Indirect 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.

Izembek 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.

Body 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.

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.

Microplastics pose a significant threat to marine ecosystems across multiple trophic levels. Spotted seals (Phoca largha) are piscivorous and occupy one of the higher trophic positions in the Bering and Chukchi seas, putting them at risk of ingesting microplastics through prey. This project aimed to determine if microplastics are present in the stomachs of spotted seals harvested for subsistence purposes and compare their presence spatially between two harvest locations, Gambell and Shishmaref, AK. Microplastics are predicted to increase in the Arctic over time due to climate warming and subsequent deposition of microplastics from melting sea ice. Therefore, we examined stomachs from 2012 and 2020 to explore temporal changes. Furthermore, as spotted seal pups (<1 yr of age) and non-pups forage differently, we expected a difference in microplastic ingestion between age classes. We processed stomachs using enzymatic digestion and vacuum filtration. Use of the enzyme digestion method enabled microplastic detection while preserving the hard parts of prey items (e.g., fish otoliths and shrimp carapaces) for diet analysis. We then examined filters with a stereomicroscope, and calculated microplastic frequency of occurrence (FO). A total of 34 (16 from 2012 and 18 from 2020) stomachs from Gambell and Shishmaref have been examined, and a total of 211 microplastic particles were isolated from 33 stomachs (97.1% FO), containing 1 to 23 particles per stomach. Our analysis showed no significant difference in FO between pups and non-pups, between the two harvesting locations, or between harvest years. Additionally, there was no significant difference in the microplastic concentration among the spotted seal stomachs examined in this study. Our data indicate that microplastic ingestion has not changed in frequency between age class, harvest location, or year. This baseline study was successful in isolating microplastics in the stomachs of spotted seals and showed that microplastics have been ingested consistently by spotted seals for at least the past decade. Furthermore, we found increased microplastic abundance in spotted seal stomachs when seals consumed prey at higher trophic levels and prey from benthic zones. Continued study of microplastic ingestion, including absorption and accumulations of the contaminants, is needed to assess potential impacts on the health of spotted seals and other ice-associated pinnipeds, who serve as indicators of ecosystem health in the Bering and Chukchi seas.

Environmental factors and physical activity have the potential to modulate skeletal muscle physiology in beneficial ways. Cold exposure and endurance exercise, specifically, may improve aerobic capacity and atrophy resistance. I utilized three models to examine the effect of cold exposure and activity level on skeletal muscle physiology: quantitation of body composition and energy expenditure estimates in humans participating in a transmountain race, comparative proteomic analysis of skeletal muscle in hibernating and summer active American black bears (Ursus americanus), and an experimental study of the combined effects of cold exposure and endurance training on white adipose tissue, and gastrocnemius and soleus muscles in Sprague-Dawley rats. Body composition analysis of participants of the transmountain race revealed significant fat but not lean body mass loss despite significant caloric deficit. Proteomic analysis of American black bear skeletal muscle revealed an upregulation of glycolytic, inflammatory, immune response, and lipid transport proteins, and a decrease of lipid, and amino acid catabolism proteins during hibernation. Modulation of metabolism and the immune system during hibernation appears to mitigate skeletal muscle atrophy, despite prolonged inactivity and fasting. In Sprague-Dawley rats, cold or exercise alone have similar effects on body composition but exert unique effects on oxidative and glycolytic skeletal muscles that overall supports enhanced aerobic capacity. When combined, cold and exercise appear to improve oxygen diffusion via reduced cross-sectional area of some fiber types in oxidative skeletal muscle but have opposing effects in glycolytic muscles. In summary, skeletal muscle is highly plastic and perturbations such as cold, fasting, and endurance training result in cellular remodeling and changes in protein expression that improves aerobic capacity and conserves skeletal muscle mass across species.

