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

Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Paternity inference using highly polymorphic codominant markers is becoming common in the study of natural populations. However, multiple males are often found to be genetically compatible with each offspring tested, even when the probability of excluding an unrelated male is high. While various methods exist for evaluating the likelihood of paternity of each nonexcluded male, interpreting these likelihoods has hitherto been difficult, and no method takes account of the incomplete sampling and error-prone genetic data typical of large-scale studies of natural systems. We derive likelihood ratios for paternity inference with codominant markers taking account of typing error, and define a statistic delta for resolving paternity. Using allele frequencies from the study population in question, a simulation program generates criteria for delta that permit assignment of paternity to the most likely male with a known level of statistical confidence. The simulation takes account of the number of candidate males, the proportion of males that are sampled and gaps and errors in genetic data. We explore the potentially confounding effect of relatives and show that the method is robust to their presence under commonly encountered conditions. The method is demonstrated using genetic data from the intensively studied red deer (Cervus elaphus) population on the island of Rum, Scotland. The Windows-based computer program, CERVUS, described in this study is available from the authors. CERVUS can be used to calculate allele frequencies, run simulations and perform parentage analysis using data from all types of codominant markers.

Statistical confidence for likelihood-based paternity inference in natural populations

Bacteria communicate with one another using chemical signal molecules. As in higher organisms, the information supplied by these molecules is critical for synchronizing the activities of large groups of cells. In bacteria, chemical communication involves producing, releasing, detecting, and responding to small hormone-like molecules termed autoinducers. This process, termed quorum sensing, allows bacteria to monitor the environment for other bacteria and to alter behavior on a population-wide scale in response to changes in the number and/or species present in a community. Most quorum-sensing-controlled processes are unproductive when undertaken by an individual bacterium acting alone but become beneficial when carried out simultaneously by a large number of cells. Thus, quorum sensing confuses the distinction between prokaryotes and eukaryotes because it enables bacteria to act as multicellular organisms. This review focuses on the architectures of bacterial chemical communication networks; how c...

/pdf/quorum-sensing-cell-to-cell-communication-in-bacteria-15ypp5joz7.pdf

QUORUM SENSING: Cell-to-Cell Communication in Bacteria

In the Hamadryas baboon, males are substantially larger than females. A troop of baboons is subdivided into a number of ‘one-male groups’, consisting of one adult male and one or more females with their young. The male prevents any of ‘his’ females from moving too far from him. Kummer (1971) performed the following experiment. Two males, A and B, previously unknown to each other, were placed in a large enclosure. Male A was free to move about the enclosure, but male B was shut in a small cage, from which he could observe A but not interfere. A female, unknown to both males, was then placed in the enclosure. Within 20 minutes male A had persuaded the female to accept his ownership. Male B was then released into the open enclosure. Instead of challenging male A , B avoided any contact, accepting A’s ownership.

Evolution and the Theory of Games

Many evolutionary studies, particularly kinship studies, have been limited by the availability of segregating genetic marker loci. Microsatellites promise to alleviate these problems. Microsatellite loci are segments of DNA with very short sequence motifs repeated in tandem; their often numerous alleles differ in the number of these repeat units. They are very common in eukaryotic DNA and can be amplified by the polymerase chain reaction, which allows the use of minute or degraded DNA samples. The alleles can be scored consistently and compared unambiguously, even across different gels.

Microsatellites and kinship

Nobel physicist talks plants with a waiter, then what? p.168 ENERGY Don't assume that renewable energies are problem-free p.168 AGEING Atul Gawande's call to action on end-of-life medical care p.167 HEALTH Lasting legacy of wartime battle against malaria p.166 Does evolutionary theory need a rethink? Researchers are divided over what processes should be considered fundamental. I n October 1881, just six months before he died, Charles Darwin published his final book. The Formation of Vegetable Mould, Through the Actions of Worms 11 sold briskly: Darwin's earlier publications had secured his reputation. He devoted an entire book to these humble creatures in part because they exemplify an interesting feedback process: earthworms are adapted to thrive in an environment that they modify through their own activities. Darwin learned about earthworms from conversations with gardeners and his own simple experiments. He had a genius for distilling penetrating insights about evolutionary processes — often after amassing years of observational and experimental data — and he drew on such disparate topics as agriculture, geology, embryol-ogy and behaviour. Evolutionary thinking ever since has followed Darwin's lead in its emphasis on evidence and in synthesizing information from other fields. A profound shift in evolutionary thinking began C harles Darwin conceived of evolution by natural selection without knowing that genes exist. Now mainstream evolutionary theory has come to focus almost exclusively on genetic inheritance and processes that change gene frequencies. Yet new data pouring out of adjacent fields are starting to undermine this narrow stance. An alternative vision of evolution is beginning to crystallize, in which the processes by which organisms grow and develop are recognized as causes of evolution. Some of us first met to discuss these advances six years ago. In the time since, as members of an interdisciplinary team, we have worked intensively to develop a broader framework, termed the extended evolutionary synthesis 1 (EES), and to flesh out its structure, assumptions and predictions. In essence, this synthesis maintains that important drivers of evolution, ones that cannot be reduced to genes, must be woven into the very fabric of evolutionary theory. We believe that the EES will shed new light on how POINT Yes, urgently Without an extended evolutionary framework, the theory neglects key processes, say Kevin Laland and colleagues.

