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61.
Zaykin DV 《Journal of evolutionary biology》2011,24(8):1836-1841
The inverse normal and Fisher's methods are two common approaches for combining P-values. Whitlock demonstrated that a weighted version of the inverse normal method, or 'weighted Z-test', is superior to Fisher's method for combining P-values for one-sided T-tests. The problem with Fisher's method is that it does not take advantage of weighting and loses power to the weighted Z-test when studies are differently sized. This issue was recently revisited by Chen, who observed that Lancaster's variation of Fisher's method had higher power than the weighted Z-test. Nevertheless, the weighted Z-test has comparable power to Lancaster's method when its weights are set to square roots of sample sizes. Power can be further improved when additional information is available. Although there is no single approach that is the best in every situation, the weighted Z-test enjoys certain properties that make it an appealing choice as a combination method for meta-analysis. 相似文献
62.
Boogaard BK Oosting SJ Bock BB Wiskerke JS 《Animal : an international journal of animal bioscience》2011,5(9):1458-1466
Over the past 50 years, the scale and intensity of livestock farming have increased significantly. At the same time, Western societies have become more urbanised and fewer people have close relatives involved in farming. As a result, most citizens have little knowledge or direct experience of what farming entails. In addition, more people are expressing concerns over issues such as farm animal welfare. This has led to increasing public demand for more sustainable ways of livestock farming. To date, little research has been carried out on the social pillar of sustainable livestock farming. The aim of this study is to provide insights into the sociocultural sustainability of livestock farming systems. This study reviews the key findings of earlier published interdisciplinary research about the social perceptions of dairy farming in the Netherlands and Norway (Boogaard et al., 2006, 2008, 2010a and 2010b) and synthesises the implications for sociocultural sustainability of livestock farming. This study argues that the (sociocultural) sustainable development of livestock farming is not an objective concept, but that it is socially and culturally constructed by people in specific contexts. It explains the social pillar of the economics/ecological/social model sustainability in terms of the fields of tensions that exist between modernity, traditions and naturality - 'the MTN knot' - each of which has positive and negative faces. All three angles of vision can be seen in people's attitudes to dairy farming, but the weight given to each differs between individuals and cultures. Hence, sociocultural sustainability is context dependent and needs to be evaluated according to its local meaning. Moreover, sociocultural sustainability is about people's perceptions of livestock farming. Lay people might perceive livestock farming differently and ascribe different meanings to it than experts do, but their 'reality' is just as real. Finally, this study calls for an ongoing collaboration between social and animal scientists in order to develop livestock farming systems that are more socioculturally sustainable. 相似文献
63.
J.C.?WilliEmail author J.O.?Mountford T.H.?Sparks 《Biodiversity and Conservation》2005,14(13):3215-3233
The last five decades have witnessed an intensification of agriculture with a marked increase in the use of agrochemicals.
This study investigated whether arable edges affect ancient woods and the extent of any modifications to the ground flora.
Plant species were recorded from a total of 84 transects into the centre of the woods, of which 59 were taken from the arable–woodland
interface and 25 were taken from non-arable land or woodland rides. Ellenberg indicator and CSR values were used to infer
fertility and features of the environment. Results suggested that, after adjusting for light and moisture conditions, elevated
nitrogen levels might occur in ancient woodlands to a distance of at least 100 m from arable farmland. Furthermore, the transects
from the arable fields had a substantially altered herb-layer with respect to species composition, notably a greater percentage
cover of ruderal and nitrophilous species, and a lower cover of stress tolerator species. Smaller woods contained a greater
cover of competitor and nitrophilous species and a lower cover of stress tolerators and ancient woodland indicator species.
We conclude that farming may be unwittingly modifying the ground flora of ancient woodlands adjacent to arable land and that
small and irregularly shaped woods are most at risk. It is recommended that farmers apply agrochemicals in such a way that
drift is minimised, and that large, valuable ancient woods be protected by a substantial buffer zone. 相似文献
64.
A.?Molassiotis G.?Diamantidis I.?TheriosEmail author K.?Dimassi 《Biologia Plantarum》2005,49(4):609-612
Ethylene concentration in the culture tubes of peach rootstock regenerants of three genotypes (Cadaman, GF-677, Myrobalan 29C) was increased by the inclusion of 20 µM salicylic acid (SA), methionine (METH) and ethephon (ETH) in the MS medium whereas it was decreased in regenerants exposed up to 20 µM AgNO3. In leaves of the regenerants the increase of ethylene concentration was accompanied with an increase of non-enzymatic antioxidant activity while remarkable genotype-depended changes in the activities of catalase, peroxidase and their isoenzymes were recorded suggesting that ethylene accumulation imposes oxidative stress responses. However, the results showed that some differences could be observed in the activity of isoenzymes in regenerants exposed to SA in respect to METH and ETH-treated ones.A. Molassiotis is grateful to the State Scholarship’s Foundation of Greece for a fellowship during this work. 相似文献
65.
