These selections represent just a few of the thousands of studies conducted by park personnel and outside researchers each year within the national park system.
The species is often thought of as the fundamental component of biodiversity, yet according to botanist and evolutionary biologist David Tank of the University of Idaho, species is a “fuzzy” word. To clarify how organisms from the same ancestry acquire new characteristics over time, and in turn how these characteristics should be used to define a species, Tank and his lab members, including post-doctoral associate Maribeth Latvis and graduate student Sarah Jacobs, are examining the flowering plant genus Castilleja. Over the past fifteen million years, this genus—many of whose members go by the common name “Indian paintbrush”—has radiated into roughly 200 different species.
Tank’s team collected plant specimens from a number of locations, including Canyonlands, Arches, Capitol Reef, Bryce Canyon, Zion, Glacier, Kenai Fjords, Wrangell–St. Elias, Mount Rainier, Olympic, Lassen Volcanic, and Great Basin National Parks. They then embarked on a multi-pronged investigation to crack the complicated Castilleja code, using DNA sequencing to uncover genetic relationships, locations to identify ecological niches, and detailed analyses of morphology.
While the full phylogeny of Castilleja is still a work in progress, Tank’s team has already produced some consequential results. For example, Castilleja meadii had been considered a subspecies or variety of the species C. ambigua, based on their similar appearance. However, genetic analyses have revealed that C. meadii is in fact its own species. It occurs only within a limited range in Napa County, California, and its designation as a unique species will likely change the way it is managed. (NPS Investigator Annual Report)
Although humans penetrated the North American Arctic as early as 6,000 years ago, archaeological findings suggest that the ancestors of today’s indigenous inhabitants arrived later in a second wave of migration. These were the Neo-Eskimo Thule, who had spread across the North American Arctic from Alaska to Greenland by about 800 years ago and ultimately developed into the modern Iñupiat and Inuit of the Arctic. To supplement the archaeological evidence, two experts in ancient DNA analysis, biological anthropologists Dennis O’Rourke and Justin Tackney, formerly of the University of Utah and now at the University of Kansas, became involved with excavations at two prehistoric sites.
Nuvuk, at Point Barrow on the northern coast of Alaska, dates from well before European contact. A Thule cemetery there had been rapidly eroding, and several years ago the local population of Barrow enlisted help from archaeologist Anne Jensen to reinter the ancient burials farther inland. Curious about their past, the inhabitants agreed that small pieces of bone could be sampled from some of the remains for genetic analysis.
Farther south in Alaska, in Kobuk Valley National Park, the site of Igliqtiqsiugvigruaq represents a much later occupation, right around the time of European contact in the early 1800s. Hoping to learn about Iñupiat culture at that point in history, including the impact of European contact, anthropologist Douglas Anderson from Brown University began excavating the site in 2009. Unexpectedly, Anderson’s team encountered human remains—a finding that, according to National Park Service (NPS) rules, should have halted any digging. However, the local tribal council, eager to know more about their history, convinced the NPS to allow research to continue, again providing an opportunity for the DNA specialists to join the investigation.
So far, O’Rourke and Tackney’s analyses at both sites have focused on mitochondrial DNA, which reveals maternal ancestry. The findings support the archaeological interpretation that the Iñupiat and Inuit peoples descend exclusively from Neo-Eskimos. The nuclear DNA, which the researchers are hoping to explore next, may provide information about potential genetic contributions from later Europeans and other earlier North American and Siberian groups. (85th Annual Meeting of the American Association of Physical Anthropologists)
Water Traffic Control
Known today as a quiet, undeveloped area, the Saint Croix National Scenic Riverway in eastern Minnesota and northwestern Wisconsin was once a major commercial waterway. That past recently resurfaced when a park ranger was paddling along the river during a time of unusually low water level and noticed a line of rocks and logs. This formation was later determined to be the remnants of a wing dam, a barrier that extends partway into a river to increase water flow in a central channel and thus reduce the accumulation of sediment there. It was one of many water-control structures built in the late 1800s by the United States Army Corps of Engineers.
The park management’s curiosity was piqued, and together with the National Park Service’s Submerged Resources Center (SRC) and the Midwest Archeological Center, they set out to document other forgotten features. The researchers pored over archival materials to gauge the locations of dams, jetties, and other constructions, and then employed sonar, surface, and underwater search methods to uncover their traces.
