关键词： bark beetle   Dendroctonus brevicomis   Entomocorticium spp.   herbivory   local adaptation   monoterpenes   mutualism   phenotype   phytochemistry   phytophagy   Pinus ponderosa   symbiosis  

摘要： Many herbivores consume microbial food sources in addition to plant tissues for nutrition. Despite the ubiquity of herbivore-microbe feeding associations, few studies examine how host plant phenotypes affect microbial symbionts of herbivores. We tested the hypothesis that chemical polymorphism in a plant population mediates the performance of nutritional microbial symbionts. We surveyed the composition of ponderosa pine resin in northern Arizona, USA, for variation in six monoterpenes, and we approximated four chemical phenotypes. We reared populations of an herbivorous tree-killing beetle (Dendroctonus brevicomis) in ponderosa pine host material, controlling for three monoterpene compositions representing an alpha-pinene to Delta-3-carene gradient. Beetles were reared in host material where the dominant monoterpene was alpha-pinene, Delta-3-carene, or a phenotype that was intermediate between the two. We isolated nutritional fungal symbionts (Entomocorticium sp. B) from beetle populations reared in each phenotype and performed reciprocal growth experiments in media amended to represent four "average'' monoterpene compositions. This allowed us to test the effects of natal host phenotype, chemical polymorphism, and the interaction between natal host phenotype and chemical polymorphism on a nutritional symbiont. Three important findings emerged: (1) fungal isolates grew 25-32% faster when acquired from beetles reared in the intermediate phenotype;(2) the mean growth rate of nutritional fungi varied up to 44% depending on which monoterpene composition media was amended with;and (3) fungal isolates uniformly performed best in the intermediate phenotype regardless of the chemical composition of their natal host. The performance of nutritional fungi related to both the chemical "history'' of their associated herbivore and the chemical phenotypes they are exposed to. However, all fungal isolates appeared adapted to a common chemical phenotype. These experiments argue in fa

关键词： Ant-plant interaction   Context-dependency   Brazil   Caatinga   Cerrado   Natural selection   Nectar glands  

摘要： Despite the general belief that the interaction between extrafloral nectaries (EFNs) and ants is mutualistic, the defensive function of EFNs has been poorly documented in South American savannas. In this article, we evaluate the potential impact of EFNs (benefits and costs) on two species of plants from the dry areas of Central Brazil, Anemopaegma album and Anemopaegma scabriusculum (Bignoniaceae). In particular, we characterize the composition of substances secreted by the EFNs, test whether EFNs attract ants, and whether ants actually present a defensive role, leading to reduced herbivory and increased plant fitness. Histochemical analyses indicated that EFNs from both species of Anemopaegma secrete an exudate that is composed of sugars, and potentially lipids and proteins. Furthermore, EFNs from both species were shown to present a significant role in ant attraction. However, contrary to common expectations, ants were not found to protect plants against herbivore attack. No effect was found between ant visitation and flower or fruit production in A. album, while the presence of ants led to a significant decrease in flower production in A. scabriusculum. These results suggest that EFNs might present a similar cost and benefit in A. album, and a higher cost than benefit in A. scabriusculum. Since the ancestor of Anemopaegma occupied humid forests and already presented EFNs that were maintained in subsequent lineages that occupied savannas, we suggest that phylogenetic inertia might explain the presence of EFNs in the species of Anemopaegma in which EFNs lack a defensive function.

关键词： Phylogenetic analysis   Mitochondria   Animal phylogenetics   Genetic loci   Speciation   Mitochondrial DNA   Mammals   Population genetics  

摘要： An important challenge for phylogenetic studies of closely related species is the existence of deep coalescence and gene tree heterogeneity. However, their effects can vary between species and they are often neglected in phylogenetic analyses. In addition, a practical problem in the reconstruction of shallow phylogenies is to determine the most efficient set of DNA markers for a reliable estimation. To address these questions, we conducted a multilocus simulation study using empirical values of nucleotide diversity and substitution rates obtained from a wide range of mammals and evaluated the performance of both gene tree and species tree approaches to recover the known speciation times and topological relationships. We first show that deep coalescence can be a serious problem, more than usually assumed, for the estimation of speciation times in mammals using traditional gene trees. Furthermore, we tested the performance of different sets of DNA markers in the determination of species trees using a coalescent approach. Although the best estimates of speciation times were obtained, as expected, with the use of an increasing number of nuclear loci, our results show that similar estimations can be obtained with a much lower number of genes and the incorporation of a mitochondrial marker, with its high information content. Thus, the use of the combined information of both nuclear and mitochondrial markers in a species tree framework is the most efficient option to estimate recent speciation times and, consequently, the underlying species tree.

