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61.
Arguing Tropical Forest Conservation: People versus Parks 总被引:2,自引:0,他引:2
Stephan Schwartzman Daniel Nepstad † and Adriana Moreira† 《Conservation biology》2000,14(5):1370-1374
62.
Association patterns among male and female spotted hyenas (Crocuta crocuta) reflect male mate choice
Micaela Szykman Anne L. Engh Russell C. Van Horn Stephan M. Funk Kim T. Scribner Kay E. Holekamp 《Behavioral ecology and sociobiology》2001,50(3):231-238
Although female animals tend to be choosier than males in selecting mates, sexual selection theory predicts that males should also be choosy when female fecundity varies. Reproductive success among female spotted hyenas varies greatly with social rank. Our goals were therefore to determine whether male hyenas preferentially associate with high-ranking females, and whether male preferences are affected by female reproductive state. Interactions between adult males and females were observed intensively, and association indices calculated for all male-female pairs, over a 7-year period in one population of free-living hyenas. Males initiated most affiliative interactions with females, and males associated most closely with females that were likeliest to be fertile. High- and middle-ranking males associated most closely with high-ranking females, but low-ranking males associated equally closely with females in all rank categories. We used molecular markers to determine the paternity of cubs born during the study period, and found that sires associated more closely with the mothers of those cubs than did non-sires, particularly during the last months before conception. These association data indicate that male spotted hyenas do indeed exhibit selective mate choice, and that they prefer females likeliest to maximize male reproductive success. 相似文献
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64.
A European model for waste and material flows 总被引:1,自引:1,他引:1
Frits Mller Andersen Helge Larsen Mette Skovgaard Stephan Moll Stphane Isoard 《Resources, Conservation and Recycling》2007,49(4):421-435
The use of materials and the generation of waste are linked to economic activities and in many projections these are assumed to be a constant ratio of the economic activities. This may be the case considering detailed economic activities and unchanged technology. However, the assumption of constant coefficients is questionable when linking material use and waste generation to aggregated economic activities. Therefore, in this paper, econometrics is used to test the assumption of constant waste coefficients empirically. The analyses show that an assumption of constant waste coefficients is not supported, generally, and a model allowing for trendwise changing coefficients is developed and used for projections of waste and material flows in 25 European countries. 相似文献
65.
66.
The production of polyhydroxyalkanoates(PHA) from wastewaters using microbial mixed cultures(MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an MMC enriched with PHA-accumulating bacteria was compared using anaerobically treated and acidified brewery wastewaters under various feeding strategies, namely pulse and batch feed addition. To obtain an enriched MMC, a sequencing batch reactor was inoculated with activated sludge fed with acetate and subjected to aerobic dynamic feeding. The enriched MMC was able to accumulate PHA up to 72.6% of cell dry weight(CDW) with pulse addition of acetate controlled by the dissolved oxygen(DO) concentration in the reactor. In a batch accumulation experiment with acetate,the PHA content achieved(28.5% CDW) was less than that of the pulse feeding strategy with the same amount of acetate(~2000 mg C/L). Using anaerobically treated and acidified brewery wastewater fed in pulses, the maximum PHA accumulated by the enriched MMC was similar for both wastewaters(45% CDW), in spite of the higher volatile fatty acid concentration in acidified brewery wastewater. The pulse feed addition controlled by the DO concentration was difficult to implement for wastewater as compared to acetate because the difference in DO concentration between substrate availability and depletion was low. For the batch addition of acidified wastewater, a slightly lower PHA content(39%CDW) was obtained. These results show that both brewery wastewaters can be utilized for PHA production with a similar maximum PHA storage capacity. 相似文献
67.
Florian Karolyi Linde Morawetz Jonathan F. Colville Stephan Handschuh Brian D. Metscher Harald W. Krenn 《Die Naturwissenschaften》2013,100(11):1083-1093
A well-developed suction pump in the head represents an important adaptation for nectar-feeding insects, such as Hymenoptera, Lepidoptera and Diptera. This pumping organ creates a pressure gradient along the proboscis, which is responsible for nectar uptake. The extremely elongated proboscis of the genus Prosoeca (Nemestrinidae) evolved as an adaptation to feeding from long, tubular flowers. According to the functional constraint hypothesis, nectar uptake through a disproportionately elongated, straw-like proboscis increases flower handling time and consequently lowers the energy intake rate. Due to the conspicuous length variation of the proboscis of Prosoeca, individuals with longer proboscides are hypothesised to have longer handling times. To test this hypothesis, we used field video analyses of flower-visiting behaviour, detailed examinations of the suction pump morphology and correlations of proboscis length with body length and suction pump dimensions. Using a biomechanical framework described for nectar-feeding Lepidoptera in relation to proboscis length and suction pump musculature, we describe and contrast the system in long-proboscid flies. Flies with longer proboscides spent significantly more time drinking from flowers. In addition, proboscis length and body length showed a positive allometric relationship. Furthermore, adaptations of the suction pump included an allometric relationship between proboscis length and suction pump muscle volume and a combination of two pumping organs. Overall, the study gives detailed insight into the adaptations required for long-proboscid nectar feeding, and comparisons with other nectar-sucking insects allow further considerations of the evolution of the suction pump in insects with sucking mouthparts. 相似文献
68.
69.
In intensively used arable areas, a contamination of the reproduction ponds with pesticides probably impairs the development of spawn and tadpoles of amphibians, based on the coincidental space and time. Therefore, the effects of the herbicide isoproturon (IPU) on the early life stages of the firebellied toad (Bombina bombina) and the closely related yellowbellied toad (Bombina variegata) were investigated. The results of the exposure with14C-labelled IPU (1 μg/L) indicated an uptake into the spawn and tadpoles of bothBombina species. The jelly capsules could not protect the embryo from effects of the herbicide. Tadpoles with complete opercula and without external gills were most sensitive to contamination by IPU. Physical and behavioral abnormalities of the tadpoles developed at concentrations, of 0.1 μg/L after 24 h exposure. At increasing IPU-concentrations the number of impaired and dead tadpoles increased significantly compared to the control. The enzymatic system of the Glutathion S-Transferase (GST) of theBombina tadpoles were influenced significantly by the duration and concentration of IPU exposure. Compared to the pure active ingredient IPU, the commercial herbicide TOLKAN FLO® provoked a stronger enzymatic response in the tadpoles. This could be caused by the presence of an emulsifier used in the TOLKAN FLO® formulation which enhanced the availability of IPU and/or the interaction between IPU and the emulsifier. 相似文献