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401.
Rapha?l?JeansonEmail author Jean-Louis?Deneubourg Anne?Grimal Guy?Theraulaz 《Behavioral ecology and sociobiology》2004,55(4):388-394
Insect societies are often confronted with choices among several options such as food sources of different richness or potential nest sites with different qualities. The mechanisms by which a colony as a whole evaluates these situations and takes the appropriate decision are of crucial importance for its survival. Here we studied how collective decisions arise from individual behaviors when a group of workers of the ant Messor barbarus is given a choice between two aggregation sites. Two hundred ants were introduced into an arena and given a choice between two tubes connected to the arena. The tubes had different physical properties: dry and transparent (termed as dry), humid and transparent (termed as humid), or dry and dark (termed as dark). After 30 min, most ants were found to be aggregated in a humid tube when paired with a dry tube, or in a dark tube when paired with a humid one. When two humid tubes were in competition, ants aggregate more in one of the sites. The choice of ants was consistent throughout experiments. An analysis of individual behaviors shows that the probability of an ant recruiting and the intensity of its trail-laying behavior strongly depend on the quality of the tubes. Our study suggests that the selection of an aggregation site does not require that individual ants directly compare sites, but rather relies on the synergy between amplification processes involving recruitment by chemical trails, and a modulation of the individual resting time in a site as a function of its population.Communicated by L. Sundström 相似文献
402.
Maud C. O. Ferrari Myles R. Brown Michael S. Pollock Douglas P. Chivers 《Chemoecology》2007,17(3):157-161
Summary. Many aquatic prey are known to use chemical alarm cues to assess their risk of predation. In fishes, such alarm cues can be
released either through damage of the epidermis during a predatory attack (capture-released) or through release from the predator
feces (diet-released). In our study, we compared the importance of capture- versus diet-released alarm cues in risk assessment
by fathead minnows (Pimephales promelas) that were na?ve to fish predators. We utilized two different fish predators: a specialized piscivore, the northern pike
(Esox lucius) and a generalist predator, the brook trout (Salvelinus fontinalis). Handling time of pike consuming minnows was much shorter than for trout consuming minnows, likely resulting in less epidermal
damage to the minnows during attacks by pike. In accordance with this, minnows showed a less intense antipredator response
to capture-released cues from pike than capture-released cues from trout. This represents a paradox in risk assessment for
the minnows as they respond to the specialized piscivore, the more dangerous predator, with a less intense antipredator response.
In contrast, the minnows showed a stronger antipredator response to the specialized piscivore than to the generalist when
given diet cues. This work highlights the need for researchers to carefully consider the nature of the information available
to prey in risk assessment. 相似文献
403.
Biotic Impoverishment and Homogenization in Unfragmented Forest Understory Communities 总被引:11,自引:0,他引:11
THOMAS P. ROONEY SHANNON M. WIEGMANN DAVID A. ROGERS D. M. WALLER 《Conservation biology》2004,18(3):787-798
Abstract: Ecological change is often hard to document because of a lack of reliable baseline data. Several recent then-versus-now surveys of temperate forest and grassland communities demonstrate losses of local plant species, but most are based on data from a single site. We resurveyed understory communities in 62 upland forest stands in northern Wisconsin (U.S.A.) for which quantitative baseline data exist from 50 years ago. These stands are within a largely unfragmented region but vary in species composition and successional stage. We collected data on changes in (1) total and native species richness, (2) the ratio of exotic to native species, (3) the relative abundance of habitat generalists, and (4) community similarity among sites. We also compared how these rates of change varied over time. Over the past 50 years, native species density declined an average of 18.5% at the 20-m2 scale, whereas the ratio of exotic species to native species increased at 80% of all sites. Habitat generalists increased, and habitat specialists declined, accounting in part for an 8.7% rise in average similarity in species composition among sites. Most of these changes cannot be related to succession, habitat loss, or invasion by exotic species. Areas without deer hunting showed the greatest declines in native species density, with parks and research natural areas faring no better than unprotected stands. Animal-pollinated and animal-dispersed species also declined, particularly at unhunted sites. These results demonstrate the power of quantitative multistand data for assessing ecological change and identify overabundant deer as a key driver of community change. Because maintaining forest habitats alone fails to preserve plant diversity at local scales, local biotic simplification seems likely to continue in the region unless active efforts are taken to protect diversity. 相似文献
404.
