• Disinfection by-product experiences in Alaskan village drinking water systems and the Caribou-Poker Creek watershed

      Narr, Jasprit (2001-08)
      The purpose of this research was to study the disinfection by-product formation potential (DBPFP) in small drinking water systems in Alaska. As per the US. E.P.A's disinfectants/disinfection by-products (D/DBP) rule, the maximum contaminant limit (MCL) for the two major DBPs namely, total trihalomethanes (TTHMs) is 80 micrograms (ug) per liter (L) and 60 micrograms/liter for the five 5 halloacetic acids (HAA5). It was decided to conduct research on the total trihalomethane formation potential (TTHMFP) and the 5- haloacetic acid formation potential (HAA5PF) of the 17 Alaskan village drinking water systems with reportedly high TTHM and HAA5 values. It was found that specific UV absorbance (SUVA) had excellent correlations with TTHM/DOC and HAA5/DOC. These correlations were used to aid in drinking water source selection in a sub-arctic watershed named the Caribou-Poker Creek Research Watershed (CPCRW).
    • Dispersal patterns and summer oceanic distribution of adult dolly Varden from the Wulik River, Alaska, evaluated using satellite telemetry

      Courtney, Michael B.; Seitz, Andrew; Zimmerman, Christian; Scanlon, Brendan (2015-05)
      In Arctic Alaska, Dolly Varden Salvelinus malma is highly valued as a subsistence fish; however, little is known about oceanic dispersal or ecology. This study addresses this knowledge gap, by using a fisheries independent method, pop-up satellite archival tags (PSATs). In spring of 2012 and 2013, we attached 52 PSATs to Dolly Varden in a river in northwestern Alaska, which flows into the Arctic Ocean, to examine the marine dispersal, behavior and habitat occupancy of this species. Tagged Dolly Varden demonstrated two types of dispersal, including offshore and nearshore dispersal. The offshore type was the first documented northwesterly dispersal and occupancy of Outer Continental Shelf (OCS) areas of the Russian Chukchi Sea. While occupying this area, tagged Dolly Varden demonstrated affinity for the first 5 m of the water column, diel patterns in depth occupancy, and dive depths of up to 50 m, while experiencing a thermal environment of generally 3-7°C. During the nearshore dispersal type, Dolly Varden transited in coastal areas of northwest Alaska, likely returning to their natal rivers to spawn. While in nearshore areas, tagged Dolly Varden always occupied shallow waters (< 6 m), and experienced a rapidly changing thermal environment (± 15°C), including some waters temperatures cooler than -1°C. This study demonstrates that PSATs offer an alternative and effective platform with which to study several aspects of large adult Dolly Varden dispersal and ecology in areas where it is not practical or feasible to capture these fish, such as in coastal and offshore regions of Arctic Alaska. Additionally, the results of this study have increased our knowledge of the summer marine distribution, behavior and thermal environment of Dolly Varden in Arctic regions of Alaska, and this knowledge is important to several stake holders for the conservation of this important subsistence species.
    • Displacing phallogocentrism: fragmented subjects & transgendered bodies

      Knight, Tara N.; Coffman, Chris; Carr, Rich; Stanley, Sarah; Hirsch, Alexander (2017-05)
      "Displacing Phallogocentrism: Fragmented Subjects and Transgendered Bodies" synthesizes theories about gender construction and identity formation as proposed by Simone de Beauvoir, Judith Butler, Julia Kristeva, Michel Foucault, and Jacques Lacan, and proposes that the cultural sediment created by heteronormativity and phallogocentrism can be displaced by the proliferative re-conceptualization and re-signification of transgendered subjects. Because the relationship between the signifier and the signified is arbitrary, Simone de Beauvoir's theory about the inner identity's desire for transcendence and Judith Butler's theory about the materiality of the signifier demonstrate how subjects are 1.) always already transgendered, and 2.) constantly reshaping the material world through re-signification. Jeanette Winterson's Sexing the Cherry dramatizes the act of displacing phallogocentrism by allegorizing the notion through the corporations and Puritans that her fragmented female protagonist, the chemist/Dog-Woman, is fighting against. Because heteronormativity and phallogocentrism can only be displaced by the fragmented and transgendered subject, Winterson shows how it is only after her male protagonist, Nicolas/Jordan, has grafted a feminine identity onto himself and become a transgendered subject when he can finally be free from the shackles of phallogocentrism and re-signify the future. Because phallogocentrism compels subjects to reiterate socially-constructed sedimentations that unevenly distribute power to some subjects while disenfranchising others, this thesis highlights the imperative need to displace the sedimentation of phallogocentrism in order to transgender the body and re-conceptualize the world.
    • Dissolved organic matter in wetland soils and streams of Southeast Alaska: Source, Concentration, and Chemical Quality