Garant D Sheldon BC Gustafsson L 《Evolution; international journal of organic evolution》2004,58(3):634-644
Despite great interest in sexual selection, relatively little is known in detail about the genetic and environmental determinants of secondary sexual characters in natural populations. Such information is important for determining the way in which populations may respond to sexual selection. We report analyses of genetic and large-scale environmental components of phenotypic variation of two secondary sexual plumage characters (forehead and wing patch size) in the collared flycatcher Ficedula albicollis over a 22-year period. We found significant heritability for both characters but little genetic covariance between the two. We found a positive association between forehead patch size and a large-scale climatic index, the North Atlantic Oscillation (NAO) index, but not for wing patch. This pattern was observed in both cross-sectional and longitudinal data suggesting that the population response to NAO index can be explained as the result of phenotypic plasticity. Heritability of forehead patch size for old males, calculated under favorable conditions (NAO index > or = median), was greater than that under unfavorable conditions (NAO index < median). These changes occurred because there were opposing changes in additive genetic variance (VA) and residual variance (VR) under favorable and unfavorable conditions, with VA increasing and VR decreasing in good environments. However, no such effect was detected for young birds, or for wing patch size in either age class. In addition to these environmental effects on both phenotypic and genetic variances, we found evidence for a significant decrease of forehead patch size over time in older birds. This change appears to be caused by a change in the sign of viability selection on forehead patch size, which is associated with a decline in the breeding value of multiple breeders. Our data thus reveal complex patterns of environmental influence on the expression of secondary sexual characters, which may have important implications for understanding selection and evolution of these characters. 相似文献
66.
马齿苋科植物的潜在价值研究 总被引:1,自引:0,他引:1
马齿苋科植物以其极高的营养价值和药用价值近年来引起了人们的普遍关注。对其生物学特性、营养成分、药用价值、开发利用等方面的研究也相继开展。概括了马齿苋科植物的植物学特征、种属特性及其分布特点,并阐述了马齿苋科植物的开发利用现状及其存在的问题。进而对其前景进行展望,探讨了其潜在的研究价值。 相似文献
67.
石蒜属植物的药用和观赏利用前景 总被引:10,自引:0,他引:10
石蒜属植物是重要的药用植物,又是一类优良观赏植物,既可用于园林配置,也可用作切花生产或盆栽。综述了石蒜属植物的药用和观赏价值并对其应用前景进行了探讨,为全面开发利用我国这一丰富的野生资源提供了一些理论基础。 相似文献
68.
Fundamental to many theories of sexual selection is the expectation that sexual traits, which males use in an attempt to increase mating success, confer costs as well as benefits to individual males. Although evolution of exaggerated male traits is predicted to be halted, by costs applied by natural selection, there is a lack of empirical work devoted to quantitatively establishing whether natural selection opposes sexual selection generated by the preferences of females. In this study, we quantified natural and sexual selection gradients on breeding values for cuticular hydrocarbon (CHC) components of male contact pheromones in Drosophila serrata. As male sexual traits may often be environmentally condition dependent, breeding values were used in the selection analysis to remove the possibility of environmental correlations between the measured trait and fitness biasing estimates of selection. The direction of natural selection was found to oppose sexual selection on a subset of CHCs examined. Opposing natural and sexual selection suggests that further evolution of the male pheromone may in part be limited by costs associated with attractive male CHC blends. 相似文献
69.
植物化感作用与生物多样性 总被引:5,自引:0,他引:5
本文简要地阐释了化感作用的含义、基本特征以及作用机制,并结合生物多样性理论,综述了化感作用研究中化感物种的多样性、化感物质的多样性及其释放途径的多样性,具体讨论了化感作用对物种多样性、遗传多样性及生态系统多样性中的种群生态、协同进化、土壤生境、生态系统功能和生物入侵等方面的可能影响。文中提出了化感作用的利用、管理应与生物多样性保护相统一的看法,并指出对化感作用与生物多样性的关系以及相互影响机制进行本质的探索,特别是对植物化感作用的生态服务功能与价值评估与探讨,可为保护生物学和系统生态学提供理论基础,这也是今后工作开展的一个重要方向。 相似文献
70.