Conservation is plagued by the issue of prioritization - what to conserve and where to conserve it - which relies on identification and assessment of risks. In this body of work, I identify some of the risks related to climate change impacts on biodiversity, as well as potential solutions. Climate changes are underway across nearly all terrestrial areas and will continue in response to greenhouse gas emissions over centuries. Other extinction drivers, such as habitat loss due to urbanization, commonly operate over localized areas. Urbanization contributes, at most, less than 2% of the total range loss for terrestrial species at risk when averaged within an ecodistrict (Chapter 2). Documented impacts of climate change, to date, include: extinction, population loss, reduction in range area, and decreased abundance for multiple taxonomic groups. Examining species’ and populations’ physiological limits provides insight into the mechanistic basis, as well as geography, of climate change impacts (Chapter 3). Climate changes, and the ecological impacts of climate changes, are scale-dependent. Thus, the biotic implications are more accurately assessed through comparisons of local impacts for populations. Under a scenario of climate change, equatorward margins may be strongly limited by climatic conditions and not by biotic interactions. Yet, geographic responses at poleward margins do not appear directly linked to changes in breeding season temperature (Chapter 4). New ideas on how regions with attenuated climate change (climate refugia) may be used to lower species climate-related extinction risk while simultaneously improving habitat connectivity should be considered in the context of potential future consequences (i.e. range disjunction, alternative biological responses) (Chapter 5). Contemporary climate refugia are identifiable along multiple climatic dimensions, and are similar in size to current protected areas (Chapter 6). Determining how, when, and where species distributions are displaced by climate change as well as methods of reducing climatic displacement involves integrating knowledge from distribution shift rates for populations, occurrence of climate refugia, and dispersal barriers. Such assessments, in the Yellowstone to Yukon region, identify dramatically different pathways for connectivity than assessments that are not informed by considerations of species richness and mobility (Chapter 7).

During the climate oscillations of the Pleistocene an ice sheet formed covering Fennoscandia. Traditionally, Scots pine and many other species were believed to have persisted in glacial refugia in the south, only returning to northern latitudes as the ice retreated. Recent studies have demonstrated the existence of glacial refugia in higher latitudes, in fact, cryptic refugia as far north as Lofoten have been suggested. I investigated the potential existence of such a refugium for Scots pine using mtDNA markers Nad 1-B/C, Nad 7-1 and NODE_new_663. Results show an east/west distribution of the mtDNA polymorphisms at Nad 1 and Nad 7 across Fennoscandia, where multi-locus mitotype bb is more common in the east and ba is more common in the west, in accordance with the hypothesis of a glacial refugium in northeast Europe. Further, the bb mitotype was discovered to be more widespread in Fennoscandia than previously documented. No unique mitotype was discovered in northwestern Fennoscandian populations to support the hypothesis of a glacial refugium along the northwest coast of Norway. Genetic diversity was high and even across Fennoscandia and differences in diversity were not significantly correlated with distance between populations, possibly due to high mutation-rates for the NODE_new_663 minisatellite locus or as a result from admixture between multiple glacial refugia in the area. No conclusive evidence regarding the existence of a glacial refugium in Fennoscandia was discovered and needs to be studied further.

Fire is a natural and essential component of forests in western North America. Fire maintains biodiversity through the creation of different habitat types, and regular fire rotations reduce the accumulation of woody fuels and thick understory plant densities that give rise to catastrophic fire. The practice of fire exclusion has altered western forests and increased the risk of widespread change under rising temperatures projected for the 21st century. To manage for the reintroduction of fire it is critical that we understand the interactions between fire and forest biota in recently fire-suppressed forests. In Chapter 2, I studied the formation and impact of small-scale fire refugia. Fire refugia are areas within burned forest that experienced relatively little change, and are recognized as important places that offer protection for forest biota (vegetation, wildlife) during and after the fire. Very few studies, however, have examined small-scale fire refugia despite their importance to many organisms (e.g., small mammals, understory plants). In a long-term forest monitoring plot in Yosemite National Park, I mapped all unburned areas ≥ 1 m2 the first year after fire. I found small fire refugia were abundant, somewhat predictable, and fostered increased survival and diversity of nearby plant life. My results suggest that small fire refugia are an important component of burned forests that should be included in management considerations. In Chapter 3, I examined possible fisher habitat in burned areas. Fishers are forest carnivores of high conservation concern due to widespread declines since European settlement and the risk of habitat loss due to fire. An isolated population remains in the Sierra National Forest, where managers are weighing the need to reintroduce fire against possible detrimental impacts to current habitat. My research examined the forest structural characteristics (vegetative cover, heights of different forest layers) surrounding fisher dens. I found suitable thresholds of these structural characteristics in recently burned areas in Yosemite, particularly after low-severity fire. My results suggest that burned areas may offer suitable denning habitat for fishers, though more research is needed to determine if this conclusion holds for all fisher activities (e.g., foraging, resting) and scales of selection.

