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  • 1
    Electronic Resource
    Electronic Resource
    Penguins, fur seals, and fishing: prey requirements and potential competition in the South Shetland Islands, Antarctica (1998)
    Springer
    Polar biology 19 (1998), S. 365-374 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Antarctic and sub-Antarctic seabirds, marine mammals, and human fisheries concentrate their foraging efforts on a single species, Antarctic krill (Euphausiasuperba). Because these predators may have a significant effect on krill abundance, we estimated the energy and prey requirements of Adelie (Pygoscelisadeliae), chinstrap (Pygoscelisantarctica), and gentoo (Pygoscelispapua) penguins and female Antarctic fur seals (Arctocephalusgazella) breeding on the South Shetland Islands, Antarctica and compared these estimates with catch statistics from the Antarctic krill fishery. Published data on field metabolic rate, population size, diet, prey energy content, and metabolic efficiency were used to estimate prey requirements of these breeding, adult, land-based predators and their dependent offspring. Due to their large population size, chinstrap penguins were the most significant krill predators during the period examined, consuming an estimated 7.8 × 108 kg krill, followed by Adelie penguins (3.1 × 107 kg), gentoo penguins (1.2 × 107 kg), and Antarctic fur seals (3.6 × 106 kg). Total consumption of all land-based predators on the South Shetland Islands was estimated at 8.3 × 108 kg krill. The commercial krill fishery harvest in the South Shetland Island region (1.0 × 108 kg) was approximately 12% of this. Commercial harvest coincides seasonally and spatially with peak penguin and fur seal prey demands, and may affect prey availability to penguins and fur seals. This differs from the conclusions of Ichii et al. who asserted that the potential for competition between South Shetland predators and the commercial krill fishery is low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050261
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of submergence on heart rate and oxygen consumption of swimming seals and sea lions (1991)
    Springer
    Journal of comparative physiology 160 (1991), S. 637-644 
    Details
    ISSN: 1432-136X
    Keywords: Heart rate ; Oxygen consumption ; Harbor seal ; Sea lion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Respiratory, metabolic, and cardiovascular responses to swimming were examined in two species of pinniped, the harbor seal (Phoca vitulina) and the California sea lion(Zalophus californianus). 1. Harbor seals remained submerged for 82–92% of the time at swimming speeds below 1.2 m·s-1. At higher speeds, including simulated speeds above 1.4 m·s-1, the percentage of time spent submerged decreased, and was inversely related to body weight. In contrast, the percentage of time spent submerged did not change with speed for sea lions swimming from 0.5 m·s-1 to 4.0 m·s-1. 2. During swimming, harbor seals showed a distinct breathhold bradycardia and ventilatory tachycardia that were independent of swimming speed. Average heart rate was 137 beats·min-1 when swimming on the water surface and 50 beats·min-1 when submerged. A bimodal pattern of heart rate also occurred in sea lions, but was not as pronounced as in the seals. 3. The weighted average heart rate (WAHR), calculated from measured heart rate and the percentage time spent on the water surface or submerged, increased linearly with swimming speed for both species. The graded increase in heart rate with exercise load is similar to the response observed for terrestrial mammals. 4. The rate of oxygen consumption increased exponentially with swimming speed in both seals and sea lions. The minimum cost of transport calculated from these rates ranged from 2.3 to 3.6 J · m-1 · kg-1, and was 2.5–4.0 times the level predicted for similarly-sized salmonids. Despite different modes of propulsion and physiological responses to swimming, these pinnipeds demonstrate similar transport costs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571261
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Diving metabolism and thermoregulation in common and thick-billed murres (1993)
    Springer
    Journal of comparative physiology 163 (1993), S. 160-166 
    Details
    ISSN: 1432-136X
    Keywords: Metabolism ; Diving ; Thermoregulation ; Energetics ; Seabird, Uria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The diving and thermoregulatory metabolic rates of two species of diving seabrid, common (Uria aalge) and thick-billed murres (U. lomvia), were studied in the laboratory. Post-absorptive resting metabolic rates were similar in both species, averaging 7.8 W·kg-1, and were not different in air or water (15–20°C). These values were 1.5–2 times higher than values predicted from published allometric equations. Feeding led to increases of 36 and 49%, diving caused increases of 82 and 140%, and preening led to increases of 107 and 196% above measured resting metabolic rates in common and thick-billed murres, respectively. Metabolic rates of both species increased linearly with decreasing water temperature; lower critical temperature was 15°C in common murres and 16°C in thick-billed murres. Conductance (assuming a constant body temperature) did not change with decreasing temperature, and was calculated at 3.59 W·m-2·oC-1 and 4.68 W·m-2·oC-1 in common and thick-billed murres, respectively. Murres spend a considerable amount of time in cold water which poses a significant thermal challenge to these relatively small seabirds. If thermal conductance does not change with decreasing water temperature, murres most likely rely upon increasing metabolism to maintain body temperature. The birds probably employ activities such as preening, diving, or food-induced thermogenesis to meet this challenge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263602
