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  • 1
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    Large-Effect Beneficial Synonymous Mutations Mediate Rapid and Parallel Adaptation in a Bacterium (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-17
    Description: Contrary to previous understanding, recent evidence indicates that synonymous codon changes may sometimes face strong selection. However, it remains difficult to generalize the nature, strength, and mechanism(s) of such selection. Previously, we showed that synonymous variants of a key enzyme-coding gene ( fae ) of Methylobacterium extorquens AM1 decreased enzyme production and reduced fitness dramatically. We now show that during laboratory evolution, these variants rapidly regained fitness via parallel yet variant-specific, highly beneficial point mutations in the N-terminal region of fae . These mutations (including four synonymous mutations) had weak but consistently positive impacts on transcript levels, enzyme production, or enzyme activity. However, none of the proposed mechanisms (including internal ribosome pause sites or mRNA structure) predicted the fitness impact of evolved or additional, engineered point mutations. This study shows that synonymous mutations can be fixed through strong positive selection, but the mechanism for their benefit varies depending on the local sequence context.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 2
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    An analysis of the diurnal cycle of precipitation over Dakar using local rain-gauge data and a general circulation model (2012)
    Wiley
    Details
    Publication Date: 2012-04-24
    Description: The representation of the diurnal cycle of local deep convection in two versions of the Laboratoire de Météorologie Dynamique–Zoom (LMDZ) General Circulation Model is evaluated using rainfall observations of a rain-gauge network in Senegal. An interpretation of the observed rainfall diurnal modes is attempted by partitioning rainfall as a function of rain-rate intensities and the origin, age and size of associated cloud systems. Our analysis shows a complex multipeak diurnal cycle and a large spatial variability over the rain-gauge domain of typically 100 km. Our results are consistent with the picture of a diurnal cycle of high convective rain rates associated with young and small cloud systems generated in the vicinity of the rain gauges, peaking in late afternoon and superimposed with precipitation associated with long propagative mesoscale convective systems or squall lines with no preferential time over the rain-gauge network. It is shown that these local observations of convection and rain can be used to evaluate the representation of the diurnal cycle of precipitation in a general circulation model with a typical horizontal resolution of 100 km. Two versions of the LMDZ model, including different parametrizations of boundary-layer turbulence, convection and clouds, are compared with observations. In the new parametrization, considering the role of boundary-layer thermals in deep convection preconditioning and the role of cold pools in its sustainment allows us realistically to shift the maximum of precipitation and cloud cover to late afternoon. Copyright © 2012 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
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  • 3
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    Synergies and Trade-Offs in Water Resources Management in the Bafing Watershed under Climate Change (2023)
    In:  Water
    Details
    Publication Date: 2023-06-07
    Description: Hydropower is the world’s largest and most widely used renewable energy source. It is expected that climate and land use changes, as well as hydraulic engineering measures, will have profound impacts on future hydropower potential. In this study, the hydropower potential of the Bafing watershed was estimated for the near future (P1: 2035–2065) and the far future (P2: 2065–2095). For this purpose, the moderate scenario ssp 126 and the medium–high scenario ssp 370 were used to explore possible climate impacts. In three management scenarios, we tested the interaction of the existing Manantali Dam with two planned dams (Koukoutamba and Boureya) using an ecohydrological water management model. The results show that, under ssp 126, a 6% increase in annual river flow would result in a 3% increase in hydropower potential in the near future compared with the historical period of 1984–2014. In the far future, the annual river flow would decrease by 6%, resulting in an 8% decrease in hydropower potential. Under ssp 370, the hydropower potential would decrease by 0.7% and 14% in the near and far future, respectively. The investment in the planned dams has benefits, such as an increase in hydropower potential and improved flood protection. However, the dams will be negatively affected by climate change in the future (except in the near future (P1) under ssp 126), and their operation will result in hydropower potential losses of about 11% at the Manantali Dam. Therefore, to mitigate the effects of climate change and adjust the operation of the three dams, it is essential to develop new adaptation measures through an optimization program or an energy mix combining hydro, solar, and wind power.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 4
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    Prediction of land use and land cover change in two watersheds in the Senegal River basin (West Africa) using the Multilayer Perceptron and Markov chain model (2023)
    In:  European Journal of Remote Sensing
    Details
    Publication Date: 2023-07-11
    Description: Land use and Land cover change (LULCC) is a major global problem, and projecting change is critical for policy decision-making. Understanding LULCCs at the watershed level is essential for transboundary river basin management. The present study aims to analyse the past and future LULCCs in two significant watersheds of the Senegal River basin (SRB) in West Africa: Bafing and Faleme. This study used Landsat images from 1986, 2006 and 2020 and the Random Forest classification method to analyze past LULCCs in these two watersheds. The results revealed: In Bafing, vegetation, settlement, agricultural areas and water increased, while the bareground decreased significantly between 1986-2020. In Faleme, two periods have different trends. Between 1986-2006, vegetation, settlement, agricultural areas and water increased, while bareground decreased. Between 2006-2020, settlement increased, while vegetation, agricul-tural areas, water and bareground decreased. To predict LULCCs in 2050 under business-as- usual assumptions, the Multilayer Perceptron and Marcov Chain model (MLP-MC) was used. The MLP-MC shows better results on Bafing than on Faleme but without questioning its application on the two watersheds. Bafing has seen a trend towards ”more people, more trees”, while Faleme has seen a trend towards ”more people, more deforestation”. These results contribute to develop appropriate land management policies and strategies to achieve or to maintain sustainable development in the SRB.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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