Brood size manipulation affects frequency of second clutches in the blue tit

The reproductive trade-off hypothesis predicts that the investment made in current reproduction determines the breeders’ future fitness as a consequence of intra-or inter-generational reproductive costs. Long-lived species are expected to favour their own reproductive value at the expense of their offspring, hence incurring in inter-generational costs, whereas short-lived species are expected to invest in the current breeding attempt even at the expense of their own survival, thus incurring in intra-generational costs. We tested whether intensity of current reproductive effort has intra-or inter-generational costs in a short-lived bird, the blue tit Parus caeruleus, with a brood size manipulation experiment. We expected more intra-generational (parental reproduction and/or survival) than inter-generational (offspring quality and survival) reproductive costs. We found that parental effort, measured as the hourly rate of parental visits to nests, increased gradually with experimental manipulation. Brood size manipulation resulted in a gradual increase in the number of fledglings per nest from reduced to increased treatments. We found an effect of the manipulation on the probability of making a second clutch, with adults rearing enlarged broods being less likely to undertake such a second reproduction during the season compared to those rearing control or decreased broods. We found no evidence of other reproductive costs; neither as adult weight after manipulation, apparent parental local survival, apparent offspring local survival or local recruitment. Although the results seem to support the a priori expectations, alternative explanations are discussed.Communicated by M. Soler     

城市生活垃圾分类回收治理激励监督机制研究

考虑政府政策激励监督对城市生活垃圾分类回收治理的影响,构建政府监管-企业处理-居民参与的演化博弈模型,借助演化博弈理论分析4种不同情境下城市生活垃圾分类回收治理的演化稳定策略,并借助数值仿真分析了政府激励监督对各方策略选择的影响.研究发现：居民进行垃圾分类获得的收益大于参与分类的成本两倍及以上时,才会主动参与垃圾分类,否则不会主动参与分类,同时居民对政府正向激励补贴的变化比企业更为敏感.政府实施较高的负向激励力度时可有效约束企业行为,但过高的监管成本会造成垃圾回收治理的管理困境.     

应用神经网络优化高速铁路动车组周转的研究

结合当前国内外对高速铁路动车组运用的相关研究,给出了动车组周转这一特大型组合优化问题的数学描述并建立神经网络模型,提出了基于分层聚类思想与模拟退火算法相结合的解决方案,降低了算法的时间复杂度,达到了减少车底在车站的停留时间,提高了车底利用效率,为优化我国在建和拟建的高速铁路、城际客运专线的动车组周转及计算机自动编制车底运用计划提供理论支持,并结合实际客运专线运用计算机模拟进行检算,证实了算法的可行性、实用性.     

城市生活垃圾自动分选技术

迅速而巨量增长的城市生活垃圾给我国带来了严峻的社会、环境压力;城市生活垃圾的资源化、无害化综合利用,对于改善人民群众生活环境、减少资源浪费、发展循环经济,都具有十分重要的意义。要使城市垃圾综合利用目的得以实现,必须突破制约垃圾处理的瓶颈问题——垃圾分类技术这一世界难题。在分析垃圾特点和各种垃圾处理方法优势的基础上,经过多年的探索与研制,开发了一种新型的用于城市生活垃圾资源化综合利用的自动分选技术。     

高校中水水源分类及基于AHP方法的优质度排序

高校是我国城市用水大户,在高校校园建立中水回用系统是节约水资源、减少水污染、建设生态校园的有效途径,选择优质的中水水源是保证中水回用系统高效运行的首要前提。目前,开辟中水水源多基于简单定性分析后加以利用,少有对水源的量化评价以及优质度的排序。文章针对高校中各个单位用水类型不同、排水水质和水量呈多样性的问题,将校园内各个水源进行综合分类并运用层次分析法(AHP)进行优质度的量化评价,以各水源优质程度排序为依据筛选出可利用的中水水源。根据实地调查及实验分析数据,以北京师范大学为例应用评价方法,并将结果与校园实际的中水回用情况对比,验证指标及方法的合理性。文章将为高校中水水源的分类及筛选的量化评价提供借鉴。     

关于城市垃圾出路的思考

本文通过对城市垃圾现象的关注,揭示出城市垃圾其实是一种宝贵的资源,并结合国内外的研究成果指出了城市垃圾的出路和解决途径,最后,对由此衍生出的“垃圾产业”进行了展望。     

Maternal characteristics and the production and recruitment of sons in the eastern kingbird (<Emphasis Type="BoldItalic">Tyrannus tyrannus</Emphasis>)

