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排序方式: 共有443条查询结果,搜索用时 187 毫秒
61.
Nayuta Yamashita Kathryn E. Stoner Pablo Riba-Hernández Nathaniel J. Dominy Peter W. Lucas 《Behavioral ecology and sociobiology》2005,58(6):618-629
The intensity of available light is important in determining how well a diurnal animal can distinguish color. Primates with different types of color vision may exhibit behaviors that maximize visual contrast during critical activities such as feeding. We hypothesized that (1) trichromatic taxa will feed in a wide range of light conditions because color constancy permits stabilized color appearance across changes in illumination, and (2) that taxa with a high proportion of dichromatic individuals will tend to feed at higher light levels to increase color contrast. We recorded light levels during feeding bouts of seven primate taxa with varying degrees of color vision: the dichromatic Lemur catta, two polymorphic species, Propithecus v. verreauxi and Ateles geoffroyi, and the routine trichromats, Alouatta palliata, Colobus guereza, Piliocolobus badius, and Cercopithecus ascanius. Results were equivocal for our hypotheses. While routinely trichromatic taxa used varying light levels, the pattern of results did not differ from the dichromatic Lemur catta. However, polymorphic taxa not only sought the highest light, but females, which are the only individuals in polymorphic taxa that can be trichromatic, fed in higher light levels than males when eating non-green foods. This result is consistent with selection operating to maintain a balanced polymorphism in these taxa, though the connection between light levels and color vision type for the females is unclear. Our results further suggest that trichromatic vision may afford a selective advantage because it permits foraging under a greater range of light levels. 相似文献
62.
Sondes Melliti Ben Garali Inès Sahraoui Pablo de la Iglesia Mohamed Chalghaf Jorge Diogène Jamel Ksouri 《Chemistry and Ecology》2020,36(1):66-82
ABSTRACTThe seasonal variations in Pseudo-nitzschia species and domoic acid (DA) concentration were investigated, at three shellfish farms in SW coastal Mediterranean. In parallel, the toxicity of mussels was tested. Two distinct groups of species were enumerated according to morphology and size (Pseudo-nizschia delicatissima and P. seriata groups). DA was detected over a nine-week period from July to October 2012 in the Lagoon, with a maximum concentration recorded in July (12.71?ng?DA?L?1). DA was positively correlated with the presence of P. seriata-group and P. delicatissima-group and was mostly occurred during P limitation period in seawater. No DA was found in mussels that were collected during the period of DA absence in seawater. Our results suggest that temperature, salinity, inorganic and organic nutrients were significant for the seasonal dynamics of P. seriata and P. delicatissima groups, but that the P limitation was the most driving factor for DA production in these areas. The relative influence of environmental factors should be further studied to better understand the recent surfacing of massive blooms of toxigenic Pseudo-nitzschia in SW Mediterranean coast. 相似文献
63.
Zooplankton of the Bristol Channel and Severn Estuary. The distribution of four copepods in relation to salinity 总被引:3,自引:0,他引:3
The seasonal variations in distribution and abundance of the common zooplankton species in the Bristol Channel and Severn Estuary were related to the salinity regimes observed over the period November 1973 to February 1975. The dominant constituents in all regions were the calanoid copepods, which reached maximum densities in July: approximately 100 times their winter levels. Four zooplankton assemblages were recognised using an objective classification program which computed similarity coefficients and used group-average sorting. The assemblages existed along the salinity gradient observed from the Severn Estuary to the Celtic Sea. The assemblages were classified as true estuarine, estuarine and marine, euryhaline marine and stenohaline marine and were characterized by the copepods Eurytemora affinis (Poppe) (<30S), Acartia bifilosa var. inermis (rose) (27 to 33.5S), Centropages hamatus (Lilljeborg) (31 to 35S) and Calanus helgolandicus (Claus) (>33S), respectively. 相似文献
64.
Klaus-Dieter Wenzel Ludwig Weiβflog Enrique Paladini Miguel Gantuz Pablo Guerreiro Carlos Puliafito Gerrit Schüürmann 《Chemosphere》1997,34(12):2505-2518
The air pollution profiles of organic xenobiotics (including chlorinated insecticides and benzenes, PCBs and PAHs) were comparatively analyzed in the climatically different regions of Leipzig-Halle (Germany) and Greater Mendoza (Argentina) using two-year-old pine needles (Pinus sylvestris L.) as passive biomonitors. In addition to total compound contents, the levels of potentially bioavailable fraction in the inner needle compartment were determined. The peak levels of chlorinated insecticides and PAHs in an urban park in Mendoza were found to exceed the maximum levels in the Leipzig-Halle region by one to two orders of magnitude, indicating the recent substantial tropospheric input of the compounds from local sources. Bioavailable fractions were observed to exhibit considerable variations for some of these compounds, which became even more distinct when needle samples from Germany and Argentina were compared. Generally speaking, an increase in permeability under semiarid climatic conditions was observed for most of the xenobiotics examined. The discussion of the results reflects the problems associated with using biomonitoring for semivolatile compounds. Interpretation takes into account pollution measurements in the air at Argentine and German reference sites. 相似文献
65.
de Koning F Olschewski R Veldkamp E Benítez P López-Ulloa M Schlichter T de Urquiza M 《Ambio》2005,34(3):224-229
Costs of reforestation projects determine their competitiveness with alternative measures to mitigate rising atmospheric CO2 concentrations. We quantify carbon sequestration in above-ground biomass and soils of plantation forests and secondary forests in two countries in South America-Ecuador and Argentina-and calculate costs of temporary carbon sequestration. Costs per temporary certified emission reduction unit vary between 0.1 and 2.7 USD Mg(-1) CO2 and mainly depend on opportunity costs, site suitability, discount rates, and certification costs. In Ecuador, secondary forests are a feasible and cost-efficient alternative, whereas in Argentina reforestation on highly suitable land is relatively cheap. Our results can be used to design cost-effective sink projects and to negotiate fair carbon prices for landowners. 相似文献
66.
