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1.
Nest-building by crested tit Parus cristatus males: an analysis of costs and benefits 总被引:1,自引:0,他引:1
In a population of crested tits in Belgium, one out of three breeding males participated in nest-building. Since variation in the amount of nest-building among 11 building males was low, analysis of male nest-building allowed a logistic regression design. The probability of building increased with male condition and for late nests. The effect of male condition decreased with date, and date was the only factor predicting nest-building for repeat broods. The effect of male condition on nest-building suggests that building entails important costs for males. Based on correlative data, we argue that building by males shortens the interval between the start of nest-building and the onset of egg-laying by about 5 days. Since clutch size, incubation and nestling time did not differ between early and late broods, male nest-building apparently affects fledging date. Since early fledgers (early dispersers) are more likely to settle in future winter flocks, building behaviour by crested tit males should be favoured by natural selection. So far, male nest-building in hole-breeding birds might have been overlooked due to the widespread use of artificial nest-boxes in behavioural studies. 相似文献
2.
草履虫──针杆藻群落对混合印染废水净化作用的条件实验 总被引:2,自引:0,他引:2
本文对混合印染废水的静态净化过程,进行了生物群落观察和条件实验。发现废水净化初期以大量细菌和草履虫(以 P. Caudatum为主)繁殖为特征,同时伴生着少量浮游藻类。随着净化过程的进行,细菌和草履虫数量下降,以针杆藻(以 S. aucs为主)为建群种的浮游藻类群落占优势。化学分析表明,净化作用与温度、光照条件及废水起始浓度有关。 相似文献
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The activity of 210Po and 210Pb was determined in mussels of the same size (3.5-4.0 cm shell length) sampled monthly over a 17-month period at the Atlantic coast of Portugal. Average radionuclide concentration values in mussels were 759 ± 277 Bq kg−1 for 210Po (range 460-1470 Bq kg−1 dry weight), and 45 ± 19 Bq kg−1 for 210Pb (range 23-96 Bq kg−1 dry weight). Environmental parameters and mussel biometric parameters were monitored during the same period. Although there was no seasonal variation of radionuclide concentrations in sea water during the study period, the concentration of radionuclide activity in mussels varied seasonally displaying peaks of high concentrations in winter and low concentrations in summer. Analysis of radionuclide data in relation to the physiological Condition Index of mussels revealed that 210Po and 210Pb activities in the mussel (average activity per individual) remained nearly constant during the investigation period, while mussel body weight fluctuated due to fat storage/expenditure in the soft tissues. Similar variation of radionuclide concentrations was observed in mussels transplanted from the sea coast into the Tejo Estuary. However, under estuarine environmental conditions and with higher food availability throughout the year, transplanted mussel Condition Index was higher than in coastal mussels and average radionuclide concentrations were 210 ± 75 Bq kg−1 (dry weight) for 210Po and 10 ± 4 Bq kg−1 (dry weight) for 210Pb, therefore lower than in coastal mussels with similar shell length. It is concluded that the apparent seasonal fluctuation and inter-site difference of radionuclide concentrations were mostly caused by mussel body weight fluctuation and not by radionuclide body burden fluctuation. This interpretation can be extended to the apparent seasonal fluctuation in concentrations of lipophilic and lipophobic contaminants in mussels, and provides an explanation for occasional high concentrations of 210Po and man-made contaminants measured in mussels far from pollution sources. 相似文献
6.
An integrated approach for performance assessment and management of safety barriers in a systemic manner is needed concerning the prevention and mitigation of major accidents in chemical process industries. Particularly, the effects of safety barriers on system risk reduction should be assessed in a dynamic manner to support the decision-making on safety barrier establishments and improvements. A simulation approach, named Simulink-based Safety Barrier Modeling (SSBM), is proposed in this paper to conduct dynamic risk assessment of chemical facilities with the consideration of the degradation of safety barriers. The main functional features of the SSBM include i) the basic model structures of SSBM can be determined based on bow-tie diagrams, ii) multiple data (periodic proof test data, continuous condition-monitoring data, and accident precursor data) may be combined to update barrier failure probabilities and initiating event probabilities, iii) SSBM is able to handle uncertainty propagation in probabilistic risk assessment by using Monte Carlo simulations, and iv) cost-effectiveness analysis (CEA) and optimization algorithms are integrated to support the decision-making on safety barrier establishments and improvements. An illustrative case study is demonstrated to show the procedures of applying the SSBM on dynamic risk-informed safety barrier management and validate the feasibility of implementing the SSBM for cost-effective safety barrier optimization. 相似文献
7.
