关键词： SAVANNA plants   PLANT growth   LEGUMES   PLANT diversity   PLANT physiology   PLANT defenses  

摘要： Herbivory contributes substantially to plant functional diversity and in ways that move far beyond direct defence trait patterns, as effective growth strategies under herbivory require modification of multiple functional traits that are indirectly related to defence. In order to understand how herbivory has shaped plant functional diversity, we need to consider the physiology and architecture of the herbivores and how this constrains effective defence strategies. Here we consider herbivory by mammals in savanna communities that range from semi-arid to humid conditions. We posited that the saplings of savanna trees can be grouped into two contrasting defence strategies against mammals, namely architectural defence versus low nutrient defence. We provide a mechanistic explanation for these different strategies based on the fact that plants are under competing selection pressures to limit herbivore damage and outcompete neighbouring plants. Plant competitiveness depends on growth rate, itself a function of leaf mass fraction (LMF) and leaf nitrogen per unit mass (N-m). Architectural defence against vertebrates (which includes spinescence) limits herbivore access to plant leaf materials, and partly depends on leaf-size reduction, thereby compromising LMF. Low nutrient defence requires that leaf material is of insufficient nutrient value to support vertebrate metabolic requirements, which depends on low N-m. Thus there is an enforced tradeoff between LMF and N-m, leading to distinct trait suites for each defence strategy. We demonstrate this tradeoff by showing that numerous traits can be distinguished between 28 spinescent (architectural defenders) and non-spinescent (low nutrient defenders) Fabaceae tree species from savannas, where mammalian herbivory is an important constraint on plant growth. Distributions of the strategies along an LMF-N-m tradeoff further provides a predictive and parsimonious explanation for the uneven distribution of spinescent and non-spinescen

关键词： FORBIO   Biodiversity-ecosystem functioning   Temperate forest   Plantation   Mixed forest  

摘要： Mixed forest with multiple tree species is expected to create heterogeneous habitat and diverse niches for the canopy arthropod community. We assessed arthropod abundance, order richness, and community composition in the crowns of saplings of nine temperate tree species in two plantations of a recently established tree diversity experiment in Belgium, and looked for relationships with the diversity and structure of the sapling's local neighbourhood. The crown arthropod community differed between the two study sites, both in terms of abundances and composition. More arthropods were found in the post-agricultural site;the arthropod community was more complex in the formerly forested site. The tree species identity of a sapling, its apparency, and the phylogenetic diversity of its local neighbourhood all affected the crown arthropod community. Our study suggests that mixing phylogenetically distant tree species creates niches for a complex crown arthropod community.

关键词： biodiversity loss   bush encroachment   elephants Loxodonta africana   extinction   Hexagon satellite   plant-herbivore interactions   remote sensing   top-down effects   tree-grass coexistence   trophic cascade  

摘要： 1. Large mammalian herbivores (LMH) exert strong effects on plants in tropical savannas, and many wild LMH populations are declining. However, predicting the impacts of these declines on vegetation structure remains challenging. 2. Experiments suggest that tree cover can increase rapidly following LMH exclusion. Yet it is unclear whether these results scale up to predict ecosystem-level impacts of LMH declines, which often alter fire regimes, trigger compensatory responses of other herbivores and accompany anthropogenic land-use changes. Moreover, theory predicts that grazers and browsers should have opposing effects on tree cover, further complicating efforts to forecast the outcomes of community-wide declines. 3. We used the near-extirpation of grazing and browsing LMH from Gorongosa National Park during the Mozambican Civil War (1977-1992) as a natural experiment to test whether megafaunal collapse increased tree cover. We classified herbaceous and tree cover in satellite images taken (a) at the onset of war in 1977 and (b) in 2012, two decades after hostilities ceased. 4. Throughout the 3620-km(2) park, proportional tree cover increased by 34% (from 0.29 to 0.39) an addition of 362 km(2). Four of the park's five major habitat zones (including miombo woodland, Acacia-Combretum-palm savanna, and floodplain grassland) showed even greater increases in tree cover (51-134%), with an average increase of 94% in ecologically critical Rift Valley habitats. Only in the eastern Cheringoma Plateau, which had historically low wildlife densities, did tree cover decrease (by 5%). 5. The most parsimonious explanation for these results is that reduced browsing pressure enhanced tree growth, survival and/or recruitment;we found no directional trends in rainfall or fire that could explain increased tree cover. 6. Synthesis. Catastrophic large-herbivore die-offs in Mozambique's flagship national park were followed by 35 years of woodland expansion, most severely in areas where pre-w