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  • 4
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    Genome-scale phylogenies reveal relationships among Parastagonospora species infecting domesticated and wild grasses (2021)
    Naturalis Biodiversity Center
    In:  Persoonia - Molecular Phylogeny and Evolution of Fungi vol. 46, pp. 116-128
    Details
    Publication Date: 2024-04-08
    Description: Several plant pathogenic Parastagonospora species have been identified infecting wheat and other cereals over the past 50 years. As new lineages were discovered, naming conventions grew unwieldy and the relationships with previously recognized species remained unclear. We used genome sequencing to clarify relationships among these species and provided new names for most of these species. Six of the nine described Parastagonospora species were recovered from wheat, with five of these species coming from Iran. Genome sequences revealed that three strains thought to be hybrids between P. nodorum and P. pseudonodorum were not actually hybrids, but rather represented rare gene introgressions between those species. Our data are consistent with the hypothesis that P. nodorum originated as a pathogen of wild grasses in the Fertile Crescent, then emerged as a wheat pathogen via host-tracking during the domestication of wheat in the same region. The discovery of a diverse array of Parastagonospora species infecting wheat in Iran suggests that new wheat pathogens could emerge from this region in the future.
    Keywords: Ecology ; Evolution ; Behavior and Systematics
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 5
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    Coevolution and Life Cycle Specialization of Plant Cell Wall Degrading Enzymes in a Hemibiotrophic Pathogen (2013)
    Oxford University Press
    Details
    Publication Date: 2013-05-10
    Description: Zymoseptoria tritici is an important fungal pathogen on wheat that originated in the Fertile Crescent. Its closely related sister species Z. pseudotritici and Z. ardabiliae infect wild grasses in the same region. This recently emerged host–pathogen system provides a rare opportunity to investigate the evolutionary processes shaping the genome of an emerging pathogen. Here, we investigate genetic signatures in plant cell wall degrading enzymes (PCWDEs) that are likely affected by or driving coevolution in plant-pathogen systems. We hypothesize four main evolutionary scenarios and combine comparative genomics, transcriptomics, and selection analyses to assign the majority of PCWDEs in Z. tritici to one of these scenarios. We found widespread differential transcription among different members of the same gene family, challenging the idea of functional redundancy and suggesting instead that specialized enzymatic activity occurs during different stages of the pathogen life cycle. We also find that natural selection has significantly affected at least 19 of the 48 identified PCWDEs. The majority of genes showed signatures of purifying selection, typical for the scenario of conserved substrate optimization. However, six genes showed diversifying selection that could be attributed to either host adaptation or host evasion. This study provides a powerful framework to better understand the roles played by different members of multigene families and to determine which genes are the most appropriate targets for wet laboratory experimentation, for example, to elucidate enzymatic function during relevant phases of a pathogen’s life cycle.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 6
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    The Impact of Recombination Hotspots on Genome Evolution of a Fungal Plant Pathogen [Population and Evolutionary Genetics] (2015)
    Genetics Society of America (GSA)
    In: Genetics
    Details
    Publication Date: 2015-11-13
    Description: Recombination has an impact on genome evolution by maintaining chromosomal integrity, affecting the efficacy of selection, and increasing genetic variability in populations. Recombination rates are a key determinant of the coevolutionary dynamics between hosts and their pathogens. Historic recombination events created devastating new pathogens, but the impact of ongoing recombination in sexual pathogens is poorly understood. Many fungal pathogens of plants undergo regular sexual cycles, and sex is considered to be a major factor contributing to virulence. We generated a recombination map at kilobase-scale resolution for the haploid plant pathogenic fungus Zymoseptoria tritici . To account for intraspecific variation in recombination rates, we constructed genetic maps from two independent crosses. We localized a total of 10,287 crossover events in 441 progeny and found that recombination rates were highly heterogeneous within and among chromosomes. Recombination rates on large chromosomes were inversely correlated with chromosome length. Short accessory chromosomes often lacked evidence for crossovers between parental chromosomes. Recombination was concentrated in narrow hotspots that were preferentially located close to telomeres. Hotspots were only partially conserved between the two crosses, suggesting that hotspots are short-lived and may vary according to genomic background. Genes located in hotspot regions were enriched in genes encoding secreted proteins. Population resequencing showed that chromosomal regions with high recombination rates were strongly correlated with regions of low linkage disequilibrium. Hence, genes in pathogen recombination hotspots are likely to evolve faster in natural populations and may represent a greater threat to the host.