Enrico Cappellini M. Thomas P. Gilbert Filippo Geuna Girolamo Fiorentino Allan Hall Jane Thomas-Oates Peter D. Ashton David A. Ashford Paul Arthur Paula F. Campos Johan Kool Eske Willerslev Matthew J. Collins 《Die Naturwissenschaften》2010,97(2):205-217
We report here the first integrated investigation of both ancient DNA and proteins in archaeobotanical samples: medieval grape (Vitis vinifera L.) seeds, preserved by anoxic waterlogging, from an early medieval (seventh–eighth century A.D.) Byzantine rural settlement in the Salento area (Lecce, Italy) and a late (fourteenth–fifteenth century A.D.) medieval site in York (England). Pyrolysis gas chromatography mass spectrometry documented good carbohydrate preservation, whilst amino acid analysis revealed approximately 90% loss of the original protein content. In the York sample, mass spectrometry-based sequencing identified several degraded ancient peptides. Nuclear microsatellite locus (VVS2, VVMD5, VVMD7, ZAG62 and ZAG79) analysis permitted a tentative comparison of the genetic profiles of both the ancient samples with the modern varieties. The ability to recover microsatellite DNA has potential to improve biomolecular analysis on ancient grape seeds from archaeological contexts. Although the investigation of five microsatellite loci cannot assign the ancient samples to any geographic region or modern cultivar, the results allow speculation that the material from York was not grown locally, whilst the remains from Supersano could represent a trace of contacts with the eastern Mediterranean. 相似文献
67.
Sound stimulates the tympanic membrane (TM) of anuran amphibians through multiple, poorly understood pathways. It is conceivable
that interactions between the internal and external inputs to the TM contribute to the nonlinear effects that noise is known
to produce at higher levels of the auditory pathway. To explore this issue, we conducted measurements of TM vibration in response
to tones in the presence of noise in the frog Eupsophus calcaratus. Laser vibrometry revealed that the power spectra (n = 16) of the TM velocity in response to pure tones at a constant level of 80 dB sound-pressure level (SPL) had a maximum
centered at an average frequency of 2,344 Hz (range 1,700–2,990 Hz) and a maximum velocity of 61.1 dB re 1 μm/s (range 42.9–66.6
dB re 1 μm/s). These TM-vibration velocity response profiles in the presence of increasing levels of 4-kHz band-pass noise
were unaltered up to noise levels of 90 dB SPL. For the relatively low spectral densities of the noise used, the TM remains
in its linear range. Such vibration patterns facilitate the detection of tonal signals in noise at the tympanic membrane and
may underlie the remarkable vocal responsiveness maintained by males of E. calcaratus under noise interference. 相似文献
68.
Making index insurance attractive to farmers 总被引:1,自引:0,他引:1
Anthony Patt Nicole Peterson Michael Carter Maria Velez Ulrich Hess Pablo Suarez 《Mitigation and Adaptation Strategies for Global Change》2009,14(8):737-753
There are several factors that influence whether people will want to participate in index insurance programs. A number of
these influence their attractiveness on economic grounds, including both the size and timing of the premium and potential
payouts, and the degree of risk aversion of the potential customers. Other factors make programs attractive for reasons that
are not economic, but no less valid. These have to do with the trust that people have in the insurance product and the organizations
involved in selling and managing it. Indeed, data from India, Africa, and South America show that these factors may be more
important than the economic ones in influencing demand. Index insurance pilot projects, in order to estimate demand for alternative
products, have typically involved a great deal of interaction with potential customers. It is important to recognize that
such interaction is crucial not just as a research tool, but also as a means to build understanding and trust in the products.
When scaling up from isolated pilots to operational programs, it is vital to recognize this trust building function by replicating
participation efforts in every community. In this paper, we examine the role of field games in establishing and building trust
in three important aspects of these projects for participants: trust in the insurance product, trust in the participating
organizations, and trust in their own ability to make good decisions. While games have previously been used as a way to gauge
interest in the product and to identify design features, we argue that these games are also valuable tools for constructing
these kinds of trust. 相似文献
69.
Jonathan Pearson G. Punzo M. Mayfield G. Brighty A. Parsons P. Collins S. Jeavons A. Tagg 《The Environmentalist》2018,38(3):318-329
Flood resilience has been rising up the political, economic and social agendas. Taking an integrated systems approach, using the right design guidance and tools and ensuring that education is in place for all stakeholders are three themes which are intrinsically linked to delivering flood resilience. This paper reviews these themes across the academic research, policy landscape and practitioner approaches, drawing conclusions on the way forward to increase our societies resilience to floods. The term ‘flood resilience’ is being increasingly used, however, it remains to be clearly defined and implemented. The UK, USA and Australia are leading the way in considering what flood resilience really means, but our review has found few examples of action underpinned by an understanding of systems and complexity. This review investigates how performance objectives & indicators are currently interpreted in guidance documents. It provides an in-depth exploration of the methods, that although developed through European and US expertise, can be used for worldwide application. Our analysis highlights that resilience is often embedded in engineering education and frequently linked to risk. This may however, mask the importance of resilience and where it differs from risk. With £2.6 billion to be spent in the UK over the next 6 years on strengthening the country’s flood and coastal defences, this is the opportunity to rethink resilience from a systems approach, and embed that learning into education and professional development of engineers. Our conclusions indicate how consolidating flood resilience knowledge between and within critical infrastructure sectors is the way forward to deliver flood resilience engineering. 相似文献
70.