https://openresearch-repository.anu.edu.au/bitstream/1885/28950/2/01_Laland_Does_evolutionary_theory_need_2014.pdf

Does evolutionary theory need a rethink

Social insects so dominate many terrestrial habitats (Wilson 1990) that they can hardly escape the attention of biologists, but even if they were rare, they would still attract special interest because of the intricate cooperation within their societies. William Morton Wheeler (1911) described the social insect colony as an organism (or as a higher-level organism or superorganism) because of the degree to which individuals appear to operate as a unit that is dedicated to the perpetuation and reproduction of the colony as a whole. The reinvention of the organism at a higher level has occurred at a number of crucial junctures in the history of life (Maynard Smith and Szathmary 1995). For example, the eukaryotic cell arose from several prokaryotic ancestors (Margulis 1970), and multicellular plants, animals, and fungi arose from single-celled ancestors (Buss 1987). Because insect societies are macroscopic, and because they span the entire range from solitary individuals to essentially superorganismal colonies, they offer an accessible model for how such transitions can happen.

Kin selection and social insects

The social amoeba, Dictyostelium discoideum, is widely used as a simple model organism for multicellular development, but its multicellular fruiting stage is really a society. Most of the time, D. discoideum lives as haploid, free-living, amoeboid cells that divide asexually. When starved, 10(4)-10(5) of these cells aggregate into a slug. The anterior 20% of the slug altruistically differentiates into a non-viable stalk, supporting the remaining cells, most of which become viable spores. If aggregating cells come from multiple clones, there should be selection for clones to exploit other clones by contributing less than their proportional share to the sterile stalk. Here we use microsatellite markers to show that different clones collected from a field population readily mix to form chimaeras. Half of the chimaeric mixtures show a clear cheater and victim. Thus, unlike the clonal and highly cooperative development of most multicellular organisms, the development of D. discoideum is partly competitive, with conflicts of interests among cells. These conflicts complicate the use of D. discoideum as a model for some aspects of development, but they make it highly attractive as a model system for social evolution.

Altruism and social cheating in the social amoeba Dictyostelium discoideum

Interest in how often female social insects mate is particularly intense because of its impact on sociality and because of the well-known extreme multiple mating in honeybees. With multiple mating, worker to brood relatedness decreases but worker versus queen interests often converge. The overwhelming majority of species of social ants, bees, and wasps mate only once. Even those species where some females mate multiply typically have effective mate numbers close to one. Ants have effective mate numbers of 1.43, which drops to 1.15 if the advanced fungus growers (2.14) and harvester ants (6.76) are excluded. Honeybees have effective mate numbers of 12.48. Stingless bees and bumblebees have effective mate numbers of only 1.06 and 1.02 respectively. Polistine wasps have effective mate numbers of 1.01. Vespine wasps have effective mate numbers of 1.12 excluding only Vespula which has effective mate numbers of 3.68. Favoring the very low mate numbers we observe for nearly all female social insects is the narrow time window for mating, lack of material gain from males, lack of male ability to harass females (who must move their sting aside to mate in most species), and lack of paternal care. Single mating may be further favored by the apparent lack of any post-copulatory sperm discrimination mechanisms. Leks and male territories, which are common in social insects, make it easier for females to choose the single best mate, further contributing to low mate numbers. Multiple mating is a rare, derived trait in a generally single-mating group. Single mating may have facilitated the origins of sociality in the Hymenoptera because it confers higher relatedness among potential workers and the brood they care for. The rare exceptions to low mate numbers all come from highly social species with single queens, morphological castes, and many workers. Multiple mating might be stable in highly social species because their highly specialized workers have few selfish responses to lowered relatedness. The unusual cases of multiple mating are most likely to be selected for because they increase genetic diversity in the brood, though empirical support for specific genetic diversity hypotheses has proved to be elusive. What is clear is that single mating is predominant in this large, evolutionarily and ecologically successful group.

Joan E. Strassmann

Papers

Microsatellites and kinship

Does evolutionary theory need a rethink

Kin selection and social insects

Altruism and social cheating in the social amoeba Dictyostelium discoideum

The rarity of multiple mating by females in the social Hymenoptera