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111.
Maryse Barrette Guy Boivin Jacques Brodeur Luc-Alain Giraldeau 《Behavioral ecology and sociobiology》2010,64(4):593-598
Models of prey choice in depleting patches predict an expanding specialist strategy: Animals should start as specialists on
the most profitable prey and then at some point during patch exploitation switch to a generalist foraging strategy. When patch
residence time is long, the switch to a generalist diet is predicted to occur earlier than when patch residence time is short.
We tested these predictions under laboratory conditions using female parasitoids (Aphidius colemani) exploiting patches of mixed instars aphid hosts (Myzus persicae, L1 and L4). The duration of patch exploitation was manipulated by changing travel time between patches. As predicted, patch
residence times increase with travel time between patches. Our results provide empirical support for the expanding specialist
prediction: Parasitoid females specialized initially on the more profitable hosts (L4), and as the patch depleted, they switched
to a generalist diet by accepting more frequently the less profitable hosts (L1). The point at which they switched from specialist
to generalist occurred later when travel times and hence patch residence times were short. By affecting the patch exploitation
strategy, travel time also determines the composition of hosts left behind, the “giving up composition.” The change in the
relative density of remaining host types alters aphid populations’ age structure. 相似文献
112.
Thomas Ducrocq Ludovic Cassan Jacques Chorda Hélène Roux 《Environmental Fluid Mechanics》2017,17(4):629-645
This paper investigates flows around a free surface piercing cylinder with Froude number F > 0.5 and Reynolds number around Re = 50,000. The aim of this work is to gain a better understanding of the flow behaviour in environmental systems such as fishways. The advances are based upon experimental and numerical results. Several flow discharges and slopes are tested to obtain both subcritical and supercritical flows. The drag force exerted on the cylinder is measured with the help of a torque gauge while the velocity field is obtained using particle velocimetry. For the numerical part, two URANS turbulence models are tested, the k-\(\omega\) SST and the RNG k-\(\varepsilon\) models using the OpenFOAM software suite for subcritical cases, and then compared with the corresponding experimental results. With fishways applications in mind, the changes in drag coefficient \(C_d\) versus Froude number and water depth are studied and experimental correlations proposed. We conclude that the most suitable URANS turbulence model for reproducing this kind of flow is the k-\(\omega\) SST model. 相似文献
113.
Gabriel Maltais-Landry Roxane Maranger Jacques Brisson Florent Chazarenc 《Environmental pollution (Barking, Essex : 1987)》2009,157(3):748-754
Greenhouse gas (GHG) emissions by constructed wetlands (CWs) could mitigate the environmental benefits of nutrient removal in these man-made ecosystems. We studied the effect of 3 different macrophyte species and artificial aeration on the rates of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) production in CW mesocosms over three seasons. CW emitted 2-10 times more GHG than natural wetlands. Overall, CH4 was the most important GHG emitted in unplanted treatments. Oxygen availability through artificial aeration reduced CH4 fluxes. Plant presence also decreased CH4 fluxes but favoured CO2 production. Nitrous oxide had a minor contribution to global warming potential (GWP < 15%). The introduction of oxygen through artificial aeration combined with plant presence, particularly Typha angustifolia, had the overall best performance among the treatments tested in this study, including lowest GWP, greatest nutrient removal, and best hydraulic properties. 相似文献
114.
Christopher W. Woodall Jacques Rondeux Pieter J. Verkerk Göran Ståhl 《Environmental management》2009,44(4):624-631
Efforts to assess forest ecosystem carbon stocks, biodiversity, and fire hazards have spurred the need for comprehensive assessments
of forest ecosystem dead wood (DW) components around the world. Currently, information regarding the prevalence, status, and
methods of DW inventories occurring in the world’s forested landscapes is scattered. The goal of this study is to describe
the status, DW components measured, sample methods employed, and DW component thresholds used by national forest inventories
that currently inventory DW around the world. Study results indicate that most countries do not inventory forest DW. Globally,
we estimate that about 13% of countries inventory DW using a diversity of sample methods and DW component definitions. A common
feature among DW inventories was that most countries had only just begun DW inventories and employ very low sample intensities.
There are major hurdles to harmonizing national forest inventories of DW: differences in population definitions, lack of clarity
on sample protocols/estimation procedures, and sparse availability of inventory data/reports. Increasing database/estimation
flexibility, developing common dimensional thresholds of DW components, publishing inventory procedures/protocols, releasing
inventory data/reports to international peer review, and increasing communication (e.g., workshops) among countries inventorying
DW are suggestions forwarded by this study to increase DW inventory harmonization. 相似文献
115.
Extra-pair paternity in the monogamous Alpine marmot revealed by nuclear DNA microsatellite analysis 总被引:8,自引:0,他引:8
Benoît Goossens Laurent Graziani Lisette P. Waits Etienne Farand Séverine Magnolon Jacques Coulon Marie-Claude Bel Pierre Taberlet Dominique Allainé 《Behavioral ecology and sociobiology》1998,43(4-5):281-288
The genetic parentage and pedigrees of 35 litters from 12 family groups of monogamous Alpine marmot (Marmota marmota) in the French Alps were analyzed using six hypervariable sequence repeat nuclear loci (microsatellites). All of the members
of these family groups were sampled during a 5-year period. Hairs taken directly from animals served as a source of DNA for
amplification of the loci. Our results indicate that the genetic mating system of the Alpine marmot is quite different from
a strictly monogamous breeding system. Extra-pair paternity occurred in 11 of the 35 litters (31.4%). Of the 134 juveniles
typed, 26 (19.4%) could be attributed to extra-pair copulation (EPC). We examine hypotheses which could explain the evolution
of EPC and discuss the different patterns of extra-pair mating.
Received: 11 July 1997 / Accepted after revision: 23 May 1998 相似文献
116.
117.
118.
Fluoranthene, in the presence of ultraviolet light (300–400 nm) induces the hemolysis of human erythrocytes. The absence of photohemolysis under anaerobic conditions proves that a photodynamic process is responsible for the light-dependent cytotoxicity. 相似文献
119.
Jacques Roger 《Die Naturwissenschaften》1965,52(12):313-319
120.
Unicoloniality emerges as a feature that characterizes successful invasive species. Its underlying mechanism is reduced intraspecific aggression while keeping interspecific competitiveness. To that effect, we present here a comparative behavioural and chemical study of the invasive ant Wasmannia auropunctata in parts of its native and introduced ranges. We tested the hypothesis that introduced populations (New Caledonia archipelago) have reduced intraspecific aggression relative to native populations (e.g., Ilhéus area, Brazil) and that this correlates with reduced variability in cuticular hydrocarbons (CHCs). As predicted, there was high intraspecific aggression in the Brazilian populations, but no intraspecific aggression among the New Caledonian populations. However, New Caledonian worker W. auropunctata remained highly aggressive towards ants of other invasive species. The chemical data corresponded with the behaviour. While CHCs of ants from the regions of Brazil diverged, the profiles of ants from various localities in New Caledonia showed high uniformity. We suggest that in New Caledonia W. auropunctata appears to behave as a single supercolony, whereas in its native range it acts as a multicolonial species. The uniformity of recognition cues in the New Caledonia ants may reflect a process whereby recognition alleles became fixed in the population, but may also be the consequence of a single introduction event and subsequent aggressive invasion of the ecosystem. Chemical uniformity coupled with low intraspecific but high interspecific aggression, lend credence to the latter hypothesis. 相似文献