关键词： 后生动物   古生物学家   系统演化   研究员   化石生物   螺旋星系   系统树   仙女座  

摘要： 发现于华南贵州的一类5．8亿年前的化石让我们开始，怀疑已知的动物系统树。因为形体像极了螺旋星系仙女座。这类被命名为“八臂仙母虫”的化石生物，将重新排序生命系统树的最早期分支。相关论文在2011年9月21日美国出版的《进化和发育》杂志以封面文章形式发表。

关键词： 油桐饼(粕)   蛋白质   脱毒方法   畜牧生产  

摘要： 本文主要介绍油桐饼(粕)资源的特点、营养价值、脱毒方法及其在畜牧生产上的应用。

关键词： 寒武纪   澄江动物群   刺胞动物   栉水母   叶足动物   古虫动物  

摘要： 自达尔文1859年在《物种起源》中提出天才的“生命之树(Tree of Life)"猜想以来,愈来愈多的形态学及分子生物学证据表明,地球上所有生命“本是同根生”,组成一棵庞大的生命谱系大树。21世纪伊始,欧美国家纷纷启动了“构建生命之树”的宏伟研究计划,致力于建立一棵完整的地球生命系统发育树,将所有现存和绝灭类群联系在一起,以阐明生命起源和进化历程、各类群生物之间的亲缘关系。生命之树由“原核生命树”、“真菌树”、“植物树”和“动物树”组成。其中,动物树之构建最受世人瞩目。西方国家对于动物树的构建依赖于现生动物的分子演化信息,而完整的动物树还需要化石的检验和补充。我国滇东地区特异埋藏的澄江动物化石宝库记载了寒武纪生命大爆发主幕的珍贵信息。澄江动物群不但延续了伊迪卡拉纪爆发的基础动物(多孔动物及双胚层的栉水母及刺胞动物)和梅树村期辐射的原口动物(三胚层较低等类群,包括环节动物、叶足动物、节肢动物、曳鳃动物、软体动物、腕足动物等),还启动了后口动物(三胚层较高等类群)的辐射演化。澄江动物群中不仅诞生了现代后口动物五大类群(棘皮类、半索类、头索类、尾索类和脊椎类)的所有早期代表,还出现一个已绝灭的后口动物原始类群——古虫动物门,标志着早期动物树已基本成型。因此,澄江动物群科学意义重大,对于早期动物谱系树的重建提供了一个绝佳的瞭望窗口。现代生物学认为,动物树主要包含三个亚界、四大类群：基础动物亚界、原口动物亚界(蜕皮类群和触手担轮类群)和后口动物亚界。基于作者对澄江动物群(二街、三街子、耳材村、马房、尖山、帽天山6个剖面)化石信息的新发现,本文不仅填补了早期动物树中部分支系的空白,而且对四大类群中一些关键节点的构建提出了新见解：1.基础动物类群：中华先光海葵的形态学新发现表明它具有纤毛滤食系统,并证实了它与刺胞动物的亲缘关系；比较生物学及分支系统学研究均表明中华先光海葵为一种干群刺胞动物；因此,这一水螅型滤食性动物可作为刺胞动物谱系的一个关键节点(最近共祖)。澄江动物群中所有栉水母(包括四个新属种)都具有矿化骨骼系统及辐射对称体制；它们可归纳入一个新纲(始栉水母纲),构成栉水母动物门的一个早期干群分枝。2.蜕皮类群：澄江叶足动物(凶猛爪网虫及具足埃舍虫等)的形态新发现指示了它们最原始的头部构型及与泛节肢动物的同源性状,揭露了早期叶足动物→现代有爪类→节肢动物头部演化模式；因此,早期叶足动物可论证为干群泛节肢动物。中间型始莱德利基虫的个体发育研究表明该三叶虫与北美的小油栉虫类和非洲的法罗特史虫类可能存在由异时发育导致的谱系演化关系,进一步证实莱德利基虫目为三叶虫纲的基干类群。3.触手担轮类群：变形廼莲虫是澄江动物群中新发现的一个珍稀物种；该生物具环绕口部的触手冠和位于体侧的前置肛门,很可能代表一种干群触手冠动物。4.后口动物类群：古虫动物的解剖学新证据进一步论证了原始咽鳃裂的存在及其适于排出咽内海水及辅助滤食／呼吸的功能,支持古虫动物为后口动物亚界的基干类群；该类群为后口动物原始体制(尤其是咽鳃裂)的起源和早期演化提供了珍贵信息。

