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

The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. 
The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. 
The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. 
The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

There is growing recognition that classifying terrestrial plant species on the basis of their function (into 'functional types') rather than their higher taxonomic identity, is a promising way forward for tackling important ecological questions at the scale of ecosystems, landscapes or biomes. These questions include those on vegetation responses to and vegetation effects on, environmental changes (e.g. changes in climate, atmospheric chemistry, land use or other disturbances). There is also growing consensus about a shortlist of plant traits that should underlie such functional plant classifications, because they have strong predictive power of important ecosystem responses to environmental change and/or they themselves have strong impacts on ecosystem processes. The most favoured traits are those that are also relatively easy and inexpensive to measure for large numbers of plant species. Large international research efforts, promoted by the IGBP–GCTE Programme, are underway to screen predominant plant species in various ecosystems and biomes worldwide for such traits. This paper provides an international methodological protocol aimed at standardising this research effort, based on consensus among a broad group of scientists in this field. It features a practical handbook with step-by-step recipes, with relatively brief information about the ecological context, for 28 functional traits recognised as critical for tackling large-scale ecological questions.

/pdf/a-handbook-of-protocols-for-standardised-and-easy-2uo4112zhh.pdf

A handbook of protocols for standardised and easy measurement of plant functional traits worldwide

Mammals are metagenomic in that they are composed of not only their own gene complements but also those of all of their associated microbes. To understand the coevolution of the mammals and their indigenous microbial communities, we conducted a network-based analysis of bacterial 16S ribosomal RNA gene sequences from the fecal microbiota of humans and 59 other mammalian species living in two zoos and in the wild. The results indicate that host diet and phylogeny both influence bacterial diversity, which increases from carnivory to omnivory to herbivory; that bacterial communities codiversified with their hosts; and that the gut microbiota of humans living a modern life-style is typical of omnivorous primates.

/pdf/evolution-of-mammals-and-their-gut-microbes-11pxmpi1dr.pdf

Evolution of mammals and their gut microbes

Plant functional traits are the features (morphological, physiological, phenological) that represent ecological strategies and determine how plants respond to environmental factors, affect other trophic levels and influence ecosystem properties. Variation in plant functional traits, and trait syndromes, has proven useful for tackling many important ecological questions at a range of scales, giving rise to a demand for standardised ways to measure ecologically meaningful plant traits. This line of research has been among the most fruitful avenues for understanding ecological and evolutionary patterns and processes. It also has the potential both to build a predictive set of local, regional and global relationships between plants and environment and to quantify a wide range of natural and human-driven processes, including changes in biodiversity, the impacts of species invasions, alterations in biogeochemical processes and vegetation–atmosphere interactions. The importance of these topics dictates the urgent need for more and better data, and increases the value of standardised protocols for quantifying trait variation of different species, in particular for traits with power to predict plant- and ecosystem-level processes, and for traits that can be measured relatively easily. Updated and expanded from the widely used previous version, this handbook retains the focus on clearly presented, widely applicable, step-by-step recipes, with a minimum of text on theory, and not only includes updated methods for the traits previously covered, but also introduces many new protocols for further traits. This new handbook has a better balance between whole-plant traits, leaf traits, root and stem traits and regenerative traits, and puts particular emphasis on traits important for predicting species’ effects on key ecosystem properties. We hope this new handbook becomes a standard companion in local and global efforts to learn about the responses and impacts of different plant species with respect to environmental changes in the present, past and future.

/pdf/new-handbook-for-standardised-measurement-of-plant-5aljxhhg5y.pdf

New handbook for standardised measurement of plant functional traits worldwide

Between 8 and 6 million years ago, there was a global increase in the biomass of plants using C4 photosynthesis as indicated by changes in the carbon isotope ratios of fossil tooth enamel in Asia, Africa, North America and South America. This abrupt and widespread increase in C4 biomass may be related to a decrease in atmospheric CO2 concentrations below a threshold that favoured C3-photosynthesizing plants. The change occurred earlier at lower latitudes, as the threshold for C3 photosynthesis is higher at warmer temperatures.

