Recent Submissions

  • Resource limitation of autotrophs and heterotrophs in boreal forest headwater streams

    Weaver, Sophie Alden; Jones, Jeremy B.; Leigh, Mary Beth; Ruess, Roger W. (2019-12)
    In stream biofilms, autotrophs and heterotrophs are responsible for the majority of in stream nutrient transformations. In boreal forest catchments, discontinuous permafrost can lead to variation in nutrient and energy resources, which can control competition for nutrients between autotrophs and heterotrophs within these biofilms. I was interested in determining what resources control nutrient utilization by autotrophs and heterotrophs in headwater streams in the boreal forest of interior Alaska. I hypothesized that the outcome of competition between autotrophs and heterotrophs for inorganic nutrients would be dependent on the availability of (i) organic carbon, (ii) light, or (iii) inorganic nutrients. To measure resource limitation and competition at both patch and reach scales, I deployed nutrient diffusing substrata and conducted nutrient uptake experiments in streams along a permafrost gradient at the Caribou-Poker Creeks Research Watershed in interior Alaska. At the patch scale, autotrophs were light and nutrient limited, whereas heterotrophs were carbon and nutrient limited, and at the reach scale, light had the largest influence on nutrient uptake. Heterotrophs exhibited a larger response to nutrient enrichment when stream ambient carbon stocks were more bioavailable. Autotrophic biomass and productivity was suppressed when labile carbon was available to heterotrophs, suggesting that heterotrophs outcompete autotrophs for nutrients when a labile carbon source is introduced. The positive responses to nutrient and carbon additions suggest that the hypothesized increased nutrient and carbon exports into fluvial networks with permafrost degradation will impact biofilm structure and function, with the potential to influence nutrient export and stream ecosystem function downstream.
  • Host-parasite ecophysiology of overwintering

    Larson, Don J.; Barnes, Brian; O'Hara, Todd; Sikes, Derek; Wipfli, Mark (2019-12)
    To survive extreme winters, parasites must overwinter either in a host, as free-living larvae, or be reintroduced yearly through migratory hosts. This thesis examines interrelations between host parasite overwintering physiology and behavior in Alaska between the trematode Ribeiroia ondatrae and their host, wood frogs (Lithobates sylvaticus). The first chapter examines overwintering physiology and behavior of wood frogs in the field. The second chapter creates a laboratory method for determining physiological responses of wood frogs to environmental transitions from summer to fall. The third chapter examines if and how R. ondatrae survive within a frozen wood frog. Free-living wood frogs investigated over two winters in Fairbanks, AK remained frozen for up to 7 months and survived temperatures as low as -18°C, values much more extreme than those previously reported (Chapter 1). Alaskan wood frogs also synthesized and released approximately one order of magnitude greater concentrations of cryoprotectant (glucose) in multiple tissues than levels previously reported. Wood frogs in the field did not experience the same slow and continuous cooling that researchers routinely subject frogs to under experimental conditions. Instead they cooled at rates of up to -1.5°C h⁻¹ for short periods in a diurnal freeze-thaw pattern repeated over one to three weeks until remaining frozen for the rest of winter. Since wood frogs only produce glucose at the initiation of freezing, I hypothesized that freeze-thaw cycling within hibernacula allowed for incremental increases of glucose resulting in higher concentrations in field wood frogs than found in laboratory frozen wood frogs. I compared patterns of diurnal freeze-thaw cycling with the standard laboratory freezing protocols for wood frogs. Wood frogs that experienced multiple freeze-thaw events responded with significant increases in glucose concentration in liver, leg, and heart tissues at each freezing with no significant losses in glucose with each following thaw period (Chapter 2). This incremental increase in glucose within wood frogs may also assist in parasite survival. Trematode metacercariae may be absorbing host glucose and using this cryoprotectant to enhance their survival (Chapter 3). This result provides evidence that host physiology in winter may both hinder (through freezing) and facilitate (through cryoprotectant production) parasite survival.
  • Validating a GPS collar-based method to estimate parturition events and calving locations for two barren-ground caribou herds

    Hepler, Joelle D.; Griffith, Brad; Falke, Jeff; Roach, Jen (2019-12)
    In remote landscapes, it is difficult and expensive to document animal behaviors such as location and timing of parturition. When aerial surveys cannot be conducted as a result of weather, personnel or fiscal constraints, analyses of GPS collar movement data may provide an alternate way to estimate parturition rates and calving ground locations. I validated two methods (population-based method and individual-based method), developed to detect calving events of sedentary woodland caribou, on multiple years of data for two different migratory barren-ground caribou herds in Alaska, the Porcupine and Fortymile herds. I compared model estimates of population parturition rates, individual calving events, calving locations and calving dates to estimates from aerial survey data for both herds. For the Porcupine herd we also compared model estimates of annual calving ground sizes and locations of concentrated calving area centroids to those found with aerial survey. More years of data would be required for additional statistical power but for both the Porcupine and Fortymile herds, we found no significant difference between the population-based and individual-based method in: 1) individual classification rate accuracy (0.85 vs. 0.88, respectively; t = -7, P = 0.09, df = 1 and 0.85 vs. 0.83, respectively; t = 0.46, P = 0.69, df = 2) or 2) annual average distance from aerial survey calving locations (8.9 vs. 7.8 km, respectively; t = 0.16, P = 0.90, and 5.2 vs. 3.7 km, respectively; t = 1.03, P = 0.20). Median date of calving was estimated within 0-3 days of that estimated by aerial survey for both methods. Population parturition rate estimates from aerial survey, the population-based and individual-based methods were not significantly different for the PCH or FCH (0.91, 0.88 and 0.95, respectively; F = 0.67, P = 0.60, df = 2, and 0.83, 0.83 and 0.96, respectively; F = 3.85, P = 0.12, df = 2). Ultimately, more years of data would be required to support or reject the lack of significant differences between methods that we observed.
  • Foliage and winter woody browse quality of an important Salix browse species: effects of presence of alder-derived nitrogen and winter browsing by Alaskan moose (Alces alces gigas)

