901 resultados para Comparative and Evolutionary Physiology
Resumo:
Stream restoration often focuses on increasing habitat heterogeneity to reverse ecosystem degradation. However, the connection between heterogeneity and ecosystem structure and processes is poorly understood. We looked to investigate this interaction from both applied and basic science perspectives. For the applied study, we examined two culvert replacements designed to mimic natural stream channels, to see if they were better at maintaining ecosystem processes within as well as upstream and downstream of culverts compared to non-replaced culverts. We measured three ecosystem processes (nutrient uptake, hydrologic characteristics, and coarse particulate organic matter retention) and found that stream simulation culvert restoration improved organic matter retention within culverts, and that there were no differences in processes measured upstream and downstream of both restoration designs. Our results suggest that measurements of ecosystem processes are more likely to show a response to restoration if they match the scale of the restoration activity. For the basic science study, we quantified the longitudinal spatial heterogeneity of physical and biofilm characteristics at microhabitat to segment scales on streams with different streambed variability. We found that all physical characteristics and biofilm characteristics were spatially independent at the macro-habitat scale and greater. Together, these studies demonstrate the importance of scale in ecological interactions and the value of incorporating considerations of scale into restoration activities.
Resumo:
Patterns of increasing leaf mass per area (LMA), area-based leaf nitrogen (Narea), and carbon isotope composition (δ13C) with increasing height in the canopy have been attributed to light gradients or hydraulic limitation in tall trees. Theoretical optimal distributions of LMA and Narea that scale with light maximize canopy photosynthesis; however, sub-optimal distributions are often observed due to hydraulic constraints on leaf development. Using observational, experimental, and modeling approaches, we investigated the response of leaf functional traits (LMA, density, thickness, and leaf nitrogen), leaf carbon isotope composition (δ13C), and cellular structure to light availability, height, and leaf water potential (Ψl) in an Acer saccharum forest to tease apart the influence of light and hydraulic limitations. LMA, leaf and palisade layer thickness, and leaf density were greater at greater light availability but similar heights, highlighting the strong control of light on leaf morphology and cellular structure. Experimental shading decreased both LMA and area-based leaf nitrogen (Narea) and revealed that LMA and Narea were more strongly correlated with height earlier in the growing season and with light later in the growing season. The supply of CO2 to leaves at higher heights appeared to be constrained by stomatal sensitivity to vapor pressure deficit (VPD) or midday leaf water potential, as indicated by increasing δ13C and VPD and decreasing midday Ψl with height. Model simulations showed that daily canopy photosynthesis was biased during the early growing season when seasonality was not accounted for, and was biased throughout the growing season when vertical gradients in LMA and Narea were not accounted for. Overall, our results suggest that leaves acclimate to light soon after leaf expansion, through an accumulation of leaf carbon, thickening of palisade layers and increased LMA, and reduction in stomatal sensitivity to Ψl or VPD. This period of light acclimation in leaves appears to optimize leaf function over time, despite height-related constraints early in the growing season. Our results imply that vertical gradients in leaf functional traits and leaf acclimation to light should be incorporated in canopy function models in order to refine estimates of canopy photosynthesis.
Resumo:
Quantifying belowground dynamics is critical to our understanding of plant and ecosystem function and belowground carbon cycling, yet currently available tools for complex belowground image analyses are insufficient. We introduce novel techniques combining digital image processing tools and geographic information systems (GIS) analysis to permit semi-automated analysis of complex root and soil dynamics. We illustrate methodologies with imagery from microcosms, minirhizotrons, and a rhizotron, in upland and peatland soils. We provide guidelines for correct image capture, a method that automatically stitches together numerous minirhizotron images into one seamless image, and image analysis using image segmentation and classification in SPRING or change analysis in ArcMap. These methods facilitate spatial and temporal root and soil interaction studies, providing a framework to expand a more comprehensive understanding of belowground dynamics.
