Biological Sciences: Recent submissions
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Nesting habitat relationships of four species of alcids at Fish Island, AlaskaTufted Puffins, Horned Puffins, Parakeet Auklets, and Pigeon Guillemots were studied at Fish Island, Alaska, 59°52, N, 147°25, W, to determine if nesting habitat relationships indicated nest separa- tion or competition. The timing of early stages of breeding and daily activity patterns overlapped broadly among all species. Aggressive interactions occurred among all species. Tufted Puffins nested in cliff edges and grassy slopes; all species used rocky slopes and cliff faces. Tufted Puffin nests in rocks differed from Pigeon Guillemot and Parakeet Auklet nests in having larger entrance height and area, and they were placed farther from the high tide line. These dif- ferences related to body size and take-off ability, and may be indica- tions of past competition for nest sites. Interspecific interactions and site use by more than one species indicated some competition may have occurred for certain sites. Overall, most evidence indicated competition had little influence on nest site use among species.
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A range extension for Carex sartwellii in Interior AlaskaMean annual temperatures and growing season length have been increasing in northern latitudes. This has impacted permafrost thaw and the water balance of northern regions, resulting in a pattern of drying lakes in the Yukon Flats, Alaska. As lakes dry, they expose lake sediments to colonization by terrestrial vegetation. Recent interest in the terrestrial response to climate change and its effects on ecosystem services led to the formation of the Yukon River Basin project. As a part of this project, we studied plant succession and diversity in the drying lake basins. In the course of our field work we encountered a sedge we believed to be previously undocumented in Alaska. Our documentation of Sartwell’s Sedge, Carex sartwellii, on nine drying lakes during fieldwork in the central Yukon Flats, Alaska, represents a range extension for this species. Previously, its range extended as far northwest as Yukon, Canada, with a reported, but lost collection, from Alaska in 1895. Two earlier collections from the Yukon Flats have been verified; one was misidentified as Carex praegracilis until 2007. Carex sartwellii’s assumed absence from Alaska and Yukon flora, misidentification of an earlier collection, and the remoteness of the Yukon Flats may have contributed to the rarity of its collection. In Alaska this species is morphologically similar to C. praegracilis, but can be distinguished using traits of the perigynia, leaf sheaths, and the production of true vegetative culms. This sedge was found extensively in alkaline drying lake basins, which are similar environments to those found during the Pleistocene. Many of the species that occurred with C. sartwellii in lake basin plant communities have been documented in paleo reconstructions of plants from the Beringian steppe. The Yukon Flats are botanically understudied as a region in Alaska and further research should focus on identifying these unique relict plant communities in the Yukon Flats and their distribution along historic Beringia into Yukon. This would likely lead to more collections of C. sartwellii and expand our knowledge of its distribution and ecology.
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Effects of juvenile mass on reproduction and calf survival in a low-density moose populationMoose (Alces alces) are a valuable big game species in Alaska and serve as a critical food source for residents. Near Nome, Alaska, the local moose population has remained at low densities for decades, and there is strong public interest in investigating the cause behind the population's failure to increase in abundance. Compared to other moose populations in Alaska, the population of moose near Nome does not appear to be nutritionally limited or close to carrying capacity. I sought to explore how juvenile mass, a widely used metric to assess moose nutritional status in Alaska, influences reproductive output and subsequent calf survival rates in the moose population in Game Management Units 22C and 22D near Nome by estimating calving rates of collared known-age and known-mass female moose and then monitoring their calves. I found that female moose that were heavier as juveniles had a higher probability of calving for the first time at age 2 or 3 and a higher probability of twinning. I found low calf survival rates (18%) through the first year of life and did not find a significant relationship between any maternal or calf characteristics and calf survival. Overall, it appears that this moose population is defined by low calf survival rates but high reproductive rates and high survival after the first year of life. Additionally, the metric of juvenile mass and primiparity as indicators of nutritional status appears to be variable within populations among years and may not be a reliable management tool. Additional research is warranted to further explore the effect of environmental factors on driving variation in primiparity probability.