    Burrows, Justin; Kielland, Knut; Wagner, Diane; Ruess, Roger (2019-12)
    In this study, I examined the relationship between soil nitrogen and winter browsing by moose on the physical and chemical characteristics of Salix alaxensis; specifically stem production, leaf nutritional quality, and stem nutritional quality of tissues produced the following growing season. I measured stem biomass production the 2013 growing season and offtake during the 2013-2014 winter browsing season at 16 sites on the Tanana River floodplain near Fairbanks, Alaska. I revisited the sites the following summer and autumn to assess regrowth and to collect soil, foliage, and stem samples. Browsing intensity and total soil nitrogen were similar in sites with and without alder, a nitrogen-fixing shrub. Soil nitrogen and browsing intensity were not consistently related to changes in stem or leaf quality, although there were significant relationships in some subsets. Soil nitrogen and browsing intensity also did not have consistent relationships with stem regrowth the following growing season. These results indicate that S. alaxensis growing in this system are able to recover from a naturally broad range of browsing utilization, including very high levels of offtake, and continue to produce nutritious leaves and stems.
  • Plant succession in the Arctic Brooks Range: floristic patterns from alpine to foothills, along a glacial chronosequence and elevation gradient

    Kasanke, Shawnee A.; Walker, Donald A.; Chapin, F. Stuart III; Mann, Daniel H. (2019-08)
    In the wake of rapid glacial retreat, alpine habitats in the Arctic are expanding as freshly exposed surfaces become vegetated. Many glaciers in alpine cirques have nearly disappeared, and little is known about the rate of colonization or pioneer communities that develop following deglaciation. Newly developed habitats may provide refugia for sensitive Arctic flora and fauna, especially in light of polar warming. To assess this process, vegetation communities developing on two recently deglaciated moraines in the Central Brooks Range were surveyed and compared with communities along a transect spanning both a glacial chronosequence (40-125,000 years since deglaciation) and an elevation gradient (1700-500 m) into the Arctic foothills. Results show that primary succession begins almost immediately following deglaciation. Within forty years fine-grained and rock substrates hosted small communities of 8-13 vascular and nonvascular plant species. Many pioneer taxa, especially lichens, persist into later stages of succession. Overall succession is directional and slow, increasing in species richness for about 10,000 years, after which richness decreases and communities stabilize. This is the first vegetation study on primary succession in the high Central Brooks Range, providing a missing link to a vegetation transect along the Arctic Bioclimatic gradient.
  • Feeding ecology of scaup ducklings across a heterogeneous boreal wetland landscape

    DuBour, Adam J.; Lindberg, Mark; Gurney, Kirsty; Hundertmark, Kris (2019-08)
    Understanding how patterns of food resources influence the behavior and fitness of free-living animals is critical in predicting how changes to such resources might influence populations. The boreal region of North America is relatively undeveloped and contains abundant freshwater lakes and wetlands. These largely pristine and stable habitats harbor high densities of aquatic invertebrates, which are a critical food source for the numerous waterbird species that breed in the boreal. Invertebrates are of particular importance for the optimal growth and survival of waterbird chicks. However, observations of long-term change to boreal aquatic habitats and their invertebrate populations associated with a warming climate has been implicated in the declines of some boreal breeding waterbirds, such as the lesser scaup (Aythya affinis). Lesser scaup are known to feed extensively on amphipods, a freshwater crustacean; however, ducklings have been shown to have a diverse diet. Our goal was to use the naturally occurring heterogeneity of aquatic invertebrates across boreal lakes within the Yukon Flats National Wildlife Refuge in interior Alaska to better understand how changes in invertebrate prey resources might affect diet selection and growth in lesser scaup ducklings. First, we used a stable isotope approach to quantify the variation in the trophic niche within our population of ducklings. We found that as a population, lesser scaup ducklings consume a variety of aquatic insects, crustaceans and mollusks, and that variation in the population diet is largely attributable to variation in diet between birds from different lakes with different invertebrate communities. Second, we used the same habitat heterogeneity to examine how gradients of invertebrate abundance relate to the growth of ducklings. We observed that lesser scaup ducklings experienced reduced growth rates in lakes that had little to no amphipods. Taken together, these results suggest that while lesser scaup ducklings are a flexible consumer that can adapt to changes in invertebrate populations, ducklings may face negative fitness repercussions when consuming prey other than amphipods.
  • Black bear denning ecology and habitat selection in interior Alaska