No description available.

Living at the northern limits of its geographic range, the Florida manatee is particularly susceptible to cold stress-related mortality during the winter months, with most deaths occurring in the lower two-thirds of the state. Contributing to this cold stress susceptibility is the manatee's limited physiological and behavioral responses available when thermally stressed. While capable of migrating south in response to falling water temperatures, manatees must still find warm water when ambient river temperature drops below 20°C for more than a few days. This is in part due to the species low metabolic rate, limited capacity for thermogenesis, and limited ability to raise its metabolic rate. Prolonged exposure to cold temperatures may result in cold stress syndrome, which involves a number of potentially life-threatening, if not fatal physiological changes. Survival during the winter months is therefore, dependent upon the manatee's ability to balance basic physiological needs, primarily the need to forage and to obtain fresh water with the need to stay warm. When identifying which animals are most susceptible and where, analyses of statewide manatee mortality records from 1996 through 2011 (n = 823) indicated that, size and location matter. Medium to large-sized calves accounted for the majority of documented death from cold stress (46.6%), while subadults and small calves were the least represented size classes (14.3 % and 9.5%, respectively). Adults slightly outnumbered subadults (15.8%). Males outnumbered females in all size classes but gender differences were not statistically significant. With regards to location, two areas of the state, the southwest and central east coasts showed the highest incidents of cold stress-related mortality. Both are regions with no primary, natural warm-water springs and whose principal warm-water refugia are power plant effluents. Brevard County on the central east coast is the area most at risk during cold weather events accounting for more than 25% of all cold stress deaths statewide. Warm-water sites within this region are few and relatively underrepresented in the literature in an area well-studied in terms of manatee abundance and distribution relative to the operational power plant. Results from cold stress data analyses emphasize the importance of identifying and characterizing the physical attributes of both known and suspected secondary warm-sites used by manatees in this region for both long and short term protection of the species, and its critical habitat. Three locations within Brevard County identified as passive thermal basins (PTBs), and classified as secondary warm-water sites, have been documented supporting in excess of 100 manatees on numerous occasions, and during winters of varying severity. Unique in physical appearance, distance to forage, hydrology including thermal profiles, and when it was used by manatees, each site challenged the accepted definitions and criteria of what constitutes an acceptable and appropriate warm-water site. Through analyses of photo-identification records, site fidelity at two of these warm-water sites, the Berkeley Canal and the Desoto Canal, was established for a minimum of 20 highly identifiable animals, 15 of which used adjacent sites within the same year, and 6 that used both sites but during different years. Observations of daily use patterns within the sites supported optimization of thermoregulation through adjustments in both vertical and horizontal movement, the latter of which seemed to follow the path of the sun. Manatees using the sites also made use of bottom sediment presumably to stay warm at all three locations. Temperature data indicated that water temperatures monitored in the sediment at secondary sites were some of the highest in the county. The predictable movements during all but the coldest weather fronts indicated that manatees utilized these sites during the early morning and afternoon hours when ambient river temperatures were coldest, gradually returning to the river to feed as ambient temperatures began to rise later in the afternoon. The availability of PTBs in proximity to primary warm-water sites within the region may provide an important component needed for manatees to successfully balance the need to forage with the need to stay warm by providing a network that allows for more efficient foraging while reducing exposure to sub-critical ambient river temperatures. The challenge of balancing the need to forage and to maintain homeostasis in the face of thermal stress is complex. This complexity was best approached and better understood through use of a manatee energetics model. The model was designed to facilitate simulation of an unlimited number of different case scenarios involving the exposure of virtually created manatees to a variety of winter conditions as might be experienced by real manatees in a natural system. Sixty-four different simulations were run