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Unveiling soil microbial communities and resistomes in northern Alaska National Wildlife RefugesMicrobial communities residing in pristine high-latitude soils play a critical role in ecosystem function, but also harbor potential threats such as acting as reservoirs of antimicrobial resistance (AMR) genes. Current knowledge about these microbial communities and the resistance genes they carry presents limits to the ability to predict how these ecosystems will respond to climate change. This knowledge gap is particularly concerning in light of the potential public health threat posed by antimicrobial resistance harbored within these communities as antibiotic-resistant human infections continue to increase. This study investigated the microbial communities and details the antimicrobial resistance gene reservoirs in previously unsurveyed soils of three northern Alaska National Wildlife Refuges representing three distinct high-latitude biomes. I used a combination of 16S rRNA gene sequencing and metagenomic sequencing to characterize microbial community diversity and composition, as well as the AMR gene resistome. Also, I analyzed soil chemical components to evaluate their potential role in shaping these communities. My findings reveal significant geographic structure in microbial communities likely driven by differences in soil properties and dispersal limitation. Additionally, I found variation in pH significantly explained differences in alpha diversity, with slightly acidic soils harboring the highest diversity. The pattern of resistome structure matched the pattern of community structure, with microbial communities within the same refuge showing less variation than communities between refuges. Additionally, the data revealed significantly fewer AMR genes in the Selawik National Wildlife Refuge than in the other refuges. I found that variation in pH and in phosphorus concentrations significantly explained variation in AMR gene abundance with higher pH and higher phosphorus resulting in more AMR genes detected. My analysis identified that over 60% of AMR genes encoded resistance to lastresort glycopeptide antibiotics. My findings reveal that soil chemistry, particularly pH, plays a key role in shaping both microbial communities and AMR gene reservoirs in these pristine high-latitude soils. This study's characterization provides a crucial foundation for understanding how climate change and human activities might impact these ecosystems. Understanding the presence and distribution of AMR genes within microbial communities of pristine soils is essential for conserving these ecosystems and mitigating public health risks, including those associated with the spread of antibiotic resistance genes, especially those encoding resistance to last-resort antibiotics.
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Adaptive strategies and energetic profiles of bacteria in permafrost and temperate environments: a comparative studyExploring microbial life in extreme conditions has not only challenged our definition of habitability but is expanding our understanding of where extraterrestrial life may occur. Permafrost, which covers approximately 27% of Earth’s surface, offers a unique window into microbial resilience in an extreme sub-zero environment, which is considered analogous to environments found on icy planets like Mars. Despite such harsh conditions, permafrost sustains diverse and active microbial communities. However, the energy dynamics and genomic adaptations that enable their survival remain largely unexplored. Here, we compare the maintenance energy requirements and genomic traits of permafrost-derived bacteria with bacteria from temperate environments to gain a better understanding of how these microbes survive in permafrost. We find that permafrost bacteria maintain stable maintenance energy levels as temperatures decrease, suggesting the presence of energy-use efficiency adaptations. Further genomic analysis of permafrost bacteria identified distinct gene adaptations related to stress response and resource acquisition, highlighting increased gene copies in pathways such as transporters and folding proteins. These results not only challenge previous assumptions about microbial energy dynamics but also provide insights into the complex mechanisms enabling microbial life to thrive under some of the most extreme conditions on Earth.