Sex allocation theory predicts that if variance in reproductive success differs between the sexes, females who are able to produce high-quality young should bias offspring sex ratio towards the sex with the higher potential reproductive success. We tested the hypothesis that high-quality (i.e., heavy) female eastern kingbirds (Tyrannus tyrannus) that bred early in the breeding season would produce male-biased clutches. A significant opportunity for sexual selection also exists in this socially monogamous but cryptically polygamous species, and we predicted that successful extra-pair (EP) sires would be associated with an excess of male offspring. Although population brood sex ratio did not differ from parity, it increased significantly with female body mass and declined with female breeding date, but was independent of the morphology and display (song) behavior (correlates of reproductive success) of social males and EP sires. Male offspring were significantly heavier than female offspring at fledging. Moreover, the probability that male offspring were resighted in subsequent years declined with breeding date, and was greater in replacement clutches, but lower when clutch size was large. Probability of resighting female offspring varied annually, but was independent of all other variables. Given that variance in reproductive success of male kingbirds is much greater than that of females, and that male offspring are more expensive to produce and have a higher probability of recruitment if fledged early in the season, our results support predictions of sex allocation theory: high-quality (heavy) females breeding when conditions were optimal for male recruitment produced an excess of sons.     

Precise sex ratios manifested by several encyrtid parasitoids (Hymenoptera: Encyrtidae) of brown soft scale, <Emphasis Type="Italic">Coccus hesperidum</Emphasis> L. (Hemiptera: Coccidae)

We examined whether several facultatively gregarious encyrtid (Hymenoptera: Encyrtidae) endoparasitoids of brown soft scale, Coccus hesperidum L., manifest precise sex allocation under field conditions. Metaphycus luteolus (Timberlake), Metaphycus angustifrons (Compere), Metaphycus stanleyi (Compere), and Microterys nietneri (Motshulsky) evince brood sex ratios that are female-biased and extremely precise (low variance in the number of sons per host). Typically, this sex allocation pattern is attributed to extreme local mate competition (LMC) in which only one foundress exploits a patch of hosts and mating occurs mostly between her offspring. However, such a pattern of sex allocation was not detected for Metaphycus helvolus (Compere). Also, a large proportion of the broods in all five species contained only daughters; thus, an excess of male-only broods was expected if unmated females (i.e., females that can produce only sons) contribute offspring before mating. All-male broods were rare in our samples. This finding coupled with the life history characteristics of these wasps, such as the exploitation of aggregated hosts and the long life span and mobility of males, suggest that nonlocal mating is frequent. Our empirical work suggests that it is advantageous to allocate precise sex ratios in cases in which mating opportunities for males are not restricted to their natal host and/or when multiple foundresses exploit large patches of hosts. Limited theoretical work also supports this prediction but more detailed studies of this taxon’s mating structure and other life history characteristics are necessary to understand their sex allocation decisions.     

矿化垃圾填埋场的综合治理

以矿化垃圾作为研究对象,对矿化垃圾填埋场进行综合治理,使填埋场垃圾得到资源化利用,将填埋场土地恢复使用,提升垃圾资源化利用后产生的经济效益。     

Opposing selective pressures on hatching asynchrony: egg viability, brood reduction, and nestling growth

At least 19 hypotheses have been proposed to explain the evolutionary significance of avian hatching asynchrony, and hatching patterns have been suggested to be the result of several simultaneous selective pressures. Hatching asynchrony was experimentally modified in the black kite Milvus migrans by manipulating the onset of incubation during the laying period. Delayed onset of incubation reduced egg viability of first-laid eggs, especially when ambient temperature during the laying period was high. Brood reduction (nestling mortality by starvation or siblicide) was more commonly observed in asynchronous nests. The growth rate was slower in synchronous broods, probably due to stronger sibling rivalry in broods with high size symmetry. Last-hatched chicks in synchronous broods fledged at a small size/mass, while in control broods, hatching order affected growth rates, but not final size. Brood reduction, variable growth rates, and the ability to face long periods of food scarcity are probably mechanisms to adjust productivity to stochastic food availability in a highly opportunistic predator. The natural pattern of hatching asynchrony may be the consequence of opposing selective forces. Extreme hatching synchrony is associated with slow growth rates, small final size of last-hatched chicks, and low viability of first-laid eggs, while extreme hatching asynchrony is associated with high mortality rates. Females seem to facultatively manipulate the degree of hatching asynchrony according to those pressures, because hatching asynchrony of control clutches was positively correlated with temperature during laying, and negatively correlated with the rate of rabbit consumption. Received: 25 October 1999 / Revised: 30 May 2000 / Accepted: 25 June 2000