      Fellman, Jason B.; Hood, Eran; Boone, Rich; Jones, Jeremy; White, Dan; D'Amore, David (2008-12)
      Dissolved organic matter (DOM) transported from terrestrial to aquatic ecosystems is an important source of C, N and energy for the metabolism of aquatic heterotrophic bacteria. I examined the concentration and chemical quality of DOM exported from coastal temperate watersheds in southeast Alaska to determine if wetland soils are an important source of biodegradable dissolved organic carbon (BDOC) to aquatic ecosystems. I addressed this question through a combination of high resolution temporal and spatial field measurements in three watersheds near Juneau, Alaska by using a replicated experimental design that characterized DOM export from three different soil types (bog, forested wetland and upland forest) within each of the watersheds. PARAFAC modeling of fluorescence excitation-emission spectroscopy and BDOC incubations were used to evaluate the chemical quality and lability of DOM. Overall, my findings show that wetland soils contribute substantial biodegradable DOM to streams and the response in BDOC delivery to streams changes seasonally, with soil type, and during episodic events such as stormflows. In particular, the chemical quality of DOM in streamwater and soil solution was similar during the spring runoff and fall wet season, as demonstrated by the similar contribution of protein-like fluorescence in soil solution and in streams. These findings indicate a tight coupling between wetland DOM source pools and streams is responsible for the export of BDOC from terrestrial ecosystems. Thus, seasonal changes in soil-stream linkages can have a major influence on watershed biogeochemistry with important implications for stream metabolism and the delivery of labile DOM to coastal ecosystems. Soil DOM additions in small streams draining the three soil types showed that DOM leached from watershed soils is readily used as a substrate by stream heterotrophs and at the same time modified in composition by the selective degradation of the proteinaceous fraction of DOM. These findings indicate terrestrial DOM inputs to streams are an important source of C to support stream heterotrophic production. Thus, the production of protein-rich, labile DOM and subsequent loss in stream runoff has the potential to be an important loss of C and N from coastal temperate watersheds.
    • Distance Activism And The Arctic National Wildlife Refuge

      Raymond-Yakoubian, Julie M.; Gladden, James (2002)
      The growing phenomenon of distance place attachment and distance activism can be seen in the extensive network of non-visitors involved in the protection of places like the Arctic National Wildlife Refuge in Alaska. This type of activism is not an anomaly, but rather an increasingly significant global phenomenon, which has gone largely unexamined by researchers of environmentalism, activism, wilderness, and place attachment. Distance activism encompasses the standard definition of activism, with the addition that distance activists must not have had physical contact with the natural environment for which they are being active. I argue that distance activists' actions and beliefs can be understood, in part, in terms of the conceptual frameworks of geopiety, topophilia, and place attachment. Furthermore, I argue that distance activism deserves a proper place in place attachment theorizing. Distance activism on behalf of the Arctic Refuge is examined as a case study of this important phenomenon. <p>
    • Distant vistas: Bradford Washburn, expeditionary science and landscape, 1930-1960