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Body condition of Pacific common eiders breeding along the Beaufort Sea coast of AlaskaPacific common eiders (Somateria mollissima v-nigrum; common eiders) are capital breeding seaducks that fast throughout their ~26 day incubation period. The incubation fast includes three metabolic phases: (I) a transition from feeding to using energy stored during the pre-breeding season, (II) the use of stored lipids for energy, and (III) the use of stored protein for energy as lipid reserves near depletion. With limited energy reserves for incubation, common eiders are more vulnerable to factors that increase the metabolic demands of reproduction, such as climate change or disturbance. We assessed the following metrics of body condition: mass, packed-cell volume, β-hydroxybutyrate, uric acid, and triacylglycerol, to estimate fasting phase of incubating common eiders. Our primary goal was to understand if common eiders breeding along the Beaufort Sea coast of Alaska entered phase III of fasting and, if so, at what point during incubation. We analyzed blood samples throughout incubation from 230 common eiders captured between Spy Island, west of Prudhoe Bay, and the U.S.-Canada Border from 2014 to 2019. Mass and packed-cell volume decreased throughout incubation which was expected as females lose up to 45% of their body mass while fasting. Serum β-hydroxybutyrate increased during incubation, indicating an increased use of stored lipids, typical during phase II of fasting. Serum uric acid decreased during incubation, also suggesting common eiders remained in phase II of fasting and were effective at protein sparing. On average, serum triacylglycerol initially decreased during incubation, consistent with phase II of fasting, then increased towards the end suggesting that some females may be feeding to augment the metabolic needs of incubation. Our body condition analysis suggests that the majority of common eiders breeding along the Beaufort Sea coast of Alaska are primarily using lipids for energy, sparing protein, and finishing incubation in phase II of fasting.
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The effect of permafrost thaw on merucry- and methane-cycling microbes and their potential interactionsIn this study, I investigated potential interactions between methane and mercury cycles in boreal forest soils. Additionally, I examined the changes in these cycles relative to shifts in soil moisture along an environmental soil moisture gradient. This investigation is pertinent due to the escalating rate of permafrost thaw driven by climate change in Arctic and subarctic ecosystems. Permafrost thaw leads to increased soil moisture, fostering favorable conditions for anaerobic microbial processes such as mercury methylation, methanogenesis, and anaerobic methanotrophy. Microbial mercury methylation creates monomethylmercury, a neurotoxin that accumulates in aquatic food webs. Methane cycling results in the production of greenhouse gases that can create a climate-warming feedback loop. In this study, I explored the mercury and methane cycles and analyzed the microbial communities involved in these cycles along an environmental soil moisture gradient. Microbial communities were analyzed by quantifying the relative abundance of taxonomic groups and by quantifying functional genes associated with mercury methylation, methanogenesis, and anaerobic methanotrophy. The relationship between soil water content and functional gene quantities was not significant. However, my findings did reveal a significant relationship between relative beta diversity and gravimetric water content along the environmental soil moisture gradient. The functional potential was predicted by quantifying net methane and net monomethylmercury production through incubations designed to measure total production in completely saturated, anoxic conditions I found that total mercury increases as soil moisture increases, methane efflux increases as soil moisture increases, and carbon dioxide efflux increases as soil moisture increases. This suggests that the activity of the mercury and methane cycles may change as permafrost continues to thaw and soil moisture content increases. In a changing climate, continuing to monitor these cycles in Alaska is pertinent due to its robust fishing industry, indigenous communities, subsistence fishing practices.
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Divergence and adaptation in Beringian birdsBeringia is a high-latitude hotspot of avian divergence and speciation. The unique biogeography of Beringia impacted avian speciation in two ways: through the cyclic appearance of the land bridge between the Asian and North American continents and through glacial refugia. These cyclic processes repeatedly split and connected avian populations, alternately reducing and increasing opportunities for gene flow between populations. In this thesis, I examine how this dynamic system impacted Beringian avian taxa using population genomic analyses. First, I examine broad patterns of divergence and gene flow across 11 lineages of birds using ultraconserved elements (UCEs), which are a multi-locus subsampling of the nuclear genome. These bird lineages contain two or more sister taxa at the population, subspecies, or species level that were likely impacted by the Bering land bridge and/or by glacial refugia. I tested models that provided key demographic information, such as population size, gene flow, and divergence time estimates. Demographic modeling showed gene flow in all cases at a wide range of rates between pairwise comparisons, and all inferred models included a divergence event during the Quaternary. Next, I focus on one species, the Song Sparrow (Melospiza melodia), in the Beringian part of its range. Five subspecies of the Song Sparrow reside in southern Alaska, from the Aleutian Islands to southeast Alaska, and have a wide range of body sizes. Using whole- genomic sequencing and morphology, I examine the phenotypic and genomic differences in these subspecies. I quantified the morphological differences, showing that the western subspecies are significantly larger than the eastern subspecies. I then determined that two candidate genes are under positive selection in the most isolated subspecies, M. m. maxima. Finally, I reconstructed a phylogeny and found that M. m. maxima is sister to the other M. melodia subspecies. These results highlight how the unique biogeography of Beringia impacted the generation of avian diversity in the region.