    Smith, Martin E.; Follmann, Erich; Dean, Fred; Hechtel, John; Bowyer, Terry (1994-12)
    To identify conflicts between existing black bear (Ursus americanus) management and human activity on Tanana River Flats, Alaska, we monitored 27 radio-collared black bears from 1988-1991. We compared denning chronology, den characteristics, den-site selection, and habitat selection across sex, age, and female reproductive classes. Mean den entry was 1 October and emergence was 21 April, with females denned earlier and emerging later than males. Marshland and heath meadow habitats were avoided, and willow-alder was selected for den-sites. Eighty-three percent of dens were excavated, 100% contained nests, 18% were previously used, and 29% had flooded. Black bears selected black spruce-tamarack and birch-aspen significantly more, and marshland and heath meadow significantly less than available. Marshland and birch-aspen were used significantly more in spring than autumn. Marshland was used less than available by all bears in all seasons. Special habitat or den-site requirements are not critical for management of Tanana River Flats black bears.
  • Human-bear interactions in the North Slope oilfields of Alaska (USA): characteristics of grizzly bear sightings and use of infrared for bear den detection

    Pedersen, Nils J. S.; Brinkman, Todd J.; Shideler, Richard T.; Brainerd, Scott; Lindberg, Mark (2019-05)
    Minimizing unsafe human-bear (Ursus spp.) interactions in the North Slope oilfields of Alaska (USA) requires knowledge of where they occur and methods to prevent them. My research goals were to characterize the spatial and temporal dynamics of grizzly bear (U. arctos) sightings during the non-denning season around industrial infrastructure in the North Slope oilfields over the past 25 years (Chapter 2), and to evaluate the efficacy of forward-looking infrared (FLIR) systems to detect grizzly bears and polar bears (U. maritimus) in their winter dens (Chapter 3). I used reports (n = 2,453) of summer grizzly bear sightings collected by oilfield security officers from 1990-2014 to estimate how the spatial distribution of sightings for food-conditioned (FC) and natural food (NF) bears changed following restriction of bear access to anthropogenic food waste (to be known hereafter as "treatment") in 2001. I found that concentrations of FC bear sightings shifted toward the landfill with medium-low effect (Hedges' g = 0.41), one of the only remaining areas with available food waste, after the treatment. The treatment also decreased NF bear sighting distances to landfill with low effect (Hedges' g = 0.15). My findings suggested that grizzly bear access to food waste should be prevented to minimize negative human-bear interactions and that an active bear reporting system facilitates adaptive management of human-bear interactions. During the winter, grizzly bears and pregnant female polar bears enter dens in areas that overlap anthropogenic activity. FLIR techniques have been used to locate occupied dens by detecting heat emitted from denned bears. However, the effects of environmental conditions on den detection have not been rigorously evaluated. I used a FLIR-equipped Unmanned Aircraft System (UAS) to collect images of artificial polar bear (APD) and grizzly bear (AGD) dens from horizontal and vertical perspectives from December 2016 to April 2017 to assess how odds of detection changed relative to den characteristics and environmental conditions. I used logistic regression to estimate effects of 11 weather variables on odds of detection using 291 images. I found that UAS-FLIR detected APDs two times better than AGDs, vertical perspective detected 4 times better than horizontal, and that lower air temperatures and wind speeds, and the absence of precipitation and direct solar radiation increased odds of detection for APDs. An increase of 1°C air temperature lowered the odds of detection by 12% for APD, and 8% for AGDs, but physical den characteristics such as den snow wall thickness determined detectability of AGDs. UAS-FLIR surveys should be conducted on cold, clear days, with calm winds and minimal solar radiation, early in the denning season. UAS-FLIR detectionof bear dens can be effective but should be confirmed by a secondary method.
  • Spatial variation in blueberry (Vaccinium uliginosum) and lingonberry (Vaccinium vitis-idaea) fruit production in Interior Alaska

