217 research outputs found

    Environmentally induced phenotypic variation in wild yellow-bellied marmots

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    We thank all the marmoteers who helped in data collection and 2 anonymous reviewers who helped us to clarify our message. AM-C was supported by a Fulbright Fellowship, and JGAM was supported by Fond Québécois de Recherche sur la Nature et les Technologies. KBA was supported by the National Science Foundation between 1962 and 2000. DTB was supported by the National Geographic Society, UCLA (Faculty Senate and the Division of Life Sciences), a Rocky Mountain Biological Laboratory research fellowship, and by the National Science Foundation (IDBR-0754247 and DEB-1119660 to DTB as well as DBI 0242960 and 0731346 to the Rocky Mountain Biological Laboratory).Peer reviewedPostprin

    Relaxation Dynamics of Electronically Excited C60− in o-Dichlorobenzene and Tetrahydrofuran Solution

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    The ultrafast response of singly negatively charged C60 fullerene in solution has been investigated by femtosecond pump-probe absorption spectroscopy and transient anisotropy in the visible and near-infrared region. Pump excitation within the near-infrared band demonstrates that this spectral feature can be described as avibrational progression associated with asingle electronic transition. Relaxation of the first electronically excited state occurs primarily by internal conversion with atime constant of 3ps, slightly depending on the solvents, tetrahydrofuran or o-dichlorobenzene, and also on the excitation wavelength. An excitation of the second electronically excited state around 530nm leads to an ultrafast internal conversion to the first excited state with apulse-limited time constant of less than 100fs. As aminor channel, stimulated emission in the spectral regime of 1150-1300nm was observed from the first electronically excited state both after near-infrared and visible excitation. After internal conversion to the electronic ground state, C60− dissipates its excess internal energy into the solvent on alonger timescale of 40-70ps. The transient anisotropy associated with directly populating the first excited state reveals an ultrafast component decaying within 100fs, which is attributed to ultrafast vibrational motions, conceivably arising from excited state pseudorotatio

    Demographic consequences of changes in environmental periodicity

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    The fate of natural populations is mediated by complex interactions among vital rates, which can vary within and among years. Although the effects of random, among-year variation in vital rates have been studied extensively, relatively little is known about how periodic, nonrandom variation in vital rates affects populations. This knowledge gap is potentially alarming as global environmental change is projected to alter common periodic variations, such as seasonality. We investigated the effects of changes in vital-rate periodicity on populations of three species representing different forms of adaptation to periodic environments: the yellow-bellied marmot (Marmota flaviventer), adapted to strong seasonality in snowfall; the meerkat (Suricata suricatta), adapted to inter-annual stochasticity as well as seasonal patterns in rainfall; and the dewy pine (Drosophyllum lusitanicum), adapted to fire regimes and periodic post-fire habitat succession. To assess how changes in periodicity affect population growth, we parameterized periodic matrix population models and projected population dynamics under different scenarios of perturbations in the strength of vital-rate periodicity. We assessed the effects of such perturbations on various metrics describing population dynamics, including the stochastic growth rate, log λS. Overall, perturbing the strength of periodicity had strong effects on population dynamics in all three study species. For the marmots, log λS decreased with increased seasonal differences in adult survival. For the meerkats, density dependence buffered the effects of perturbations of periodicity on log λS. Finally, dewy pines were negatively affected by changes in natural post-fire succession under stochastic or periodic fire regimes with fires occurring every 30 years, but were buffered by density dependence from such changes under presumed more frequent fires or large-scale disturbances. We show that changes in the strength of vital-rate periodicity can have diverse but strong effects on population dynamics across different life histories. Populations buffered from inter-annual vital-rate variation can be affected substantially by changes in environmentally driven vital-rate periodic patterns; however, the effects of such changes can be masked in analyses focusing on inter-annual variation. As most ecosystems are affected by periodic variations in the environment such as seasonality, assessing their contributions to population viability for future global-change research is crucial.European Research Council Advanced Grant; H2020 Marie Skłodowska-Curie Actions; Mammal Research Institute, University of Pretoria; MAVA Foundation; Ministerio de Economía y Competitividad; National Geographic Society; U.S. National Science Foundation; Rocky Mountain Biological Laboratory research fellowship; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung and UCLA (Faculty Senate and Division of Life Sciences).https://onlinelibrary.wiley.com/r/ecyhj2023Mammal Research Institut

    Estimating the number of cases of podoconiosis in Ethiopia using geostatistical methods

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    Background: In 2011, the World Health Organization recognized podoconiosis as one of the neglected tropical diseases. Nonetheless, the number of people with podoconiosis and the geographical distribution of the disease is poorly understood. Based on a nationwide mapping survey and geostatistical modelling, we predict the prevalence of podoconiosis and estimate the number of cases across Ethiopia. Methods: We used nationwide data collected in Ethiopia between 2008 and 2013. Data were available for 141,238 individuals from 1,442 villages in 775 districts from all nine regional states and two city administrations. We developed a geostatistical model of podoconiosis prevalence among adults (individuals aged 15 years or above), by combining environmental factors. The number of people with podoconiosis was then estimated using a gridded map of adult population density for 2015. Results: Podoconiosis is endemic in 345 districts in Ethiopia: 144 in Oromia, 128 in Southern Nations, Nationalities and People’s [SNNP], 64 in Amhara, 4 in Benishangul Gumuz, 4 in Tigray and 1 in Somali Regional State. Nationally, our estimates suggest that 1,537,963 adults (95% confidence intervals, 290,923-4,577,031 adults) were living with podoconiosis in 2015. Three regions (SNNP, Oromia and Amhara) contributed 99% of the cases. The highest proportion of individuals with podoconiosis resided in the SNNP (39%), while 32% and 29% of people with podoconiosis resided in Oromia and Amhara Regional States, respectively. Tigray and Benishangul Gumuz Regional States bore lower burdens, and in the remaining regions, podoconiosis was almost non-existent. Discussion: The estimates of podoconiosis cases presented here based upon the combination of currently available epidemiological data and a robust modelling approach clearly show that podoconiosis is highly endemic in Ethiopia. Given the presence of low cost prevention, and morbidity management and disability prevention services, it is our collective responsibility to scale-up interventions rapidly
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