      Sfraga, Michael P.; Pearson, Roger (1997)
      Bradford Washburn is primarily known for his Alaskan mountaineering accomplishments and mountain photography. Between 1930 and 1960, Washburn led 19 expeditions to Alaska and Canada's Yukon Territory on which he surveyed, photographed and mapped some of the last unexplored mountain regions in North America. This study, however, analyzes Washburn's lesser known role in directing interdisciplinary field research involving high altitude physics, glaciology, cartography and geology, which he accomplished by linking such disparate entities as the motion picture industry, geographic organizations, the U.S. military, and prominent U.S. scientists. Washburn's career can be viewed as an intersection of nineteenth and twentieth century geographic traditions. He combined emerging technologies with new and innovative vehicles of exploration to more accurately study geological, geographical and environmental phenomenon in mountainous regions. During the Second Great Age of Discovery, which began with the Renaissance, explorers ventured into the heart of the world's continents by utilizing various vehicles of exploration such as canoes and pack animals. This style continued into the middle of the twentieth century when the present day Third Great Age of Discovery, characterized by the use of remote sensing platforms and space age satellites, allows for a more accurate geographic study and inventory of our planet. Washburn's interdisciplinary field work reflects the fundamental goals and patterns of expeditionary science found in both ages of discovery. In this study three important themes are examined: Washburn's role as innovative field scientist; geography as a disciplinary bridge; and the work of the independent geographer. By analyzing Washburn's work in the pre World War Two and Cold War era, we gain an understanding of the ways in which expeditionary science was funded and carried out within two fundamentally different political and economic frameworks. Moreover, this study provides an important window into our understanding of interdisciplinary earth sciences in the mid twentieth century. It also explores the often unappreciated link between environmental science and geography in the American context.
    • Distribution and abundance of the Pacific razor clam, Siliqua patula (Dixon) on the eastside Cook Inlet beaches, Alaska

      Szarzi, Nicole J. (1991-05)
      Three questions were asked about the population of the Pacific razor clam Siliqua patula (Dixon) on eastside Cook Inlet beaches: (1) can density be estimated by a three-stage stratified random sampling plan; (2) can age composition data be used for age-structured population estimation; (3) does substrate composition affect clam density? Field studies of Coho, Ninilchik and Clam Gulch beaches obtained precise density estimates for Clam Gulch beach only (coefficient of variation = 14.6%, 1988, and cv = 13.6%, 1989). A heavily exploited area of high density at Clam Gulch was resampled extensively in 1989 to determine if a significant harvest rate was detectable. No significant harvest rate was detected. A catch-at-age model was successfully applied to age-structured data, and estimates of abundance for ages 4 through 11+ in years 1977 to 1989 were generated. There is some evidence from substrate analyses that clams are found in higher abundance where grain sizes 0.125 to 0.400 mm predominate.
    • Distribution and biogeography of the Alaskan hare (Lepus othus)

      Cason, Michelle M.; Olson, Link; Booms, Travis; Hundertmark, Kris; Sikes, Derek (2016-05)
      The Alaskan Hare (Lepus othus Merriam 1900) is the largest lagomorph in North America but remains one of the most poorly studied terrestrial mammals on the continent. Its current distribution is restricted to western Alaska south of the Brooks Range, but historical anecdotal accounts of occurrences north of the Brooks Range (the North Slope) have led to confusion over its past, present, and predicted distribution. To clarify the historical range of L. othus, we surveyed North American museum collections and georeferenced voucher specimens (Supplemental File Appendix 1.1). We also located a specimen from the North Slope of Alaska long presumed lost and whose identity had come to be questioned. The rediscovery of this missing specimen suggests the occurrence of at least one Alaskan Hare on the North Slope as recently as the late 1800s. Because unforested ecosystems such as tundra and Arctic grasslands have decreased in Alaska since the last glacial maximum, and L. othus occurs in unforested habitat, we expected to observe low genetic diversity in the mitochondrial control region of L. othus. However, with recently collected specimens from regions in Alaska that were poorly represented in the past (i.e. Alaska Peninsula, Little Diomede, and Kotzebue Sound), we discovered more genetic diversity and population structure than was found in previous studies, including similar haplotypes from the Alaska Peninsula and from eastern Russia. This suggests there may have been 2 distinct colonization events of northern hares in Alaska, or introgression from L. timidus and a mitochondrial sweep that has been restricted to the Alaska Peninsula and Bristol Bay area. Our morphological analyses of the difference between the two subspecies, L. o. othus and L. o. poadromus, were ambiguous, with principal components analysis and simple linear regression indicating the presence of a latitudinal size cline and discriminant function analysis revealing successful group assignment that is not solely based on latitude. Our research clarifies the current and recent distribution of the Alaskan Hare and reveals more genetic diversity than previously suspected in the mitochondrial control region. We also observed a new biogeographic pattern and closer mtDNA association with L. timidus, which, combined with new island specimens and observations, suggests gene flow across the Bering Strait. It also highlights the importance of maximizing sample sizes and sampling widely across a taxon’s geographic distribution.
    • Distribution and ecology of exotic plants in Wrangell-St. Elias National Park and Preserve, Alaska

