The early radiation and relationships of the major arthropod groups

Cambrian arthropods are now well known, but there has been little agreement on how they contribute to an understanding of arthropod phylogeny. Fossils have either been lumped together as "trilobitomorphs" or, more recently, have been the subject of speculation invoking a multiple polyphyletic origin of arthropods. Cladistic analysis of characters of Cambrian and living representatives (excluding Uniramia) shows that trilobites and chelicerates are relatively advanced compared with "crustaceans," and there are doubts whether the latter constitute a national group. An undue emphasis on singular autapomorphies of problematic fossils has obscured these relationships in the past. "Trilobitomorphs" were simply an artificial taxon based on shared primitive characters. The arthropods that evolved during the Cambrian radiation show no more apparent morphological diversity than do the living groups. The evidence of wellpreserved problematica is critical to understanding the nature of this radiation and the affinities of the groups that remain today.     

Ancestral hierarchy and conflict

Ancestral Pan, the shared predecessor of humans, bonobos, and chimpanzees, lived in social dominance hierarchies that created conflict through individual and coalitional competition. This ancestor had male and female mediators, but individuals often reconciled independently. An evolutionary trajectory is traced from this ancestor to extant hunter-gatherers, whose coalitional behavior results in suppressed dominance and competition, except in mate competition. A territorial ancestral Pan would not have engaged in intensive warfare if we consider bonobo behavior, but modern human foragers have the potential for full-scale war. Although hunter-gatherers are able to resolve conflicts preemptively, they also use mechanisms, such as truces and peace pacts, to mitigate conflict when the costs become too high. Today, humans retain the genetic underpinnings of both conflict and conflict management; thus, we retain the potential for both war and peace.     

Switching skeletons: hydrostatic support in molting crabs

Skeletal support systems are essential for support, movement, muscular antagonism, and locomotion. Crustaceans shed their rigid exoskeleton at each molt yet are still capable of forceful movement. We hypothesize that the soft water-inflated body of newly molted crabs may rely on a hydrostatic skeleton, similar to that of worms and polyps. We measured internal hydrostatic pressure and the force exerted during claw adduction and observed a strong correlation between force and hydrostatic pressure, consistent with hydrostatic skeletal support. This alternation between the two basic skeletal types may be widespread among arthropods.     

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.     

Skeleton of the Oldest Known Pinniped, Enaliarctos mealsi

A nearly complete skeleton of the archaic pinniped Enaliarctos, found in late Oligocene or early Miocene rocks (approximately 23 million years old) of California, provides new evidence on the origin of pinnipeds. Enaliarctos retains many primitive features expected in the hypothesized common ancestor of pinnipeds. Skeletal modifications seen in Enaliarctos document swimming adaptations and indicate that pinnipeds primitively used the axial skeleton and both fore and hindflippers as sources of propulsion. Elongate hindlimbs with prominent bony processes (reflecting powerful musculature) suggest that Enaliarctos was more active on land than modern pinnipeds.     

Water balance in desert arthropods. Despite their small size, arthropods may be highly adapted for life in xeric conditions

As judged by the number of species, or of individuals, arthropods are an extremely successful group of desert inhabitants. There is very great structural and physiological diversity within the group, and since adaptations to desert life open to one are not open to all. we should not expect to find the maximum possible development of adaptive features in any arthropod simply because it lives in a desert. Most adult insects fly; their larvae and all other arthropods do not, and their adaptations will differ accordingly. Desert beetles have very impermeable cuticles and tolerate high body temperatures, while desert cockroaches live below the sand. have more permeable cuticles, and absorb water vapor.There is probably no single respect in which all desert arthropods differ from insects of other environments. Perhaps a profitable way of viewing desert animals is to recognize that each is a whole organism with a specific collection of adaptations that must be consistent within themselves and which are associated with a specific mode of life and a specific evolutionary history. The arthropod organization is capable of producing highly efficient desert species. There is, however, a converse way of looking at the situation, Which is often neglected but which may be of general biological interest: does the evolution of adaptations to desert environments necessarily involve loss of viability in more mesic habitats? If so, then what are these disavantages- what, for example, is the disadvantage of a highly impermeable cuticle? In some cases the answer is clear: sandroaches need sand dunes to live in because they are morphologically and behaviorly specialized for this habitat. More often the answer is not obvious.     