using six virtual manatees of differing ages, gender, physical parameters, and knowledge of warm-water sites. Simulations were conducted using actual winter water temperature data from Brevard secondary sites and the ambient river from both a mild and a severe winter season. Outcomes, measured as changes in physical parameters indicative of body condition (i.e. mass, percent body fat, blubber depth, girths, etc.), showed that all else being equal, calves in the 2 year-old range fared poorly in all scenarios when compared to individuals of larger size. Subadults fared better than larger adults. This outcome illustrates the complex relationship between size, energy requirements and the synergistic effects of body mass, body fat and blubber thickness on SA:V ratio. Model outcomes agree closely with manatee cold stress mortality analyses predicting that medium to large-sized calves are most susceptible to CS, followed by adults, then subadults. Because all models are simplifications of complex systems, the manatee energetics model is not without its flaws and limitations. The current version of the model could not predict the point at which cold stress mortality would occur. However, a cold stress warning system incorporated into the design alerts the user if potential CSS is likely based on changing physical parameters. Another limitation was the inability of the model to account for the behavioral plasticity of individual subjects since virtual manatees respond to water temperatures based on the user defined rules. A number of additional limitations related to gaps in existing manatee data the gaps were identified and defined. Despite these gaps, the model is designed to allow for incorporation of additional interactions, feedback loops and relevant data as it becomes available and as additional physiological interactions and energy requirements are more clearly defined. Sensitivity analyses, a feature of the model that allowed for modifications in a number of physical as well as environmental parameters, provided an otherwise unlikely opportunity to see how incremental changes in input values, specifically the starting values for mass, percent body fat and blubber depth affected the model's outcome. Ultimately the goal of the model was to facilitate a better understanding of complex relationships by challenging our preconceived understanding of the manatee and its environment.

Lake Victoria is known for its cichlid fish species flock of 500 or more, which have been drastically decreased due to mass extinction. The lake's fisheries transformed from artisanal to industrial, with exotic species displacing the indigenous flock, changes linked to local and global anthropogenic consequences. Cage aquaculture has been established in the lake as a result of dwindling catch fisheries, a growing human population, and increased demand for fish. This dissertation investigates: 1) the distributional ecology of fishes along a limnological gradient in Lake Victoria, Kenya; and 2) the effects of cage aquaculture in the lake on limnology and fish communities, as well as the scientific and social correlates of proper implementation and growth. In April/May and July/August 2017, fish distribution patterns in the lake were surveyed using gillnets at eleven littoral sites and trawls at thirty lake-wide locations. From November 2018 to July 2019, four sites arrayed on an inshore-offshore gradient were sampled using paired cages and control stations. Using established protocols, water quality variables were sampled and analyzed. The status of variables and their associations were investigated using descriptive and exploratory statistics in the R statistical programming language. There was a limnological gradient, with nutrient concentrations, chlorophyll-a, and turbidity decreasing dramatically from the inner gulf to the outer waters. In the gulf's eutrophic waters, indigenous catfishes and cyprinids were abundant, while Nile perch and haplochromines were abundant in the open less eutrophic waters. Along the inner gulf-open lake gradient, Nile perch population structure, size at 50% maturity, and feeding patterns differed. There were no significant variations in environmental metrics between the paired cage farms and the controls, implying that inputs like sewage and agricultural runoff contribute more to eutrophication and the state of the gulf. Near cages, the average monthly total fish biomass was higher than in control areas. In the inner gulf, non-haplochromine fishes were many and diversified, with some species being particularly prevalent near cages. Based on biophysical constraints and overlap between cage aquaculture, fisheries, and biodiversity conservation in the lake, it was projected that cages could yield 250,000 metric tons of Nile tilapia per year. The findings indicate that, when correctly managed, cage aquaculture in Lake Victoria has a positive impact on both biodiversity and economic prosperity in the region.

