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431.
Spotted bowerbirds<Emphasis Type="Italic"> Chlamydera maculata</Emphasis> do not prefer rare or costly bower decorations 总被引:2,自引:0,他引:2
Females target elaborate secondary sexual traits to acquire either direct benefits, represented or provided by the trait, or indirect benefits usually in the form of genetic components. The link between a males trait and his potential genetic contribution is often unclear. Bowers are extreme examples of secondary sexual traits, built and decorated by males and targeted by females. However, why females should base their mate choice on such structures is unclear. One of the simplest suggestions is that bowers are sites where males exhibit collections of objects that are inherently highly costly, indicating male quality to the choosy female. Such costs can be imposed in two ways, acquisition from the local area, and maintenance in the face of degradation. We studied bowers of spotted bowerbirds Chlamydera maculata at three sites in central Queensland and tested whether components of the bowers that best predict mating success were some of the most costly in the local environment by measuring their abundance, physical dimensions and rate of decay. We also tested whether rare objects per se found on the bowers, were relatively good predictors of mating success. Finally, we experimentally tested whether males preferentially chose rare, and hence costly, objects to use as decorations. We found that objects used on bowers were not unusually costly. Specific objects identified as good predictors of mating success were also some of the more common objects found in the area. They were not the largest objects used on bowers and decayed slowly relative to other objects available for use as decorations. Rare objects in general were not good predictors of mating success and males did not prefer to use rare objects when offered choices. In conclusion, we found no support for the theory that by simply inspecting numbers of decorations and assessing their costs of acquisition and maintenance females can easily obtain information regarding the owners quality. This is due to the fact that decorations used by spotted bowerbirds are not inherently costly.Communicated by J. Graves 相似文献
432.
Summary. Summary. Oilseed rape, Brassica napus L. (cv Express),
plants were grown under three different sulphur regimes:
sulphur-free (S0), normal sulphur (Sn, normal field concentration)
and a sulphur-rich (S+, 2 × concentration of Sn). We
performed dual choice oviposition assays with the diamondback
moth, Plutella xylostella, using real plants and,
for the first time with this insect, artificial leaves sprayed
with methanolic leaf-surface extracts. The results mirrored
those of a separate study of preferences for whole plants.
Females laid more eggs on surrogate leaves that were
treated with Sn extracts than on S0 plants, while only a
slight, not significant, difference was observed between
extracts of normal and sulphur-rich plants. This shows
that chemical compounds on the leaf surface mediate the
oviposition preference and that the female insect can
perceive the quality of the host-plants in terms of their
fertilisation status.Since leaf volatiles are known to be oviposition stimulants,
we investigated the effects of leaf-surface extracts on
insect olfactory responses using electroantennograms
(EAGs). In agreement with the behavioural data, we found
that extracts of sulphur-treated plants yielded higher EAG
amplitudes than the S0 extracts. Since the leaf content of the
volatiles isothiocyanates is influenced by sulphur nutrition,
we analysed the extracts for these compounds. Above the
detection threshold of our GC-MS system, no isothiocyanates
were found. Thus, other compounds present in the
surface extracts must be perceived by the antenna.However, the HPLC analysis revealed 11 different
glucosinolates. Progoitrin (2-Hydroxy-3-butenyl) and
gluconapoleiferin (2-Hydroxy-4-pentenyl), which belong to
the hydroxy-alkene class of glucosinolates, were the most
abundant compounds. The total glucosinolate content
sharply increased from S0 to Sn plants, whereas it was slightly
lower in n versus S+ plants. Since it is known that glucosinolates
can stimulate oviposition, it seems likely that the
increased content we observed was influencing the insect
preference in this study too. 相似文献
433.
城市旅游地旅游安全评价指标体系研究 总被引:3,自引:0,他引:3
在深入分析城市旅游安全系统构成的基础上,分析了影响城市旅游安全的主要因素,构建了测评城市旅游安全状态的指标体系,应用层次分析方法建立了测评的数学模型,并提出建设安全旅游城市的策略与措施,以期为城市旅游安全管理提供决策依据。 相似文献
434.
Repetitive flood victims and acceptance of FEMA mitigation offers: an analysis with community-system policy implications 总被引:1,自引:0,他引:1
Of all natural disasters, flooding causes the greatest amount of economic and social damage. The United States' Federal Emergency Management Agency (FEMA) uses a number of hazard mitigation grant programmes for flood victims, including mitigation offers to relocate permanently repetitive flood loss victims. This study examines factors that help to explain the degree of difficulty repetitive flood loss victims experience when they make decisions about relocating permanently after multiple flood losses. Data are drawn from interviews with FEMA officials and a survey of flood victims from eight repetitive flooding sites. The qualitative and quantitative results show the importance of rational choices by flood victims in their mitigation decisions, as they relate to financial variables, perceptions of future risk, attachments to home and community, and the relationships between repetitive flood loss victims and the local flood management officials who help them. The results offer evidence to suggest the value of a more community-system approach to FEMA relocation practices. 相似文献
435.