螟黄足盘绒茧蜂复合群系统发育分析(膜翅目:茧蜂科:小腹茧蜂亚科)

对螟黄足盘绒茧蜂复合群Cotesia flavipes complex(膜翅目：茧蜂科：小腹茧蜂亚科)分布全世界的5个种和外群螟蛉盘绒茧蜂Cruficrus,粘虫盘绒茧蜂Ckariyai,粉蝶盘绒茧蜂eglomerata的24个性状进行比较研究,并运用支序分析的方法探讨螟黄足盘绒茧蜂复合群5个种种间系统发育关系．支序分析表明,螟黄足盘绒茧蜂复合群是一单系群,芦螟盘绒茧蜂C．chiloluteelli和汉寿盘绒茧蜂C．hanshouensis亲缘关系靠近,共有同一节点,二者与大螟盘绒茧蜂C．sesamiae构成姐妹群,此姐妹群再与二化螟盘绒茧蜂C．chilonis共有同一最近共同祖先,最后与螟黄足盘绒茧蜂C．tlavipes构成螟黄足盘绒茧蜂复合群单系群．     

Chimpanzees recruit the best collaborators

Humans collaborate with non-kin in special ways, but the evolutionary foundations of these collaborative skills remain unclear. We presented chimpanzees with collaboration problems in which they had to decide when to recruit a partner and which potential partner to recruit. In an initial study, individuals recruited a collaborator only when solving the problem required collaboration. In a second study, individuals recruited the more effective of two partners on the basis of their experience with each of them on a previous day. Therefore, recognizing when collaboration is necessary and determining who is the best collaborative partner are skills shared by both chimpanzees and humans, so such skills may have been present in their common ancestor before humans evolved their own complex forms of collaboration.     

Rapid spread of a bacterial symbiont in an invasive whitefly is driven by fitness benefits and female bias

Maternally inherited bacterial symbionts of arthropods are common, yet symbiont invasions of host populations have rarely been observed. Here, we show that Rickettsia sp. nr. bellii swept into a population of an invasive agricultural pest, the sweet potato whitefly, Bemisia tabaci, in just 6 years. Compared with uninfected whiteflies, Rickettsia-infected whiteflies produced more offspring, had higher survival to adulthood, developed faster, and produced a higher proportion of daughters. The symbiont thus functions as both mutualist and reproductive manipulator. The observed increased performance and sex-ratio bias of infected whiteflies are sufficient to explain the spread of Rickettsia across the southwestern United States. Symbiont invasions such as this represent a sudden evolutionary shift for the host, with potentially large impacts on its ecology and invasiveness.     

稻鸭共作系统中主要捕食性天敌的生态位

【目的】探明稻鸭共作系统中主要捕食性天敌类群对资源的利用程度及在资源分配上的内在关系。【方法】在对稻鸭共作和常规稻作系统中主要捕食性天敌进行田间调查的基础上,研究主要捕食性天敌群落的结构和生态位,分析各类群在资源序列上分布的数量特征和资源利用状况。【结果】常规稻作区、稻鸭共作区中主要捕食性天敌的优势类群均为微蛛、园蛛、狼蛛和肖蛸科,以园蛛科的优势度指数为最高,分别为0.4999和0.6665。稻田养鸭对主要捕食性天敌类群的数量和分布格局有直接或间接的影响,使其时—空二维生态位宽度、生态位重叠度与生态位相似性比例均发生了不同程度的改变。其中微蛛、园蛛和肖蛸的生态位宽度值低于常规区,微蛛与球蛛、肖蛸与跳蛛、跳蛛与管巢蛛及管巢蛛与瓢虫的二维生态位重叠度比常规区增加了70.65%—75.57%。【结论】稻鸭共作使主要捕食性天敌在同一资源等级上的竞争加强,在时间上的同步性更为明显,尽管捕食性天敌的总个体数比常规区下降了19.56%,但天敌充分利用了时间资源序列中的较多等级,且分布更为均匀,发生时间长,可对害虫种群进行持续控制,因而控虫效果更为显著。     

