两维缺陷分析:用于保护规划和实施生物多样性政策的有效手段

在景观水平的管理中,为了保护具有代表性和连接成片的生境网络,以达到维持生物多样性的目的,就必须在不同规模上将保护、经营和生境恢复等几项工作有机结合.我们认为将自然和社会科学融为一体的两维缺陷分析方法是实施生物多样性政策的有效工具.这个工具把与生物相关的"水平"生态学问题与"垂直"的制度体制和其它社会问题有机结合考虑.以森林生物多样性为例,本文将演示如何将与生物多样性保护有关的生态学和制度等方面的问题综合考虑,从而促进整个区域发展的环境可持续性.尤其,我们用区域性缺陷分析方法,即先确定对"绿色基础设施"起功能性连接作用的重点森林类型和生境模型,以此作为工具进行"水平"缺陷分析.就"垂直"范围而论,通过鉴别政策实施中的体制性障碍我们指出社会科学如何用于在实际景观范围内评估生物多样性政策实施是否成功.研究表明,多学科间的合作方法能应用于其它各类环境,包括其它陆生生物和水生生态系统,在这些生态系统中,重要栖息地的连接性、对栖息地丧失的非线性响应,以及社会和经济问题在同一景观内交织在一起.     

NitroGenius:氮决策支持系统--荷兰氮污染问题最佳解决方案的一个游戏模拟实验

利用计算机模拟的方法,我们为第二届国际氮会议研制开发了一个游戏形式的氮决策支持系统.研制这一系统的目的是:①使科学工作者和决策者们都能认识到荷兰氮污染问题的复杂性,因为荷兰是一个农业、工业和运输业活动密集的区域;②探索以最低的社会经济代价解决氮污染的最佳方案.NitroGenius由有关时空范围内的氮流动模型组成,其中包括氨和氮氧化合物的释放及其对地表水和地下水的污染.NitroGenius中还包括了一个经济模型,它描述了各个重要经济部门之间的关系,以及不同氮排放控制措施对国民生产总值(GDP)、失业率、能源消耗和环境的影响.在第二次国际氮会议期间,大约有50个研究组对NitroGenius进行了测试,结果表明,如果认真进行计划并选择适当的治理措施,就能够以适当的代价解决荷兰的氮污染问题.     

Cytoskeletal elements in the bacterium Mycoplasma pneumoniae

Mycoplasma pneumoniae is a pathogenic eubacterium lacking a cell wall. Three decades ago, a "rod", an intracellular cytoskeletal structure, was discovered that was assumed to define and stabilize the elongated cell shape. Later, by treatment with detergent, a "Triton shell" (i.e. a fraction of detergent-insoluble cell material) could be obtained, believed to contain additional cytoskeletal elements. Now, by application of a modified Triton X-100 treatment, we are able to demonstrate that M. pneumoniae possesses a cytoskeleton consisting of a blade-like rod and a peripheral lining located close to the inner face of the cytoplasmic membrane, exhibiting features of a highly regular network. Attached "stalks" may support the cytoplasmic membrane. The rod was connected to the cell periphery by "spokes" and showed a defined ultrastructure. Its proximal end was found to be attached to a wheel-like complex. Fibrils extended from the proximal end of the rod into the cytoplasm.     

Fuel breaks affect nonnative species abundance in Californian plant communities.

We evaluated the abundance of nonnative plants on fuel breaks and in adjacent untreated areas to determine if fuel treatments promote the invasion of nonnative plant species. Understanding the relationship between fuel treatments and nonnative plants is becoming increasingly important as federal and state agencies are currently implementing large fuel treatment programs throughout the United States to reduce the threat of wildland fire. Our study included 24 fuel breaks located across the State of California. We found that nonnative plant abundance was over 200% higher on fuel breaks than in adjacent wildland areas. Relative nonnative cover was greater on fuel breaks constructed by bulldozers (28%) than on fuel breaks constructed by other methods (7%). Canopy cover, litter cover, and duff depth also were significantly lower on fuel breaks constructed by bulldozers, and these fuel breaks had significantly more exposed bare ground than other types of fuel breaks. There was a significant decline in relative nonnative cover with increasing distance from the fuel break, particularly in areas that had experienced more numerous fires during the past 50 years, and in areas that had been grazed. These data suggest that fuel breaks could provide establishment sites for nonnative plants, and that nonnatives may invade surrounding areas, especially after disturbances such as fire or grazing. Fuel break construction and maintenance methods that leave some overstory canopy and minimize exposure of bare ground may be less likely to promote nonnative plants.     

Prey vulnerability in relation to sexual coloration of prey

Sexual selection that results in the evolution of exaggerated secondary sexual characters has been hypothesized to impose production and maintenance costs of such traits on their bearers. Costs arising from sexual selection could increase the intensity of predator-mediated natural selection, leading to the prediction that species with exaggerated secondary sexual characters should be particularly susceptible to predation. We tested this prediction in a comparative analysis based on 31,745 prey individuals belonging to 66 species of birds collected from a total of 937 breeding events by 33 to 66 different pairs of European sparrowhawks Accipiter nisus annually during a period of 21 years. To assess vulnerability of different species we estimated a prey vulnerability index based on the difference in the logarithmically transformed absolute abundance of prey minus the logarithmically transformed expected abundance as determined by population density of breeding birds. The prey vulnerability index was predicted by sexual dichromatism, accounting for 23% of the variance in risk of predation among species, even when considering similarity in phenotype among species due to common descent (in the latter case explaining 12% of the variance). This finding suggests that sexual selection is an important evolutionary force-affecting predator–prey interactions.Electronic Supplementary Material Supplementary material is available for this article at     

Experimental evidence for helping and hindering by previous offspring in the cooperative-breeding Seychelles warbler Acrocephalus sechellensis

Prebreeding Seychelles warblers (Acrocephalus sechellensis) frequently act as helpers on their natal territory, aiding in territory defence, predator mobbing, nestbuilding, incubation (only females) and feeding dependent young of their parents. In some cases helpers could attain breeding status (e.g. by joint-nesting) in their natal group and become co-breeders. Comparisons of group size and reproductive success on a given quality territory suggest that the presence of alloparents (helpers and cobreeders) significantly affects the reproductive success of their parents. The influence of alloparents on reproductive success was examined by removing alloparents from breeding units and comparing the success of natural-sized and artificially reduced groups. Removal experiments, controlled for territory quality, group size and breeder age, showed that the presence of one alloparent significantly improved the reproductive success of its parents. Analysis strongly suggests that this was entirely due to helping behaviour (i.e. providing care to offspring of their parents), thereby improving the helper's inclusive fitness benefits from staying at home. However, these experiments showed also that the presence of two or more alloparents in medium-quality territories significantly decreased reproductive success, compared with groups with one alloparent. Several lines of evidence suggest that this may have been due to the joint-nesting and reproductive competition that could occur in breeding groups, or simply to resource depression when a large number of previous offspring remained on their natal territory.