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Lessons from the old school: phenological responses of the horsetail Equisetum arvense to experimental air and soil warming in Interior Alaskan boreal forestAlthough there are many studies on plant phenological shifts due to climate change, few of them focus on the phenological responses of seedless vascular plant species to warming climate. The boreal forest biome contains ~ 30% of the carbon stored by forests globally and horsetails with their circumboreal distribution are abundant in the boreal forest. Understanding the phenological response of horsetails to warming air and the timing of ground thaw is an important component for understanding how much carbon will be fixed by plants in the boreal biome in the future warmer climate. To examine the effects of air and soil warming on the phenology of Equisetum arvense L. in interior Alaskan boreal forest near Fairbanks, Alaska, we carried out a two-by-two full factorial warming experiment using open topped warming chambers (air warming) and snow removals to advance ground thaw (soil warming). Warming soil by 1 °C caused E. arvense to emerge sooner, and warming air by 0.7 °C caused E. arvense to grow faster and advance to photosynthetic activity sooner. Warmed E. arvense stems also entered senescence earlier than stems in un-warmed control plots, but the advance was greater in the spring, leading to an overall maximum extension of their growing season by 6%, or 6.7 days, for plants that were exposed to both air and soil warming. This is double the average growing season extension of 3% (1.5 days) documented in similar warming experiments of arctic seed plants, and more than the mean growing season extension per decade for seed plants in Europe (4.8 days) and China (6.2 days). Such season expansion at relatively low temperature increases suggests that E. arvense has potential to fix more carbon in future boreal forests.
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Survival, harvest, and abundance of waterfowl populations using tag-recoveries, harvest data, and Bayesian estimationAnnual harvest, survival, and abundance are three of the most monitored vital rates of waterfowl populations in North America. Annual harvest and survival probabilities are estimated from harvest tag-recovery data, which is a form of capture-mark-recapture data, while abundance estimation varies with species. While tag-recovery models were parameterized over 30 years ago, modern applications of these models often estimate harvest and survival probabilities as random effects drawn from Normal distributions. We evaluated tag-recovery models for reliable parameter estimation relative to different 1) monitoring scenarios varying by total individuals tagged annually, 2) prior distributions for the standard deviations of random effects, and 3) life history traits. When sample sizes of tag-recovery datasets were modest, hierarchical mean estimates of harvest and survival probability were reliably estimated but annual estimates of these parameters tended to underestimate true variation due to parameter shrinkage. The sample sizes required to capture true parameter variation with tag-recovery models likely only exist for a few species like mallards (Anas platyrhynchos) and lesser snow geese (Anser caerulescens caerulescens). Abundance of waterfowl populations is increasingly monitored using Lincoln’s index, which estimates annual abundance by dividing annual harvest count data by annual harvest probability. We demonstrated that harvest probabilities estimated from tag-recovery models can be used with Lincoln’s method, which improves the certainty of parameter estimates and increases the power to evaluate different hypotheses about harvest vulnerability within tagged samples. Our work indicates tag-recovery models should be used to assess for different harvest vulnerabilities between recently tagged individuals and individuals alive for at least one year after being tagged. If unmodeled heterogeneity in the form of different harvest vulnerabilities exist within a tagged sample and are not accounted for, inference about annual harvest, survival, and Lincoln’s abundance index will be biased.