    Parkinson, Linsey Viann; Mulder, Christa; Hollingsworth, Teresa; Spellman, Katie (2019-05)
    There are over 50 species of plants in Alaska that produce fleshy fruits (hereafter: "berries"), of which people consume 25. Berries are a key cultural and nutritional resource in rural Alaska and an important source of calories for a range of animals including bears (Ursus spp.), foxes (Vulpes vulpes), geese (e.g., Branta hutchinsii), and voles (e.g., Myodes rutilus). Berry production, from bud development to ripe fruit, takes at least 15 months and may be affected by factors even a year or two before that. Many studies in the circumpolar North focus on these interannual effects on fruit production but few assess how local variation within a forested region may affect berry numbers. Changes in the frequency and severity of wildfires in the boreal forest has affected soil conditions and plant community structure, which may alter the range of circumstances a species must respond to, influencing overall fruit production at a site. I studied how fruit production in Vaccinium uliginosum (blueberry) and V. vitis-idaea (lingonberry), responded to factors such as pollen load, floral resources, canopy cover, and soil conditions within forest sites of Interior Alaska. I found two distinct habitat types in the Interior Alaskan forest, upland and lowland, which differed by elevation, soil moisture (lower in upland sites), and active layer (deeper in upland sites). We found lingonberry was more pollen limited than blueberry, and plants in lowland sites were more pollen limited while plants in upland sites were more resource limited. Additionally, canopy cover had a significant negative effect on a ramet's investment in flowers, berries, and leaves, versus structural growth, in upland sites but little effect in lowland sites. I was able to explain more of the variation in berry production and resource allocation in upland sites than lowland sites. Pollen and resource limitation differed between the two species and between uplands and lowlands suggesting Vaccinium berry production and resource allocation is partially defined by spatial variability of the landscape.
  • Reproductive success of American and Pacific golden-plovers (Pluvialis dominica and P. fulva) in a changing climate

    Overduijn, Kelly S.; Powell, Abby N.; Handel, Colleen M.; Sikes, Derek (2019-05)
    Climate change is increasing air temperatures and altering hydrologic systems in arctic environments, which will create positive feedbacks on shrub growth and advance the phenology of arthropods, important prey for many Arctic-breeding birds. Little is understood about how such climate-induced changes in habitat and prey availability may affect reproductive success of migratory birds during the short arctic breeding season. Worldwide, declines in shorebird populations, including arctic-breeding species, have recently become apparent. Projected changes in climate are expected to benefit Arctic-breeding shorebirds in the short-term by increasing reproductive success and survival, primarily through prolongation of summer. Over time, however, reductions in the quantity and quality of open tundra habitat and changes in prey availability may adversely affect shorebird reproduction and exacerbate current population declines. I evaluated the reproductive success of two shorebird species, American (Pluvialis dominica) and Pacific (P. fulva) Golden-Plovers, in relation to vegetation extent and phenology. I collected data over two field seasons (2012-2013) on the Seward Peninsula, Alaska. Both species selected nest sites with less cover of tall shrubs and other tall vegetation than available at random sites within their territories. American Golden-Plovers selected territories and nest sites that were higher in elevation and had more rocky substrates and less graminoid vegetation than those selected by Pacific Golden-Plovers. Nest survival was equivalent in the two species and similar to that found in other arctic-breeding shorebirds. Over the 27-d incubation period the probability of a nest having at least one egg survive to hatch averaged 0.39 (95% CI: 0.28, 0.49). Nest survival was not explicitly associated with habitat features at nest sites; however, nest survival was lower during the year with earlier spring phenology and declined with the age of the nest, both of which may have been at least partially related to growth of vegetation. Future research should examine reproductive success in a comprehensive manner, in which multiple aspects of a species' reproductive ecology is evaluated, allowing a more complete understanding of the effects of climate change on recruitment into populations through the combined effects of habitat structure, food resources, and climate.
  • Diet, breeding success, detectability, and density of the great horned owl (Bubo virginianus) at its northern range limit

    McConnell, Madison H.; Kielland, Knut; Breed, Greg; Shook, John (2019-05)
    I studied the diet, breeding success, detectability, and density of great horned owls (Bubo virginianus) in the Middle Fork of the Koyukuk Valley in Arctic Alaska. The study extended from the southern slopes of the Brooks Range to latitudinal tree line, the northern breeding limit of the species, and included what are likely to be the northernmost great horned owl nests on record (up to 68.0113 degrees north). I completed the study during the 2017 and 2018 breeding seasons, during years of high snowshoe hare (Lepus americanus) abundance. The focus of this study was to gain an understanding of how high snowshoe hare abundance influences the recruitment, diet, and distribution of this apex generalist predator, and to determine best methods of detecting great horned owls for similar studies in the future. I used motion sensor cameras on nests as well as pellet analysis for diet and breeding studies, and call surveys for information on detectability and density. Great horned owl diet consisted mostly of snowshoe hares by mass (mean 80%, range 65-99%), with an average prey size of 714 g (95% CI ± 34.26). Nestlings received an average of 459 g (95% CI ± 75) of prey per chick per day, and the proportion of hares in their diet positively correlated with fledging success (P = 0.01). During call surveys, length of playback was the most important factor in detecting great horned owls throughout 12 minute surveys, reaching 23% (95% CI = ± 6.4) at 3 minutes, and up to 80% (95% CI = ± 6.1) at 9 minutes. Inclusion of silent listening periods may lessen the chance of detecting great horned owls during playback surveys, though a larger sample size is needed (P = 0.18). There was no correlation between cloud cover and probability of detection (P = 0.60) or wind speed and probability of detection (P = 0.28). However, there was a positive correlation between temperature and probability of detection (P = 0.02). Call surveys gave an estimate of 4.1 great horned owls per square kilometer (z = 4.302, 95% CI = ± 2.63). This was the northernmost study of North America's most widespread year-round bird of prey, and the first density estimate at their northern breeding limit.
  • Microbial ecology and biodegradation potential of a sulfolane-contaminated, subarctic aquifer