Response of Fish and Macroinvertebrate Bioassessment Indices to Water Chemistry in a Mined Appalachian Watershed 总被引:1,自引:0,他引:1
Multimetric indices based on fish and benthic macroinvertebrate assemblages are commonly used to assess the biological integrity
of aquatic ecosystems. However, their response to specific stressors is rarely known. We quantified the response of a fish-based
index (Mid-Atlantic Highlands Index of Biotic Integrity, MAH-IBI) and a benthic invertebrate-based index (West Virginia Stream
Condition Index, WV-SCI) to acid mine drainage (AMD)-related stressors in 46 stream sites within the Cheat River watershed,
West Virginia. We also identified specific stressor concentrations at which biological impairment was always or never observed.
Water chemistry was extremely variable among tributaries of the Cheat River, and the WV-SCI was highly responsive across a
range of AMD stressor levels. Furthermore, impairment to macroinvertebrate communities was observed at relatively low stressor
concentrations, especially when compared to state water quality standards. In contrast to the WV-SCI, we found that the MAH-IBI
was significantly less responsive to local water quality conditions. Low fish diversity was observed in several streams that
possessed relatively good water quality. This pattern was especially pronounced in highly degraded subwatersheds, suggesting
that regional conditions may have a strong influence on fish assemblages in this system. Our results indicate that biomonitoring
programs in mined watersheds should include both benthic invertebrates, which are consistent indicators of local conditions,
and fishes, which may be indicators of regional conditions. In addition, remediation programs must address the full suite
of chemical constituents in AMD and focus on improving linkages among streams within drainage networks to ensure recovery
of invertebrate and fish assemblages. Future research should identify the precise chemical conditions necessary to maintain
biological integrity in mined Appalachian watersheds. 相似文献
8.
Joel W. McGlothlin Deborah L. Duffy Jessica L. Henry-Freeman Ellen D. Ketterson 《Behavioral ecology and sociobiology》2007,61(9):1391-1399
Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition
dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources.
White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment
nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined
the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce
replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers
grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather
growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger
in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together,
these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition
dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may
lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness. 相似文献
9.
Martin Plath Katja U. Heubel Francisco J. García de León Ingo Schlupp 《Behavioral ecology and sociobiology》2005,58(2):144-151
We examined the preference of Atlantic molly females (Poecilia mexicana) to associate with a well-fed or a starved male in simultaneous choice tests. Females from three different populations were tested in three treatments: (1) the females could choose on the basis of multiple cues from the males (visual plus non-visual); (2) only non-visual cues could be perceived in darkness, (3) only visual cues were presented. The three tested populations differ clearly in their ecology: one population occurs in a typical river habitat, the second one in a milky sulfur creek outside a cave, and the third population occurs in a cave habitat (cave molly). In the river-dwelling population, females never showed a preference. In the population from the sulfur creek, females preferred to associate with the well-nourished male when visual cues from the males were available. Only cave molly females exhibited a strong preference for well-nourished males in all treatments. A morphological comparison demonstrated that wild-caught males from river habitats are typically in a good nutritional state. In the sulfur creek, males showed signs of starvation. Cave molly males were in an even worse nutritional state. In the cave population, saturated males probably indicate high fitness, thereby driving the evolution of the preference for good male nutritional state.Communicated by K. Lindström 相似文献
10.
利用2014年铜川市空气质量指数(AQI)、常规气象资料和NECP/NCAR再分析资料,分析2014年铜川市AQI与首要污染物的时间分布,并探讨典型重污染时段的气象条件。结果表明:夏季AQI小于全年均值,首要污染物以臭氧为主,秋冬AQI较高,首要污染物以PM为主。2月的环流条件不利于污染物的扩散,500 hpa位势高度与AQI的变2.5化存在一定相关性,高空条件是2月持续污染的一个重要原因。春节和元宵节期间AQI均达到重度污染等级,对此间出现的连续性空气重度污染的气象条件分析得出,在高空稳定的平直纬向西风,配合地面的弱低压这一天气形势下,相对稳定的大气层结和持续较强逆温使得污染物难以扩散进而堆积,是持续数日重度污染的重要原因。 相似文献