上海郊区旱作农田氮素流失研究 总被引:3,自引:0,他引:3
通过测坑和大田小区试验,研究了上海郊区旱作农田氮素降雨径流和降雨渗漏流失的特征、相关因素和流失负荷。结果表明:平水年重质土麦地总氮流失负荷为18. 38 kg·hm-2,其中降雨径流总氮流失负荷为4. 4kg·hm-2,渗漏为13. 98kg·hm-2;菜地总氮流失量为55. 65kg·hm-2,其中降雨径流总氮流失负荷为21. 6kg·hm-2,渗漏为34. 05kg·hm-2;旱田氮素流失以硝态氮为主,占总氮90%左右。施用有机肥可较大幅度地减少旱田的氮素渗漏流失。 相似文献
405.
氮在水稻中的行为及其品种间的差别 总被引:3,自引:1,他引:3
目前氮肥的利用效率很低,很多研究重点放在氮肥在土壤过程中的损失,对植物本身的氮素损失较少注意。作者利用^15NH4^ 和^15NO3^-双标记,对Indica和Japonica水稻亚种进行水培,在分蘖期、幼穗分化期、开花期施用,将培养液ρ(N)20mg/L的NH4NO3换成相同质量浓度的^15NH4^ NO3或NH^15NO3^;部分水稻在一周后收获,其他分别在分蘖期、幼穗分化期、开花期、成熟期收获。植株分成根系、地上部和穗部,对各自的全氮、^15N进行测定,计算植物的总吸收量。从施用量、植株总吸收量以及三部分总和的植株氮残存量的比较来研究氮素在两种水稻亚种中的行为。研究结果表明,两种植物都近100%吸收了所施用的^15NH4NO3或NH4^15NO3,但^15NH4^ 和^15NO3^-在Japonica的残存量要比Indica多,损失的部分可能往大气中散失了,意味着两种水稻亚种有着明显不同的氮素利用率。比较^15NH4^ 和^15NO3^-的残存量,结果表明^15NH4^ 留在植株体内要比^15NO3^-多,尤其在抽穗期施用的情况下,植物体在后期对^15NO3^-的转化能力大大减弱,但这部分的氮如何损失掉尚不清楚。比较植株体内各部分的氮素含量,发现Japonica的穗部比Indica含有更多的氮素,表明氮在前者的体内转化效率和利用效率高。试验结果表明,不同水稻亚种对氮素的利用以及不同氮素形态在其体内的行为不同。 相似文献
406.
407.
408.
409.
通过介绍环境空气中二氧化氮的测定方法──自动仪器监测法,对有关问题进行了初步探讨和研究,为正确使用该方法和仪器,确保监测工作的顺利进行提供了依据。 相似文献
410.
Bruno Brambati Giuseppe Simoni Maurizio Travi Cesare Danesino Lucla Tului Orsola Privitera Sabine Stioui Silvana Tedeschi Silvia Russo Paola Primignani 《黑龙江环境通报》1992,12(10):789-799
Transabdominal chorionic villus sampling (TA-CVS) was attempted in 328 high-risk pregnancies at 6–7 weeks of gestation. Sampling was feasible in 97.7 per cent of cases; chorionic tissue specimens of more than 10 mg were obtained in 94.4 per cent ofcases at the first needle insertion and in 100 per cent after a second attempt. Fetal karyotyping succeeded in 99.4 per cent of cases, while no diagnostic failures were reported in enzymatic and DNA analyses. Fetal loss rate in the first 4 weeks after CVS was significantly higher than in the later CVS series (7.2 vs. 2.5 per cent), but 50 per cent of losses were observed within 2 weeks in cases of inviable aneuploidies. A high incidence of severe limb abnormalities (1.6 per cent) was detected in pregnancies intended to continue, confirming the aetiological role of early CVS. Unclear visualization of the placental limits and poor control of the needle path are thought to be the main reasons for the vascular disruption of the chorionic plate, and thereby hypoxic embryo tissue damage. A better selection of cases, together with high-resolution vaginal ultrasound visualization, and analytical techniques requiring a minimal amount of tissue should avoid any teratogenic effect of early CVS. 相似文献