    Kasanke, Christopher P.; Leigh, Mary Beth; Barnes, David; Jones, Jeremy; Takebayashi, Naoki (2019-05)
    Contaminant biodegradation is one of many ecosystem services aquifer microbiota can provide to humans. Sulfolane is a water-soluble emerging contaminant that is associated with one of the largest contaminated groundwater plumes in the state of Alaska. Despite being widely used, the biodegradation pathways and environmental fate of sulfolane are poorly understood. In this study, we investigated the biodegradation of sulfolane by the microbial community indigenous to this contaminated subarctic aquifer in order to better understand the mechanisms and rates of loss, as well as the environmental factors controlling them. First, we conducted aerobic and anaerobic microcosm studies to assess the biodegradation potential of contaminated subarctic aquifer substrate and concluded that the aquifer microbial community can readily metabolize sulfolane, but only in the presence of oxygen, which is at low concentration in situ. We also investigated the impacts of nutrient limitations and hydrocarbon co-contamination on sulfolane biodegradation rates. To identify exactly which community members were actively degrading sulfolane, we combined DNA-based stable isotope probing (SIP) with genome-resolved metagenomics methods. We found a Rhodoferax sp. to be the primary sulfolane degrading microorganism in this system and obtained a near-complete genomic sequence of this organism, which allowed us to propose a new metabolic model for sulfolane biodegradation. Finally, we assessed the distribution of sulfolane-degrading bacteria throughout the contaminated subarctic aquifer by sequencing 16S rRNA genes from 100 groundwater samples and two sulfolane treatment systems and screening for the sulfolane degrader previously identified using SIP. This assessment revealed that sulfolane biodegradation potential is widespread throughout the aquifer but is not likely occurring under normal conditions. However, the sulfolane-metabolizing Rhodoferax sp. was the most dominant microbe in an effective experimental air-sparge system, suggesting that injecting air into the aquifer can stimulate sulfolane biodegradation in situ. These studies are the first to investigate sulfolane biodegradation potential in a subarctic aquifer. Through this work, we learn there are several important factors limiting biodegradation rates, we expand the known taxonomic distribution of sulfolane biodegradation, and we shed insights into the mechanisms underlying an effective in situ sulfolane remediation system.
  • Shining light on hibernator genomes: using radiation to reveal DNA damage and repair dynamics in Arctic ground squirrels

    Yancey, Krysta L.; Podlutsky, Andrej; Drew, Kelly; Harris, Michael (2018-12)
    Mammalian hibernation is characterized by dynamic changes in metabolism and body temperature; it may be sustained for up to nine months in some species. The majority of hibernation is spent in torpor, a dormant state, which is regularly interrupted by brief periods of activity referred to as interbout arousal. Upon arousal thermogenesis begins in vascularized fat and ends with whole-body shivering until the animal reaches a body temperature around 36-37 °C. Interbout arousal is usually less than a day long and is commonly thought to be necessary for maintenance and repair of tissues, in addition to the cycling and replenishment of metabolites. While physiologically extreme, torpor-arousal cycles do not drastically impact the health of hibernators. Rather, hibernators are recognized for their longevity and resistance to a variety of stresses, such as ischemia/reperfusion and the brain damage that typically follows. It remains unknown how the process of hibernation challenges genome stability and the basic molecular mechanisms of DNA repair. Therefore, this thesis begins with a review on current knowledge of genome maintenance in the context of mammalian hibernation, distinguishing it from other similar and often correlated conditions like hypothermia. Then, we present the first cellular and molecular study to be conducted on DNA damage and repair dynamics in a hibernator using the Alaskan arctic ground squirrel. Our results indicate that hibernators can avoid genome instability during torpor-arousal cycles through status-specific combinations of strategies for preventing DNA damage and efficient DNA repair, paired with anti-apoptotic environments. The unique suite of adaptations necessary to endure torpor-arousal cycles may help explain the longevity and radio-resistance that are often observed in hibernating species.
  • Studies assessing insulin signaling dependent neuronal morphology and novel animal sorting methods in a C. elegans model