The Arctic is warming rapidly due to anthropogenic greenhouse gas emissions. Concurrent with warming, some Arctic plant communities have transformed from short statured evergreen and graminoid shrub tundra to tall deciduous shrubs in recent decades. As warming continues, plant-plant interactions will likely change and influence future community composition. Alnus viridis ssp. fruticosa (Siberian alder) is rapidly expanding across Arctic regions and is particularly important because Siberian alder is the Arctic's only large N-fixing shrub, may alter N-cycling to further influence both C-cycling and community composition as it spreads. This dissertation addressed two main questions to better understand how Arctic deciduous shrub communities have changed, and may continue to change as Arctic warming proceeds. First, how did the climate sensitivity of Siberian alder's growth change over the past century (1920 - 2017), and how did climate sensitivity change as Siberian alder grew older? Second, how has Siberian alder affected the long-term growth of two nearby dominant deciduous shrub species: Betula nana ssp. exilis (dwarf birch) and Salix pulchra (diamondleaf willow)? I used dendrochronological techniques to assess how sensitive the growth of each of these three species was to climate over the last century. For dwarf birch and diamondleaf willow, I compared growth near and away from Siberian alder. I hypothesized that Siberian alder shrubs would become more sensitive to climate as they grew both older and larger. I expected that older alder would enhance soil N availability over time, due to the accumulated products of N-fixation. I also expected that the growth of larger, older alders would be more sensitive to climate than the growth of younger alder, because of having both a greater photosynthetic capacity (enabling more growth under good conditions), but also higher maintenance respiration (leading to less growth under poor conditions). I found that Siberian alder overall has become more sensitive to July air temperatures in the second half of the past century as climate has warmed. Also, older shrubs were more sensitive to June and July air temperatures than younger shrubs. Thus, these findings support my hypothesis. Siberian alder frequently grows in close association with dwarf birch and diamondleaf willow. However, these two deciduous neighbors differ in several functional traits. Dwarf birch is a low statured, many branched shrub that mainly grows laterally, and thus is often found on the margins of the Siberian alder canopy. In contrast, diamondleaf willow has fewer branches, grows more vertically, and often is found almost entirely within the Siberian alder canopy. Thus, I hypothesized Siberian alder would facilitate the growth of dwarf birch growth, by alleviating both resource and abiotic stressors, but would reduce diamondleaf willow growth, due to increased light competition. Siberian alder promoted dwarf birch growth and reproduction, likely by alleviating N-limitations and reducing frost damage, though growth was delayed by two weeks. In contrast, diamondleaf willows growing near alder had much smaller growth rings than diamondleaf willows growing away from alder, likely due to light competition. This negative effect on willow growth near alder occurred despite these willows likely receiving greater access to soil N and protection from herbivory damage from the neighboring alder. Overall, these results demonstrate that Siberian alder will likely grow better as they get both older and larger, and as the Arctic continues to warm. Siberian alder influence the growth of neighboring deciduous shrubs over the long term, and those effects are species-specific because they depend on the functional traits of their neighbors. Thus, the continued spread of Siberian alder will likely alter vegetation community composition, and thus influence C and N cycling.

