Ocean currents mediate evolution in island lizards

Islands are considered to be natural laboratories in which to examine evolution because of the implicit assumption that limited gene flow allows tests of evolutionary processes in isolated replicates. Here we show that this well-accepted idea requires re-examination. Island inundation during hurricanes can have devastating effects on lizard populations in the Bahamas. After severe storms, islands may be recolonized by over-water dispersal of lizards from neighbouring islands. High levels of gene flow may homogenize genes responsible for divergence, and are widely viewed as a constraining force on evolution. Ultimately, the magnitude of gene flow determines the extent to which populations diverge from one another, and whether or not they eventually form new species. We show that patterns of gene flow among island populations of Anolis lizards are best explained by prevailing ocean currents, and that over-water dispersal has evolutionary consequences. Across islands, divergence in fitness-related morphology decreases with increasing gene flow. Results suggest that over-water dispersal after hurricanes constrains adaptive diversification in Anolis lizards, and that it may have an important but previously undocumented role in this classical example of adaptive radiation.     

Spatial synchronization of vole population dynamics by predatory birds

Northern vole populations exhibit large-scale, spatially synchronous population dynamics. Such cases of population synchrony provide excellent opportunities for distinguishing between local intrinsic and regional extrinsic mechanisms of population regulation. Analyses of large-scale survey data and theoretical modelling have indicated several plausible synchronizing mechanisms. It is difficult, however, to determine the most important one without detailed data on local demographic processes. Here we combine results from two field studies in southeastern Norway--one identifies local demographic mechanisms and landscape-level annual synchrony among 28 enclosed experimental populations and the other examines region-level multi-annual synchrony in open natural populations. Despite fences eliminating predatory mammals and vole dispersal, the growth rates of the experimental populations were synchronized and moreover, perfectly linked with vole abundance in the region. The fates of 481 radio-marked voles showed that bird predation was the synchronizing mechanism. A higher frequency of risky dispersal movements in slowly growing populations appeared to accelerate predation rate. Thus, dispersal may induce a feedback-loop between predation and population growth that enhances synchrony.     

木本克隆植物中国沙棘种群林缘扩散规律研究

通过对中国沙棘林缘扩散过程和规律进行分析,揭示了中国沙棘的克隆生长过程.结果显示:中国沙棘以年龄最大的分株为中心向两侧实施克隆扩散,形成中间分株大、密度小以及越向两侧分株越小、密度越大的双向“阶梯式”种群外貌.然而,种群向两侧的扩散并不对称,其原因在于扩散过程受到土壤水分状况的影响.向土壤水分条件较好的一侧,林缘扩散种群以分株较大、密度较高为特征,克隆生长格局倾向于“聚集型”;向土壤水分较差的一侧,林缘扩散种群以分株较小、密度较低为特征,克隆生长格局倾向于“游击型”.由此表明在不同的土壤水分状况下,中国沙棘通过克隆生长调节形成与之相适应的克隆生长格局,即觅养对策.     

关于牛布鲁氏菌病多斑块动力学模型的分析（英文）

The dissemination of cattle brucellosis in Zhejiang province of China can be attributed to the transport of cattle between cities within the province. In this paper,an n-patch dynamical model is proposed to study the effect of cattle dispersal on brucellosis spread. Theoretically,we analyze the dynamical behavior of the muti-patch model. For the 2-patch submodel,sensitivity analyses of the basic reproduction number R0 and the number of the infectious cattle in term of model parameters are carried out. By numerical analysis,it is obtained that the dispersal of susceptible cattle between patches and the centralization of infected cattle to the large scale patch can alleviate the epidemic and are in favor of the control of disease in the whole region.     

关于牛布鲁氏菌病多斑块动力学模型的分析

The dissemination of cattle brucellosis in Zhejiang province of China can be attributed to the transport of cattle between cities within the province. In this paper,an n-patch dynamical model is proposed to study the effect of cattle dispersal on brucellosis spread. Theoretically,we analyze the dynamical behavior of the muti-patch model. For the 2-patch submodel,sensitivity analyses of the basic reproduction number R0 and the number of the infectious cattle in term of model parameters are carried out. By numerical analysis,it is obtained that the dispersal of susceptible cattle between patches and the centralization of infected cattle to the large scale patch can alleviate the epidemic and are in favor of the control of disease in the whole region.     