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Towards reciprocity in common ravens, corvus corax, near anthropogenic food sources in interior Alaska during winterRavens, Corvus corax, and other corvids are intelligent birds that are the focus of many studies, such as in-depth dives into potential facial recognition and tool use to name a few. Despite these numerous behavioral studies, ravens lack an accessible basic universal ethogram and have rarely been observed in their undisturbed, natural state. Due to this, my study focuses on free-roaming common raven behavior in Fairbanks, Alaska, for which I utilize exploratory analysis to identify patterns in collected data. In doing so, I show how data mining and machine learning can further support behavior research with a systems perspective in the Anthropocene using pattern recognition. Using an ethogram and machine learning techniques on open access data for two winter seasons, I examine what factors affect common raven behavior around human-subsidized food sources in Fairbanks, Alaska by answering: 1) What consistent reactions do wild ravens communities show to objects, people, and other organisms (typically small songbirds or dogs) and 2) Do other factors, such as daylight or location, contribute to differing raven behaviors? I found that ravens exhibit predictable responses that vary based on urbanization level. In addition, I found an unusual pattern in raven behavior that indicates that ravens adjust their behavior based on hourly and daily human activity, indicating that raven behavior is scheduled. These results provide evidence that merging modern and classic techniques into behavioral research reveals patterns that may be missed by traditional methods alone.
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Differential use of willow species by moose in AlaskaPatterns of differential winter utilization of willow by moose in Interior Alaska and the Kenai Peninsula were studied during 1977 and 1978. Knowledge of such patterns is important to the wildlife manager who must evaluate the relative importance of different habitat types for moose. The study areas were composed of sites dominated by mature and seral habitat types.
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Effects of hunting pressure on the spatial dynamics of a subarctic caribou herdIndirect effects of hunting can have important ecological and hunt management implications, and little has been done to quantify these indirect effects on caribou (Rangifer tarandus). To assess effects of hunting pressure on caribou spatial dynamics, we used GPS locations that spanned fall and winter 2010-2022 from the semi-migratory Fortymile caribou herd in interior Alaska. We analyzed these locations using integrated step selection analysis to evaluate step lengths (i.e., movement rates) and selection of distance to roads and trails, and forest cover across 3 hunting pressure levels (none, low, and high) as well as road crossings during hunting compared to non-hunting periods. We found that the caribou response to hunting pressure varied by season and, within the fall season, by hunting pressure level. Relative to no hunting pressure, caribou in fall showed a very strong avoidance of roads at high hunting pressure and a lower avoidance at low hunting pressure. Similarly, caribou in fall showed an avoidance of trails at high hunting pressure although, unlike roads, the avoidance continued at low hunting pressure. Conversely, relative to no hunting pressure, caribou did not change their selection of forest cover in either season nor did they alter their selection of roads or trails in winter. Furthermore, in both seasons, changes in step lengths in response to hunting pressure were less than we expected. Last, caribou avoided road crossings more during hunting compared to non-hunting periods in both seasons. Overall, caribou response to hunting pressure could have implications for caribou availability to hunters, especially during the fall season, as well as caribou distribution in relation to roads across both seasons. Hunt managers and public stakeholders could use our results to inform how changes to caribou harvest management might indirectly impact caribou movements and hunter opportunity.
