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31.
M. Javier Klaich Paul G. KinasSusana N. Pedraza Mariano A. Coscarella Enrique A. Crespo 《Ecological modelling》2011,222(15):2642-2650
In animal behaviour studies, association indices estimate the proportion of time two individuals (i.e. a dyad) spend in association. In terms of dyads, all association indices can be interpreted as estimators of the probability that a dyad is associated. However, traditional indices rely on the assumptions that the probability to detect a particular individual (p) is either approximately one and/or homogeneous between associated and not associated individuals. Based on marked individuals we develop a likelihood based model to estimate the probability a dyad is associated (ψ) accounting for p < 1 and possibly varying between associated and not associated individuals. The proposed likelihood based model allows for both individual and dyadic missing observations. In addition, the model can easily be extended to incorporate covariate information for modeling p and ψ. A simulation study showed that the likelihood based model approach yield reasonably unbiased estimates, even for low and heterogeneous individual detection probabilities, while, in contrast, traditional indices showed moderate to strong biases. The application of the proposed approach is illustrated using a real data set collected from a population of Commerson's dolphin (Cephalorhynchus commersonii) in Patagonia Argentina. Finally, we discuss possible extensions of the proposed model and its applicability in animal behaviour and ecological studies. 相似文献
32.
Nuxia L. Espinoza-Fuenzalida Martin Thiel Enrique Dupre J. Antonio Baeza 《Marine Biology》2008,155(6):623-635
Sexual systems vary considerably among caridean shrimps and while most species are gonochoric, others are described as sequential
protandric hermaphrodites or simultaneous hermaphrodites with an early male phase. At present, there is confusion about the
sexual system exhibited by several species mostly because those studies attempting to reveal their sexual system draw inferences
solely from the distribution of the sexes across size classes. Here we investigated the sexual system of the shrimp Hippolyte williamsi from Chile to determine if the species is protandric or gonochoric with sexual dimorphism (males smaller than females). Morphological
identification and size frequency distributions indicated that the population comprised small males, small immature females,
and large mature females, which was confirmed by dissections. No transitional individuals were found. Males maintained in
the laboratory molted 1–8 times, and many grew up to reach sizes observed in only a small fraction of males in the field.
No indication of sex change was recorded. Our results indicate that H. williamsi is a sexually dimorphic gonochoric species and emphasizes the importance of using several kinds of evidence (size measurements,
growth experiments, morphological dissections, and histological studies) to reveal the sexual system of Hippolyte species. Whether the observed size dimorphism between males and females in many species of Hippolyte is expression of contrasting sexual and natural selection, and whether divergent sexual fitness functions can contribute
to the evolution of hermaphroditism remains to be revealed in future studies. 相似文献
33.
Gotzon Gangoiti Milln M. Milln Rosa Salvador Enrique Mantilla 《Atmospheric environment (Oxford, England : 1994)》2001,35(36):2163
During the warm season (March–September), high ozone concentrations have been reported at the coastal and mountain monitoring stations of the eastern Iberia coast (Millán et al., J. Geophys. Res. 102 (D7) 8811, J. Appl. Meteorol. 4 (2000) 487). The vegetation protection threshold of current Directive 92/72/EEC and the World Health Organisation guideline for the protection of crops and semi-natural vegetation are systematically exceeded during the whole period. The main objective of the present study is to search for the origin of these chronic pollution levels: to search for the reason(s) for such high O3 concentrations during such a long period. A mesoscale model is used to reproduce the diurnal cycle of winds and stability/layering over the Western Mediterranean Basin (WMB), at a sufficient space/temporal resolution, under a typical recursive synoptic condition during the warm season: data from the flight tracks of the European Project—Regional Cycles of Air Pollution in the West-Central Mediterranean Area—are used to substantiate the model results. Times of residence and the final distribution of pollutants entering the WMB are estimated using single-particle Lagrangian trajectories and a multiple-particle dispersion model. Our results show that the marine boundary layer and the lower troposphere in the region between the Balearic Islands and eastern Iberia are subject to a flow regime that tends to accumulate pollutants within large circulations, covering the entire western basin. We have also shown a diurnal pulsation of the Tramontana/Mistral wind regime, which can transport new pollutants into the area (background concentrations of 50–65 ppb of O3 of continental European origin) that are added to local emissions and re-circulated within the coastal breezes at eastern Iberia for periods of more than five days. Local emissions and wind configuration contribute to increase the O3 concentrations up to 100 ppb and even more. 相似文献
34.
