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  • 1
    Language: English
    In: Science (New York, N.Y.), 04 January 2013, Vol.339(6115), pp.38-9
    Description: The ribosome is a versatile enzyme, but it cannot synthesize all proteins equally well--certain combinations of amino acids pose problems. Ribosome stalling by fairly long amino acid motifs can regulate gene expression in a variety of organisms, from bacteria to humans (, ). In these cases, the nascent peptide interacts with the peptide exit channel of the ribosome to induce a conformation that prevents peptide bond formation. Two papers in this issue, by Doerfel et al. on page 85 and Ude et al. on page 82 , reveal that stalling is common and fundamental: Short, proline (Pro)-rich motifs impede protein synthesis, and stalling is alleviated by a poorly understood elongation factor, EF-P. These studies offer a model of the biological function and mechanism of EF-P through a convergence of biochemical and genetic methods. [PUBLICATION ]
    Keywords: Peptide Chain Elongation, Translational ; Escherichia Coli -- Metabolism ; Escherichia Coli Proteins -- Biosynthesis ; Peptide Elongation Factors -- Metabolism ; Peptides -- Metabolism ; Proline -- Metabolism ; Ribosomes -- Metabolism ; Trans-Activators -- Biosynthesis
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 2
    Language: English
    In: Oikos, June, 2011, Vol.120(6), p.906(9)
    Description: To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2010.18845.x Byline: Josh Van Buskirk Abstract: The distributions of many freshwater organisms correlate with a gradient in canopy cover, ranging from sunny wetlands to closed woodland ponds. Little is known about mechanisms that exclude species from some sections of the gradient while allowing persistence in others. I addressed this question by manipulating shading in 740-l outdoor mesocosms and measuring several ecologically-relevant traits in three species of amphibian larva (Rana temporaria and Triturus alpestris, generalists occupying the entire gradient; and Hyla arborea, a specialist in open habitats). Shading caused delayed development, but had no effect on survival and increased the growth rate of R. temporaria. Body and tail color were darker in the shade. Plasticity in morphological shape, consisting of reduced gut width and increased tail size under shaded conditions, may reflect poor food availability and low dissolved oxygen. The canopy generalist R. temporaria increased activity in the shade, spent more time basking in shallow water, and maintained high larval performance. Unexpectedly, the specialist H. arborea was also highly plastic. These results describe extensive phenotypic plasticity induced by shade, and highlight traits that may influence performance along the canopy gradient. Author Affiliation: (1)Inst. of Evolutionary Biology and Environmental Studies, Univ. of Zurich, CH-8057 Zurich, Switzerland Article History: Paper manuscript accepted 4 October 2010 Article note: J. Van Buskirk, Inst. of Evolutionary Biology and Environmental Studies, Univ. of Zurich, CH-8057 Zurich, Switzerland. E-mail: josh.vanbuskirk@ieu.uzh.ch
    Keywords: Ponds ; Evolutionary Biology ; Amphibians
    ISSN: 0030-1299
    E-ISSN: 16000706
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  • 3
    In: Journal of Accounting Research, May 2012, Vol.50(2), pp.433-442
    Description: Jin, Livnat, and Zhang (JLZ) examine the predictive ability of two option characteristics – volatility skew and volatility spread – around significant information events such as earnings announcements and unscheduled corporate announcements. They conclude that option traders have an information advantage over equity traders prior to a variety of information events, as well as after unscheduled events. I discuss some of the major themes that arose during JLZ’s conference presentation, including the distinction between information processing and information acquisition; the volatility measures used by JLZ; and JLZ’s interpretation of their results.
    Keywords: Business;
    ISSN: 0021-8456
    E-ISSN: 1475-679X
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  • 4
    In: Journal of Evolutionary Biology, March 2014, Vol.27(3), pp.585-592
    Description: Theory defines conditions under which sympatric speciation may occur, and several possible examples of the process in action have been identified. In most cases, organisms specialize onto habitats that fall into discrete categories, such as host species used by herbivores and parasites. Ecological specialization within a continuous habitat gradient is theoretically possible, but becomes less likely with increasing gene flow among clinal habitat types. Here, I show that habitat race formation is underway in a frog, , along a continuous and spatially mosaic habitat gradient. Tadpoles from 23 populations raised in an outdoor mesocosm experiment showed adaptive phenotypic variation correlated with the predator density in their pond of origin. A survey of microsatellite markers in 48 populations found that neutral genetic divergence was enhanced between ponds with very different densities of predators. This represents a new example of habitat specialization along a continuous habitat gradient with no spatial autocorrelation in habitat.
    Keywords: Behaviour ; Local Adaptation ; Mesocosm Experiment ; Morphology ; Predation
    ISSN: 1010-061X
    E-ISSN: 1420-9101
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  • 5
    In: Evolution, June 2017, Vol.71(6), pp.1670-1685
    Description: Theory holds that adaptive phenotypic plasticity evolves under spatial or temporal variation in natural selection. I tested this prediction in a classic system of predator‐induced plasticity: frog tadpoles () reacting to predaceous aquatic insects. An outdoor mesocosm experiment manipulating exposure to dragonfly larvae revealed plasticity in most characters: growth, development, behavior, and external morphology. I measured selection by placing 1927 tadpoles into enclosures within natural ponds; photographs permitted identification of the survivors six to nine days later. Fitness was defined as a linear combination of growth, development, and survival that correlates with survival to age 2 in another anuran species. In enclosures with many predators, selection‐favored character values similar to those induced by exposure to in mesocosms. The shift in selection along the predation gradient was strongest for characters that exhibited high predator‐induced plasticity. A field survey of 50 ponds revealed that predator density changes over a spatial scale relevant for movement of individual adults and larvae: 17% of variation in predation risk was among ponds separated by tens to thousands of meters and 81% was among sites ≤10 m apart within ponds. These results on heterogeneity in the selection regime confirm a key tenant of the standard model for the evolution of plasticity.