Land bridge and long-distance dispersal——Old views, new evidence

The theory of sea-floor spreading and continental drift is one of the most important achievements in the last century with large ramification for biogeography[1]. Similarly, cladistics, which was started in the 1960s, has been widely employed in systemati…     

An evolutionarily stable strategy approach to indiscriminate spite

AN individual behaves spitefully when it harms itself in order to harm another individual more(1). Hamilton(1,2) predicted that spite may evolve if it is expressed only in those encounters that occur between individuals of less than average relatedness. More recently Verner(3) suggested that territory size may become super-optimal because of a selective advantage arising from the spiteful exclusion of others from limited resources. His model is essentially different from Hamilton's in that spite is directed at individuals indiscriminately with respect to relatedness. Recently Rothstein(4) has shown analytically that the initial spread of spiteful traits will be very slow in all but the smallest populations. He also argued verbally that indiscriminate spite can never be evolutionarily stable even if it should spread (see also Davies(5)). The question of evolutionary stability is clearly important, but its resolution requires an analytical approach. We report here an approach based on Maynard Smith's(6) concept of the evolutionarily stable strategy (ESS), a strategy which, when common, does better than any alternative strategy played by a rare mutant. We show that spite can be an ESS, but that the magnitude of spite will be small in large populations.     

DNA reveals high dispersal synchronizing the population dynamics of Canada lynx

Population dynamics of Canada lynx (Lynx canadensis) have been of interest to ecologists for nearly sixty years. Two competing hypotheses concerning lynx population dynamics and large-scale spatial synchrony are currently debated. The first suggests that dispersal is substantial among lynx populations, and the second proposes that lynx at the periphery of their range exist in small, isolated patches that maintain cycle synchrony via correlation with extrinsic environmental factors. Resolving the nature of lynx population dynamics and dispersal is important both to ecological theory and to the conservation of threatened lynx populations: the lack of knowledge about connectivity between populations at the southern periphery of the lynx's geographic range delayed their legal listing in the United States. We test these competing hypotheses using microsatellite DNA markers and lynx samples from 17 collection sites in the core and periphery of the lynx's geographic range. Here we show high gene flow despite separation by distances greater than 3,100 km, supporting the dispersal hypothesis. We therefore suggest that management actions in the contiguous United States should focus on maintaining connectivity with the core of the lynx's geographic range.     

云南沙棘种子蛋白谱带多样性分析

利用聚丙烯酰胺凝胶电泳对云南沙棘 4个居群的 2 9个个体种子蛋白谱带进行了分析 ,结果表明 :云南沙棘在蛋白质水平居群间差异较明显 ,在居群内个体间变异程度不同 ,居群 1,2个体间变异较明显 ,居群 3完全一致 ,居群 4变异程度较低 .变异成因与其生境和鸟、兽远距离传播种子有关 .蛋白质层次的变异很可能也是云南沙棘居群间和居群内形态变异的基础 .     

乙肝病毒感染数量的一个数学模型

乙型肝炎是由乙型肝炎病毒(HBV)引起的肝病,该病毒干扰肝功能并造成病理损害.一小部分受感染者无法消灭该病毒而成为慢性感染,进而面临极高的死于肝硬化和肝癌的危险.乙型肝炎病毒通过与受感染者的血液或体液接触传播,这与人类免疫缺陷病毒(艾滋病毒)的方式相同.但是,乙型肝炎病毒的感染性比艾滋病毒高50至100倍.接种乙型肝炎疫苗是预防乙型肝炎的主要方法.如何有效防控乙肝的传染,不只是政府的事,也是每个国民应关注的问题.文章建立一个乙肝病毒传染的数学模型,并对模型进行实证分析;同时,对乙肝病毒的传染也做了一个预测.     

Wolbachia在灰飞虱体内的分布

灰飞虱（Laodelphax striatellus)能传播水稻条纹叶枯病,是我国主要的水稻害虫,有些灰飞虱体内含有细胞内共生菌－Wolbachia。Wolbachia是一种细胞质遗传的细胞内共生菌,这类细菌改变了宿主的生殖行为,引起细胞质不相容（CI）,雌性化及孤雌生殖等现象,导致带有Wolbachia的宿主具有生殖优势。采用PCR和Western杂交的方法分析Wolbachia的灰飞虱体内不同组织的分布状况,发现灰飞虱体内Wolbachia除存在于生殖组织外,还广泛分布在头、胸、腹、唾液腺、消化道等非生殖组织中。这种广泛的分布状态说明Wolbachia是在昆虫体内引入、表达与传播外源基因的良好媒介。     