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Biogeographic history of the world's marmots and the genetic basis of melanism in an Alaskan population of hoary marmotsThis dissertation addresses questions related to the phylogenetics, molting phenology, and genetic basis of melanism in marmots. Marmots (genus Marmota) are large, diurnal ground squirrels that hibernate for 7-8 months each year and have a broad Holarctic distribution. In Chapter 1, I use ultraconserved elements from all 15 extant species to better resolve the phylogeny of Marmota and shed light on the biogeographic history of marmots. The results indicate marmots originated in North America ~16.3 Ma and crossed the Bering Land Bridge into Eurasia ~3-4 Ma. In addition, the Woodchuck (M. monax) and the Alaska Marmot (M. broweri) are more closely related to Eurasian species than to other North American species, and the Hoary Marmot (M. caligata) may be paraphyletic with respect to the Vancouver Island Marmot (M. vancouverensis) and the Olympic Marmot (M. olympus). Chapter 2 is a review of molt phenology in mammals, with a primary emphasis on marmots. Molting is a metabolically expensive process that is generally timed around other costly events such as lactation, parturition, and dispersal. In this chapter I summarize what is known of molting phenology in marmots, which may be particularly informative as to how precise control over molt timing evolved because of the short active period over which molting and all other costly life history events must occur. In addition, I present evidence that the Olympic Marmot only molts once annually, in contrast to other reports that it is the only biannually molting marmot. Chapter 3 is an investigation of melanism in the Hoary Marmot, which is observed in this species only in SE Alaska. I show that melanism is at least partially caused by a gain-of-function mutation in melanocortin-1-receptor (MC1R), a gene that affects melanin deposition in the skin and hair. The mutation affects hair agouti banding such that the middle light band is reduced in length relative to the brown base and black tip, resulting in the melanistic phenotype.
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Changes in benthic prey availability and quality suggest less favorable foraging conditions for threatened Steller's eiders (Polysticta stelleri) molting at Izembek Lagoon, AlaskaIzembek Lagoon, located in the Alaskan southern Bering Sea, is designated as critical molting and wintering habitat for the Alaska-breeding population of Steller's eiders (Polysticta stelleri), listed as Threatened under the United States Endangered Species Act. During the nonbreeding season, the lagoon also hosts a large proportion of the Pacific population of Steller's eiders that nest along the coast of northeastern Russia, and the lagoon is an important stopover site for many other species of migratory water birds. Since the early 1980s, there has been a decline of Steller's eiders in their known nonbreeding range in the southern Bering Sea, but especially in Izembek Lagoon during their remigial molt in the fall. The cause of this decline is unknown; however, in recent years, higher sea temperatures have been observed in Izembek Lagoon and warming ocean temperatures have been associated with shifts in benthic community structure elsewhere. If forage conditions are less favorable in Izembek Lagoon, Steller's eiders may need to redistribute to other locations, or the population at Izembek Lagoon may decline due to reduced survival. To determine if forage conditions have changed, we replicated a 1998 benthic sampling effort in fall of 2018 and 2019 to understand if prey availability has become less favorable to Steller's eiders during their molt in Izembek Lagoon. We compared forage conditions based on the relative biomass (%), overall biomass (g/m2), and size (mm) of organisms belonging to the marine benthic groups: Bivalvia, Gastropoda, Crustacea, and Polychaeta between the two time points. The results suggest a shift in these taxa with an associated change in their biomass and size. The community shifted from being dominated by bivalves in 1998 to more predominantly polychaetes in 2018 and 2019. In addition to a significant reduction of bivalve and crustacean biomass in 2019 as compared to 1998 (p = 0.04, p = 0.02, respectively), bivalves and gastropods were significantly smaller (p < 0.01, p < 0.01, respectively). The decline of Steller's eiders' use of this critical habitat may reflect shifting benthic prey availability. As it has been suggested that Steller's eiders may prefer hard-shelled prey (e.g., bivalves, gastropods) and larger sized bivalves during the molt period specifically, contemporary foraging conditions at Izembek Lagoon may be less favorable or insufficient for supporting historical numbers of Steller's eiders during an energetically taxing time in their annual cycle. Therefore, the molting Steller's eider population at Izembek Lagoon may have difficulty recovering to historical numbers if available forage conditions are of inadequate quality and abundance.