    Hunter, Skyler C.; Bult-Ito, Abel; Taylor, Barbara; Podlutsky, Andrej; Vayndorf, Elena (2018-12)
    The purpose of this work is two-part. The primary goal of this thesis is to identify a list of significant target insulin-like peptides (ILPs) that influence the maintenance of neuronal morphology in an aged animal model of Caenorhabditis elegans (C. elegans) and determine whether or not morphological changes have bearing on neuronal function. The second goal is to address and devise a solution for a common laboratory difficulty encountered within the research community, difficulty maintaining large age-synchronous populations of the model organism, C. elegans. Chapter 1 discusses the importance of insulin signaling and how it pertains to the morphology of aging neurons. A reverse genetic screen was conducted to knockdown the expression of individual ILPs in a C. elegans model. The results identify a subfamily of ILPs that play significant roles in maintaining regular morphology of aging mechanosensory neurons. These data corroborate previously published work demonstrating that aberrant morphology of mechanosensory neurons does not directly influence their function and that these two parameters, morphology and function, can be uncoupled and considered mutually exclusive. Chapter 2 describes a main difficulty associated with using C. elegans as a model organism; the problem of maintaining a large age-synchronous population on solid media. To address this difficulty a novel piece of equipment, named the Caenorhabditis Sieve, and an accompanying methodology for its application, were created to mechanically sort and clean C. elegans. The use of this new device facilitates the implementation of assays with animals cultivated on solid media that are normally cost and resource prohibitive. Presented with the protocol for device construction and implementation, are standard experiments that were conducted to verify "proof of concept" of the tool's efficacy. The results demonstrate that the Caenorhabditis Sieve effectively transfers animals from one culture plate to the next in a manner that does not influence common markers of physiological stress; thus validating the sieve's use in future experiments among the research community, as well as highlighting the success of creating a cost-effective, efficient, fast, and simple process to mitigate difficulties and ease progress in research fields using small model organisms.
  • Distribution of hunter groups and environmental effects on moose harvest in Interior Alaska

    Hasbrouck, Tessa R.; Brinkman, Todd; Stout, Glenn; Kielland, Knut (2018-12)
    Moose (Alces alces) is one of the most valuable wild game resources in Interior Alaska. In recent years, residents of rural indigenous communities have expressed concern that climate change and competition from non-local hunters are challenging local moose harvest opportunities. I collaborated with wildlife agencies and village tribal councils to co-design two studies to address rural community hunter concerns. The first study assessed the spatial and temporal distribution of local and non-local hunter groups to examine areas of potential competition. The second study addressed changing environmental factors and their impacts on moose harvest. Although competition among local hunters or among non-local hunters certainly occurs, competition between local and non-local hunters, or between resident and non-resident hunters is a more common and reoccurring issue. Local hunters are those who hunt in the area in which they reside whereas non-local hunters travel away from the area they reside to hunt. I assessed hunting patterns by local and non-local hunters in a remote hunting region near the interior villages of Koyukuk and Nulato to quantify moose harvest overlap between these two user groups to assess potential competition. I used Alaska Department of Fish and Game (ADFG) moose harvest records to develop a relative competition index that identified locations and time periods within the hunting season where the greatest overlap occurred from 2000-2016. I determined that the highest competition occurred between 16-20 September (i.e., peak harvest period) and was concentrated predominantly along major rivers. To decrease overlap and mitigate potential competition between hunter groups we recommend providing information on competition hotspots to hunters, or lifting the no-fly regulation in the Koyukuk Controlled Use Area with the caveat that hunting with the use of aircraft must occur 1.6 km from the Koyukuk River corridor. These actions may provide hunters information on how to re-distribute themselves across the landscape and allow hunters to use areas away from rivers, where most harvest currently occurs. Additionally, climate change and seasonal variability have anecdotally been documented to impact moose hunting opportunities. Specifically, warm temperatures, delayed leaf drop, and fluctuating water levels are concerns expressed by some local hunters. I quantified changes in temperature, leaf drop, and water level near Koyukuk and Nulato and the subsequent relationships between these environmental variables and the total number of moose harvested using linear regression models. I used temperature data, gauging station data (i.e., water level), remote sensing data (i.e., leaf drop analysis), and ADFG moose harvest records and explored previously untested hypotheses and to quantify relationships from 2000-2016. I concluded that non-local hunter harvest success was more dependent than local harvest success on environmental conditions. Non-local harvest significantly increased with higher water levels from 6-10 Sept (p=0.02), 11-15 Sept (p=0.02), and 16-20 Sept (p<0.01), and decreased with warmer temperatures in the same three time periods (p<0.01, p=0.02, p<0.01, respectively). Local harvest increased with higher water levels from 16-20 Sept (p<0.01). These results quantitatively show that environmental factors do impact hunter success. I speculate that local hunter harvest success is less dependent on environmental variability because they have the ability to harvest opportunistically, rely more heavily on the resource, and reside near the hunting area. This ability to opportunistically hunt and adapt may give them an advantage over non-local hunters as environmental conditions shift with climate change.
  • Assessing effects of climate change on access to ecosystem services in rural Alaska