Accurate knowledge of divergence and speciation processes is critical for understanding key aspects of biodiversity. As a well-known, speciose group of vertebrates, an increased understanding of how birds diverge and speciate allows us to better manage extant avian diversity and understand how it develops over time. Additionally, birds often exhibit complex and variable patterns of divergence, resulting in complexes of taxonomic uncertainty. Filling gaps in our knowledge of divergence across time and space increases our ability to correctly identify and understand not just avian diversity but clade-level patterns in speciation processes. These higher-order findings give us tools to compare and understand biodiversity more broadly across a wide range of taxa. In this thesis, I investigated both temporal and spatial elements of avian divergence, with an emphasis on the high-latitude system of Beringia, which is of particular interest for speciation due to its position at the meeting point of the Eurasian and American continental avifaunas. Chapter 1 describes my investigation of the temporal dynamics of Beringian divergence. The cyclic opening and closing of the Bering Strait due to glacial cycles intermittently isolated and reunited Asia and North America during the Pleistocene (2.6 Mya to 10 Kya). This was hypothesized to produce an uncertain number of associated 'pulses' of avian divergence events spanning that time period. I used a pairwise sampling approach among 39 taxa and a mitogenomic dataset under Bayesian modeling and found no statistical evidence for multiple vicariance events. Instead, divergence times were spread fairly evenly across a large period of time, appearing as a single vicariance event. This is biologically unusual given the system and the cyclic nature of the most likely abiotic driver (glacial cycles) and may be the result of multiple overlaid periods of divergence and gene flow in taxa with older divergence dates. In Chapter 2, I examine the relative contributions of phenotypic and genetic divergence in pairwise comparisons of diverging bird lineages in high- versus low-latitude systems in Beringia and the Philippines. Phenotypic divergence in birds is assumed to be largely due to selection (Price 2008), with genetic divergence assumed to be more driven by time in isolation. I hypothesize that the Beringian system should have less divergence overall than the Philippines, but that a greater proportion of the divergence should be phenotypic, due in part to increased population connectivity in high-latitude systems as a result of larger long- term range fluctuations as a result of Pleistocene glacial cycles. Increased connectivity should be particularly effective in removing neutral, rather than phenotypic, divergence, where selection may be in operation, in part due to a nonlinear, inverse relationship between gene flow and neutral divergence. To test this, I used standardized measures of phenetic and genetic divergence and used linear regressions to quantify the relationship between divergence metrics and the rates of divergence in each system. Beringia showed lower levels of genetic and phenotypic divergence than the Philippines, but the relationship between data types was stronger and the rate of divergence higher than in the Philippine system. I suggest that this is a result of decreased time spent in allopatry in high-latitude systems, but recognize that an increased rate of phenotypic divergence, possibly due to increased selection pressure at high latitudes, also might play a role.

Deicing winter roads with chlorides has been common practice in northern areas. Corrosion of vehicles, structures, and pavements has resulted in damage, and roadside vegetation and public water supplies have been severely impacted by heavy salt usage. Calcium magnesium acetate (CMA) was identified as a promising alternative to chloride salts. This research focused on the effects on planktonic algae and bacteria in small ponds, to help assess the environmental acceptability of CMA in Alaska. The most serious consequence resulting from CMA was a dissolved oxygen concentration decrease, partly attributable to increased bacteria populations utilizing oxygen during degradation of acetate. Algal biomass recovered toward the end of the summer indicating that the algae may be utilizing some of the carbon dioxide being released by the bacteria. Rapid turnover times of acetate by bacteria in the fall and continued low dissolved oxygen indicated that some of the acetate was being recycled.

"My objective was to assess the potential effects of military overflights on home range size, movement rates, habitat use, and habitat selection of female Dall's sheep (Ovis dalli) during 2-week sequential periods, April-July, 1999-2002. I examined sheep in 2 study areas overlain with designated military training airspace within the Yukon-Tanana uplands, Alaska. I examined the effects of study area, year, and sequential time period on: 1) mean home range size, 2) mean minimum hourly distance traveled by sheep, and 3) mean use and selection ratios for the habitat variables of elevation, slope, terrain ruggedness, aspect, and landcover class. Mean number of daily military sorties within sequential periods was used as a covariate in all analyses. I assessed habitat selection at 3 successive spatial scales defined as: 1) the regional geographical range of female Dall's sheep in the Yukon-Tanana uplands, 2) study areas (defined as the distribution of sheep within a localized area), and 3) selection within individual 2-week home ranges. Sheep home range size, movement rates, habitat use and selection ratios at the scale of region and study area differed between study areas, among years within study areas, and among sequential time periods within years within study areas, but did not vary in relation to military overflight intensity. I detected an effect of sorties on selection ratios at the home range scale; however, sorties explained <4% of the residual variation in these variables. I conclude that increases in intensity of military training operations during Major Flying Exercises (MFE's) over the Yukon-Tanana uplands were a relatively insignificant source of variance in activity and habitat use compared to the effects of seasons, years, and study areas"--Leaf iii