Patricia Briones-Fourzán Marisol Pérez-Ortiz Enrique Lozano-Álvarez 《Marine Biology》2006,149(2):227-239
The congeneric spiny lobsters Panulirus argus and P. guttatus co-occur throughout the Caribbean Sea, where they may share the coral reef habitat. Despite their phylogenetic closeness, both species have many different life-history traits that may partially explain their coexistence. However, even though both species may face the same predators, their defense mechanisms and antipredator strategies had not been compared. We compared the performance between species in 18 morphological and behavioral defense mechanisms commonly expressed by most spiny lobsters, including predator-avoidance mechanisms (activity schedule, sheltering behavior, delay to disturbance, and effect of conspecific damage-released scents on shelter choice) as well as antipredator mechanisms (body size, several parameters of the escape response and limb autospasy, clinging strength, antennal strength, and cooperative defense). As hypothesized, both species expressed all these defense mechanisms (except cooperative defense, shown only by P. argus), reflecting their phylogenetic closeness, but performed significantly differently in most, in accordance with their particular ontogenetic traits. Their comparative performance in individual defense mechanisms as well as the antipredator strategies displayed by groups of lobsters of each species in the presence of a common predator (the triggerfish Balistes vetula) showed that, in general, the defensive behavioral type of P. argus is more bold and that of P. guttatus more shy. Therefore, their distinct defensive behaviors contribute to their niche differentiation. 相似文献
35.
The paper presents an overview of the present situation of the Mexico City Metropolitan Area (MCMA). The analysis indicates an urgent need to radically improve the current water supply and wastewater management practices, to become sustainable. The MCMA is one of the most rapidly growing urban centers of the world, with a population of about 21 million people, a very high rate of immigration and numerous illegal settlements. In order to meet the increasing water demand, successive governments have focused almost exclusively on supply management and engineering solutions, which have resulted in investments of hundreds of millions of USD and the construction of major infrastructure projects for interbasin water transfer. Environmental, economic and social policies associated with water management are mostly inadequate and insufficient, which is resulting in increasing deterioration in the environment, health and socioeconomic conditions of a population living in one of the largest urban agglomerations of the world. Surprisingly, however, no long-term strategies on demand-management, reuse, conservation, and improved water-management practices have been developed so far. 相似文献
36.
Marie-Paule?CharnayEmail author Christian?Mougin Adrien?Farrugia Enrique?Barriuso 《Environmental Chemistry Letters》2004,2(1):27-30
We studied the 14C-tagged biochemical compartments such as proteins, lipids and polysaccharides from bacterial and fungal cultures supplied with 14C-pesticides and 14C-glucose. We showed that 14C incorporation depends both on the substrate structure and on the nature of the micro-organism. Both bacterial and fungal cells incorporated glucose 14C mainly into cell wall proteins. By contrast, glyphosate 14C was mainly incorporated into cytoplasm carbohydrates by fungi. On the other hand, 2,4-dichlorophenoxyacetic acid 14C was mainly found in the carbohydrate fractions of the bacteria walls. 相似文献
37.
The aim of this paper is to evaluate the soybean production and industrial processing stages in Brazil using the emergy accounting methodology and economic cost and revenue estimation in order to assess the environmental and economic inputs to the soybean chain and to evaluate the amount of emergy and nutrients exported to European countries. The main findings of this work were that the agricultural stage uses the highest amount of resources. The emergy exchange ratio shows that farmers are delivering around six times more emergy in the soybean that is being sold than the emergy they are receiving with the money paid for it. Results demonstrate that producing raw soybean and soy meal for international markets makes Brazil lose a great amount of emergy and nutrients. Besides that, soybean production is nowadays providing low profitability to farmers because of low prices for soybean products and high prices for the chemicals used in soybean farming. Therefore, at present conditions, exporting soybean as a commodity results in low profit per unit of area. 相似文献
38.
José F. Molina-Azorín Enrique Claver-Cortés Jorge Pereira-Moliner Juan José Tarí 《Journal of Cleaner Production》2009,17(5):516-524
The impact of environmental practices on firm performance raises an ongoing debate in which the review of the existing literature yields no conclusive results. Different methods have been used to study this relationship and most of the analyses have focused on manufacturing companies. This paper examines the link between environmental practices and firm performance in the Spanish hotel industry using two methods: a cluster analysis and a regression analysis. First, three groups were defined according to their environmental proactivity, and hotels showing a stronger commitment to environmental practices proved to reach higher performance levels. Second, through the regression analysis, findings showed that environmental practices impact significantly on several performance variables. 相似文献
39.
The selective forces imposed by primary receivers and unintended eavesdroppers of animal signals often act in opposite directions, constraining the development of conspicuous coloration. Because iridescent colours change their chromatic properties with viewer angle, iridescence offers a potential mechanism to relax this trade-off when the relevant observers involved in the evolution of signal design adopt different viewer geometries. We used reflectance spectrophotometry and visual modelling to test if the striking blue head coloration of males of the lizard Lacerta schreibeiri (1) is iridescent and (2) is more conspicuous when viewed from the perspective of conspecifics than from that of the main predators of adult L. schreibeiri (raptors). We demonstrate that the blue heads of L. schreiberi show angle-dependent changes in their chromatic properties. This variation allows the blue heads to be relatively conspicuous to conspecific viewers located in the same horizontal plane as the sender, while simultaneously being relatively cryptic to birds that see it from above. This study is the first to suggest the use of angle-dependent chromatic signals in lizards, and provides the first evidence of the adaptive function of iridescent coloration based on its detectability to different observers. 相似文献
40.