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11.
Riviane R. Hora Claudie Doums Chantal Poteaux Renée Fénéron Jorge Valenzuela Jürgen Heinze Dominique Fresneau 《Behavioral ecology and sociobiology》2005,59(2):285-292
Social parasites exploit the worker force of colonies of other social insects to rear their own young. Social parasitism occurs in several Hymenoptera and is particularly common in several tribes of the ant subfamilies Myrmicinae and Formicinae. Here, we document the occurrence of miniaturized queens (microgynes) in colonies of Ectatomma tuberculatum, an ant belonging to the subfamily Ectatomminae. Behavioral observations and genetic analyses show that microgynes concentrate their reproductive efforts almost exclusively on the production of sexual offspring (microgynes and males), whereas the regular, large queens (macrogynes) produce workers in addition to sexuals. According to mitochondrial and nuclear markers, gene flow between microgynes and macrogynes is extremely limited. Whereas the co-occurrence of microgynes and macrogynes in the related species Ectatomma ruidum constitutes an intraspecific polymorphism associated with alternative dispersal tactics, microgynes found in colonies of E. tuberculatum appear to be a distinct species and to represent the first case of social parasitism in the poneromorph subfamilies of ants. 相似文献
12.
Assessment of environmental changes in the Orinoco River delta 总被引:1,自引:0,他引:1
H. Echezuría J. Córdova M. González V. González J. Méndez C. Yanes 《Regional Environmental Change》2002,3(1-3):20-35
Major anthropogenic driven changes in the hydrologic and sedimentation patterns of the Orinoco River have had an impact on
environmental conditions in the delta. The abrupt water flow reduction from 3,600 to 200 m3 s–1 in one of its major distributaries resulting from dam construction forced its transformation from a fresh-water body into
a tidal channel with an increase in salinity level (as far as 100 km upstream) and with well-mixed water at the mouth and
estuarine connection to the Paria Gulf. Three different sectors along this distributary can be identified (indicated by the
Na/Cl ratio in the water). As a result, noticeable changes have occurred in the mangrove community which moved about 60 km
further upstream. The changes have also promoted the formation of new islands of sediment progradation at the mouth of this
distributary, where successional colonization and species replacement by different species of grasses and mangroves take place.
Electronic Publication 相似文献
13.
14.
Thierry Rousseau Nicole Laurent Christel Thauvin-Robinet Stéphanie Lionnais Christine Durand Laurence Faivre Paul Sagot 《黑龙江环境通报》2002,22(8):692-696
Fraser syndrome (MIM 219000) is a rare disorder of autosomal recessive inheritance, characterized by the association of cryptophthalmos, syndactyly and genital abnormalities. Here we report on two cases of Fraser syndrome (cryptophthalmos syndrome) in a non-consanguineous couple, with variable expression in echographic, clinical and autopsy findings. Furthermore, we highlight the difficulties in prenatal diagnosis of Fraser syndrome. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
15.
A. Migné D. Davoult N. Spilmont D. Menu G. Boucher J.-P. Gattuso H. Rybarczyk 《Marine Biology》2002,140(4):865-869
This paper describes a closed-chamber method for measuring CO2 fluxes in intertidal soft sediments during periods of emersion. The method relies on closed-circuit incubations of undisturbed sediment and measurement of CO2 exchanges using an infrared gas analyser. The method was assessed during field experiments, both in light and dark conditions, on an exposed sandy beach and in an estuary. The rates of gross community production measured under moderate irradiance (4.2 mg C m-2 h-1 on the exposed sandy beach and 35 mg C m-2 h-1 in the estuary) are in good agreement with rates reported in the literature. In conjunction with appropriate sampling strategies, this method can be useful for estimating and comparing production of intertidal areas or for assessing factors that influence production. 相似文献
16.
