in the West played a key role in pushing the pine beetle outbreak into a true regional epidemic, the outbreak continued to gain ground even after temperature and precipitation levels returned to levels nearer the long-term averages, said Chapman of CU-Boulder’s geography department. The beetles continued to decimate lodgepole pine forests by moving into wetter and higher elevations and into less susceptible tree stands — those with smaller diameter lodgepoles sharing space with other tree species.
“In recent years some researchers have thought the pine beetle outbreak in the southern Rocky Mountains might have started in one place and spread from there,” said Chapman. “What we found was that the mountain pine beetle outbreak originated in many locations. The idea that the outbreak spread from multiple places, then coalesced and continued spreading, really highlights the importance of the broad-scale drivers of the pine beetle epidemic like climate and drought.”
A paper on the subject was recently published in the journal Ecology. Co-authors on the study include CU-Boulder geography Professor Thomas Veblen and Tania Schoennagel, an adjunct faculty member in the geography department and a research scientist at CU-Boulder’s Institute of Arctic and Alpine Research. The National Science Foundation funded the study.
Mountain pine beetles are native insects that have shaped the forests of North America for thousands of years. They range from Canada to Mexico and are found at elevations from sea level to 11,000 feet. The effects of pine beetles are especially evident in recent years on Colorado’s Western Slope, including Rocky Mountain National Park, with a particularly severe epidemic occurring in Grand and Routt counties.
Chapman said the most recent mountain pine beetle outbreak began in the 1990s, primarily in scattered groups of lodgepole pine trees living at low elevations in areas of lower annual precipitation. Following the 2001-02 drought, the outbreak was “uncoupled” from the initial weather and landscape conditions, triggering a rise in beetle populations on the Western Slope and propelling the insects over the Continental Divide into the northern Front Range to infect ponderosa pine, Chapman said.
The current pine beetle epidemic in the southern Rocky Mountains was influenced in part by extensive forest fires that ravaged Colorado’s Western Slope from roughly 1850 to 1890, said Chapman. Lodgepole pine stands completely burned off by the fires were succeeded by huge swaths of seedling lodgepoles that eventually grew side by side into dense mature stands, making them easier targets for the pine beetles.
“The widespread burning associated with dry years in the 19th century set the stage for the current outbreak by creating vast areas of trees in the size classes most susceptible to beetle attack,” said Chapman.
Veblen said a 1980s outbreak of the pine beetle centered in Colorado’s Grand County ended when extremely low minimum temperatures were reached in the winters of 1983 and 1984, killing the beetle larvae. But during the current outbreak, minimum temperatures during all seasons have been persistently high since 1996, well above the levels of extreme cold shown to kill beetle larvae in laboratory experiments.
“This implies that under continued warming trends, future outbreaks will not be terminated until they exhaust their food supply — the pine tree hosts,” said Veblen.
Chapman said there has been a massive and unprecedented beetle epidemic in British Columbia, which also began in the early 1990s and has now has affected nearly 70,000 square miles. “It is hard to tell if this current beetle epidemic in the Southern Rockies is unprecedented,” she said. “While warm periods in the 16th century may have triggered a large beetle epidemic, any evidence would have been wiped out by the massive fires in the latter part of the 19th century.”
Veblen said while the rate of spread of the mountain pine beetle in lodgepole pine forests has declined in the southern Rocky Mountains during the past two years because of a depletion of host pine population, U.S. Forest Service surveys indicate the rate of beetle spread in ponderosa pine forests on the Front Range has increased sharply over the past three years. “The current study suggests that under the continued warmer climate, the spread of the beetle in ponderosa pines is likely to grow until that food source also is depleted,” Veblen said.
“Our results emphasize the importance of considering different patterns in the population dynamics of mountain pine beetles for different host species, even under similar regional-scale weather variations,” said Chapman. “Given the current outbreak of mountain pine beetles on the Front Range, their impact on ponderosa pines is certainly something that needs further study.”
A 2012 study by CU-Boulder Professor Jeffry Mitton and graduate student Scott Ferrenberg showed some Colorado pine beetles, which had been known to produce only one generation of tree-killing offspring annually, are producing two generations per year due to rising temperatures and a longer annual warm season. Because of the extra annual generation of beetles, there could be up to 60 times as many beetles attacking trees in any given year, according to the study.
In addition, a 2011 study led by CU-Boulder graduate student Evan Pugh indicated the infestation of trees by mountain pine beetles in the high country across the West could potentially trigger earlier snowmelt and increase water yields from snowpack that accumulates beneath affected trees.
New CU-Boulder study clarifies diversity, distribution of cutthroat trout in Colorado
Sep 24th
Will the real greenback cutthroat trout please stand up?
A novel genetic study led by the University of Colorado Boulder has helped to clarify the native diversity and distribution of cutthroat trout in Colorado, including the past and present haunts of the federally endangered greenback cutthroat trout.
The study, led by CU-Boulder postdoctoral researcher Jessica Metcalf, was based largely on DNA samples taken from cutthroat trout specimens preserved in ethanol in several U.S. museums around the country that were collected from around the state as far back as 150 years ago. The new study, in which Metcalf and her colleagues extracted mitochondrial DNA from fish to sequence genes of the individual specimens and compared them with modern-day cutthroat trout strains, produced some startling results.
The biggest surprise, said Metcalf, was that the cutthroat trout native to the South Platte River drainage appears to survive today only in a single population outside of its native range — in a small stream known as Bear Creek that actually is in the nearby Arkansas River drainage. The strain from Bear Creek is thought to have been collected from the South Platte River drainage in the 1880s by an early hotelier who stocked the fish in a pond at the Bear Creek headwaters to help promote an early tourist route up Pikes Peak.