Resumo:
Herbivory requires animals to manage intake of toxic phytochemicals. Detoxification and excretion of these chemicals prevents toxicity, but is energetically expensive. I investigated the relationship between investment in detoxification and nutritional condition for moose on Isle Royale National Park (Alces alces) during winter, using urinary indices from urine samples collected in snow. The ratio of urinary urea nitrogen:creatinine is an indicator of nutritional condition, and the ratio of glucuronic acid:creatinine is an indicator of investment in detoxification. Nutritional condition declined with greater investment in detoxification. An alternative means of managing defensive chemical intake is to diversify the diet. Microhistological analysis of fecal pellets determined diet composition. Diet diversity was weakly associated with improved nutritional condition. However, the strongest predictors of nutritional condition were winter severity and proportion of balsam fir in the diet (a dominant food for moose in this ecosystem).
Resumo:
Ungulates are important components of a variety of ecosystems worldwide. This dissertation integrates aspects of ungulate and forest ecology to increase our understanding of how they work together in ways that are of interest to natural resource managers, educators, and those who are simply curious about nature. Although animal ecology and ecosystem ecology are often studied separately, one of the general goals of this dissertation is to examine how they interact across spatial and temporal scales. Forest ecosystems are heterogeneous across a range of scales. Spatial and temporal habitat use patterns of forest ungulates tend to be congregated in patches where food and/or cover are readily available. Ungulates interact with ecosystem processes by selectively foraging on plants and excreting waste products in concentrated patches. Positive feedbacks may develop where these activities increase the value of habitat through soil fertilization or the alteration of plant chemistry and architecture. Heterogeneity in ecosystem processes and plant community structure, observed at both stand and local scales, may be the integrated outcome of feedbacks between ungulate behavior and abiotic resource gradients. The first chapter of this dissertation briefly discusses pertinent background information on ungulate ecology, with a focus on white-tailed deer (Odocoileus virginianus) in the Upper Great Lakes region and moose (Alces acles) in Isle Royale National Park, Michigan, USA. The second chapter demonstrates why ecological context is important for studying ungulate ecology in forest ecosystems. Excluding deer from eastern hemlock (Tsuga canadensis) stands, which deer use primarily as winter cover, resulted in less spatial complexity in soil reactive nitrogen and greater complexity in diffuse light compared to unfenced stands. The spatial patterning of herbaceous-layer cover was more similar to nitrogen where deer were present, and was a combination of nitrogen and light within deer exclosures. This relationship depends on the seasonal timing of deer habitat use because deer fertilize the soil during winter, but leave during the growing season. The third chapter draws upon an eight-year, 39-stand data set of deer fecal pellet counts in hemlock stands to estimate the amount of nitrogen that deer are depositing in hemlock stands each winter. In stands of high winter deer use, deer-excreted nitrogen inputs consistently exceeded those of atmospheric deposition at the stand scale. At the neighborhood scale, deer-excreted nitrogen was often in excess of atmospheric deposition due to the patchy distribution of deer habitat use. Spatial patterns in habitat use were consistent over the eight-year study at both stand and neighborhood scales. The fourth chapter explores how foraging selectivity by moose interacts with an abiotic resource gradient to influence forest structure and composition. Soil depth on Isle Royale varies from east to west according to glacial history. Fir saplings growing in deeper soils on the west side are generally more palatable forage for moose (lower foliar C:N) than those growing in shallower soils on the east side. Therefore, saplings growing in better conditions are less likely to reach the canopy due to moose browsing, and fir is a smaller overstory component on the west side. Lastly, chapter five focuses on issues surrounding eastern hemlock regeneration failure, which is a habitat type that is important to many wildlife species. Increasing hemlock on the landscape is complicated by several factors including disturbance regime and climate change, in addition to the influence of deer.
