The cost of mating with a non-virgin male in a monandrous butterfly: experimental evidence from the speckled wood, Pararge aegeria

Contrary to vertebrates, sperm production in insects may bear considerable costs for males. This is especially true in species that donate spermatophores containing sperm and nutrient-rich accessory gland products like in butterflies. Hence, spermatophores at first and subsequent copulations can differ in a quantitative and qualitative way. Such effects have particularly been shown in polyandrous species providing large spermatophores. Here we experimentally tested the effect of male mating status (virgin male vs recently mated male) on copulation duration, spermatophore size and females’ fitness components in a monandrous butterfly Pararge aegeria that typically donates small spermatophores. Copulations with non-virgin males lasted on average five times longer than that with virgin males and resulted in a spermatophore which was on average three times smaller. Number of eggs laid and female life span were not affected by the mating status treatment, but there was a significant effect on the number of living caterpillars a female produced, as copulations with virgin males resulted in higher numbers of larval offspring. Interestingly, the difference in spermatophore mass at the first and the second copulation increased with male body size. This suggests differential spermatophore allocation decisions among males of different size. Consequences for females and potential mechanisms influencing female fitness components are discussed. Given the small absolute size of spermatophores in P. aegeria, components other than consumable nutrients (perhaps hormones) should cause the observed effects.     

Female house martins (Delichon urbica) reduce egg androgen deposition in response to a challenge of their immune system

Female birds deposit in the yolks of eggs substantial amounts of androgens, such as testosterone and androstenedione. These androgens have been shown to speed up nestling development, induce a fast development of ornaments and increase dominance in adults. Experiments in several species have reported that females invest greater amounts of androgens in the eggs fathered by attractive males, suggesting that yolk androgen is a costly investment for either the offspring or the mother. There is some evidence that nestling immunocompetence may be partially suppressed by high levels of yolk androgens, but it is not known whether this is also the case for females. We tested this hypothesis in the house martin by inducing an immune challenge through an injection of sheep red blood cells, a standard challenge of the humoral immune system. Experimental birds laid eggs with lower amounts of yolk androstenedione than controls, and there was a similar non-significant trend for testosterone. Furthermore, the probability of laying a replacement clutch was higher for birds that had laid a first clutch with relatively high levels of yolk testosterone. These results suggest that yolk androgen deposition is limited by immune costs in the female, and that only females in good condition may afford to invest high levels of androgen in eggs in this species.     

Are blue eggs a sexually selected signal of female collared flycatchers? A cross-fostering experiment

Impressive variation in egg colouration among birds has puzzled evolutionary biologists for a long time. The most frequently studied selective forces moulding egg colouration—predation and brood parasitism—have either received little empirical support or may play a role in only a minority of species. A novel hypothesis has suggested that egg colour may be significantly influenced by sexual selection. Females may deposit a blue-green pigment biliverdin into eggshells instead of using it for themselves as a powerful antioxidant. By this handicap, females may signal their quality to males, which are then hypothesized to increase their paternal effort. We experimentally tested the hypothesis in the collared flycatcher (Ficedula albicollis), a species laying blue-green eggs. We cross-fostered clutches between nests to disentangle effects of female/territory quality and egg colour on paternal effort and nestling quality. The results supported two assumptions of sexual signalling through egg colour hypothesis: Blue pigment seems to be a limited resource for females, and female quality is positively correlated with the intensity of the blue-green colour. However, we did not find support for the main prediction of the hypothesis, as male parental effort parameters (feeding frequencies to nestlings and intensity of nest defence) were unrelated to egg colour. We discuss possible reasons for the discrepancy between our results and previous correlative analyses that supported the hypothesis that blue egg colour may be a postmating, sexually selected signal in females.     

Past reproductive effort affects parental behaviour in a cichlid fish,Cichlasoma nigrofasciatum: a comparison of inexperienced and experienced breeders with normal and experimentally reduced broods

Defensive and parental care behaviour of convict cichlids that differed in past effort was compared. Before testing, some fish were bred three times while others were not bred. Age was held constant; all individuals in this study were approximately 20 months old (±2 months) at test time. Furthermore, half of the pairs in this study had their broods experimentally reduced by 50%. Results indicated that past effort across breeding attempts affects investment in the current brood. Experienced pairs were more aggressive toward a model predator than inexperienced parents. However, no major differences were observed in depreciable care (i.e. fanning). Contrary to previous studies, brood size had minor effects on parental care. This discrepancy could be due to the age of the parents; individuals in this study were significantly older than fish tested in previous studies. The results support parental investment theory and suggest that past effort is not only important within breeding episodes but also within an animal's lifetime.     

浅论现代企业安全管理中的十个关系

从安全工程学、安全经济学、人机工程学入手,结合金川公司安全生产工作的实际,对现代企业安全管理中的十个关系进行了探讨。     

环境保护投资的市场化运作

环境保护投资是解决环境问题的重要保障。分析了我国环境保护投资存在的主要问题及其原因，对我国环境保护投资的市场化运作进行分析，提出了社会主义市场经济体制下筹集环境保护投资、环境保护管理及环境保护设施管理的主要措施。     

GIM（1）灰色模型预测环保投资趋势的可行性探析

环保投资作为环保系统的一个子系统，并不一定具有指数函数规律。本文利用ＧＩＭ（１）灰色模型，探析了它在环保投资趋势预测应用中的可行性。初步应用表明，在序列不完全满足光滑化条件时，ＧＩＭ（１）灰色模型对系统变量的“白化”能力较ＧＭ（１，１）强，而与ＧＳＭ（１）灰色模型相当，信息利用率高，是分析、预测环保投资动态发展趋势一条切实可行的途径。     

略论国际投资与贸易中的环境法律问题

本文分析了环境与国际经济贸易的关系，国际条约、公约中有关环境与贸易关系的规定，环境问题对我国外经贸事业的影响以及我国应采取的相应法律对策等。     

土地复垦投资

讨论了土地复垦投资内涵、特点、基本原则、基本运行过程、基本模式及国内外土地复垦投资现状及问题。     

生态价值的整体性研究

生态价值的自然基础是生态系统，生态系统、生态系统功能和能值衡量都具有整体性特征。生态价值的主体意识体现着人类的需求，生态恢复和生态消费需要社会整体的规划和管理。生态价值的自然基础和主体需要决定了它的整体性特征，这对宏微观经济发展都具有重要的指导意义。