Branquinho C Serrano HC Pinto MJ Martins-Loução MA 《Environmental pollution (Barking, Essex : 1987)》2007,146(2):437-443
The several established criteria to define a hyperaccumulator plant were applied to a rare and endangered species, Plantago almogravensis, and to the 3rd most abundant element in the earth crust, Al. Using the most common criteria, P. almogravensis undoubtedly is an Al hyperaccumulator plant. If the recent proposed requirements were considered, most of them matching those for a plant to be used in phytoextraction, it can only be considered an unusual accumulator of Al. A discussion is made concerning the several criteria of a hyperaccumulator plant in order to include rare and endemic ones and abundant elements. In ecological terms, the enrichment in Al and Fe observed may account for the differences in the vegetation pattern. Due to the rarity and endangered nature of this plant, the contribution of this work is also relevant for the ecological understanding and the development of conservation options of this endemic species. 相似文献
17.
18.
Alletto L Benoit P Bergheaud V Coquet Y 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):678-688
Laboratory studies were conducted to evaluate the effects of temperature and water pressure head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84 d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives (T1/2) were measured in the seedbed samples under MT at 25 °C and −33 cm water pressure head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter. 相似文献
19.
Svendsen TC Vorkamp K Rønsholdt B Frier JO 《Journal of environmental monitoring : JEM》2007,9(11):1213-1219
Atlantic salmon (Salmon salar) populations from four locations, two from isolated Swedish lake systems, one of the Baltic Sea and one of the North Atlantic, were analyzed to determine the concentrations and spatial variations of polybrominated diphenyl ethers (PBDEs) and organochlorines (DDT, PCB and HCH). Levels in both liver and muscle were in the same range as previously reported in Atlantic salmon, except for elevated concentrations found per lipid weight (lw) in the muscle samples of salmon from the North Atlantic ( summation PBDE 263 ng g(-1) lw, summation PCB 3262 ng g(-1) lw, summation DDT 4063 ng g(-1) lw summation HCH 131 ng g(-1)). In general, elevated concentrations in the muscles compared to the liver were observed, especially in lipid depleted migrating salmon, possibly caused by a faster lipid depletion compared with the redistribution of PBDEs, PCBs and DDTs. These findings indicated that the life stage and thereby the lipid dynamics of the fish must be considered prior to comparison based on lipid weight, especially as Atlantic salmon experience large variations in lipid content during periods of migration. The dominating PBDE congener was BDE-47, representing more than 25% in all fish. The PBDE pattern changed between locations, with a significant separation of the fish from the freshwater and marine environment when analyzed using principal component analysis. 相似文献
20.
Christian Fuchs 《Environment, Development and Sustainability》2008,10(3):291-309
This paper discusses the relationship of new information and communication technologies (ICTs) and sustainable development.
It deconstructs popular myths about a sustainable information society. One myth is that telework has reduced the need to travel
and hence environmental pollution. The reality is that teleworkers make up only a small share of the total workforce, telework
can generate new social relationships and hence the need for more travelling, work-related travel produces only a small amount
of the total carbon dioxide emissions, and that the total distance travelled per employee is constantly rising. Another myth
is that information economy is weightless and dematerialized which reduces environmental impacts. The energy and resource
intensities of the ICT sector are indeed lower than the one of the total economy. The ICT sector also emits less CO2 than the total economy. But the ICT sector constitutes only a small portion of the total value added and fossil fuel combustion
is still the dominant activity of modern industrial economies. Some stakeholders argue that virtual products allow resource,
energy, and transport savings. But burning digital music on compact discs and DVDs, printing digital articles and books, etc.
results in rebound effects that cause new material and energy impacts, computers have a low life span of 2–3 years, reusable
and upgradeable computers and computer equipment are hardly used and might not be as profitable as non-reusable ones, computers
are consuming much energy. Alternatives such as energy consumption labels on ICTs and green ICTs that consume less energy
contradict dominant economic interests. A sustainable information society is a society that makes use of ICTs and knowledge
for fostering a good life for all human beings of current and future generations by strengthening biological diversity, technological
usability, economic wealth for all, political participation of all, and cultural wisdom. Achieving a sustainable information
society costs, it demands a conscious reduction of profits by not investing in the future of capital, but the future of humans,
society, and nature. 相似文献