    Cold, Helen S.; Brinkman, Todd J.; Hollingsworth, Teresa N.; Brown, Caroline L.; Verbyla, David L. (2018-12)
    Across the planet, climate change is altering the way human societies interact with the environment. Amplified climate change at high latitudes is significantly altering the structure and function of ecosystems, creating challenges and necessitating adaptation by societies in the region that depend on local ecosystem services for their livelihoods. Rural communities in Interior Alaska rely on plants and animals for food, clothing, fuel and shelter. Previous research suggests that climate-induced changes in environmental conditions are challenging the abilities of rural residents to travel across the land and access local resources, but detailed information on the nature and effect of specific conditions is lacking. My objectives were to identify climate-related environmental conditions affecting subsistence access, and then estimate travel and access vulnerability to those environmental conditions. I collaborated with nine Interior Alaskan communities within the Yukon River basin and provided local residents with camera-equipped GPS units to document environmental conditions directly affecting access for 12 consecutive months. I also conducted comprehensive interviews with research participants to incorporate the effects of environmental conditions not documented with GPS units. Among the nine communities collaborating on this research, 18 harvesters documented 479 individual observations of environmental conditions affecting their travel with GPS units. Environmental conditions were categorized into seven condition types. I then ranked categories of conditions using a vulnerability index that incorporated both likelihood (number of times a condition was documented) and sensitivity (magnitude of the effect from the condition) information derived from observations and interviews. Changes in ice conditions, erosion, vegetative community composition and water levels had the greatest overall effect on travel and access to subsistence resources. Environmental conditions that impeded travel corridors, including waterways and areas with easily traversable vegetation (such as grass/sedge meadows and alpine tundra), more strongly influenced communities off the road network than those connected by roads. Combining local ecological knowledge and scientific analysis presents a broad understanding of the effects of climate change on access to subsistence resources, and provides information that collaborating communities can use to optimize adaptation and self-reliance.
  • The evolutionary history of Madagascar's tenrecs (mammalia: Tenrecidae): systematics, phylogeography, and species delimitation

    Everson, Kathryn Michelle; Olson, Link; Jansa, Sharon; Sikes, Derek; Takebayashi, Naoki (2018-08)
    Madagascar is renowned for its exceptionally diverse, unique, and threatened biota, yet much of the island's flora and fauna remains undescribed, and the underlying drivers of diversification and endemism are poorly understood. The family Tenrecidae is one of four extant terrestrial mammal lineages to have colonized and diversified on Madagascar from continental Africa. The goal of this dissertation is to elucidate the evolutionary history of tenrecs at both deep and shallow time scales, and to use tenrecs as a proxy to understand the drivers of diversification on Madagascar. In Chapter 1 I generate the first rigorously inferred phylogeny of tenrecs to include every currently recognized species, revealing that they colonized Madagascar 30-56 million years ago. I also demonstrate that speciation rates have been higher in humid habitats compared to arid habitats - a finding that sets the groundwork for my next three chapters. To better understand the patterns and processes of diversification in the humid forest, I next explore the phylogeography of a species endemic to that region, Oryzorictes hova, in Chapter 2. Using genetic and morphometric data, I identify three populations (later identified as cryptic species) within O. hova that correspond to northern, central, and southern regions of the island. The same phylogeographic pattern has been observed in some of Madagascar's other humid-forest taxa, and it had been hypothesized that population structure is driven by low-elevation breaks between Madagascar's northern, central, and southern highlands. In Chapter 3, using genetic data from 20 small mammals and five reptiles codistributed along the island's humid-forest belt, I find this structure is directly related to the distribution of high-elevation areas and is congruent (spatially and temporally) across many species. This result demonstrates that the highlands have played an important role in recent diversification on Madagascar, most likely by functioning as refugia during Quaternary climate cycles. Finally, in Chapter 4 I continue to explore diversification in Madagascar's humid forests by studying species limits and patterns of gene flow in a clade of shrew tenrecs endemic to that region (M. fotsifotsy, M. soricoides, and M. nasoloi). Using a massively multi-locus genetic dataset, I demonstrate that M. soricoides and M. fotsifotsy (which are broadly sympatric) have hybridized in the past, and that this has caused conflicting phylogenetic results between different genetic datasets. I also recover two distinct clades of M. fotsifotsy: one that occurs only in the far north of Madagascar, and one that is widespread and broadly sympatric with M. soricoides. Evidence of reproductive isolation, plus subtle but significant morphometric differences between these clades, lead me to recognize them as distinct species. While I accomplished my primary aim of clarifying the phylogeny and taxonomy of Madagascar's tenrecs, my findings will also be important to scientists outside that initial scope. This research illuminates one of the mechanisms by which Madagascar's flora and fauna became so diverse -namely, that diversification has been driven by latitudinally segregated high-elevation refugia along the humid forests that historically spanned the island's eastern escarpment - and it reaffirms the need for continued collection and preservation of specimens in one of the world's hottest biodiversity hotspots as these forests face unprecedented rates of anthropogenic alteration.
  • Bridging the gap between pupping and molting phenology: behavioral and ecological drivers in Weddell seals