Resumo:
Silver Bow Creek runs approximately 25 miles from Butte to Warm Springs, where it joins Warm Springs Creek to form the Clark Fork River. This historic creek was terribly contaminated with mine wastes around the turn of the 20th century, leaving many "slickens" that persisted into the 21st century, when it became a Superfund remediation project. More than 5.5 million cubic yards of stream-deposited mine waste have been removed and 1,650 acres revegetated. Chief contaminants are copper, zinc, and arsenic, but acidic soils are often equally or more limiting to plants. The stream was relocated, and mine wastes were replaced with biologically inert cover soil. Richard A. Prodgers is currently a plant ecologist with Bighorn Environmental Sciences in Dillon, Montana.
Resumo:
Local hypoxia, as due to trauma, surgery, or arterial occlusive disease, may severely jeopardize the survival of the affected tissue and its wound-healing capacity. Initially developed to replace blood transfusions, artificial oxygen carriers have emerged as oxygen therapeutics in such conditions. The aim of this study was to target primary wound healing and survival in critically ischemic skin by the systemic application of left-shifted liposomal hemoglobin vesicles (HbVs). This was tested in bilateral, cranially based dorsal skin flaps in mice treated with a HbV solution with an oxygen affinity that was increased to a P(50) (partial oxygen tension at which the hemoglobin becomes 50% saturated with oxygen) of 9 mmHg. Twenty percent of the total blood volume of the HbV solution was injected immediately and 24 h after surgery. On the first postoperative day, oxygen saturation in the critically ischemic middle flap portions was increased from 23% (untreated control) to 39% in the HbV-treated animals (P < 0.05). Six days postoperatively, flap tissue survival was increased from 33% (control) to 57% (P < 0.01) and primary healing of the ischemic wound margins from 6.6 to 12.7 mm (P < 0.05) after HbV injection. In addition, higher capillary counts and endothelial nitric oxide synthase expression (both P < 0.01) were found in the immunostained flap tissue. We conclude that left-shifted HbVs may ameliorate the survival and primary wound healing in critically ischemic skin, possibly mediated by endothelial nitric oxide synthase-induced neovascularization.
Resumo:
This investigation was based on 23 isolates from several European countries collected over the past 30 years, and included characterization of all isolates. Published data on amplified fragment length polymorphism typing of isolates representing all biovars as well as protein profiles were used to select strains that were then further characterized by polyamine profiling and sequencing of 16S rRNA, infB, rpoB and recN genes. Comparison of 16S rRNA gene sequences revealed a monophyletic group within the avian 16S rRNA group of the Pasteurellaceae, which currently includes the genera Avibacterium, Gallibacterium and Volucribacter. Five monophyletic subgroups related to Gallibacterium anatis were recognized by 16S rRNA, rpoB, infB and recN gene sequence comparisons. Whole-genome similarity between strains of the five subgroups and the type strain of G. anatis calculated from recN sequences allowed us to classify them within the genus Gallibacterium. In addition, phenotypic data including biochemical traits, protein profiling and polyamine patterns clearly indicated that these taxa are related. Major phenotypic diversity was observed for 16S rRNA gene sequence groups. Furthermore, comparison of whole-genome similarities, phenotypic data and published data on amplified fragment length polymorphism and protein profiling revealed that each of the five groups present unique properties that allow the proposal of three novel species of Gallibacterium, for which we propose the names Gallibacterium melopsittaci sp. nov. (type strain F450(T) =CCUG 36331(T) =CCM 7538(T)), Gallibacterium trehalosifermentans sp. nov. (type strain 52/S3/90(T) =CCUG 55631(T) =CCM 7539(T)) and Gallibacterium salpingitidis sp. nov. (type strain F150(T) =CCUG 15564(T) =CCUG 36325(T) =NCTC 11414(T)), a novel genomospecies 3 of Gallibacterium and an unnamed taxon (group V). An emended description of the genus Gallibacterium is also presented.
