抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

In the early 1980s, a strategy for graphical representation of multivariate (multi-species) abundance data was introduced into marine ecology by, among others, Field, et al. (1982). A decade on, it is instructive to: (i) identify which elements of this often-quoted strategy have proved most useful in practical assessment of community change resulting from pollution impact; and (ii) ask to what extent evolution of techniques in the intervening years has added self-consistency and comprehensiveness to the approach. The pivotal concept has proved to be that of a biologically-relevant definition of similarity of two samples, and its utilization mainly in simple rank form, for example ‘sample A is more similar to sample B than it is to sample C’. Statistical assumptions about the data are thus minimized and the resulting non-parametric techniques will be of very general applicability. From such a starting point, a unified framework needs to encompass: (i) the display of community patterns through clustering and ordination of samples; (ii) identification of species principally responsible for determining sample groupings; (iii) statistical tests for differences in space and time (multivariate analogues of analysis of variance, based on rank similarities); and (iv) the linking of community differences to patterns in the physical and chemical environment (the latter also dictated by rank similarities between samples). Techniques are described that bring such a framework into place, and areas in which problems remain are identified. Accumulated practical experience with these methods is discussed, in particular applications to marine benthos, and it is concluded that they have much to offer practitioners of environmental impact studies on communities.

Non-parametric multivariate analyses of changes in community structure

Human alteration of Earth is substantial and growing. Between one-third and one-half of the land surface has been transformed by human action; the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning of the Industrial Revolution; more atmospheric nitrogen is fixed by humanity than by all natural terrestrial sources combined; more than half of all accessible surface fresh water is put to use by humanity; and about one-quarter of the bird species on Earth have been driven to extinction. By these and other standards, it is clear that we live on a human-dominated planet.

/pdf/human-domination-of-earth-s-ecosystems-5eevmqq987.pdf

Human Domination of Earth's Ecosystems

Pseudoreplication is defined. as the use of inferential statistics to test for treatment effects with data from experiments where either treatments are not replicated (though samples may be) or replicates are not statistically independent. In ANOVA terminology, it is the testing for treatment effects with an error term inappropriate to the hypothesis being considered. Scrutiny of 176 experi- mental studies published between 1960 and the present revealed that pseudoreplication occurred in 27% of them, or 48% of all such studies that applied inferential statistics. The incidence of pseudo- replication is especially high in studies of marine benthos and small mammals. The critical features of controlled experimentation are reviewed. Nondemonic intrusion is defined as the impingement of chance events on an experiment in progress. As a safeguard against both it and preexisting gradients, interspersion of treatments is argued to be an obligatory feature of good design. Especially in small experiments, adequate interspersion can sometimes be assured only by dispensing with strict random- ization procedures. Comprehension of this conflict between interspersion and randomization is aided by distinguishing pre-layout (or conventional) and layout-specifit alpha (probability of type I error). Suggestions are offered to statisticians and editors of ecological j oumals as to how ecologists' under- standing of experimental design and statistics might be improved.

/pdf/pseudoreplication-and-the-design-of-ecological-field-44o8kzdaoi.pdf

Pseudoreplication and the Design of Ecological Field Experiments

Consistent spatial patterns in multiple trophic levels occur around artificial habitats

Dramatic perturbations of ecological communi- ties through rapid shifts in environmental regime do not always result in complete mortality of residents. Instead, legacy individuals may remain and inXuence the succession and composition of subsequent communities. We used a reciprocal transplant experiment to investigate whether a legacy eVect is detectable in communities experiencing an abrupt increase or decrease in hydrothermal Xuid Xux at deep-sea vents. Vent habitats are characterized by strong gradients in productivity and physico-chemical stressors, both of which tend to increase with increasing vent Xuid Xux. In our experiments, many species survived transplan- tation from cool (water temperatures <2°C above ambient) to warm (4-30°C above ambient) habitats, resulting in sig- niWcantly higher species richness on transplanted than remaining experimental substrata. A legacy eVect was much less apparent in transplantation from warm to cool habitat, although a few vestimentiferan tubeworms, nor- mally restricted to warm habitat, survived transplantation. The asymmetry in inXuence of legacy individuals suggests that productivity enhancement may outweigh potential physiological stress in setting limits to distributions of vent invertebrates. This inXuence of biological processes contrasts with theory developed in the rocky intertidal that predicts the predominance of physical control at the high- stress end of an environmental gradient. Prediction of successional transitions in vents and other habitats experi- encing regime shifts in which remnant species may survive must take into account the possible inXuence of historical

Imprint of past environmental regimes on structure and succession of a deep-sea hydrothermal vent community

The typical decline in community species diversity following an environmental perturbation is often explained by appeal to interspecific biological interactions which effect a dynamic functional reorganization of the community. A neutral (non-interactive) model is developed to calculate the expected effect of a perturbation on the species diversity of a community in which component species are mutually independent. In this non-interactive model, (1) the probability of a drop in diversity is shown to be great and (2) the expected species diversity is shown to decline as an immediate result of mortality, even though all species react independently and with equal probabilistic susceptibility to the perturbation. Consequently, in studies of the effects of any perturbation one cannot view the decline in diversity due to immediate mortality as evidence of an interactive reorganization of community structure.

Species diversity and perturbations: predictions of a non-interactive model

Monitoring and Modeling of the Neuse River Estuary, Phase 2: Functional Assessment of Environmental Phenomena Through Network Analysis

Aquacultural production of northern quahogs, Mercenaria mercenaria (Linnaeus, 1758): High water temperatures in the nursery and growth penalties of predator control by gravel

Charles H. Peterson

Papers

Consistent spatial patterns in multiple trophic levels occur around artificial habitats

Imprint of past environmental regimes on structure and succession of a deep-sea hydrothermal vent community

Species diversity and perturbations: predictions of a non-interactive model

Monitoring and Modeling of the Neuse River Estuary, Phase 2: Functional Assessment of Environmental Phenomena Through Network Analysis

Aquacultural production of northern quahogs, Mercenaria mercenaria (Linnaeus, 1758): High water temperatures in the nursery and growth penalties of predator control by gravel