关键词： 树鼩   非肥胖型非酒精性脂肪肝   胆固醇   发病机理   脂蛋白脂酶   动物模型  

摘要： 非酒精性脂肪肝病(non-alcoholic fatty liver disease，NAFLD)是由酒精之外的其他因素导致的肝脏中以脂肪积累为主要特征的临床病理综合征，高能量食物（尤其是高脂高胆固醇食物）的过多摄入和多坐少动等都是它的诱发因素。目前其正在逐渐成为一个严重的公共健康问题，在西方发达国家，大约有20-30％的人患有非酒精性脂肪肝，而在中国，也有12-24％的人承受同样的疾病折磨。　　一般而言，患有非酒精性脂肪肝的患者同时也伴有肥胖、高血糖、高血脂、胰岛素抵抗甚至2型糖尿病等代谢综合征(metabolic syndrome)的症状，对于这一类非酒精性脂肪肝已经建立了诸多的动物模型来供人们研究，尽管目前对其发病机理了解的不是很透彻，但还是取得了一些进展;但是，另一方面，在亚太地区，一些非酒精性脂肪肝患者(15-21％)却并没有表现出肥胖和糖尿病症状，因此被称为是非肥胖型非酒精性脂肪肝(non-obese NAFLD)，遗憾的是，目前并没有十分理想的动物模型可用来对其开展研究，这也导致我们对这种非肥胖型非酒精性脂肪肝的发病机理知之甚少。　　树鼩(tree shrew)是一种小型哺乳动物，它在生物分类学上的位置介于啮齿类和灵长类之间，其进化地位比啮齿类更为高级。正因为如此，树鼩不断被应用于生物学研究领域，包括神经生物学、病毒学（乙型和丙型肝炎病毒等）、行为学（应激和抑郁等）、癌症和代谢性疾病等方面的研究。然而树鼩能否被用来研究非酒精性脂肪肝还不得而知。　　为了回答上述问题，在本研究中，首先，我们用不同高热量食物的组合（如高糖、高脂、高糖高脂以及高脂高胆固醇等）来对树鼩（Tupaia belangeri chinensis）进行食物诱导。结果发现，诱导之后，各组树鼩表现出不同程度的肝功能受损，同时伴随有高脂血症，但血糖并未呈现明显变化。进一步通过组织切片检查其肝脏组织发现，所有树鼩都出现肝脏脂肪积累，这意味着我们成功诱导了树鼩脂肪肝。但令人惊奇的是，和对照组树鼩相比，这些脂肪肝树鼩的体重并没有增加，而且在皮下和腹腔等处也没有脂肪组织的出现，说明它们没有形成肥胖。因此，我们认为树鼩可以作为一种较好的研究非肥胖型非酒精性脂肪肝的动物模型。　　接着，我们用高脂高胆固醇食物进一步研究发现，树鼩不仅能够形成非酒精性脂肪肝的早期阶段（单纯性脂肪肝），还能够出现脂肪性肝炎和纤维化，也就是说树鼩能够完整模拟非酒精性脂肪肝的发病过程，并且模拟这一过程需要的时间只有小鼠模型的三分之一。同时，在发病机理方面，经过对脂代谢基因的筛选，我们发现肝脏脂蛋白脂酶(lipoprotein lipase，LPL)在高脂高胆固醇诱导下高表达，而将LPL抑制之后，动物水平上，高脂高胆固醇导致的脂肪肝症状得到了明显的恢复;细胞水平上，氧化型LDL引起的树鼩肝脏原代细胞内的脂肪积累现象也得到了显著改善。因此我们的研究结果说明，LPL在高脂高胆固醇诱导的树鼩非肥胖型非酒精性脂肪肝发病过程中起着关键作用。　　此外，在上述基础上，为了探究肝脏LPL的高表达到底是高脂和高胆固醇的共同作用诱导的、还是单独的胆固醇诱导的以及这其中蕴藏着怎样的调控机制等问题，我们在小鼠上设计了单独不同浓度的胆固醇诱导以及不同浓度的胆固醇与高脂组合诱导的实验并做了肝脏转录组检测，结果显示，单独的一定浓度胆固醇就可以诱导肝脏LPL的高表达。然而，由于转录组数据分析还在进行之中，因此关于这其中的调控机理还需要等待转录组数据的分析结果和实验验证来回答。

关键词： alien species   biological invasions   wilding pines   pest mammal   seedling recruitment   restoration   succession  

摘要： Pinus contorta is a widespread and ecologically damaging invasive tree in the southern hemisphere. Land managers want control methods that limit reinvasion by P. contorta and promote the recovery of native plant communities and ecosystem functions. Recovery of native vegetation may be slow if native seed supply is limited and/or introduced mammals destroy seeds and seedlings. We investigated how tree control method (felling or poisoning), seed addition, and exclusion of introduced mammals affected subsequent seedling establishment in montane stands of invasive P. contorta. Tree control method had a significant effect on seedling establishment: felling trees promoted establishment of P. contorta seedlings, whereas poisoning trees favoured establishment of native seedlings (provided seeds were available). Native seedling establishment was higher where seeds were sown, indicating native seed limitation at these sites. Excluding introduced mammals increased P. contorta seedling establishment, but did not have a significant effect on native seedling establishment. Our results indicate that poisoning P. contorta is a better management approach than felling where native seedling establishment is the desired outcome, and that this outcome can be enhanced by sowing native seed.