      McKee, Paul Christian (2004-12)
      The distribution of exotic plants and site factors influencing their abundance on roads and trails were studied in Wrangell-St. Elias National Park and Preserve during the summer of 2003. Seventeen species of exotic plants were found in the park at 173 locations. The most common species (Taraxacum officinale, Plantago major) were present at all study sites, while some (Trifolium spp., Bromus inermis, Leucanthemum vulgare) were restricted to specific disturbance types and particular areas. Though sampling was limited to areas in which exotic plants were growing, percent cover of exotics was not a significant component of sample sites, and exotic species richness was low at all sampling locations at 1.42 species per m². Data were analyzed using ordination and multiple regression to determine variables most responsible in explaining variation in exotic plant communities. Statistically significant site variables correlated with percent cover of exotics included percent cover of vascular native plants, percent cover litter, and percent bare soil at most study sites. The importance of these variables indicates that the presence of exotic plants in Wrangell-St. Elias is closely linked to disturbance, and that the invasion of exotic plants is in the initial phases.
    • Distribution and movement of juvenile tanner crabs Chionoecetes bairdi in Glacier Bay National Park

      Nielsen, Julie Kristine (2005-12)
      Spatial segregation of adult and juvenile Tanner crabs was observed in conjunction with glacial landscape features during a comprehensive systematic survey of Glacier Bay National Park, Alaska, in 2002. Hot spots (clusters of high values) of catch per unit effort for juveniles occurred mainly in two narrow glacial inlets, whereas most adult hot spots occurred in the central portion of the bay. Overall, juveniles were associated with shallower depths and warmer temperatures than adults. However, in juvenile hot spot areas, where adults were rare, juveniles were associated with greater depths and colder temperatures than adults. Glaciated landscapes may provide spatial refuges from predation and nursery areas for juveniles. Tagging methods with high trans-molt retention need to be developed for direct measurement of ontogenetic movement. A laboratory study was conducted to determine trans-molt survival and retention of Floy T-bar tags in juvenile Tanner crabs. Approximately half of crabs in all tagging treatments survived and retained tags through a molt. Trans-molt retention of Floy tags is hindered by complex morphology of the Tanner crab carapace.
    • The distribution and phylogeography of the Alaska marmot (Marmota broweri)

      Gunderson, Aren M. (2007-12)
      The taxonomic and distributional status of the Marmota broweri has been the subject of much debate and confusion since it was first described as a subspecies of the hoary marmot (M caligata). Through a review of all museum specimens, published accounts of this species, field surveys, and the identification of previously unidentified marmot specimens we have determined the current distribution of the Alaska marmot to include the Brooks Range, the Ray Mountains, and the Kokrines Hills of northern Alaska. The Yukon River forms the boundary between the peripatric distributions of M broweri and M caligata in Alaska. Since M broweri was a resident of Beringia during the Pleistocene, I expect the phylogeographic structure of Alaska marmots (M broweri) to exhibit the signature of persistence in Beringia and subsequent expansion into glaciated areas. My objective is to investigate the phylogeographic structure of Alaska marmot populations through phylogenetic tree construction, measures of genetic diversity, a mismatch distribution, and nested clade analysis of DNA sequence data from the mitochondrial cytochrome b gene. I found significant geographic structure across the range of M broweri. The results of my analyses suggest a recent population expansion from central Alaska (Beringia) into the formerly glaciated Brooks Range
    • Distribution of hexachlorobenzene concentrations in spruce needle samples across Alaska