Resumo:
The Mycoplasma mycoides cluster consists of six pathogenic mycoplasmas causing disease in ruminants, which share many genotypic and phenotypic traits. The M. mycoides cluster comprises five recognized taxa: Mycoplasma mycoides subsp. mycoides Small Colony (MmmSC), M. mycoides subsp. mycoides Large Colony (MmmLC), M. mycoides subsp. capri (Mmc), Mycoplasma capricolum subsp. capricolum (Mcc) and M. capricolum subsp. capripneumoniae (Mccp). The group of strains known as Mycoplasma sp. bovine group 7 of Leach (MBG7) has remained unassigned, due to conflicting data obtained by different classification methods. In the present paper, all available data, including recent phylogenetic analyses, have been reviewed, resulting in a proposal for an emended taxonomy of this cluster: (i) the MBG7 strains, although related phylogenetically to M. capricolum, hold sufficient characteristic traits to be assigned as a separate species, i.e. Mycoplasma leachii sp. nov. (type strain, PG50(T) = N29(T) = NCTC 10133(T) = DSM 21131(T)); (ii) MmmLC and Mmc, which can only be distinguished by serological methods and are related more distantly to MmmSC, should be combined into a single subspecies, i.e. Mycoplasma mycoides subsp. capri, leaving M. mycoides subsp. mycoides (MmmSC) as the exclusive designation for the agent of contagious bovine pleuropneumonia. A taxonomic description of M. leachii sp. nov. and emended descriptions of M. mycoides subsp. mycoides and M. mycoides subsp. capri are presented. As a result of these emendments, the M. mycoides cluster will hereafter be composed of five taxa comprising three subclusters, which correspond to the M. mycoides subspecies, the M. capricolum subspecies and the novel species M. leachii.
Resumo:
The objective of this paper is to discuss EU lobbying in the area of copyright. Legislation needs to regulate the legal position of various different stakeholders in a balanced manner. However, a number of EU copyright provisions brought into effect over recent years were highly controversial and have led to suggestions that powerful lobbying forces may have had some influence. This article investigates the effects of lobbying on copyright law-making in Europe. A specific comparative and multi-faceted analysis is provided of the legislative process for two recently adopted directives: 2011/77/EU which extends the term of protection of sound recordings and 2012/28/EU which introduces certain permitted uses of orphan works (some references are also made to the ACTA case). Firstly, a short presentation is given of the legal bases for the EU consultation process and lobbying. Next, an analysis is provided of the two cases, taking into consideration the policy-making procedures (with special focus on how the consultation process was handled), the legal solutions proposed and adopted and the various stakeholders’ claims. Lastly, it asks why some interest groups were successful and some others failed (the analysis identifies two types of factor for the effectiveness of lobbying: those resulting from stakeholders’ actions and those connected with the consultation process).
Resumo:
Genetic relationships among bacterial strains belonging to the genus Aeromonas were inferred from 16S rRNA, gyrB and rpoB gene sequences. Twenty-eight type or collection strains of the recognized species or subspecies and 33 Aeromonas strains isolated from human and animal specimens as well as from environmental samples were included in the study. As reported previously, the 16S rRNA gene sequence is highly conserved within the genus Aeromonas, having only limited resolution for this very tight group of species. Analysis of a 1.1 kb gyrB sequence confirmed that this gene has high resolving power, with maximal interspecies divergence of 15.2 %. Similar results were obtained by sequencing only 517 bp of the rpoB gene, which showed maximal interspecies divergence of 13 %. The topologies of the gyrB- and rpoB-derived trees were similar. The results confirm the close relationship of species within the genus Aeromonas and show that a phylogenetic approach including several genes is suitable for improving the complicated taxonomy of the genus.