The team found evidence of forty-nine different structures— more than twice the number they expected. Many were still in good condition, even a dam made of brush. SRC archaeologist Jessica Keller observed that the structures intended to aid river traffic at any particular location had broader ramifications, such as affecting the erosion or build-up of sediment downstream and likely altering the habitat for fish and waterfowl. (Submerged Resources Center Technical Report No. 36)
Following catastrophic wildfires in the early 1900s, a national effort to suppress forest fires began. A lesson learned, however, is that burning—which occurs naturally in many landscapes—can clear understory vegetation, reducing the severity of future wildfires. For that reason, controlled burning has become an increasingly popular management tool to safeguard human property and resources. Less obvious is how fires may affect animals relying on specific forest environments that may be maintained by occasional burns.
Historic accounts indicate that in the xeric, or dry, pine-oak forests of Great Smoky Mountains National Park, certain bird species declined during active fire suppression in the twentieth century. Ecologists Eli Rose and Theodore Simons of North Carolina State University wondered how different bird species were affected by fire frequency and severity. Over the course of three breeding seasons, they identified and counted birds living around more than 300 points, with and without a record of fire, in the park’s forests.
Of the twenty-four bird species they tabulated, the researchers found that thirteen lived more frequently in burned areas, while only two tended to shun such areas. Within the burned areas, both the fire’s severity and the amount of time elapsed since it occurred affected the numbers of all species studied. But the patterns were not uniform. For example, the blue-gray gnatcatcher (Polioptila caerulea), associated with forest openings, seemed to do best when large forest patches experienced infrequent high-severity fires, whereas the red-cockaded woodpecker (Leuconotopicus borealis), which relies on shortleaf-pinedominated habitats, may thrive with frequent, low-severity fires.
Rose and Simons recommend that, rather than suppressing fires, management efforts in Great Smoky Mountains incorporate at least three different fire regimes: frequent, low-severity fire; infrequent, low-severity fire; and infrequent, high-severity fire. (The Condor: Ornithological Applications)
Understanding the geological processes that created the North American continent and continue to change its structure is the ambition of EarthScope, begun in 2003. This massive project includes the Plate Boundary Observatory, a network of more than 1,100 Global Positioning System (GPS) sites and other measurement devices. It is operated by the University Navigation and Satellite Timing and Ranging Consortium, better known as UNAVCO.
Several of the GPS sites lie within Joshua Tree National Park in southern California, near the San Andreas Fault. These sites allow researchers to monitor how the Earth’s crust deforms in the vicinity of that famously dangerous rift. The Pinto Mountain Fault, which runs along the northern boundary of the park, also produced four or five large earthquakes in the past 10,000 years. According to Chris Walls, the southwest region manager for the Plate Boundary Observatory, “The GPS stations in Joshua Tree were used to help define the location of faults and the probability of them producing an earthquake in the future.”
One benefit of the GPS sites is that they provide data continuously, at a rate of one reading per second. An earthquake earlywarning system known as ShakeAlert, which relies on these data streams, is currently being developed by the United States Geological Survey. Additionally, by comparing the delay between different GPS signals, such groups as the National Weather Service can calculate atmospheric water vapor and integrate that information into early warnings of floods. Surveyors can also use the GPS data to refine their maps. (NPS Investigator Annual Report)
Trail Ridge Road, the highest continuous paved road in the United States, is a popular destination for visitors to Rocky Mountain National Park, providing them with breathtaking vistas above the tree line. Roughly six miles of the road are underlain by permafrost, however, and climate warming could weaken some of this foundation. To determine whether and how temperatures are changing around the road, in 2008 geomorphologist Jason Janke of the Metropolitan State University of Denver and colleagues installed thirty temperature recorders in the nearby alpine tundra. Since then, they have been continuously logging the temperature at the soil surface and at depths of up to about twenty inches.
The investigators have found that areas of coarse rock tend to have the coldest recorded temperatures along Trail Ridge Road, most likely because cold air settles in the open spaces between the rocks. Thick snow cover, on the other hand, acts as an insulator, and the soil underneath does not get cold enough for permafrost to form.
Janke and his team have also detected temperature trends in Rocky Mountain National Park: winters are getting colder, while summers are getting hotter. For example, from 2009 to 2014, surface soil temperatures during the winter months of November through January cooled by an average of 1.0° Celsius. Of greater concern, however, were the changes during the summer months. In June, soil temperatures increased by about 3.5° C, and in July and August by 2.0–2.5° C. Such trends could lead to melting of permafrost and cause subtle shifts in the ground beneath Trail Ridge Road. (NPS Investigator Annual Report)
The Mesozoic Era, which spans from about 251 million to 65 million years ago, encompasses the Triassic, Jurassic, and Cretaceous Periods, all associated with the so-called Age of Dinosaurs. In the early stages of the Triassic, however, dinosaurs did not yet dominate the Earth. Although some dinosaurs started to appear by 220 million years ago, in the Upper Triassic Epoch, they were rare and small. What animals filled the ecological niches later taken over by dinosaurs?