    Keywords: Adaptive Landscape ; Amphibian ; Fitness ; Phenotypic Plasticity ; Predation ; Natural Selection
    ISSN: 0014-3820
    E-ISSN: 1558-5646
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  • 6
    Article
    Article
    Language: English
    In: Science, 08 October 2004, Vol.306(5694), pp.238-239
    Description: What determines the size of the home ranges of mammals of different sizes? In his Perspective, Buskirk discusses a recent analysis (Jetz et al.) that reveals how frequency of interactions with same-species neighbors influences the size of home ranges. It turns out that large mammals have larger than predicted home ranges because they are unable to traverse their home ranges often enough to exclude intrusive neighbors that seek a share of their resources.
    Keywords: Biological sciences -- Biology -- Zoology ; Biological sciences -- Biology -- Zoology ; Biological sciences -- Biology -- Physiology ; Social sciences -- Human geography -- Social geography ; Biological sciences -- Biochemistry -- Metabolism ; Social sciences -- Population studies -- Population characteristics ; Biological sciences -- Biology -- Zoology ; Biological sciences -- Ecology -- Ecological processes
    ISSN: 00368075
    E-ISSN: 10959203
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  • 7
    Language: English
    In: Oecologia, 2012, Vol.169(2), pp.535-539
    Description: Interactions among and within three species of predators were estimated in terms of their effects on prey survival using short-term predation experiments. The prey were tadpoles ( Rana temporaria) , and the predators were dragonfly larvae ( Anax imperator ), newts ( Triturus alpestris ), and backswimmers ( Notonecta glauca ). Mortality rate per predator imposed by Triturus and Notonecta did not decline with predator density, whereas the predation rate of Anax was strongly reduced when the number of predator individuals increased. Impacts of all three predators were not altered by the presence of other species in pairwise combinations. This system is therefore characterized by interference between individual dragonflies but relatively independent effects of predator species. These results were largely predictable based on the natural history of the predators and are encouraging for attempts to model communities as assemblages of interacting species.
    Keywords: Multiple predator species ; Additive effects ; Emergent effects ; Density dependence
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 8
    In: Oikos, August 2011, Vol.120(8), pp.1235-1239
    Description: In many systems, the number of prey killed by predators increases with prey density. This in turn generates higher levels of the indirect signals that prey use to assess predation risk. A model developed by Peacor (2003) showed that prey that respond to predator cues without accounting for conspecific density will consistently over‐ or under‐estimate risk and therefore invest improperly in anti‐predator defense. We tested this model using tadpoles as prey and dragonfly larvae as predators. As assumed by the model, prey reduced risky activity with increasing concentrations of predator kairomones and increased activity at high prey density. However, prey did not react to changes in cue or density if the ratio of cue‐to‐density remained constant. Prey therefore monitored their per capita risk, strongly supporting Peacor's model.
    Keywords: Evolutionary Biology ; Risk Assessment;
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 9
    Language: English
    In: Plant physiology, January 2012, Vol.158(1), pp.52-60
    Description: Plant development and growth are extremely plastic in response to changes in ambient light conditions. Light is not only the ultimate energy source for photosynthesis; its physical parameters, such as quality, intensity, direction, and duration, also serve as key environmental and time cues ([Chen
    Keywords: Light ; Signal Transduction ; Photoreceptors, Plant -- Physiology ; Phytochrome -- Chemistry
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 10
    Language: English
    In: Journal of Mammalogy, 1 February 2012, Vol.93(1), pp.29-37
    Description: The pygmy rabbit (Brachylagus idahoensis), a leporid of the Great Basin and southern Wyoming, resides in habitats dominated by big sagebrush (Artemisia tridentata). Because of the patchy distribution of mature big sagebrush in southern Wyoming, we expected pygmy rabbits to exhibit genetic attributes associated with genetic isolation: high levels of spatially structured differentiation. We also predicted some reduction in genetic diversity in the peninsular Wyoming portion of the geographic range, relative to its Great Basin core. We used 14 microsatellite loci to compare genetic attributes between geographically distinct pygmy rabbit populations, and a subset of these microsatellite loci to compare with those of 2 sympatric cottontails (Sylvilagus spp.), both presumptive habitat generalists. Pygmy rabbits displayed moderate genetic diversity that was lower than that reported from locations near the core of the geographic range (Idaho and Montana). We observed only low levels of genetic differentiation in pygmy rabbits among sampling sites within Wyoming. Similarly, we observed low levels of differentiation in one species of cottontail sympatric with pygmy rabbits; however, the other species of sympatric cottontail displayed levels of differentiation congruent with those of populations at panmixia. Isolation-by-distance was the dominant genetic pattern observed, although examination of our data suggested that a 4-lane highway (Interstate 80) might affect gene flow measurably. In the recent evolutionary past, habitat connectivity and dispersal capacity for pygmy rabbits have been high enough to maintain gene flow among sites across southern Wyoming. Conservation of the species should focus on maintaining the connectivity among preferred habitats: old stands of big sagebrush.
    Keywords: Biological sciences -- Biology -- Zoology ; Biological sciences -- Biology -- Genetics ; Biological sciences -- Biology -- Genetics ; Biological sciences -- Biology -- Evolutionary studies ; Biological sciences -- Biology -- Genetics ; Biological sciences -- Biology -- Genetics ; Biological sciences -- Biology -- Conservation biology ; Biological sciences -- Biology -- Genetics ; Biological sciences -- Biology -- Genetics ; Biological sciences -- Biology -- Genetics
    ISSN: 00222372
    E-ISSN: 15451542
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