Adaptive population shifts in response to climate change Ing. Michaela Horníková, Doctoral thesis Abstract Understanding of species' reactions to past climate and environmental changes is a hot topic in many fields of biology as it is relevant also for addressing species' future under the contemporary climate change. Using an emerging model species, the bank vole, I combine genomic phylogeographic data with information on known intraspecific functional variability and environmental niche modelling and aim to elucidate the particular role of intraspecific variation and ultimately selection in shaping the species' response to the climatic and environmental changes after the end of the last glaciation. Based on the mtDNA markers, bank voles exhibit a complex phylogeographic pattern suggesting population replacement events during the postglacial recolonization of Europe and thus possible involvement of selection in the process. An extensive dataset of more than 6000 SNPs was used to search for signs of population replacement in the bank vole genomic DNA and to investigate the species' postglacial recolonization history throughout its European distribution range. The genomic data revealed even more complex population history than previously detected with mtDNA markers, including not only admixture but also...

<p>The objectives of this thesis are to establish a chronological framework for environmental changes during the last 15,000 years in northwest Romania, to reconstruct the vegetation development, and to evaluate the underlying processes for forest dynamics. Furthermore, an overview of earlier and ongoing pollenstratigraphic work in Romania is provided. </p><p>Sediments from two former crater lakes, Preluca Tiganului and Steregoiu, situated in the Gutaiului Mountains, on the western extremity of the Eastern Carpathians at 730 m and 790 m a.s.l., respectively were obtained and analysed for high-resolution pollen, macrofossils, charcoal, mineral magnetic parameters and organic matter. The chronostratigraphic framework was provided by dense AMS ¹⁴C measurements. </p><p>Cold and dry climatic conditions are indicated by the occurrence of open vegetation with shrubs and herbs, and cold lake water prior to 14,700 cal. yr BP. The climatic improvement at the beginning of the Lateglacial interstadial (around 14,700 cal. yr BP) is seen by the development of open forests. These were dominated by <i>Pinus</i> and <i>Betula</i>, but contained also new arriving tree taxa, such as <i>Populus</i>, <i>Alnus</i> and <i>Prunus</i>. The gradual establishment of forests may have led to a stabilization of the soils in the catchment. Between ca. 14,100 and 13,800 cal. yr BP the forest density became reduced to stands of <i>Pinus</i>, <i>Betula</i>, <i>Alnus</i>, <i>Larix</i> and <i>Populus</i> trees and grassland expanded, suggesting colder climatic conditions. <i>Picea</i> arrived as a new taxon at around 13,800 cal. yr BP, and between 13,800 and 12,900 cal. yr BP, the surroundings of the sites were predominantly covered by <i>Picea </i>forest. This forest included <i>Betula</i>, <i>Pinus</i>, <i>Alnus</i>, <i>Larix</i> and <i>Populus</i> and, from 13,200 cal. yr BP onwards also <i>Ulmus</i>. At ca. 12,900 cal. yr BP, the forest became significantly reduced and at 12,600 cal. yr BP, a recurrence of open vegetation with stands of <i>Larix</i>, <i>Pinus</i>, <i>Betula</i>, <i>Salix</i> and <i>Alnus</i> is documented, lasting until 11,500 cal. yr BP. This distinct change in vegetation may by taken as a strong decline in temperature and moisture availability.</p><p>At the transition to the Holocene, at ca. 11,500 cal. yr BP, <i>Pinus</i>, <i>Betula</i> and <i>Larix</i> quickly expanded (from small local stands) and formed open forests, probably as a response to warmer and more humid climatic conditions. At 11,250 cal. yr BP<i> Ulmus</i> and <i>Picea</i> expanded and the landscape became completely forested. The rapid increase of <i>Ulmus</i> and <i>Picea</i> after 11,500 cal. yr BP may suggest the existence of small residual populations close to the study sites during the preceding cold interval. <i>Ulmus</i> was the first and most prominent deciduous taxa in the early Holocene in the Gutaiului Mountains. From ca. 10,750 cal. yr BP onwards <i>Quercus,</i> <i>Tilia</i>, <i>Fraxinus </i>and <i>Acer</i> expanded and <i>Corylus</i> arrived. A highly diverse, predominantly deciduous forest with <i>Ulmus</i>, <i>Quercus</i>, <i>Tilia</i>,<i> Fraxinus</i>, <i>Acer</i>, <i>Corylus</i> and <i>Picea</i> developed between 10,700 and 8200 cal. yr BP, which possibly signifies more continental climatic conditions. The development of a <i>Picea-Corylus</i> dominated forest between 8200 and 5700 cal. yr