      Billings, Shane (2000-05)
      The global distribution of persistent organic pollutants has initiated considerable effort towards understanding long range atmospheric transport and partitioning of these potentially damaging compounds. Apparent latitude dependent concentration gradients of organic pollutants in otherwise pristine environments has given rise to a global fractionation model, coined the cold finger effect. According to the cold finger theory, semi-volatile persistent organic pollutant will show a preference for partitioning from the atmosphere to the ground and vegetation at northern latitudes. Here we present a study of hexachlorobenzene in spruce needle samples across Alaska, which offers a large range of climates, from its southern coastal rain forests to the northern arctic. The large variation in climate across Alaska should result in a measurable latitude dependent concentration gradient for HCB, if the cold finger effect is being realized. Spruce needle samples were extracted, cleaned, and analyzed by GC/MS. According to principle component regression analysis, HCB concentrations in all the spruce needle samples across Alaska show a strong positive correlation with lipid content of the needles. The HCB concentrations also show two distinct latitude trends. The spruce needle samples taken from the coast to approximately 63° north show relatively high HCB concentrations and a possible negative correlation with latitude. The samples between 63° and 68° north show a definite positive correlation between HCB concentration and latitude, which is consistent with the cold finger effect.
    • 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.
    • Distribution of large calanoid copepods in relation to physical oceanographic conditions and foraging auklets in the western Aleutian Islands

      Coyle, Kenneth Orval (1997)
      Acoustic measurements and net sampling were used to estimate zooplankton abundance and biomass relative to water mass types and flow fields in the western Aleutian Islands during June and July, 1992 and 1993. Observations are interpreted relative to the distribution and abundance of least auklets (Aethia pusilla), which forage on zooplankton. Highest zooplankton biomass (up to 7 g m$\sp{-3}$) occurred during June 1992, in the pycnocline separating the upper mixed layer from the cold intermediate layer north of a front separating Bering Sea and Alaska Stream water. The large calanoid Neocalanus flemingeri had highest abundance but the larger Neocalanus cristatus accounted for most of the biomass. N. cristatus and N. flemingeri were absent south of the Bering Sea front, where the community was dominated by Neocalanus plumchrus and Eucalanus bungii. Auklets were foraging almost exclusively north of the Bering Sea front. Neocalanus spp. abundance in the upper mixed layer was much lower in July 1993, than in June 1992. Neocalanus occurred primarily in scattered aggregates near the pycnocline over Bering Sea Intermediate water and at the surface in Pacific water. Auklets shifted their foraging activities to passes and shelf areas among the islands, where tidally generated divergences and convergences upwelled and concentrated prey into patches in the mixed layer. Elevated densities of Neocalanus were observed in convergence zones in Delarov Pass and over a ridge south of Kiska Island. Convergence zones were identified by intense sound scattering from entrained bubbles and by deceleration of the horizontal velocity components in acoustic doppler current data, a record of current speed and direction beneath the vessel. Densities of auklet prey in the study area during June were apparently influenced by the position of the front between Bering Sea and Pacific water masses. The position of the front was influenced by Alaska Stream flow anomalies lasting for several years. Prey densities on the shelves and in the passes during July were influenced by tidal currents at spatial scales of tens of meters to ten kilometers and lasting one tidal cycle.
    • Distribution, Growth And Egg Production Of Euphausiids In The Northern Gulf Of Alaska