Diversity considerations in HIV-1 vaccine selection

Globally, human immunodeficiency virus-type 1 (HIV-1) is extraordinarily variable, and this diversity poses a major obstacle to AIDS vaccine development. Currently, candidate vaccines are derived from isolates, with the hope that they will be sufficiently cross-reactive to protect against circulating viruses. This may be overly optimistic, however, given that HIV-1 envelope proteins can differ in more than 30% of their amino acids. To contend with the diversity, country-specific vaccines are being considered, but evolutionary relationships may be more useful than regional considerations. Consensus or ancestor sequences could be used in vaccine design to minimize the genetic differences between vaccine strains and contemporary isolates, effectively reducing the extent of diversity by half.     

双子叶植物和单子叶植物的关系

本文主要讨论了三个问趔:双子叶植物和单子叶植物胚的关系、比较和进化的关系。单子叶植物一个可能的祖先是双子叶植物的毛莨目,单子叶植物的百合目由毛莨目进化而来。双子叶型胚由于一片子叶功能的改变或面积缩小而退化或消失形成了单子叶型胚,而不是两片子叶愈合成一片子叶的结果。     

海南4个地区犬体表蜱种鉴定及其无形体携带情况

为研究海南省犬体表蜱虫的种类及其携带无形体的情况,对4个地区犬蜱进行形态学、分子生物学鉴定及进化分析,且基于16S rRNA和gltA基因,通过PCR检测犬蜱携带无形体的情况。形态学及分子生物学鉴定结果表明,所有蜱类为血红扇头蜱（Rhipicephalus sanguineus）,基于蜱虫线粒体16S rDNA基因的系统发育树表明,研究中所获得的HN-01和HN-02基因序列处于不同的遗传进化分支,HN-01与已知的来自美国的血红扇头蜱(MH018842)处于同一分支,HN-02与来自泰国（KC170744）的血红扇头蜱处于同一分支,与我国甘肃省、北京市所获得的血红扇头蜱（JF979377、KC203362）序列亲缘关系较远。基于扁平无形体（Anaplasma platys）gltA基因的PCR结果表明,犬蜱携带有扁平无形体,其阳性率为1.1%(6/546)。基于16S rRNA基因的PCR检测结果表明,研究中获得的犬体表蜱未携带嗜吞噬细胞无形体（Anaplasma pagocytophilum）和牛无形体（Anaplasma bovis）。     

Morphological disparity in the cambrian

An analysis of the range of morphology among arthropods demonstrates that disparity among living arthropods is similar to that in Cambrian arthropods. The range of morphological design resulting from the Cambrian "explosion" has been overestimated, reflecting a tendency to separate as "problematic" taxa that cannot be accommodated in the classification on the basis of the living biota. Problematic taxa are largely an artifact of an inadequate taxonomy. Special evolutionary processes may not be necessary to explain the early radiation of the metazoans.     

Comparing brains

Some animals have larger brains than others, but it is not yet known why. Species differences in life-style, including dietary habits and patterns of development of the young, are associated with variation in brain weight, independently of the effects of body weight and evolutionary history. Taken together with behavioral and neuroanatomical analyses, these studies begin to suggest the evolutionary pressures that favor different sized brains and brain components.     

Mitochondrial evolution

The serial endosymbiosis theory is a favored model for explaining the origin of mitochondria, a defining event in the evolution of eukaryotic cells. As usually described, this theory posits that mitochondria are the direct descendants of a bacterial endosymbiont that became established at an early stage in a nucleus-containing (but amitochondriate) host cell. Gene sequence data strongly support a monophyletic origin of the mitochondrion from a eubacterial ancestor shared with a subgroup of the alpha-Proteobacteria. However, recent studies of unicellular eukaryotes (protists), some of them little known, have provided insights that challenge the traditional serial endosymbiosis-based view of how the eukaryotic cell and its mitochondrion came to be. These data indicate that the mitochondrion arose in a common ancestor of all extant eukaryotes and raise the possibility that this organelle originated at essentially the same time as the nuclear component of the eukaryotic cell rather than in a separate, subsequent event.     

