Queen control of sex ratio in fire ants

The haplodiploid sex-determination system of ants gives rise to conflict between queens and workers over colony sex ratios, and the female-biased allocation ratios seen in many species suggest that workers often prevail in this conflict. We exchanged queens between male- and female-specialist colonies of the fire ant Solenopsis invicta. These exchanges quickly reversed the sex-ratio biases of adopting colonies. The sex ratio of queen-laid eggs differed strongly between male- and female-specialist colonies. These findings suggest that queens can force workers to raise male sexuals by limiting the number of female brood and help to explain why sex investment ratios lie between the queen and worker equilibria in this and many other ant species.     

Local mate competition and parental investment in social insects

Efforts to develop formulas for contrasting genetic interests of workers and queens in social Hymenoptera are complicated by many factors, including multiple matings by queens, oviposition by unmated females, and mating rivalry among genetic relatives (Hamilton's "local mate competition"). Because of haplodiploid sex determination in Hymenoptera, when such influences are absent, queens benefit from 1:1 sex ratios of investment (male: female) in reproductive offspring, workers from 1:3 ratios among reproductive siblings. Reports of variable ratios, including many well above 1:3, and female biases in nonsocial Hymenoptera and diplodiploid termites, implicate local mate competition and raises questions about previous interpretations that workers have their way.     

Conditional Manipulation of Sex Ratios by Ant Workers: A Test of Kin Selection Theory

Variable queen mating frequencies provide a unique opportunity to study the resolution of worker-queen conflict over sex ratio in social Hymenoptera, because the conflict is maximal in colonies headed by a singly mated queen and is weak or nonexistent in colonies headed by a multiply mated queen. In the wood ant Formica exsecta, workers in colonies with a singly mated queen, but not those in colonies with a multiply mated queen, altered the sex ratio of queen-laid eggs by eliminating males to preferentially raise queens. By this conditional response to queen mating frequency, workers enhance their inclusive fitness.     

Genetic relatedness in colonies of tropical wasps with multiple queens

The evolution of worker behavior in the social insects is usually explained by kin selection: although workers do not produce offspring, they do reproduce their genes by aiding the reproduction of relatives. The most difficult case for kin selection theory would be species in which workers are fully capable of reproducing but instead opt to rear brood of low relatedness. These conditions are perhaps best fulfilled by the swarm-founding wasps because they have little caste differentiation and their colonies usually have multiple queens, which should lower relatedness. Estimates of within-colony relatedness for three species in this group confirm that it is sometimes (but not always) very low. Inbreeding is negligible in these species, so the hypothesis that inbreeding may raise relatedness is not supported. The maintenance of worker behavior in such species is a significant challenge for kin selection theory.     

Wasp gene expression supports an evolutionary link between maternal behavior and eusociality

The presence of workers that forgo reproduction and care for their siblings is a defining feature of eusociality and a major challenge for evolutionary theory. It has been proposed that worker behavior evolved from maternal care behavior. We explored this idea by studying gene expression in the primitively eusocial wasp Polistes metricus. Because little genomic information existed for this species, we used 454 sequencing to generate 391,157 brain complementary DNA reads, resulting in robust hits to 3017 genes from the honey bee genome, from which we identified and assayed orthologs of 32 honey bee behaviorally related genes. Wasp brain gene expression in workers was more similar to that in foundresses, which show maternal care, than to that in queens and gynes, which do not. Insulin-related genes were among the differentially regulated genes, suggesting that the evolution of eusociality involved major nutritional and reproductive pathways.     

Nestmate and kin recognition in interspecific mixed colonies of ants

Recognition of nestmates and discrimination against aliens is the rule in the social insects. The principal mechanism of nestmate recognition in carpenter ants (Camponotus) appears to be odor labels or "discriminators" that originate from the queen and are distributed among, and learned by, all adult colony members. The acquired odor labels are sufficiently powerful to produce indiscriminate acceptance among workers of different species raised together in artificially mixed colonies and rejection of genetic sisters reared by different heterospecific queens.     

Ancestral monogamy shows kin selection is key to the evolution of eusociality

Close relatedness has long been considered crucial to the evolution of eusociality. However, it has recently been suggested that close relatedness may be a consequence, rather than a cause, of eusociality. We tested this idea with a comparative analysis of female mating frequencies in 267 species of eusocial bees, wasps, and ants. We found that mating with a single male, which maximizes relatedness, is ancestral for all eight independent eusocial lineages that we investigated. Mating with multiple males is always derived. Furthermore, we found that high polyandry (>2 effective mates) occurs only in lineages whose workers have lost reproductive totipotency. These results provide the first evidence that monogamy was critical in the evolution of eusociality, strongly supporting the prediction of inclusive fitness theory.     