Importance of stirring in the development of an iron-fertilized phytoplankton bloom

The growth of populations is known to be influenced by dispersal, which has often been described as purely diffusive. In the open ocean, however, the tendrils and filaments of phytoplankton populations provide evidence for dispersal by stirring. Despite the apparent importance of horizontal stirring for plankton ecology, this process remains poorly characterized. Here we investigate the development of a discrete phytoplankton bloom, which was initiated by the iron fertilization of a patch of water (7 km in diameter) in the Southern Ocean. Satellite images show a striking, 150-km-long bloom near the experimental site, six weeks after the initial fertilization. We argue that the ribbon-like bloom was produced from the fertilized patch through stirring, growth and diffusion, and we derive an estimate of the stirring rate. In this case, stirring acts as an important control on bloom development, mixing phytoplankton and iron out of the patch, but also entraining silicate. This may have prevented the onset of silicate limitation, and so allowed the bloom to continue for as long as there was sufficient iron. Stirring in the ocean is likely to be variable, so blooms that are initially similar may develop very differently.     

Synchronization of animal population dynamics by large-scale climate

The hypothesis that animal population dynamics may be synchronized by climate is highly relevant in the context of climate change because it suggests that several populations might respond simultaneously to climatic trends if their dynamics are entrained by environmental correlation. The dynamics of many species throughout the Northern Hemisphere are influenced by a single large-scale climate system, the North Atlantic Oscillation (NAO), which exerts highly correlated regional effects on local weather. But efforts to attribute synchronous fluctuations of contiguous populations to large-scale climate are confounded by the synchronizing influences of dispersal or trophic interactions. Here we report that the dynamics of caribou and musk oxen on opposite coasts of Greenland show spatial synchrony among populations of both species that correlates with the NAO index. Our analysis shows that the NAO has an influence in the high degree of cross-species synchrony between pairs of caribou and musk oxen populations separated by a minimum of 1,000 km of inland ice. The vast distances, and complete physical and ecological separation of these species, rule out spatial coupling by dispersal or interaction. These results indicate that animal populations of different species may respond synchronously to global climate change over large regions.     

Ectoparasite infestation and sex-biased local recruitment of hosts.

Dispersal patterns of organisms are a fundamental aspect of their ecology, modifying the genetic and social structure of local populations. Parasites reduce the reproductive success and survival of hosts and thereby exert selection pressure on host life-history traits, possibly affecting host dispersal. Here we test experimentally whether infestation by hen fleas, Ceratophyllus gallinae, affects sex-related recruitment of great tit, Parus major, fledglings. Using sex-specific DNA markers, we show that flea infestation led to a higher proportion of male fledglings recruiting in the local population in one year. In infested broods, the proportion of male recruits increased with brood size over a three year period, whereas the proportion of male recruits from uninfested broods decreased with brood size. Natal dispersal distances of recruits from infested nests were shorter than those from uninfested nests. To our knowledge, this study provides the first evidence for parasite-mediated host natal dispersal and local recruitment in relation to sex. Current theory needs to consider parasites as potentially important factors shaping life-history traits associated with host dispersal.     

捕食者具有传染病的捕食系统的全局稳定性

疾病可以在不同的种群之间传播。研究疾病在相互作用种群之间的传播规律,是种群生态学与传染病动力学的一种结合。通过假设捕食者和食饵均是密度制约、捕食者具有传染病、染病的捕食者不能捕食、染病的捕食者可以恢复但具有暂时的免疫力,建立了一类食饵一捕食系统的SIS传染病模型,利用比较定理研究了解的有界性,利用特征根法和Hurwitz判据分析了系统的无病平衡点和地方病平衡点的局部稳定性,通过构造Lyapunov函数,讨论了无病平衡点和地方病平衡点的全局渐近稳定性,从而得到了疾病流行与否的阈值R,并证明当R≤1时无病平衡点全局渐近稳定,从而疾病消除;当R〉1时,地方病平衡点全局渐近稳定,从而疾病流行。     

