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Louvain-la-Neuve, Belgium

Dufour C.O.,CEA Saclay Nuclear Research Center | Sommer J.L.,French National Center for Scientific Research | Zika J.D.,French National Center for Scientific Research | Gehlen M.,CEA Saclay Nuclear Research Center | And 3 more authors.
Journal of Climate | Year: 2012

To refine the understanding of how the Southern Ocean responds to recent intensification of the southern annularmode (SAM), a regional oceanmodel at two eddy-permitting resolutions was forced with two synthetic interannual forcings. The first forcing corresponds to homogeneously intensified winds, while the second concerns their poleward intensification, consistent with positive phases of the SAM. Resulting wind-driven responses differ greatly between the nearly insensitive Antarctic Circumpolar Current (ACC) and the more sensitivemeridional overturning circulation (MOC).As expected, eddiesmitigate the response of theACC and MOC to poleward-intensified winds. However, transient eddies do not necessarily play an increasing role in meridional transport with increasing resolution. As winds and resolution increase, meridional transport from standing eddies becomes more efficient at balancing wind-enhanced overturning. These results question the current paradigms on the role of eddies and present new challenges for eddy flux parameterization. Results also indicate that spatial patterns of wind anomalies are at least as important as the overall change in intensity in influencing the Southern Ocean's dynamic response to wind events. Poleward-intensified wind anomalies from the positive trend in the SAMare farmore efficient in accelerating the ACCthan homogeneouswind anomalies. © 2012 American Meteorological Society. Source


Ligot G.,University of Liege | Balandier P.,IRSTEA | Courbaud B.,IRSTEA | Jonard M.,Earth and Life Institute | And 2 more authors.
Forest Ecology and Management | Year: 2014

Close-to-nature management of forests has been increasingly advocated. However forest managers often face difficulties in maintaining mixtures of species with different shade tolerance. In uneven aged stand management, understory light can be manipulated by modifying stand structure and composition, in addition to stand density. Using a forest radiative transfer model, we analyzed how different cutting strategies could modify light availability under the post-harvest canopy. To calibrate the model, we measured and mapped trees in 27 plots with structures ranging from secondary-successional oak forests to late-successional beech forests. We measured understory light and crown openness and verified that our forest radiative transfer model well captured the variability of understory light among the studied stands (R2=87%). We then compared cutting strategies varying in type and intensity and provided indications to promote the regeneration of mixtures of species of different shade tolerances. In particular, creating gaps of about 500m2 provided adequate light for small regeneration clumps. Cutting from below, species-specific cutting and uniform cutting were also appropriate for tree regeneration but uniform cutting required higher harvest intensity. Cutting from above slightly increased understory light and promoted more shade tolerant species. © 2014 Elsevier B.V. Source


Nieberding C.M.,Leiden University | Nieberding C.M.,Earth and Life Institute | Fischer K.,University of Greifswald | Saastamoinen M.,Leiden University | And 7 more authors.
Ecology Letters | Year: 2012

Although olfaction is a primary mode of communication, its importance in sexual selection remains understudied. Here, using the butterfly Bicyclus anynana, we address all the parameters of importance to sexual selection for a male olfactory signal. We show that variation in the male sex pheromone composition indicates male identity and male age. Courting males of different ages display small absolute (c. 200ng) but large relative (100%) change of one specific pheromone component (hexadecanal) which, unlike the other components, showed no heritability. Females prefer to mate with mid-aged over younger males and the pheromone composition is sufficient to determine this preference. Surprisingly refined information is thus present in the male olfactory signal and is used for sexual selection. Our data also reveal that there may be no 'lek paradox' to resolve once the precise signal of importance to females is identified, as hexadecanal is, as expected, depleted in additive genetic variation. © 2012 Blackwell Publishing Ltd/CNRS. Source


van Bergen E.,Leiden University | van Bergen E.,University of Cambridge | Brakefield P.M.,Leiden University | Brakefield P.M.,University of Cambridge | And 4 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2013

Inbreeding depression results from mating among genetically related individuals and impairs reproductive success. The decrease in male mating success is usually attributed to an impact on multiple fitness-related traits that reduce the general condition of inbred males. Here, we find that the production of the male sex pheromone is reduced significantly by inbreeding in the butterfly Bicyclus anynana. Other traits indicative of the general condition, including flight performance, are also negatively affected in male butterflies by inbreeding. Yet, we unambiguously show that only the production of male pheromones affects mating success. Thus, this pheromone signal informs females about the inbreeding status of their mating partners. We also identify the specific chemical component (hexadecanal) probably responsible for the decrease in male mating success. Our results advocate giving increased attention to olfactory communication as a major causal factor of mate-choice decisions and sexual selection. © 2013 The Author(s) Published by the Royal Society. All rights reserved. Source


Henrard A.,Royal Museum for Central Africa | Henrard A.,Earth and Life Institute | Jocque R.,Royal Museum for Central Africa
Zootaxa | Year: 2015

A new genus, Suffrica, is described from Tanzania and Kenya. It contains three new species occurring in the Eastern Arc Mountains and the adjacent Mkomazi Game Reserve: S. exotica, S. chawia and S. gus. They are characterized by a remarkable combination of features which has not been documented in spiders so far: a pair of femoral organs on each leg, a gland on the dorsal side of the abdomen in both sexes and a dorsal abdominal groove in males. A dual femoral organ appears to occur in species of the genus Suffasia Jocqué, 1991 and Asceua Thorell, 1887. The discovery of a new African genus close to Suffasia is remarkable since the latter genus is known only from Asia. Copyright © 2015 Magnolia Press. Source

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