意蜂蜂王酒精提取液对中蜂行为的影响

每天以一定剂量的意大利蜜蜂 (意蜂 )蜂王酒精提取液 ,点滴在有分蜂热的中华蜜蜂 (中蜂 )蜂群的上梁上 ,可明显抑制中蜂群的分蜂 .表现在 :中蜂群春季自然换王时间推迟至秋季 ,王台内小蜂王幼虫被拖弃和台基被完全毁掉 ;秋季蜂王自然交替时间延长 ,且有新、老蜂王同巢产卵和越冬前新王停产推迟现象 .对照群在春季如期营造自然王台和分蜂 ,越冬前蜂王停产早 .蜂群失王后 ,如果立即连续点滴蜂王酒精提取液 ,可抑制工蜂产卵 .无王群出现产卵工蜂后 ,如果用蜂王酒精提取液也能有效解除工蜂的产卵行为     

中华蜜蜂群内工蜂监督研究

以中华蜜蜂(Apis cerana cerana)为实验材料,对处女蜂王分别进行单雄和双雄人工授精,并以自然交尾作为多雄交配对照。然后用标准的方法检测各蜂群对蜂王产的未受精卵(QUG)和工蜂产的未受精卵(WUG)的监督效果,结果表明:在自然交尾、双雄授精或单雄授精3种蜂群中,都明显存在工蜂监督现象。     

Phenotypic basis of reproductive success in a social insect: genetic and social determinants

Social insects live in societies that include both reproductive and nonreproductive adults. Understanding the factors that determine which individuals become successful reproductives is necessary to explain the evolution of these societies. The phenotypic effects of the gene Pgm-3 (or a closely linked gene) that may cause workers of the fire ant Solenopsis invicta to selectively execute all queens of a specific genotype were investigated. These effects, which involve differences in queen reproductive development, are expressed only in colonies exhibiting a particular type of social organization (multiple-queen colonies), and it is only in such colonies that selective execution on the basis of genotype occurs. This is an unusual example of genotype-environment interaction in gene expression in which the environmental component is the social environment. The queens executed are, surprisingly, those with the greatest reproductive development. Thus, there is a counterintuitive relation between the potential and realized reproductive success of queens in multiple-queen societies of this ant.     

分子生物技术在蜜蜂育种研究上的应用

综述了应用微卫星 DNA技术、线粒体 DNA(mt DNA)技术、随机扩增多态性 DNA(RAPD)、聚合酶链式反应 (PCR)和 DNA指纹等分子生物技术所进行的蜜蜂育种研究现状 .其应用主要包括估计蜂群内亚家系(父系 )的组成数目和分析工蜂间的遗传相关 ,推断蜂王的多雄水平和鉴定蜜蜂种性 ,构建连锁图和区别数量性状位点 ,鉴定基因型和区别全胞、半胞姐妹以及分析精子受精力的倾向性等     

Sex Ratio of Parental Investment in Colonies of the Social Wasp Polistes fuscatus

Field estimates of parental investment in the two sexes in the social paper wasp Polistes fuscatus indicate that the mother's interests, rather than those of her worker offspring, are realized. Local competition for mates seemed to be absent, and the population investment ratio was not significantly different from 1:1. Workers are not more closely related to the brood they tend than they would be to their own offspring. The 3/4 relationship between sisters in haplodiploid species cannot account for the maintenance of eusociality in this case.     

Evolution of a balanced sex ratio by frequency-dependent selection in a fish

Balanced (1 to 1) sex ratios are thought to evolve by a process known as frequency- dependent selection of the minority sex. Five populations of a fish with genetically based variation in temperature-dependent sex determination were maintained for 5 to 6 years in artificial constant-temperature environments that initially caused the sex ratio to be highly skewed. Increases in the proportion of the minority sex occurred in subsequent generations until a balanced sex ratio was established, thus confirming a central premise underlying the theory of sex-ratio evolution.     

The many selves of social insects

Social insects show multiple levels of self identity. Most individuals are sterile workers who selflessly labor for their colony, which is often viewed as a superorganism. The superorganism protects itself with colony recognition systems based on learned odors, typically cuticular hydrocarbons. Transfer of these odors within the colony obscures separate clan identities. Residual individual interests do appear to cause conflicts within colonies over sex ratio, male production, caste, and reproductive dominance. However, genomic imprinting theory predicts that the individual's maternal and paternal genes will evolve separate infraorganismal identities, perhaps leaving virtually no coherent individual identity.     