    Beltran, Roxanne Santina; Burns, Jennifer; Breed, Greg; Testa, J. Ward; O'Brien, Diane; Barnes, Brian (2018-08)
    In Antarctica, the narrow window of favorable conditions constrains the life history phenology of female Weddell seals (Leptonychotes weddellii) such that pupping, breeding, foraging, and molting occur in quick succession during summer; however, the carry-over effects from one life history event to another are unclear. In this dissertation, I characterize the phenological links between molting and pupping, and evaluate feeding behavior and ice dynamics as mechanistic drivers. First, I review the contributions of natural and sexual selection to the evolution of molting strategies in the contexts of energetics, habitat, function, and physiology. Many polar birds and mammals adhere to an analogous biannual molting strategy wherein the thin, brown summer feathers/fur are replaced with thick, white winter feathers/fur. Polar pinnipeds are an exception to the biannual molting paradigm; most rely on blubber for insulation and exhibit a single molt per year. Second, I describe the duration and timing of the Weddell seal molt based on data from 4,000 unique individuals. In adult females, I found that successful reproduction delays the molt by approximately two weeks relative to non-reproductive individuals. Using time-depth recorder data from 59 Weddell seals at the crucial time between pupping and molting, I report a striking mid-summer shallowing of seal dive depths that appears to follow a vertical migration of fishes during the summer phytoplankton bloom. The seals experience higher foraging success during this vertical shift in the prey distribution, which allows them to re-gain mass quickly before the molt. Across four years of study, later ice break-out resulted in later seal dive shallowing and later molt. In combination, the data presented in this dissertation suggest that molting, foraging, and pupping phenology are linked in Weddell seals and are affected by ice break-out timing.
  • Molecular phylogenetics of arvicoline rodents

    Conroy, Christopher John; Cook, Joseph A. (1998)
    The impetus for this dissertation was an interest in geographic variation in Microtus longicaudus with a particular focus on populations in the Alexander Archipelago of southeastern Alaska. To establish a framework for interpreting intraspecific variation in M. longicaudus, I examined the phylogenetics of 28 species of the genus Microtus, including all North American species (Chapters 2 and 4). That study, which corroborates a rapid pulse of diversification noted in the fossil record, necessitated a deeper phylogenetic perspective. Thus, a third objective of the dissertation was to investigate relationships among genera of arvicolines within the framework of other murid rodents. I examined variation in the mitochondrial cytochrome b and ND4 genes using maximum parsimony, distance, and maximum likelihood phylogenetic analyses. Relationships at several taxonomic levels appear intractable due to rapid accumulation and survival of genetic lineages. These rapid radiations were found among species, genera, and possibly subfamilies; however, strong support at these levels for other taxa (e.g., the monophyly of Microtus) suggests these genes have strong phylogenetic signal. Many of the well-supported sister species pairs within Microtus (Chapters 2 and 4) had been previously identified based on morphologic or allozyme work (e.g., M. pennsylvanicus and M. montanus, M. pinetorum and M. quasiater). The sequence data supported a clade of taiga dwelling species in North America and a clade of eastern and central Asian species. The southernmost arvicoline species of Mexico and Guatemala, though previously suggested to be derived from a single ancient invasion, did not appear to be either ancient or monophyletic. Within M. longicaudus, a large east-west phylogeographic break was detected that is equivalent in genetic distance to other sister species pairs in the genus. This break may indicate mid to late-Pleistocene differentiation (Chapter 3) within the genus. At higher latitudes, populations of M. longicaudus exhibited evidence of recent range expansion including absence of correlation between geographic and genetic structure; and pairwise mismatches among DNA sequences with a single peak and few differences.
  • Foraging ecology and conservation biology of African elephants: Ecological and evolutionary perspectives on elephant-woody plant interactions in African landscapes

    Dudley, Joseph Paine; Bryant, John P. (1999)
    The available scientific evidence indicates that African forest elephants and bush elephants are ecologically and evolutionarily distinct taxa. The current practice of regarding these two taxa as ecotypes of a single species, Loxodonta africana (i.e., L. a. africana Blumenbach 1797, L. a. cyclotis Matschie 1900) appears unwarranted, and obscures issues of major significance to the conservation biology of African elephants. Under a proposed taxonomic revision, the African bush elephant retains the designation Loxodonta africana Blumenbach 1797 while the African forest elephant is recognized as Loxodonta cyclotis Noack 1906. The browsing of woody plants by African bush elephants is a major factor in the structural dynamics of semi-arid woodland and scrubland habitats in Hwange National Park (HNP) and the Sengwa Wildlife Research Area (SWRA), Zimbabwe. Drought, frost and fire also influence the structure and species composition of woody vegetation within HNP. Interactions among these three abiotic factors and elephant browsing may have significant impacts on the dynamics of semi-arid woodland and scrubland habitats of HNP. Mortality attributable to elephant damage was identified as a principal cause of death among large trees (>5.0 in height), and a relatively minor but not insignificant cause of death for shrubs and trees in the 1.0--5.0 in height class. The responses of Colophospermum mopane in SWRA to fertilization treatments corresponded to those predicted by the carbon/nutrient hypothesis of plant anti-herbivore defense. Comparisons of these results with those of previous studies suggest possible changes in the ecology and population biology of elephants in HNP during the past decade. Observed differences in the age-specific mortality of elephant in HNP during die-offs in 1993--1995 and 1980--1984 provide independent evidence of changes in the ecology of elephants in HNP during the period 1983--1993. The population of L. a. africana inhabiting the Matabeleland-Ngamiland-Okavango region of southern central Africa (which includes the HNP population), is the largest extant elephant population on Earth. The magnitude of this population (110,000--120,000), and the high proportion of its range currently under protection as wildlife reserves, indicate that this population may rank as the most viable and potentially sustainable elephant population on Earth.

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