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Controls over visitation rates to mineral licks by snowshoe hares (Lepus americanus) in Northern AlaskaGeophagy, or soil consumption, is a common behavior of several avian and mammalian herbivore species. This activity has been attributed to providing essential nutrients and improving digestion of forage high in plant secondary metabolites. Recently, this behavior has been observed in snowshoe hares (Lepus americanus) and is thought to influence both their nutritional ecology and population dynamics. The purpose of this study was to examine the possible ecological controls over snowshoe hare visitation rates to mineral licks using a camera trap study at four sites near Wiseman, AK, from 2017 to 2020. Data visualization and modeling showed hare activity was strongly influenced by season and time of day, with visitation rates being significantly higher during the summer and at night. Vegetation cover was linked to higher visitation at some sites, however, the pattern was not consistent across all licks. Knowing that mineral licks influence the distribution and movement of hares, these habitat features may similarly influence the movements of hare predators. Thus, this study provides valuable insights into the complex relationships between snowshoe hares, mineral soil, and the broader ecosystem.
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Geochemical variation in the muscle of Aleutian Steller Sea Lion preyBody tissue chemistry has been extensively utilized as biomarkers about the cryptic life histories of Steller sea lions (Eumetopias jubatus) in the western and central Aleutian Islands, Alaska, specifically tissue total mercury concentrations and stable isotope ratios of carbon and nitrogen. As patterns in these biomarkers can be associated with either trophic dynamics or environmental conditions, I examined spatiotemporal and biological variability of bulk carbon and nitrogen stable isotope ratios and total mercury concentrations in the muscle tissue of ten fishes and two cephalopods found in Steller sea lion diets. I hypothesized that the complex bathymetry and oceanography of the region associated with deep-water "oceanic passes" separating islands may limit movement of these species between island groups, compartmentalizing communities in a manner to create distinct geochemical groups. In my first chapter, I found that several oceanic passes act as break points in an east to west decrease in carbon and nitrogen stable isotope ratios in most species sampled, suggesting island groups of the Aleutian Islands have distinct environmental baseline chemistry and/or primary production dynamics. In my second chapter, I found that total mercury concentrations in muscle tissues decrease with distance from the Rat Island group. When this spatial variation was accounted for and species were grouped by feeding guild, benthic invertebrate consumers had the highest mercury concentrations, followed by piscivores and then zooplankton consumers. Multiple species-specific relationships between length and each of these trophic biomarkers provided additional insight into trophic dynamics of these prey species in addition to spatial variation. Considered together, trophic biomarker patterns in Steller sea lion prey suggest trophic networks in the Aleutian Islands are spatially compartmentalized, and variation in sea lion tissue biochemistry will depend on where and what they forage upon in remarkably nuanced manners.
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Influence of fire on boreal stream metabolismWildfires are becoming more severe, frequent, and intense in the boreal forest, which has large repercussions for ecosystem processes, such as carbon and nutrient cycling. Combustion of terrestrial soils and biomass can propagate to influence streams, including increased nutrient inputs, flashier discharge, and changes to the light regime. Due to a warming climate, fire regimes are changing in concert with precipitation regimes, including more frequent and larger storms, which can scour primary producers and remove poorly attached detritus. Changing physicochemical attributes of streams resulting from fire and precipitation could influence metabolic processes that in turn influence carbon (C) storage and flux to the atmosphere. I modeled rates of gross primary production (GPP) and ecosystem respiration (ER) during the ice-free period in nine boreal streams of Interior Alaska that drained watersheds varying in fire history and across up to four years that varied in timing and magnitude of precipitation. Gross primary production and ER increased with watershed size. Average rates of GPP and ER were greater in streams of unburned compared to burned watersheds while controlling for watershed size. Streams were typically heterotrophic and net ecosystem production (NEP, GPP - ∎ER∎) was greater in burned than in unburned watersheds. GPP was correlated with physicochemical attributes including water temperature, whereas ER was unrelated to measured attributes of streams. Temporal patterns in GPP were explained by precipitation at seasonal and daily timescales, with reduced cumulative GPP in the year of greatest cumulative precipitation. Gross primary production declined and remained low following storms that occurred in late summer, but returned to pre-storm rates when storms occurred earlier in the open-water season. Increases in frequency of wildfire are expected to decrease the contribution of aquatic metabolism to CO₂ emissions from streams of the boreal forest due to higher rates of NEP, whereas increased precipitation will likely increase C emissions by suppressing GPP.