面对当前汞污染日益严峻的趋势,分析了燃煤锅炉烟气其它污染物(如二氧化硫、氮氧化物、颗粒物)控制设施及其运行情况,结合所燃用的煤质情况,介绍了燃煤锅炉烟气汞减排各种经济实用的方法,以及选择汞排放控制措施的“抉择树”。根据燃煤锅炉烟气实际情况,确定可采用的汞减排控制技术,必要时采取活性炭喷射脱汞技术(ACI),最大限度地提高协同除汞效果。同时提出了应注重燃煤残留物中汞的二次污染问题。 相似文献
436.
Abstract This study is to investigate what factors and how they affect tours (trip chains) behavior. The key issue is the understanding and definition of tour and tour level mode. Also, these definitions should fit for the data. A semi-home based tour definition is stated, and a competing mode based tour mode is defined. Based on the definition, this study used Madison Area Data from National Household Survey to estimate a MNL structured model. It is found that travel distance could be a positive factor for car mode. Meanwhile, the number of trips is also a positive factor for choosing car. 相似文献
437.
处理好发展经济与保护环境的关系,尤其是项目建设与节能减排的关系,这是实现可持续发展的关键。近年来,一些地区和城市,把节能减排作为促进科学发展的重要手段,推进经济可持续发展,取得了可喜的成绩。但是,也存在着不少障碍。在肯定对节能减排初见成效的基础上,对节能减排障碍进行了剖析,为了加大节能减排与环境保护力度,阐述了国家节能减排的行业政策,提出了节能减排的十项路径选择。 相似文献
438.
为分析驾驶人高速公路施工区合流选择意愿的影响因素,基于非集计理论构建多属性施工区驾驶人合流选择意愿模型。利用SP调查法自主设计调查问卷,获得328份有效施工区驾驶人合流选择数据;利用Pearson相关系数分析施工区合流选择意愿与驾驶人因素和道路交通环境因素的相关性;以上游过渡区、警告区Ⅰ和警告区Ⅱ 3个合流区域作为选择肢,从驾驶人和道路交通环境特征属性2个方面归纳出6个因素对施工区合流选择意愿的影响,应用分类变量处理方法将其定义为6种指标,并进行赋值。结合非集计理论,以328份有效问卷为建模数据,建立施工区合流选择意愿的MNL模型,并利用似然比、优度比和模型命中率3个指标判断模型的拟合程度。结果表明:模型拟合程度较好;驾龄、施工区类型、道路条件、交通控制标志、速度条件和限速策略对驾驶人施工区合流选择意愿有显著影响。 相似文献
439.
af Wåhlberg AE 《Journal of Safety Research》2006,37(1):43-51
INTRODUCTION: The driver celeration behavior theory predicts that this variable is superior to all other variables as a predictor of individual traffic accident involvement, including the ever-important speed parameter. The study was undertaken to test this prediction. Also, it was expected that most variables would associate fairly strongly. METHOD: The use of speed choice as a predictor of individual traffic accident record was discussed, and four different variants of this variable (maximum, net mean, gross mean, and standard deviation of speed) identified. These variables were then compared to celeration behavior as predictors of accident record of bus drivers in the same set of data. RESULTS: Celeration behavior was found to be slightly superior, in accordance with the prediction made from the driver celeration behavior theory, although the differences were not significant. Furthermore, the predictor variables were found to associate fairly strongly between themselves, with the exception of gross mean speed, and to have fair stability over time, especially when aggregated. CONCLUSIONS: These results tentatively confirm some of the predictions made from the driver celeration behavior theory. As the results for accidents were in the expected direction, but not significant, and the maximum speed variable may have suffered from a ceiling effect, the conclusion is provisional. Impact on industry: The correlations found were strong enough to warrant the use of celeration behavior as a predictive variable for transportation companies in their safety work. 相似文献
440.
管道线路优化中的环境问题 总被引:1,自引:0,他引:1
石油工业干线管道的建设和运营给沿线周围环境带来了诸多不利影响。针对管道系统的主要破坏原因及其环境影响,提出在考虑环境保护前提下优选线路的经济分析模式,并推荐了环境损害的估算方法。 相似文献