中国近海浮游动物群落结构及季节变化

2006年7-8月、12月-2007年2月、2007年4-5月、2007年10-12月,对中国近海进行了4个航次生物、化学和水文等专业综合调查。根据采集的浮游动物样品分析鉴定结果,对中国近海浮游动物群落结构、种类组成及优势种的季节变化进行研究。结果表明,中国近海浮游动物有1330种,隶属于7门19大类群,浮游幼体47类,其中,节肢动物为最优势类群,有782种,占58.80%,其次为刺胞动物,有324 种,占24.36%。在浮游动物群落结构中,4个海区均以桡足类和水母类的种类和数量占绝对优势。中国近海4个海区浮游动物种类数有明显季节变化,渤海和黄海,浮游动物种类数夏、秋季多于春、冬季;东海和南海,浮游动物种类数春、夏季多于秋、冬季。中国近海浮游动物群落大体可划分为6个主要生态类群:近岸低盐类群、低温高盐类群、高温高盐类群、低温广盐类群、高温广盐类群和广温广盐类群。结合同步调查的其它生物、水文、化学环境参数的分析结果,对中国近海浮游动物群落种类丰度与环境因子进行生物与环境变量关系分析,结果表明,浮游动物群落结构与水温、盐度、水深、溶解氧、硝酸盐和pH存在明显相关关系。水温和盐度是影响浮游动物群落结构最重要的两个环境因子。     

Pierolapithecus catalaunicus, a new Middle Miocene great ape from Spain

We describe a partial skeleton with facial cranium of Pierolapithecus catalaunicus gen. et sp. nov., a new Middle Miocene (12.5 to 13 million years ago) ape from Barranc de Can Vila 1 (Barcelona, Spain). It is the first known individual of this age that combines well-preserved cranial, dental, and postcranial material. The thorax, lumbar region, and wrist provide evidence of modern ape-like orthograde body design, and the facial morphology includes the basic derived great ape features. The new skeleton reveals that early great apes retained primitive monkeylike characters associated with a derived body structure that permits upright postures of the trunk. Pierolapithecus, hence, does not fit the theoretical model that predicts that all characters shared by extant great apes were present in their last common ancestor, but instead points to a large amount of homoplasy in ape evolution. The overall pattern suggests that Pierolapithecus is probably close to the last common ancestor of great apes and humans.     

Bivoltinism as an antecedent to eusociality in the paper wasp genus Polistes

To learn the evolutionary trajectories of caste differentiation in eusocial species is a major goal of sociobiology. We present an explanatory framework for caste evolution in the eusocial wasp genus Polistes (Vespidae), which is a model system for insect eusocial evolution. We hypothesize that Polistes worker and gyne castes stem from two developmental pathways that characterized the bivoltine life cycle of a solitary ancestor. Through individual-based simulations, we show that our mechanistic framework can reproduce colony-level characteristics of Polistes and, thereby, that social castes can emerge from solitary regulatory pathways. Our explanatory framework illustrates, by specific example, a changed perspective for understanding insect social evolution.     

Putative skeletal neural crest cells in early late ordovician vertebrates from colorado

Two vertebrates from the Colorado Formation are known to have acellular bone and dentine, tissues found in heterostracan fishes and proposed as the primitive exoskeleton. High-resolution optical microscopy and scanning electron microscopy indicate that a third vertebrate is represented by a quite distinct exoskeleton of denticles, with many cell and cell process spaces throughout, tissue that resembles that of osteostracans more than heterostracans. Cellular bone coexists with cellular dentine in this Ordovician vertebrate, demonstrating that these skeletal tissues are as old as acellular bone. Both are proposed to come from neural crest because denticles are considered homologous with teeth.