/pdf/global-vegetation-change-through-the-miocene-pliocene-zzgvagjfoe.pdf

Global vegetation change through the Miocene/Pliocene boundary

The stable isotopic composition of modern soil carbonate and its relationship to climate

The objectives of this synthesis are (1) to review the factors that influence the ecological, geographical, and palaeoecological distributions of plants possessing C4 photosynthesis and (2) to propose a hypothesis/model to explain both the distribution of C4 plants with respect to temperature and CO2 and why C4 photosynthesis is relatively uncommon in dicotyledonous plants (hereafter dicots), especially in comparison with its widespread distribution in monocotyledonous species (hereafter monocots). Our goal is to stimulate discussion of the factors controlling distributions of C4 plants today, historically, and under future elevated CO2 environments. Understanding the distributions of C3/C4 plants impacts not only primary productivity, but also the distribution, evolution, and migration of both invertebrates and vertebrates that graze on these plants. Sixteen separate studies all indicate that the current distributions of C4 monocots are tightly correlated with temperature: elevated temperatures during the growing season favor C4 monocots. In contrast, the seven studies on C4 dicot distributions suggest that a different environmental parameter, such as aridity (combination of temperature and evaporative potential), more closely describes their distributions. Differences in the temperature dependence of the quantum yield for CO2 uptake (light-use efficiency) of C3 and C4 species relate well to observed plant distributions and light-use efficiency is the only mechanism that has been proposed to explain distributional differences in C3/C4 monocots. Modeling of C3 and C4 light-use efficiencies under different combinations of atmospheric CO2 and temperature predicts that C4-dominated ecosystems should not have expanded until atmospheric CO2 concentrations reached the lower levels that are thought to have existed beginning near the end of the Miocene. At that time, palaeocarbonate and fossil data indicate a simultaneous, global expansion of C4-dominated grasslands. The C4 monocots generally have a higher quantum yield than C4 dicots and it is proposed that leaf venation patterns play a role in increasing the light-use efficiency of most C4 monocots. The reduced quantum yield of most C4 dicots is consistent with their rarity, and it is suggested that C4 dicots may not have been selected until CO2 concentrations reached their lowest levels during glacial maxima in the Quaternary. Given the intrinsic light-use efficiency advantage of C4 monocots, C4 dicots may have been limited in their distributions to the warmest ecosystems, saline ecosystems, and/or to highly disturbed ecosystems. All C4 plants have a significant advantage over C3 plants under low atmospheric CO2 conditions and are predicted to have expanded significantly on a global scale during full-glacial periods, especially in tropical regions. Bog and lake sediment cores as well as pedogenic carbonates support the hypothesis that C4 ecosystems were more extensive during the last glacial maximum and then decreased in abundance following deglaciation as atmospheric CO2 levels increased.

C 4 photosynthesis, atmospheric CO 2 , and climate

The isotope enrichment ɛ* of 13C between tooth enamel of large ruminant mammals and their diet is 14.1 ± 0.5‰. This value was obtained by analyzing both the dental enamel of a variety of wild and captive mammals and the vegetation that comprised their foodstuffs. This isotope enrichment factor applies to a wide variety of ruminant mammals. Non-ruminant ungulates have a similar isotope enrichment, although our data cannot determine if it is significantly different. We also found a 13C isotope enrichment ɛ* of 3.1 ± 0.7‰ for horn relative to diet, and 11.1 ± 0.8‰ for enamel relative to horn for ruminant mammals. Tooth enamel is a faithful recorder of diet. Its isotopic composition can be used to track changes in the isotopic composition of the atmosphere, determine the fraction of C3 or C4 biomass in diets of modern or fossil mammals, distinguish between mammals using different subpathways of C4 photosynthesis,and identify those mammals whose diet is derived from closed-canopy habitats.

Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies.

CARBON isotopes from soil carbonate1–4 and soil organic matter5,6 yield palaeoecological information because the carbon in the soil carbonate forms in isotopic equilibrium with local soil CO2 (refs 1, 7), the isotopic composition of which is in turn determined by local plant cover. Siwalik Group sediments in northern Pakistan contain a well exposed palaeosol record spanning the past 18 Myr. Here we report on stable-carbon-isotope results from associated pedogenic carbonate which indicate a dramatic ecological shift from to dominated floodplain biomass beginning ∼7.4–7.0 Myr ago. The earlier C3 floodplain biomasses were probably mainly composed of trees and shrubs, whereas C4 grasslands dominated in the Plio-Pleistocene. Oxygen isotopes also exhibit a shift in the latest Miocene, probably corresponding to a major climate change which may have induced the forest-to-grassland transition. This dramatic ecological shift in the latest Miocene may mark the inception or a marked strengthening of the Asian monsoon system.

Thure E. Cerling

Papers

Global vegetation change through the Miocene/Pliocene boundary

The stable isotopic composition of modern soil carbonate and its relationship to climate

C 4 photosynthesis, atmospheric CO 2 , and climate

Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies.

Development of Asian monsoon revealed by marked ecological shift during the latest Miocene in northern Pakistan