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981.
The persistence of mutualisms despite the strong incidence of exploiters could be explained if exploiters deny one or more services (i.e., cheat) while eventually supplying some subtler but critical services. Pulp feeders usually ingest fruit reward without dispersing seeds and thus are considered to be mainly cheaters or thieves of seed-disperser mutualisms. By consuming the fruit pulp, however, they could release seeds from pulp inhibitory effect, enhancing germination and, potentially, subsequent seedling emergence, growth, survival, and thus local recruitment. We evaluated such a largely neglected hypothesis by considering the interaction between Pyrus bourgaeana and its pulp feeders. We experimentally showed that pericarp removal had a consistent strong positive effect on seed performance (e.g., lower rotting and higher germination percentages) and seedling fate (greater emergence, growth, and survival to two years old). Interestingly, these relatively large positive effects of depulpation on plant fitness persisted for a surprisingly long time. Though seedlings experienced higher mortality under fruiting conspecifics, the benefits of depulpation were not overridden by high propagule mortality beneath fruiting trees or in adverse microhabitats after two years of monitoring. Specifically, the cumulative probability of establishment for depulped seeds was 4-25 times higher than for seeds in whole ripe fruits. Thus, under some circumstances, pulp feeders can provide essential services to endozoochorous plants. Our study contributes to clarifying the apparent paradox of plant-frugivore mutualisms that persist in the face of exploitation by pulp feeders. Because "thieves" and "mutualists" refer to the extremes of a complex continuum, and because organisms displaying concurrent cheating and honest behaviors during different host stages are likely prevalent, the persistent language of mutualists vs. thieves, cheaters, or exploiters might be misleading. 相似文献
982.
Hany Alonso José P. Granadeiro Vitor H. Paiva Ana S. Dias Jaime A. Ramos Paulo Catry 《Marine Biology》2012,159(6):1197-1207
In pelagic seabirds, who often explore distant food resources, information is usually scarce on the level of trophic segregation
between parents and their offspring. To investigate this issue, we used GPS tracking, stable isotopes and dietary information
of Cory’s shearwaters Calonectris diomedea breeding in contrasting environments. Foraging trips at Selvagem Grande (an oceanic island) mainly targeted the distant African
coast, while at Berlenga island (located on the continental shelf), shearwaters foraged mainly over nearby shelf waters. The
degree of isotopic segregation between adults and chicks, based on δ13C, differed markedly between the two sites, indicating that adult birds at Selvagem fed their chicks with a mixture of shelf
and offshore pelagic prey but assimilated more prey captured on coastal shelf waters. Isotopic differences between age classes
at Berlenga were much smaller and may have resulted from limited dietary segregation or from age-related metabolic differences.
The diet of shearwaters was also very different between the two colonies, with offshore pelagic prey only being detected at
Selvagem Grande. Our findings suggest that spatial foraging constraints influence resource partitioning between pelagic seabirds
and their offspring and can lead to a parent–offspring dietary segregation. 相似文献
983.
Chemical signals are important for mate and species recognition. If variation in chemical signals occurs between populations
of the same species, these differences could later preclude mating between populations and lead to speciation. In the Iberian
wall lizard, Podarcis hispanica, the lipophilic fraction of femoral secretions of males is mainly a mix of steroids and fatty acids. Among steroids, the
most abundant compounds are cholesterol and cholesta-5,7-dien-3-ol, which are implicated in intraspecific communication and
sexual selection. Interpopulational differences in chemical signals of males, and in response to these chemicals, could contribute
to reproductive isolation between populations, which would explain the known genetic differences between these populations.
Chemical analyses indicated that five distinct populations of this lizard from Madrid (Central Spain) differed in the proportions
of two steroids (cholesterol and cholesta-5,7-dien-3-ol) in femoral secretions. Moreover, lizards discriminated and had high
chemosensory responses (i.e., high tongue-flick rates) to these steroids, but showed interpopulational differences. Lizards
from populations with cold temperatures and high relative humidity (i.e., northern Madrid) elicited higher responses to these
steroids, whereas the converse occurred for lizards from populations occupying dry and hot habitats (i.e., southern Madrid).
Interestingly, the magnitude of the chemosensory responses to cholesta-5,7-dien-3-ol in each population mirrored the abundance
of this compound in secretions of males of that population. These results suggest that the importance of cholesta-5,7-dien-3-ol
in males’ secretions might be lower for lizards from the southern populations. These differences in the relative importance
of chemical signals could explain reproductive isolation and cryptic speciation between populations of this lizard. 相似文献
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985.
M Martínez-Córcoles M Schöbel FJ Gracia I Tomás JM Peiró 《Journal of Safety Research》2012,43(3):215-221
IntroductionSafety participation is of paramount importance in guaranteeing the safe running of nuclear power plants.MethodThe present study examined the effects of empowering leadership on safety participation.ResultsBased on a sample of 495 employees from two Spanish nuclear power plants, structural equation modeling showed that empowering leadership has a significant relationship with safety participation, which is mediated by collaborative team learning. In addition, the results revealed that the relationship between empowering leadership and collaborative learning is partially mediated by the promotion of dialogue and open communication.ConclusionsThe implications of these findings for safety research and their practical applications are outlined.Impact on IndustryAn empowering leadership style enhances workers' safety performance, particularly safety participation behaviors. Safety participation is recommended to detect possible rule inconsistencies or misunderstood procedures and make workers aware of critical safety information and issues. 相似文献
986.
Laurent Perrin Felipe Muñoz-Giraldo Olivier Dufaud André Laurent 《Safety Science》2012,50(7):1502-1512
During the past 30 years, safety and environmental topics have moved up on the list of society’s significant concerns. Administrations and regulatory bodies have to publish rules for the protection of the public, decide whether to authorize the use of a chemical product or the construction of a new plant, limit the environmental impact, regulate waste disposal, etc. All these rules i.e. the legislative, normative and procedural corpus of a country, a state, a city or a factory can be designated to a barrier function. These barriers are indispensable and play an important role in industrial safety management. In developed countries, growth during the past few years in the number of laws directed at regulating environmental and safety aspects in industry is well known to everyone. Now the definition, classification and performance of the legislative and normative barriers definitely allow the management of technological risks. So it is possible to permit the identification of the flux of hazard and to perform risk reduction in order to enhance the acceptability in a regional context. A systemic risk analysis methodology was applied to Colombian industrial sectors. The current legislation was analyzed with three scenarios. A global panorama of the different existing instruments allowing future management opportunities was suggested. The obtained analysis results propose a point of view, which could be useful for a local government or a whole national system to evaluate or improve the risk legislative and normative barriers. This modeling can be applied to other countries and to other industrial sectors. 相似文献
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