    Print ISSN: 0016-6731
    Topics: Biology
    Published by Genetics Society of America (GSA)
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  • 7
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    Global benefits of invasive mammal eradication [Applied Biological Sciences] (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-04-13
    Description: More than US$21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction....
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Globally threatened vertebrates on islands with invasive species (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2017-10-26
    Description: Global biodiversity loss is disproportionately rapid on islands, where invasive species are a major driver of extinctions. To inform conservation planning aimed at preventing extinctions, we identify the distribution and biogeographic patterns of highly threatened terrestrial vertebrates (classified by the International Union for Conservation of Nature) and invasive vertebrates on ~465,000 islands worldwide by conducting a comprehensive literature review and interviews with more than 500 experts. We found that 1189 highly threatened vertebrate species (319 amphibians, 282 reptiles, 296 birds, and 292 mammals) breed on 1288 islands. These taxa represent only 5% of Earth’s terrestrial vertebrates and 41% of all highly threatened terrestrial vertebrates, which occur in 〈1% of islands worldwide. Information about invasive vertebrates was available for 1030 islands (80% of islands with highly threatened vertebrates). Invasive vertebrates were absent from 24% of these islands, where biosecurity to prevent invasions is a critical management tool. On the 76% of islands where invasive vertebrates were present, management could benefit 39% of Earth’s highly threatened vertebrates. Invasive mammals occurred in 97% of these islands, with Rattus sp. as the most common invasive vertebrate (78%; 609 islands). Our results provide an important baseline for identifying islands for invasive species eradication and other island conservation actions that reduce biodiversity loss.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Hitchhiking Selection Is Driving Intron Gain in a Pathogenic Fungus (2014)
    Oxford University Press
    Details
    Publication Date: 2014-06-26
    Description: The variability of intron density among eukaryotes is puzzling and still debated. Most previous studies have been limited because of the near absence of intron presence–absence polymorphism (IPAP) within species or because comparisons could be made only between distantly related species. We conducted population genetic analyses on eight loci showing IPAP to investigate the effect of natural selection on intron dynamics in a global collection of the panmictic fungal plant pathogen Zymoseptoria tritici and its very close relatives. Five of these loci likely represent recent intron gains because their absence is fixed among the closest relatives of Z. tritici , and three likely represent recent intron losses because their presence is fixed among the close relatives. We analyzed signatures of selection by comparing allele frequencies, nucleotide diversities, and rates of recombination and found compelling evidence that at least two out of the five intron-gain loci, a SWIM zinc-finger gene and a sugar transporter, are under directional selection favoring alleles that gained the intron. Our results suggest that the intron-present alleles of these loci are sweeping to fixation, providing a genetic hitchhiking mechanism to explain rapid intron gain in Z. tritici . The overall findings are consistent with the hypothesis that intron gains are more likely to be driven by selection while intron losses are more likely to be due to neutral processes such as genetic drift.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 10
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    Quantitative Trait Locus Mapping of Melanization in the Plant Pathogenic Fungus Zymoseptoria tritici (2014)
    Genetics Society of America (GSA)
    Details
    Publication Date: 2014-12-16
    Description: Melanin plays an important role in virulence and antimicrobial resistance in several fungal pathogens. The wheat pathogen Zymoseptoria tritici is important worldwide, but little is known about the genetic architecture of pathogenicity, including the production of melanin. Because melanin production can exhibit complex inheritance, we used quantitative trait locus (QTL) mapping in two crosses to identify the underlying genes. Restriction site–associated DNA sequencing was used to genotype 263 (cross 1) and 261 (cross 2) progeny at ~8500 single-nucleotide polymorphisms and construct two dense linkage maps. We measured gray values, representing degrees of melanization, for single-spore colonies growing on Petri dishes by using a novel image-processing approach that enabled high-throughput phenotyping. Because melanin production can be affected by stress, each offspring was grown in two stressful environments and one control environment. We detected six significant QTL in cross 1 and nine in cross 2, with three QTL shared between the crosses. Different QTL were identified in different environments and at different colony ages. By obtaining complete genome sequences for the four parents and analyzing sequence variation in the QTL confidence intervals, we identified 16 candidate genes likely to affect melanization. One of these candidates was PKS1 , a polyketide synthase gene known to play a role in the synthesis of dihydroxynaphthalene melanin. Three candidate quantitative trait nucleotides were identified in PKS1 . Many of the other candidate genes were not previously associated with melanization.
    Electronic ISSN: 2160-1836
    Topics: Biology
    Published by Genetics Society of America (GSA)
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