烟株不同叶位及接种方式对TMV传播的影响

为进一步弄清烟草普通花叶病毒病的传毒规律.试验以烟草品种K326为材料,连续3a以不同接种方式对健康烟株进行TMV接种试验.结果表明:烟草普通花叶病不通过烟叶气孔传毒,而是通过微伤口、大伤口和叶面与叶面接触渠道传播病毒,而且病毒人口离生长中心越近,病毒传播表现的速度更快,病毒的潜伏期为15～30 d,且在接种30～45d内,烟叶的发病率有一高峰值;烟草普通花叶病毒在烟株的幼嫩叶片上更易传播,症状表现在接种以上的叶片上,带病症的老叶片随着烟株的生长,症状会慢慢消失;在20～35℃的范围内,高温高湿有利于病毒的侵染和症状的表现.杜绝烟草幼嫩叶片摩擦伤口和TMV接触,是防治烟株上TMV传播的有效途径.     

Programmed cell death in Laminaria japonica (Phaeophyta) tissues infected with alginic acid decomposing bacterium

TdT-mediated dUTP-biotin nick end labeling (TUNEL) is a sensitive and valid method for detecting DNA cleavage in programmed cell death (PCD). Using this method, DNA cleavage was observed in Laminaria japonica sporophytic tissues, which were infected with alginic acid decomposing bacterium. It was found that DNA cleavage occurred 5 min after the infection, the fragments with 3′-OH groups of cleaved nuclear DNA increased with time of infection and spread from the infection site. Although no typical DNA ladder (200 bp/180 bp) was detected by routine agarose gel electrophoresis, the cleavage of nuclear DNA fragments of 97～48.5 kb could be detected by pulsed field gel electrophoresis (PFGE). By using CaspGLOWTM fluorescein active caspase-3 staining method, caspase-3 activity has been detected in response to the infection of alginic acid decomposing bacterium. Our results are similar to the observations in hypersensitive response (HR) of higher plant, suggesting that the rapid cell death of L. Japonica infected by alginic acid decomposing bacterium might be involved in PCD, and indicating that the occurrence of PCD is an active defense process against the pathogen's infection.     

西瓜幼苗枯萎病侵染的解剖学研究

本试验对西瓜抗、感枯萎病品种幼苗侵染的解剖学进行了研究。结果表明，西瓜幼苗根毛区是枯萎病菌最易侵染的部位。病菌由根表皮入侵后，菌丝向皮层、维管束横向扩展的同时，也沿着根的纵轴方向在各种组织中扩展，且纵向扩展比横向扩展更快。下胚轴菌丝侵染的途经是根的纵向传导和表皮入侵。下胚轴表面的凹陷较根、茎部多，内部结构也不相同。凹陷处表皮细胞体积大，排列疏松，细胞间有空隙，菌丝在此常大量聚积并入侵。西瓜抗、感病品种接种后，根表菌量和病菌侵染速度存在明显差异。抗病品种根表菌量少，病菌侵入慢。感病品种则相反。     

Local dispersal promotes biodiversity in a real-life game of rock-paper-scissors

One of the central aims of ecology is to identify mechanisms that maintain biodiversity. Numerous theoretical models have shown that competing species can coexist if ecological processes such as dispersal, movement, and interaction occur over small spatial scales. In particular, this may be the case for non-transitive communities, that is, those without strict competitive hierarchies. The classic non-transitive system involves a community of three competing species satisfying a relationship similar to the children's game rock-paper-scissors, where rock crushes scissors, scissors cuts paper, and paper covers rock. Such relationships have been demonstrated in several natural systems. Some models predict that local interaction and dispersal are sufficient to ensure coexistence of all three species in such a community, whereas diversity is lost when ecological processes occur over larger scales. Here, we test these predictions empirically using a non-transitive model community containing three populations of Escherichia coli. We find that diversity is rapidly lost in our experimental community when dispersal and interaction occur over relatively large spatial scales, whereas all populations coexist when ecological processes are localized.     

杉木炭疽病与针叶中几种生化物质之间的关系

在同一生态环境中，历年发病与不发病的杉木群体间针叶生化物质量值存在着差异。不发病的健康杉木具有低的过氧化物酶活性和比活性、低的Ｎ、Ｐ含量及高的Ｋ和纤维素含素。炭疽病菌侵入当年新梢在发病盛期不发病，可能此时正值新梢生长盛期，寄主抗病性强之故。翌年，历年病株先年秋梢顶端表现出炭疽病症状，与还原糖含量高有利于病菌打破潜伏浸染状态，且由于该部位针叶维生素含量低也有利于病菌扩展从而导致寄主发病。随着病害的发