      Pinchuk, Alexei I.; Hopcroft, Russell (2006)
      The euphausiids Thysanoessa inermis, Thysanoessa spinifera and Euphausia pacifica are key pelagic grazers and important prey for many vertebrates in the Gulf of Alaska (GOA). This thesis provides the first account of distribution, egg production, growth, development, and temporal variability in abundance of the euphausiids in relation to environmental variations in the northern GOA. T. inermis and T spinifera were abundant on the shelf within 120-130 km from the coast, while E. pacifica originated from offshore and was advected onto the shelf during summer. E. pacifica produced multiple broods with brood size strongly related to ambient chlorophyll a concentrations. In contrast, T. inermis released eggs once in the season and its brood size did not depend on chlorophyll content. Early development of these species showed a remarkably similar response to changes in temperature. The highest molting increments were observed during the spring phytoplankton bloom for T. inermis, and in summer for T. spinifera and E. pacifica, suggesting coupling with food availability. The molting rates were strongly influenced by temperature. Growth rates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm d-1 or 0.023 d -1 for T. inermis) and July (0.091 mm d-1 or 0.031 d-1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm d -1 (0.016 d-1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5�C) and ambient chlorophyll-a concentration fit a Michaelis-Menten curve (r2=0.48), but such relationships were not significant for T. spinifera or E. pacifica. Reproduction of T. inermis occurred during April in 1998 and 2003, and was extended through May in 1999-2002. The spawning of T. inermis and T. spinifera was related to the spring diatom bloom on the inner shelf, while the spawning of E. pacifica occurred later in season, when the water temperature increased. A strong increase in abundance of T. inermis, associated with the extended colder phase in the North Pacific, indicates that progressive cooling in 1999-2002 may have resulted in greater reproductive success of early spawning T. inermis on the inner shelf.
    • Disturbance History In The Tanana River Basin Of Alaska: Management Implications

      Roessler, James S.; Packee, Edmond C. (1997)
      The forests of Tanana River Basin in Interior Alaska have a history of disturbance. Four issues reflecting forest disturbance, important to include in current management strategies for these lands, were researched: (1) disturbance history of the Tanana Valley; (2) Alaska Interagency Fire Management Plan: a case study; (3) prescribed natural fire in Alaska: possibilities and complexities; and (4) past use of prescribed fire in white spruce: a summary with particular reference to Alaska. Through researching historical archives, conducting field visits, interviewing land and fire managers and reviewing current planning documents, I reached four major conclusions: (1) there is lack of use of historical facts regarding human-induced changes on the landscapes; (2) past involvement of public stakeholders in fire planning in Alaska was inadequate; (3) the Alaska Interagency Fire Management Plans need to identify scientific prescription parameters which address specific land management objectives; and (4) management-ignited prescribed fire must become a more common prescription after harvesting of white spruce. <p>
    • Divergence, gene flow, and the speciation continuum in trans-Beringian birds

      McLaughlin, Jessica F.; Winker, Kevin; Takebayashi, Naoki; Hundertmark, Chris (2017-08)
      Understanding the processes of divergence and speciation, particularly in the presence of gene flow, is key to understanding the generation of biodiversity. I investigated divergence and gene flow in nine lineages of birds with a trans-Beringian distribution, including pairs of populations, subspecies, and species, using loci containing ultraconserved elements (UCEs). I found that although these lineages spanned conditions from panmixia to fully biologically isolated species, they were not smoothly distributed across this continuum, but formed two discontinuous groups: relatively shallow splits with gene flow between Asian and North American populations, no fixed SNPs, and lower divergence; and relatively deeply split lineages with multiple fixed SNPs, higher divergence, and relatively low rates of gene flow. All eight lineages in which two populations were distinguishable shared the same divergence model, one with gene flow without a prolonged period of isolation. This was despite the diversity of lineages included that might not have responded in the same ways to the glacial-interglacial cycles of connection and isolation in Beringia. Together, these results highlight the role of gene flow in influencing divergence in these Beringian lineages. Sample size is a critical aspect of study design in population genomics research, yet few empirical studies have examined the impacts of small sample sizes. Using split-migration models optimized with full datasets, I subsampled the datasets from Chapter 1 at sequentially smaller sample sizes from full datasets of 6 - 8 diploid individuals per population and then compared parameter estimates and their variances. Effective population size parameters (ν) tended to be underestimated at low sample sizes (fewer than 3 diploid individuals per population), migration (m) was fairly reliably estimated until under 2 individuals per population, and no trend of over- or underestimation was found in either time since divergence (T) or Θ (4Nrefμ) . Lineages that were split above the population level (subspecies and species pairs) tended to have lower variance at smaller sample sizes than population-level splits, with many parameters reliably estimated at levels as low as 3 diploid individuals per population, whereas shallower splits (i.e., populations) often required at least 5 individuals per population for reliable demographic inferences. Although divergence levels may be unknown at the outset of study design, my results provide a framework for planning appropriate sampling, and for interpreting results if smaller sample sizes must be used.