“We thought one way to get to the question of which cutthroat trout strains are native to particular drainages was to go back to historical samples and use their DNA as a baseline of information,” said Metcalf of the chemistry and biochemistry department and a former postdoctoral researcher at the Australian Centre for Ancient DNA. “Our study indicates the descendants of the fish that were stocked into Bear Creek in the late 1800s are the last remaining representatives of the federally protected greenback cutthroat trout.”
A second, key set of data was all of the Colorado cutthroat trout stocking records over the past 150 years, a task spearheaded by study co-author and fish biologist Chris Kennedy of the U.S. Fish and Wildlife Service. Between 1889 and 1925, for example, the study showed that more than 50 million cutthroat trout from the Gunnison and Yampa river basins were stocked in tributaries of all major drainages in the state, jumbling the picture of native cutthroat strains in Colorado through time and space.
Originating from the Pacific Ocean, cutthroat trout are considered one of the most diverse fish species in North America and evolved into 14 recognized subspecies in western U.S. drainages over thousands of years. In Colorado, four lineages of cutthroats were previously identified: the greenback cutthroat, the Colorado River cutthroat, the Rio Grande cutthroat and the extinct yellowfin cutthroat.
The museum specimens used in the study came from the California Academy of Sciences, the Smithsonian Museum of Natural History in Washington, D.C., the Academy of Natural Sciences in Philadelphia and the Harvard University Museum of Comparative Zoology. Colorado cutthroat trout specimens were collected by a number of early naturalists, including Swiss scientist and former Harvard Professor Louis Agassiz and internationally known fish expert and founding Stanford University President David Starr Jordan.
The new study, published online today in Molecular Ecology, follows up on a 2007 study by Metcalf and her team that indicated there were several places on the Front Range where cutthroat populations thought to be greenbacks by fish biologists were actually a strain of cutthroats transplanted from Colorado’s Western Slope in the early 1900s.
CU graduate researcher, Sierra Stowell (pictured here as a teenager) was a co-author of the study. She spends a lot of time in or near the water where cutthroat trout live.
Other co-authors on the new study included CU-Boulder Professor Andrew Martin and CU-Boulder graduate students Sierra Stowell, Daniel McDonald and Kyle Keepers; Colorado Parks and Wildlife biologist Kevin Rogers; University of Adelaide scientists Alan Cooper and Jeremy Austin; and Janet Epp of Pisces Molecular LLC of Boulder.
“With the insight afforded by the historical data, we now know with a great deal of certainty what cutthroat trout strains were here in Colorado before greenbacks declined in the early 20th century,” said Martin of CU’s ecology and evolutionary biology department. “And we finally know what a greenback cutthroat trout really is.”
Metcalf and her colleagues first collected multiple samples of tissue and bone from each of the ethanol-pickled trout specimens, obtaining fragments of DNA that were amplified and then pieced together like a high-tech jigsaw puzzle to reveal two genes of the individual specimens. The tests were conducted on two different continents under highly sterile conditions and each DNA sequencing effort was repeated several times for many specimens to ensure accuracy in the study, Metcalf said.
Roughly half of the study was conducted at CU-Boulder and half at the Australian Center for Ancient DNA at the University of Adelaide, where Metcalf had worked for two years. “By conducting repeatable research at two very different, state-of-the-art laboratories, we were able to show the Bear Creek trout was the same strain as the cutthroats originally occupying the South Platte River drainage.”
The Bear Creek trout strain is now being propagated in the Colorado Parks and Wildlife hatchery system and at the USFWS Leadville National Fish Hatchery.
In addition to identifying the Bear Creek cutthroat trout, Metcalf and her colleagues discovered a previously unknown cutthroat strain native to the San Juan Basin in southwestern Colorado that has since gone extinct. The study also confirmed that the yellowfin cutthroat, a subspecies from the Arkansas River headwaters that grew to prodigious size in Twin Lakes near Leadville, also had gone extinct.
Fortunately, most fish preserved by naturalists before 1900 were “fixed” in ethanol, which makes it easier for researchers to obtain reliable DNA than from fish preserved in a formaldehyde solution, a practice that later became popular. Prior to the new study — which included DNA from specimens up to about 150 years old — scientists working in ancient DNA labs had only performed similar research on ethanol-preserved museum vertebrate specimens less than 100 years old.
“One of the exciting things to come from this research project is that it opens up the potential for scientists to sequence the genes of other fish, reptiles and amphibian specimens preserved in ethanol further back in time than ever before to answer ecological questions about past diversity and distribution,” said Metcalf, who conducts her research at CU’s BioFrontiers Institute.
Funding for the study was provided by agencies of the Greenback Cutthroat Trout Recovery Team, including the USFWS, the U.S. Forest Service, the Bureau of Land Management, the National Park Service and Trout Unlimited.
“I think in many cases success depends less on the application of a new technology and more on the convergence of people with shared interest and complementary skills necessary for solving difficult problems,” said Martin. “Our greenback story is really one about what can be discovered when dedicated and talented people collaborate with a shared purpose.”
“We’ve known for some time that the trout in Bear Creek were unique,” said Doug Krieger, senior aquatic biologist for Colorado Parks and Wildlife and the Greenback Cutthroat Trout Recovery Team leader. “But we didn’t realize they were the only surviving greenback population.”
The decline of native cutthroats in Colorado occurred because of a combination of pollution, overfishing and stocking of native and non-native species of trout, said Metcalf. “It’s ironic that stocking nearly drove the greenback cutthroat trout to extinction, and a particularly early stocking event actually saved it from extinction,” she said.
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