Resumo:
The aim of this study was to improve the definition and identification of a group of veterinarily important bacteria referred to as the [Pasteurella] aerogenes-[Pasteurella] mairii-[Actinobacillus] rossii complex. These organisms have mainly been isolated from the reproductive and intestinal tracts of pigs and in most cases have been considered as opportunistic pathogens. A collection of 87 strains were characterized by phenotypic analysis from which 41 strains were selected for 16S rRNA gene sequence comparison, out of which 23 have been sequenced in the present study. One group of 21 strains phenotyped as biovars 1, 3-5, 9-11, 19 and 25-27, including the type strain of [P.] aerogenes, showed 16S rRNA gene sequence similarities of 99.6 % or higher; another group of 18 strains including biovars 2, 6-8, 12-15, 21, 23, 24 and 26A and the type strain of [A.] rossii showed 97.8 % or higher 16S rRNA gene sequence similarity. Between the two groups, 93.8-95.7 % 16S rRNA gene sequence similarity was observed. Strains of [P.] mairii showed 99.5 % similarity, with 95.5-97.2 and 93.8-95.5 % similarity to strains of [P.] aerogenes and [A.] rossii, respectively. Four strains could not be classified with any of these groups and belonged to other members of Pasteurellaceae. Comparisons were also made to DNA-DNA hybridization data. Biovars 1, 9, 10, 11 and 19, including the type strain of [P.] aerogenes, linked at 70 % DNA reassociation, whereas strains identified as biovars 2, 6, 7, 8, 12, 15 and 21 of [P.] aerogenes linked at 81 %. The latter group most likely represents [A.] rossii based on the 16S rRNA gene sequence comparisons. DNA reassociation between the [P.] aerogenes and [A.] rossii groups was at most 37 %, whereas 47 % was the highest DNA reassociation found between [P.] aerogenes and [P.] mairii. The study showed that [P.] aerogenes, [P.] mairii and [A.] rossii can not be easily separated and may consequently be misidentified based on current knowledge of their phenotypic characteristics. In addition, these taxa are difficult to separate from other taxa of the Pasteurellaceae. A revised scheme for separation based upon phenotypic characters is suggested for the three species [P.] aerogenes emend., [P.] mairii emend. and [A.] rossii emend., with the respective type strains ATCC 27883T, NCTC 10699T and ATCC 27072T.
Resumo:
Earlier investigations have shown that 'Haemophilus somnus', 'Haemophilus agni' and 'Histophilus ovis' represent the same species. In the present investigation, the taxonomic position of this species is explored further by sequencing the 16S rRNA and rpoB genes of strains that were investigated previously by DNA-DNA hybridization. These results clearly support the allocation of this species to a novel genus within the family PASTEURELLACEAE: The phenotypic separation of Histophilus somni gen. nov., sp. nov. from other members of the family can, for most strains, be based on capnophilia, yellowish pigmentation and indole production. However, due to phenotypic variation, the use of a species-specific PCR test based on the 16S rRNA gene is included in the species description. This is justified by the high sequence similarity of the 16S rRNA gene within the species and the fact that the highest sequence similarity to any other taxon within the family is 93.4 %. The type strain, 8025(T)=ATCC 43625(T)=CCUG 36157(T), was isolated in the USA from a bovine brain with lesions of thromboembolic meningoencephalitis.
Resumo:
Prevotella nigrescens, Prevotella intermedia and Porphyromonas gingivalis are oral pathogens from the family Bacteroidaceae, regularly isolated from cases of gingivitis and periodontitis. In this study, the phylogenetic variability of these three bacterial species was investigated by means of 16S rRNA (rrs) gene sequence comparisons of a set of epidemiologically and geographically diverse isolates. For each of the three species, the rrs gene sequences of 11 clinical isolates as well as the corresponding type strains was determined. Comparison of all rrs sequences obtained with those of closely related species revealed a clear clustering of species, with only a little intraspecies variability but a clear difference in the rrs gene with respect to the next related taxon. The results indicate that the three species form stable, homogeneous genetic groups, which favours an rrs-based species identification of these oral pathogens. This is especially useful given the 7% sequence divergence between Prevotella intermedia and Prevotella nigrescens, since phenotypic distinction between the two Prevotella species is inconsistent or involves techniques not applicable in routine identification.