关键词： 树鼩   钠-牛磺胆酸共转运多肽   动物模型  

摘要： [目的]慢性乙型病毒性肝炎是影响人类健康的一种常见传染性疾病,其预防和治疗是肝脏疾病相关研究领域中的重点内容。然而,在慢性乙型肝炎动物模型的建立过程中,缺乏合适的实验动物且多为“一过性”感染,是阻碍建立动物模型及后续研究的重要因素。近年一些研究表明,树鼩对乙肝病毒具有易感性,且钠-牛磺胆酸共转运多肽(Na+/taurocholate cotransporting Polypeptide,NTCP)被证实为是乙肝病毒的受体,并可通过化学药物等方式上调其表达水平。本课题通过探索使树鼩NTCP过表达有效的干预方式,建立树鼩NTCP过表达动物模型,增加树鼩对乙肝病毒的易感性,优化树鼩慢性感染HBV动物模型的建模方法,从而为后续研究慢性乙型病毒性肝炎及相关疾病的预防与治疗方案提供理论基础。[方法]第一部分：探索NTCP在树鼩不同年龄段的表达异同。随机选取新生期(7日龄内)树鼩3只；幼年期(4-6周龄)树鼩3只；成年期(4-6月龄)树鼩3只。行ELISA检测,测定NTCP浓度并比较其差异;第二部分：采用不同干预方式,探索建立树鼩NTCP过表达动物模型。实验组1：成年树鼩(6只,4-6月龄),将消胆胺研成粉末加至树鼩饲料中喂食4天；实验组2:成年树鼩(6只,4-6月龄),地塞米松腹腔注射,一天一次,干预4天；实验组3:成年树鼩(6只,4-6月龄),消胆胺、地塞米松合用,干预方式同实验组1、2；并分别为实验组1、2设置阴性对照组。同样取血行ELISA及取肝脏行Western Blot、Real-time PCR测定NTCP蛋白及基因水平并比较各组间差异；[结果](1)经统计学分析,新生期树鼩NTCP浓度分别与幼年期及成年期相比较,P<0.05,具有统计学意义,新生期树鼩NTCP浓度分别与幼年期及成年期存在差异；(2)幼年期及成年期相比较,P>0.05,差异无统计学意义,暂不能认为幼年期与成年期树鼩NTCP浓度有差异；(3)实验组1、实验组2的树鼩NTCP浓度分别与其阴性对照组行统计学分析,P<0.05,存在统计学意义,消胆胺和地塞米松均改变了树鼩肝内NTCP的表达水平；(4)实验组3分别与实验组1、实验组2行统计学分析,P<0.05,存在统计学意义,表明消胆胺与地塞米松联用改变树鼩NTCP表达水平的效果与单一应用消胆胺或地塞米松的效果存在差异。(5)采集不同时间段树鼩血清及肝脏标本,检测NTCP浓度进行组内比较,行统计学分析,P>0.05,无统计学意义。[结论](1)新生期树鼩NTCP浓度低于幼年期和成年期；(2)自幼年期开始,树鼩NTCP表达水平已升高至成年水平,其表达量趋于稳定。(3)消胆胺及地塞米松均能增加树鼩肝内NTCP表达水平,且联合用药的效果要优于单一用药。(4)树鼩NTCP升高程度与药物干预时间无关。

摘要： The Japanese tree frog, a representative of the Manchurian fauna, is characterized by an outstanding cold resistance among the anuran amphibian species studied so far. Almost 70% of the specimens from the population inhabiting the middle Amur River withstand the cooling down to–30°C;some animals, down to–35°C. This exceeds more than twofold the cold hardiness of the wood frog (Lithobates sylvaticus LeConte, 1825), which has been considered earlier to be the most cold-resistant species. The ability of H. japonica to survive for four months in the frozen state at low temperatures makes this species independent of the temperature overwintering conditions. © 2016, Pleiades Publishing, Ltd.

