Traditionally it has been assumed by ecologists that the dispersion of positions with respect to leks of female capercaillies
during the mating season is superior to the dispersion of positions of male capercaillies. However some recently published
articles suggest the idea that dispersion is not sex-biased, but both sexes show a similar dispersion. This article introduces
a mathematical model to approach the study of the above question by means of an indexed dispersion criterion. This model is
developed in detail thus deriving its main mathematical properties. On this basis, the model is applied to the analysis of
the motivating problem with real data of positions of leks and female and male capercaillies. The results derived by means
of the model put into doubt the traditional assumption of a superior dispersion of females supporting the new theories, that
is, both sexes show a similar dispersion. 相似文献
Journal of Polymers and the Environment - Since biodegradable materials are unwittingly mixed with synthetic materials, this work aimed to study the feasibility of reliably identifying some... 相似文献
Climate exerts an important role on grape production and wine quality. For one of the main areas protected under the denomination of origin Rías Baixas, in Galicia, Spain, we explore the relationships among grape production, wine quality, rainfall and temperature for the period 1987–2005. The influence of climatic variability was analysed in terms of the relationship between the productivity of the grapevines and the main meteorological teleconnection patterns affecting the North Atlantic region. We also investigate the daily variation in atmospheric circulation through the study of the influence of weather types derived using an automated daily classification. We consider three bioclimatic indices for viticultural zoning, Winkler and Huglin, and the hydrothermic index of Branas, Bernon and Levadoux. While significant trends were identified in the Winkler and Huglin indices, there were no significant trends in the Branas, Bernon and Levadoux index, for the period 1958–2005. For the coming decades, using the scenario A1B evaluated by the regional climate models used in the ENSEMBLES project, the positive trends of Winkler and Huglin indices continue, while Branas, Bernon and Levadoux implies a negative trend. In all cases, these trends induce significant changes in the viticulture of the region. 相似文献
Three different systems of designating protected areas in a Mediterranean region in southeastern Spain were studied, referring
to their effectiveness and efficiency for protecting both the breeding territories and the suitable habitat of a set of ten
raptor species. Taking into consideration the varying degrees of endangerment of these species, a map of multispecies conservation
values was also drawn up and superimposed on the three protected-area systems studied. In order to compare the levels of protection
afforded by the three systems, we considered two indices that measured their relative effectiveness and efficiency. The effectiveness
estimated the proportion of territories or optimal habitat protected by the networks while efficiency implicitly considered
the area of each system (percentage of breeding territories or optimal habitat protected per 1% of land protected). Overall,
our results showed that the most efficient system was that formed by the set of regional parks and reserves (17 protected
breeding territories per 100 km2), although, given its small total area, it was by far the least effective (only protecting the 21% of the breeding territories
of all species and 17% of the area of high conservation value). The systems formed by the Special Protection Areas (designated
under the EU “Birds Directive”) and by the Special Conservation Areas (designated under the EU “Habitats Directive”) notably
increased the percentages of protected territories of all species (61%) and area of high conservation value (57%), but their
efficiency was not as high as expected in most cases. The overall level of protection was high for all species except for
the Lesser Kestrel (Falco naumanni), an endangered falcon that inhabits pseudo-steppe and traditional agricultural habitats, which are clearly underrepresented
in the protected-area network of the study region. 相似文献
We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate
trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies
reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing
on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important
in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge
in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an
assessment of whether such contamination represents a real risk to the city’s inhabitants and therefore how this risk can
be addressed. 相似文献
Signal attributes should show different degrees of variability depending on the information to be conveyed. Species identity
is usually associated with stereotyped features of a signal, whereas other types of information such as individual quality
and motivation are associated with signal plasticity. Lusitanian toadfish males form aggregations during the breeding season
and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle
can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study
how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement
signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian
toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male
signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could
still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among
males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide
on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest
that inter-individual differences in call characteristics and call plasticity may mediate both male–male assessment and mate
choice. 相似文献
Changes in saprophytic organism's gut microbial communities may present a threat to organic matter breakdown which can ultimately lead to soil function impairment. In this study, Amplified Ribosomal DNA Restriction Analysis (ARDRA) was evaluated as a potential simple molecular tool to assess shifts in bacterial community structure in hindgut populations of Porcellio dilatatus exposed to contaminated food. This prospective tool can also be used for a variety of purposes and samples prior to the use of more specific and sophisticated methods. 相似文献
The economic viability of the split-phase glycolysis process for the recycling of any kind of flexible polyurethane foam waste employing crude glycerol as cleavage agent has been demonstrated. First, experiments at pilot plant scale were carried out to check that the process can be extrapolated to larger scales. With the goal of scaling-up the process from laboratory scale to pilot plant, geometric similarity criteria were applied together with dynamic similarity for laminar flow in agitated tank reactors. Hence, a pilot plant installation was designed with geometrically similar equipment to those used for lab scale, obtaining analogous results in terms of recovered polyol properties. Then, the basic design of a split-phase glycolysis industrial plant with a capacity for treating 270 Tm per year of flexible PU foams scraps was proposed. Finally, the economic feasibility of such recycling process was confirmed because of the obtention of a Net Present Value (NPV) of 1,464,555€, with an Internal Rate of Return (IRR) of 27.99%, and a payback time between 4 and 5 years.