BP is likely connected to a more humid and cooler climate. The establishment of <i>Carpinus</i> and <i>Fagus</i> was dated to 5750 cal. yr BP and 5200 cal. yr BP, respectively. The dominance of <i>Fagus</i> during the late Holocene, from 4000 cal. yr BP onwards, may have been related to cooler and more humid climatic conditions. First signs of human activities are recorded around 2300 cal. yr BP, but only during the last 300 years did local human impact become significant. </p><p>The vegetation development recorded in the Gutaiului Mountains during the Lateglacial is very similar to reconstructions based on lowland sites, whereas higher elevation sites seem not to have always experienced visible vegetation changes. The time of tree arrival and expansion during the past 11,500 cal. yr BP seems to have occurred almost synchronously across Romania. The composition of the forests during the Holocene in the Gutaiului Mountains is consistent with that reconstructed at mid-elevation sites, but differs from the forest composition at higher elevations. Important differences between the Gutaiului Mountains and other studied sites in Romania are a low representation of <i>Carpinus </i>and a late and weak human impact. </p><p>The available data sets for Romania give evidence for the presence of coniferous and cold-tolerant deciduous trees before 14,700 cal. yr BP. Glacial refugia for <i>Ulmus</i> may have occurred in different parts of Romania, whereas the existence of <i>Quercu</i>s, <i>Tilia</i>, <i>Corylus</i> and <i>Fraxinus</i> has not been corroborated. </p>

Water temperature in rivers and streams is an important factor for aquatic ecosystem health. Measurement of stream temperature has traditionally been accomplished by point temperature measurements, continuous point temperature loggers, and more recently, airborne remote sensing techniques such as Forward-Looking Infrared Radar (FLIR) or Thermal Infrared Radiometry. While each of these measurement techniques has certain advantages, none allows for the combined spatial and temporal information provided by Distributed Temperature Sensing (DTS). DTS employs fiber optic signals to measure temperature and is a relatively new temperature measurement technology for hydrologic sensing applications. Nine DTS stream temperature datasets were collected in the Middle Fork John Day River (MFJDR) as part of a basin-wide stream monitoring effort. The datasets encompassed five 1-3 kilometer long reaches, some monitored over three summers (2009-2011). In contrast to existing stream temperature measurement technologies, DTS can provide stream temperature data in both the spatial and temporal domains. Techniques and challenges of interpreting DTS stream temperature data were documented, and three applications of the technology to stream temperature monitoring were explored. Cold water patches, potentially used by fish as thermal refugia during stream temperature maximums, were located using DTS. No identified cold patch exceeded 2.31°C cooler than ambient stream temperature. Tributary inflows provided some of the most temperature-differentiated cold patches. These findings provide a reference for the degree of thermal heterogeneity in the MFJDR system and beg the question of whether fish respond to small (<3°C) spatial temperature variations. Theoretical predictions of stream mixing potential (Richardson number and cavity flow mixing predictions) suggested that increasing stream thermal heterogeneity would require channel modification to decrease stream flow velocity in select areas. The combined spatial and temporal coverage of a DTS stream temperature dataset on the Oxbow Conservation Area allowed diagnosis of a 2°C longitudinal stream temperature decrease observed in multiple Thermal Infrared Radiometry (TIR) and Forward-Looking Infrared Radiometry (FLIR) datasets collected on that reach. Advection velocity and channel depth, rather than groundwater or tributary inflows, were the main cause of the decrease, and the magnitude of the decrease peaked in the early afternoon, disappearing completely by evening. This finding suggests caution for interpretation of FLIR and TIR stream temperature datasets, which represent "snapshot" temperature measurements. For these datasets, knowledge of flow conditions (velocity and depth) may help avoid misinterpretation of temporally-transient temperature anomalies. Diurnal slope periodicity was observed in linear-like spatial trends in four DTS datasets, and an analysis was made to examine this subtle spatially and temporally varying phenomenon. The phase of the diurnal slope variation differed between river reaches, suggesting that propagation of larger-scale thermal waves might be one driving mechanism. Temporally-constant offsets between slope magnitudes within reaches suggested some intra-reach differences in heat fluxes. / Graduation date: 2012