关键词： 树鼩   大脑   图谱   磁共振成像   扩散张量成像  

摘要： 树鼩是外形像松鼠的小型哺乳动物,目前普遍将其划分为攀鼩目。树鼩拥有很多作为模式动物的理想特征,例如:成年体型小、繁殖周期和寿命短、饲养费用低和脑重/体重比率大。比较研究表明树鼩比啮齿类拥有更高的灵长类的基因和神经解剖学特征的相似性。数十年来,树鼩一直被提议为比啮齿类更加适合、可作为灵长类的替代品用于生物医学研究。在神经精神疾病研究方面,树鼩模型已经被用于近视、社会心理应激/抑郁、老年疾病、帕金森疾病和药物成瘾。磁共振成像(Magnetic Resonance Imaging,MRI)已经成为人和动物大脑结构与功能研究的常规手段。开展MRI神经影像学大脑研究往往需要数字化的图谱和模板,用以确定感兴趣区域进行形态学分析和结构与功能连接研究。目前使用MRI研究树鼩大脑的工作开展得极少,此外,树鼩大脑的解剖学知识还很不完善,如:缺少详细的白质纤维束信息。本文的主要目标是开展基于MRI的树鼩大脑解剖与脑图谱的研究。本文的内容包括:1)构建T2加权MRI树鼩脑图谱,标注主要的脑结构。;2)使用扩散张量成像(Diffusion Tensor Imaging,DTI)和超分辨轨迹密度成像(Track-Density Imaging,TDI)揭示树鼩大脑灰质结构的微观构造;3)使用DTI全面探索树鼩大脑内白质纤维束结构,制作基于DTI树鼩大脑白质图谱,并从进化的角度讨论了树鼩脑白质结构的特征。第一章介绍了树鼩的基本情况、MRI成像技术和本研究的目的及方案。从树鼩的进化地位、树鼩神经精神疾病模型和树鼩脑研究这三个方面介绍了树鼩的基本情况,MRI成像技术只介绍了本研究使用到的MRI和扩散加权MRI的基本原理。第二章利用常规T2加权结构MRI制作了树鼩大脑图谱,标注了主要的灰质结构和少许白质结构。第三章利用DTI和超分辨TDI研究树鼩灰质结构的微观构造。研究结果表明:DTI能很好的揭示树鼩上丘和海马的层状结构,能区别初级和次级视皮层以及杏仁和丘脑的部分核团;较DTI而言,超分辨TDI增强了各结构的可视能力,同时能揭示更多的解剖学信息,如:丘脑外背侧和前腹侧核、初级视皮层的层状结构等。第四章利用DTI进行了树鼩全脑白质纤维束的探究,同时使用了免疫组织化学手段揭示某些难理解白质结构的微观属性,最后制作了基于DTI的树鼩脑白质图谱。本章的研究结果还表明树鼩大脑白质结构更像灵长类,与啮齿类有显著的不同,如:树鼩存在雏形态的灵长类极外囊和弓状束白质纤维束,啮齿类动物不存在类似结构。第五章对本文的整个研究进行了总结,阐述了研究的不足,并对今后进一步制作更加完善的MRI树鼩脑图谱提供了建议。

关键词： Agroecology   Exclosure experiment   Leaf damage   Spatial scales   Tree cover   Tropics  

摘要： Birds and predatory arthropods are often implicated in pest control, but their relative impact and how this is mediated by variation in tree cover requires elucidation. We excluded birds and ground predatory arthropods from rapeseed plants in 2.5 x 1 m plots in 26 homegardens in Ethiopia, leaving the same sized control plots. From six groups of plants in bird exclosure and control plots, respectively, three groups were excluded from ground predatory arthropods. Data on leaf damage were surveyed four times at weekly intervals. The tree cover and land-use composition within 100 x 100 m surrounding each plots were recorded in the field and from a satellite image within 200 and 500 m buffer zones. The results show that the mean leaf damage was higher on rapeseed plants from which predatory arthropods were excluded than on control plants. However, excluding birds had no or only a weak impact on leaf damage. The mean leaf damage within predatory arthropod exclosures decreased with increasing tree, forest and perennial cover but increased with increasing grazing land cover and annual crop cover, while on control plants it was low across the tree cover variation. This pattern may indicate the presence of a higher density of herbivores on rapeseed plants and also more predatory arthropods (i.e., to control them) in tree-poor homegardens compared to tree-rich homegardens. Hence, tree-poor homegardens in this landscape have sufficient habitat heterogeneity to support natural enemies to deliver significant pest control on rapeseed. Our results show that there was variation in the dynamics of pests and predatory arthropods across the tree cover variation, suggesting changes in landscape composition could affect the pest control services and the outcomes for local farmers. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Book reviews   Childrens picture books  

摘要： On the African savanna there are predators, there are prey, and everyone runs from the mighty lions. Diverse animals are spotlighted on two-page spreads, from the well known, such as leopards and zebras, to the lesser known, such as caracals and impalas. The language is simple, often just a few words describing the animal at hand moving through its environment.