There is a concern that artificial reefs (AR) may act purely as fishing aggregation devices. Predators attracted to ARs can
influence the distribution and abundance of prey fish species. Determining the role of predators in AR is important in advancing
the understanding of community interactions. This paper documents the effects of predation on fish assemblages of AR located
near a coastal lagoon fish nursery. The Dicentrarchus labrax is a very opportunistic species preying on juveniles (0+ and 1+ age classes) of several demersal fish species on the ARs. Reef prey and sea bass abundance were negatively correlated. The
mean numbers of prey per sea bass stomach increased with the increase of reef fish prey abundance, suggesting that predation
has a significant influence, resulting in a decrease in prey abundance. Prey mortality (4–48%) of demersal reef fish associated
species depends on bass density. Prey selection was related both with prey abundance and vulnerability. Results showed that
D. labrax predation on AR-fish associated species can increase prey natural mortality. However, the role of bass predation on the ecological
functioning of exploited ARs is not clear. There may be increases in local fishing yields due either to an increase in predator
biomass through aggregation of sea bass attracted to ARs or to greater production. In contrast, predation on juveniles of
economically important reef fish preys, especially the most frequent and abundant (Boops boops), can contribute to a decrease in recruitment to the fishery. Our results indicate that inter-specific interactions (predator–prey)
are important in terms of conservation and management, as well as for the evaluation of the long-term effects of reef deployment.
Thus, it is necessary to consider ecological interactions, such as predation, prior to the development and deployment of artificial
habitats as a tool for rehabilitation. 相似文献
Over 6-million pairs of sooty terns Sterna fuscata breed once a year in the southwest Indian Ocean, mostly on three islands of the Mozambique Channel (Europa, Juan de Nova
and Glorieuses) and in the Seychelles region. Seasonal reproduction in either winter or summer is the dominant strategy in
the area, but non-seasonal reproduction also occurred in some places like at Glorieuses Archipelago. The feeding ecology of
the sooty tern was investigated during the breeding seasons to determine whether terns showed significant differences in their
trophic ecology between locations. Regurgitations were analyzed to describe the diet of individuals when breeding, and stable
isotopes and mercury concentrations were used to temporally integrate over the medium-term of the trophic ecology of both
adults and chicks. Overall, the diet was composed of fish, flying squid and fish larvae in different proportions. At Europa
and Aride in the Seychelles, where winter reproduction occurs, large epipelagic prey like flying fish or squid dominated the
diet. At Juan de Nova, sooty terns reproduce in summer and rely mostly on fish larvae. At Glorieuses (non-seasonal breeding),
the diet was intermediate with fish larvae and flying squid being important prey items. The stable-carbon and nitrogen isotope
values in blood confirm the differences observed in dietary analysis, and demonstrate different feeding strategies between
colonies. δ13C values of feathers showed spatial segregation between birds from the Mozambique Channel and the Seychelles region. Terns
from the Seychelles had also higher δ15N values. Feather δ13C values also suggest a significant shift from summer to wintering habitat for birds from Juan de Nova. This study emphasizes
the high phenotypic plasticity of the species, which may explain its numerical dominance in all tropical waters of the World’s
Ocean. 相似文献