The objectives of this thesis are to establish a chronological framework for environmental changes during the last 15,000 years in northwest Romania, to reconstruct the vegetation development, and to evaluate the underlying processes for forest dynamics. Furthermore, an overview of earlier and ongoing pollenstratigraphic work in Romania is provided. Sediments from two former crater lakes, Preluca Tiganului and Steregoiu, situated in the Gutaiului Mountains, on the western extremity of the Eastern Carpathians at 730 m and 790 m a.s.l., respectively were obtained and analysed for high-resolution pollen, macrofossils, charcoal, mineral magnetic parameters and organic matter. The chronostratigraphic framework was provided by dense AMS 14C measurements. Cold and dry climatic conditions are indicated by the occurrence of open vegetation with shrubs and herbs, and cold lake water prior to 14,700 cal. yr BP. The climatic improvement at the beginning of the Lateglacial interstadial (around 14,700 cal. yr BP) is seen by the development of open forests. These were dominated by Pinus and Betula, but contained also new arriving tree taxa, such as Populus, Alnus and Prunus. The gradual establishment of forests may have led to a stabilization of the soils in the catchment. Between ca. 14,100 and 13,800 cal. yr BP the forest density became reduced to stands of Pinus, Betula, Alnus, Larix and Populus trees and grassland expanded, suggesting colder climatic conditions. Picea arrived as a new taxon at around 13,800 cal. yr BP, and between 13,800 and 12,900 cal. yr BP, the surroundings of the sites were predominantly covered by Picea forest. This forest included Betula, Pinus, Alnus, Larix and Populus and, from 13,200 cal. yr BP onwards also Ulmus. At ca. 12,900 cal. yr BP, the forest became significantly reduced and at 12,600 cal. yr BP, a recurrence of open vegetation with stands of Larix, Pinus, Betula, Salix and Alnus is documented, lasting until 11,500 cal. yr BP. This distinct change in vegetation may by taken as a strong decline in temperature and moisture availability. At the transition to the Holocene, at ca. 11,500 cal. yr BP, Pinus, Betula and Larix quickly expanded (from small local stands) and formed open forests, probably as a response to warmer and more humid climatic conditions. At 11,250 cal. yr BP Ulmus and Picea expanded and the landscape became completely forested. The rapid increase of Ulmus and Picea after 11,500 cal. yr BP may suggest the existence of small residual populations close to the study sites during the preceding cold interval. Ulmus was the first and most prominent deciduous taxa in the early Holocene in the Gutaiului Mountains. From ca. 10,750 cal. yr BP onwards Quercus, Tilia, Fraxinus and Acer expanded and Corylus arrived. A highly diverse, predominantly deciduous forest with Ulmus, Quercus, Tilia, Fraxinus, Acer, Corylus and Picea developed between 10,700 and 8200 cal. yr BP, which possibly signifies more continental climatic conditions. The development of a Picea-Corylus dominated forest between 8200 and 5700 cal. yr BP is likely connected to a more humid and cooler climate. The establishment of Carpinus and Fagus was dated to 5750 cal. yr BP and 5200 cal. yr BP, respectively. The dominance of Fagus during the late Holocene, from 4000 cal. yr BP onwards, may have been related to cooler and more humid climatic conditions. First signs of human activities are recorded around 2300 cal. yr BP, but only during the last 300 years did local human impact become significant. The vegetation development recorded in the Gutaiului Mountains during the Lateglacial is very similar to reconstructions based on lowland sites, whereas higher elevation sites seem not to have always experienced visible vegetation changes. The time of tree arrival and expansion during the past 11,500 cal. yr BP seems to have occurred almost synchronously across Romania. The composition of the forests during the Holocene in the Gutaiului Mountains is consistent with that reconstructed at mid-elevation sites, but differs from the forest composition at higher elevations. Important differences between the Gutaiului Mountains and other studied sites in Romania are a low representation of Carpinus and a late and weak human impact. The available data sets for Romania give evidence for the presence of coniferous and cold-tolerant deciduous trees before 14,700 cal. yr BP. Glacial refugia for Ulmus may have occurred in different parts of Romania, whereas the existence of Quercus, Tilia, Corylus and Fraxinus has not been corroborated.