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Smoke without fire: wildfire smoke affects phenolic composition of wild blueberry fruits (Vaccinium uliginosum)Wildfire smoke can induce changes in plant growth, phenology, and chemical composition. The frequency and intensity of wildfires have increased over the last thirty years in Alaska, and smoke has the potential to affect important wild fruit plants, such as bog blueberry (Vaccinium uliginosum L.), a food source for many Alaskans and wild animals. We exposed bog blueberry plants to wood smoke at different stages in fruit development: early-season when the plants were flowering ("early-smoked"), mid-season when fruits were unripe ("mid-smoked"), and late-season when fruits were fully ripe ("late-smoked"). We measured anthocyanins, proanthocyanidins, and total phenolics in the ripe fruits, as well as branch growth, leaf anthocyanin levels, fruit set, and flower, fruit, and leaf phenology. Impact of smoke exposure on anthocyanins depended on fruit developmental state: fruits exposed late in the season had no changes in anthocyanin concentration, while early- and mid-smoked fruits showed increases in anthocyanins. Changes in proanthocyanidins followed a similar pattern to anthocyanins, but differences between treatments were not statistically significant. Total phenolic compounds were not different across treatments. Leaf anthocyanins from mid-smoked and late-smoked plants were higher than the control, while early-smoked leaves were unaffected. Early-smoked plants had lower fruit set than the control, but there was no effect of smoke exposure on mid- and late-smoked fruit abundance. Smoke caused treated plants to lose leaves at a faster rate than control plants, but did not change the timing of leaf color change. Smoke did not affect branch growth or flower and fruit phenology. Our study shows that smoke has immediate effects on bog blueberry in the increase of anthocyanins in leaves and fruits, and seasonal effects in lower leaf longevity and limited fruit set in plants exposed while flowering. These results indicate higher stress levels in smoke-exposed plants that might result in higher fruit quality due to the health benefits of anthocyanins, but at the expense of fruit abundance.
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Effects of desformylflustrabromine on compulsive-like and social behaviors in mouse models of OCD and autismObsessive-Compulsive Disorder (OCD) and autism spectrum disorders (ASD) share a number of similar deficits, including altered cholinergic activity in the central nervous system (CNS), manifestation of repetitive, restricted, and compulsive-like patterns of behavior, and frequent co-morbid presentation. Desformylflustrabromine is a novel positive allosteric modulator of α4β2 nicotinic acetylcholine receptors, which has recently been shown to be able to reduce compulsive-like behavior in a non-induced mouse model of OCD. In this study, I attempted to replicate the compulsive-like behavior-reducing effects of desformylflustrabromine in the mouse model of OCD, as well as expose the model to a novel assessment; social behavior, as measured by the 3-Chamber Social test. Furthermore, I altered the model with prenatal exposure to valproic acid to induce an ASD-like construct. This ASD animal model has been used extensively to study the social deficits and neurochemistry of ASD, although limited data exists on co-morbid models. By exposing the OCD model to valproic acid, I attempted to establish two additional models; a comorbid OCD / ASD model in the compulsive-like high-activity (HA) strain and an ASD model in the non-compulsive-like low-activity (LA) strain. All mouse models and controls participated in a battery of behavioral tests quantifying compulsive-, anxiety-, and depression-like behaviors, as well as the 3-chamber social test to quantify social preference behaviors. The ASD model was not strongly established, and the desformylflustrabromine appeared to be inactive in all strains and models. I assessed potential reasons for the failure to establish a robust ASD construct in the OCD mouse model, and the failure of desformylflustrabromine to have any significant effect, in contrast with previous research using the drug in the OCD mouse model.