While remnants of the Lower and Middle Triassic strata have been uncovered in Antarctica and Africa, one of the next places to pick up the fossil record is in the United States. Paleontologist Christian Sidor and his team from the University of Washington’s Burke Museum have been excavating at Petrified Forest National Park, Arizona—home to an exemplary sequence of Triassic rocks and fossils. There they have found bones of several different ancestral vertebrates including a number of archosaurs (a group of reptiles) as well as metoposaurs, which Sidor describes as “giant salamander-like creatures.”
Their most exciting discovery so far has been a quarry that includes parts of at least twenty individual shuvosaurids. These were small, toothless, herbivorous, bipedal relatives of the crocodile. Unusual under any circumstances, the shuvosaurid fossils found at Petrified Forest likely represent a previously unknown species. According to Sidor, “Even though the park’s been around for over a hundred years, it’s producing more and more fossils in the last decade or so than ever before.” (NPS Investigator Annual Report)
Large herds of caribou (Rangifer tarandus) travel between northern and southern areas in Alaska and Canada seeking more comfortable temperatures, more abundant food, and respite from predators and parasites during different times of year. However, human development of the land seems to be altering the animals’ habitat and movements, which could have broad effects on their populations. Wildlife researcher Ryan Wilson of The Wilderness Society (now with the U.S. Fish and Wildlife Service), along with colleagues from the Alaska Department of Fish and Game and the National Park Service, set out to learn how an industrial road cutting east-west across northwest Alaska, near Cape Krusenstern National Monument, affects caribou’s autumn migration southward.
Over several years, the team fitted more than 200 female caribou with Global Positioning System collars to track their routes from August until December. Many of the collared animals stayed north or east of the road’s extent, but twenty-eight came within fifteen kilometers of the road and eventually crossed it. Based on these animals’ movements before they approached the road, Wilson and colleagues created an estimate for how long it should have taken each individual to cross the road and continue south.
Twenty of the twenty-eight caribou crossed in the expected amount of time—about a day—as if the road were no obstacle. The other eight were “slow crossers,” taking thirty-three days, on average, to make it past what was a low-traffic, two-lane road. Such a delay could affect an animal’s fitness by postponing its access to preferred foraging areas during the wintertime. The slow crossers also walked much longer distances overall during their migration, which could drain their energy. As plans are discussed to build longer roads across Alaska, Wilson says his team’s findings “add another question that should be asked before development proceeds.” (Biological Conservation)
Sylvatic plague, a wildlife disease caused by the bacterium Yersinia pestis, likely entered North America through San Francisco around 1900. Usually fatal in prairie dogs, the disease was long thought to be restricted to the western part of the United States, but recently cases of plague have been documented in prairie dog colonies east of that “naturalized plague zone.”
To measure the extent to which the disease-causing bacterium may have spread, biologists Erica Mize (now with the U.S. Fish and Wildlife Service) and Hugh Britten of the University of South Dakota focused on Y. pestis’s most common transmission vector: fleas. Over three years, they swabbed the burrows of black-tailed prairie dogs (Cynomys ludovicianus) to collect more than 3,000 fleas from Badlands, Theodore Roosevelt, and Wind Cave National Parks, as well as Scotts Bluff and Devils Tower National Monuments.
Two hundred of the collected fleas (Oropsylla hirsuta and O. tuberculata) carried Y. pestis, with infected fleas coming from roughly fourteen percent of the prairie dog burrows. Plague was present at all of the national park units studied except for Devils Tower National Monument, which has just one fairly isolated prairie dog colony. These results indicate that Y. pestis is now endemic throughout the black-tailed prairie dog’s range, including areas of North Dakota, South Dakota, and Nebraska east of the naturalized plague zone.
The insecticide deltamethrin can be used to control these fleas, and therefore Y. pestis; studies into its optimal application are ongoing. Mize also notes that as long as people are careful when interacting with nature—wearing closed-toe shoes, applying insect repellant, and not touching wildlife—our national parks are safe to enjoy. (Vector-Borne and Zoonotic Diseases)