Co-residence patterns in hunter-gatherer societies show unique human social structure

Contemporary humans exhibit spectacular biological success derived from cumulative culture and cooperation. The origins of these traits may be related to our ancestral group structure. Because humans lived as foragers for 95% of our species' history, we analyzed co-residence patterns among 32 present-day foraging societies (total n = 5067 individuals, mean experienced band size = 28.2 adults). We found that hunter-gatherers display a unique social structure where (i) either sex may disperse or remain in their natal group, (ii) adult brothers and sisters often co-reside, and (iii) most individuals in residential groups are genetically unrelated. These patterns produce large interaction networks of unrelated adults and suggest that inclusive fitness cannot explain extensive cooperation in hunter-gatherer bands. However, large social networks may help to explain why humans evolved capacities for social learning that resulted in cumulative culture.     

Conditional use of sex and parthenogenesis for worker and queen production in ants

The near-ubiquity of sexual reproduction in animal species has long been considered a paradox because sexually reproducing individuals transmit only half of their genome to their progeny. Here, we show that the ant Cataglyphis cursor circumvents this cost by using alternative modes of reproduction for the production of reproductive and nonreproductive offspring. New queens are almost exclusively produced by parthenogenesis, whereas workers are produced by normal sexual reproduction. By selectively using sex for somatic growth and parthenogenesis for germline production, C. cursor has taken advantage of the ant caste system to benefit from the advantages of both sexual and asexual reproduction.     

农民工人力资本、社会资本投资行为影响因素分析

随着经济发展,我国靠传统物质资本投资拉动经济增长的方式需要改变。而此时,人力资本、社会资本作为经济增长的内生变量,其作用受到越来越多学者的关注。本文基于资本投资决策理论,以农民工为对象,利用调查数据,采用有序Logistic模型,对投资影响因子展开深入分析,探讨决定微观个体人力资本、社会资本投资的主要影响因素。结果表明,工资性收入显著影响人力资本、社会资本的投资,工资性收入每增加一个单位,投资则增加0.5个单位。农民工动机内容影响资本投资,越倾向返回农村则投资性越强。人力资本禀赋、性别、生命周期对农民工的人力资本投资有显著影响,对社会资本投资影响不大。研究揭示了农民工在人力资本投资上是理性经济人行为,对投入产出具有理性的权衡;而对社会资本的认知和行为要弱于人力资本。     

Constraints in the evolution of sex ratio adjustment

When the relative fitness of male and female offspring varies with environmental conditions, evolutionary theory predicts that parents should adjust the sex of their offspring accordingly. Qualitative and even quantitative support for this prediction is striking in some taxa but much less convincing in others. Explaining such variation across taxa in the fit of sex ratio theory remains a major challenge. We use meta-analysis to test the role of two constraints in the evolution of sex ratios. Based on analysis of sex ratio skews in birds and wasps, we show that (i) mechanisms of sex determination do not necessarily constrain the evolution of sex ratio adjustment, and (ii) parental ability to predict their offsprings' environment influences the evolution of sex ratio patterns across taxa. More generally, our results show that multiple constraints may determine the precision of adaptation.     

农民工性亚文化研究——基于珠三角的实地调研分析

基于对珠三角地区东莞、珠海、惠州3市农民工的问卷调查,分析了农民工性文化的独特特征:他们已脱离了传统生殖功能观,将性与爱联系在一起;对性行为的结果有担忧,但对性病的担忧较少,且呈现年龄差异;他们在日常中对性语言的使用较为宽容,但对性越轨行为的宽容局限于婚姻;他们不排斥商业性行为,其性规范体现出了较为宽松特点,且具有群体传染性,通过群体压力稳固化。这要求全社会加强对农民工的关爱,营造一个宽松的性交流氛围。     

Io's Sodium Cloud

The first two-dimensional images of the source region of Io's neutral sodium cloud have been acquired by ground-based observation. Observed asymmetries in its spatial brightness distribution provide new evidence that the cloud is supplied by sodium that is ejected nonisotropically from Io or its atmosphere. Complementary, high-time-resolution, calibrated image sequences that give the first comprehensive picture of the variations of the fainter regions of the cloud extending more than 10(5) kilometers from Io were also obtained. These data demonstrate that the cloud exhibits a persistent systematic behavior coupled with Io's orbital position, a distinct "east-west orbital asymmetry," a variety of spatial morphologies, and true temporal changes. The geometric stability of the sodium source is also indicated. Isolation of the cloud's temporal changes constitutes an important milestone toward its utilization as a long-term probe of Io and the inner Jovian magnetosphere.