关键词： arthropod phylogeny   anatomy   fossils   molecular data   phylogenomics  

摘要： Arthropods are the most diverse group of animals and have been so since the Cambrian radiation. They belong to the protostome clade Ecdysozoa, with Onychophora (velvet worms) as their most likely sister group and tardigrades (water bears) the next closest relative. The arthropod tree of life can be interpreted as a five-taxon network, containing Pycnogonida, Euchelicerata, Myriapoda, Crustacea, and Hexapoda, the last two forming the clade Tetraconata or Pancrustacea. The unrooted relationship of Tetraconata to the three other lineages is well established, but of three possible rooting positions the Mandibulata hypothesis receives the most support. Novel approaches to studying anatomy with noninvasive three-dimensional reconstruction techniques, the application of these techniques to new and old fossils, and the so-called next-generation sequencing techniques are at the forefront of understanding arthropod relationships. Cambrian fossils assigned to the arthropod stem group inform on the origin of arthropod characters from a lobopodian ancestry. Monophyly of Pycnogonida, Euchelicerata, Myriapoda, Tetraconata, and Hexapoda is well supported, but the interrelationships of arachnid orders and the details of crustacean paraphyly with respect to Hexapoda remain the major unsolved phylogenetic problems.

关键词： HELMINTHIASIS   RAIN forests   SAVANNA ecology   HOSTS (Biology)   SPECIES diversity   PROTEOCEPHALIDAE  

摘要： Anurans from the rainforest (Okomu National Park) and derived savanna (Agbede) locations in Nigeria were investigated for their role either as intermediate or paratenic hosts of helminth infections. A total of 269 anuran specimens (157 from the Okomu National Park and 112 from Agbede) were examined. Metacercariae of a strigeoid trematode, two nematode species, a proteocephalid cestode, and an acanthocephalan were recovered from infected hosts. Except for the strigeoid trematode, which was only recorded in the rainforest, there was no ecological dichotomy in the distribution of the larval parasites recorded. Tree frogs from the rainforest only served as second intermediate hosts for the strigeoid trematode. The two nematode larvae (type I and type II) found in the body cavity of the infected host are believed to use them as paratenic hosts. Tree frogs were the predominant intermediate hosts of the proteocephalid cestode larvae in the rainforest, while Ptychadena and Phrynobatrachus spp. served this function in the derived savanna. The occurrence of cystacanths in the anurans from both biotopes confirms their known role as paratenic host for acanthocephalans. Afrixalus dorsalis is a new host record for the ascaridoid nematode while the finding of the strigeoid trematode, the proteocephalid cestode larvae and acanthocephalan cystacanths in the anurans investigated represents new geographical records. © 2012 Abigail A. Imasuen et al.

关键词： 墨尔本   澳大利亚   新西兰北岛   十字星   羊毛制品   生态游  

摘要： 2012年4月,民间环保组织绿家园组织了赴澳大利亚与新西兰的生态游。在这次生态游中,我看到了很多,也思考了很多。走进大树体内去拍照一到新西兰基督城,负责接待的当地华人殷晓雷就问我们:"要不要走进一棵大树去拍照?"走进大树?大树也能走进去吗?带着好奇,我们真的走进了大树。原来这棵树一

关键词： 动物化石   恐龙   科学家   古生物学家   古脊椎动物   美国科学院   研究所   古人类  

摘要： 古生物学家认为，鸟类是由恐龙进化来的，而且许多恐龙也是凶猛的肉食动物，那么，刚披上羽毛的恐龙能飞上树吗？近日，《美国科学院院刊》将在线发表中科院古脊椎动物与古人类研究所的最新发现：它们可以飞上树!因为它们能逮食树栖动物。