Comparing assemblages of Asteraceae and their insect herbivores under different land‐use regimens

Accelerated tropical landscape changes occurring over recent decades have produced environmental mosaics comprising remaining isolated green areas and mixed land‐use types. Our objective was to study the effects of alterations in the natural landscape on the species composition and structure of assemblages of Asteraceae and their endophagous insects through comparisons between cerrado (savanna), pastures and Eucalyptus stands. We first investigated whether similarities between assemblages of Asteraceae and their insects varied among land uses or localities. Secondly, we asked whether assemblages of Eucalyptus stands and pastures are subsets of those within the cerrado. We sampled within randomly deployed transects in 15 areas. Land use was found to be an important factor in determining plant composition similarity; however, locality did not exert any significant influence. Pastures were less similar to one another, suggesting high beta diversity. Similarities among insect assemblages were correlated with plant assemblage composition, but not with land use or locality. Species of Tephritidae were distributed along localities independently of land use. High beta diversity in Asteraceae assemblages among cerrados and pastures was supported by nestedness analysis. Plant assemblages in Eucalyptus stands were subsets of cerrado, but pasture assemblages were only partial subsets. A higher degree of nestedness in insect assemblages than in plant assemblages indicated lower beta diversity within these herbivores. Our data indicate that many herbivores are specialized on widely distributed plant genera. Conservation of Asteraceae species and their flower head insects depends not only on maintenance of landscape fragments but also on the correct matching of management form and land use. Such management may contribute to reducing isolation of plant and insect species by increasing the connectivity of remaining cerrado tracts, allowing population maintenance even at low abundances.     

甘肃东乡晚中新世新发现的副板齿犀(奇蹄目、犀科)化石

副板齿犀 (Ｐａｒｅｌａｓｍｏｔｈｅｒｉｕｍ)是Ｋｉｌｌｇｕｓ( 1 92 3 )根据采自山西的标本建立的 ,属型种为山西副板齿犀 (Ｐ .ｓｃｈａｎｓｉｅｎｓｅ)。邱占祥和谢骏义 ( 1 998)记述了产自甘肃东乡汪集的简饰副板齿犀 (Ｐ .ｓｉｍｐｌｕｍ)化石 ,但其准确的层位不能肯定。最近在汪集西南约 1 1ｋｍ的那勒寺乡有确切层位的晚中新世地层中发现一些新材料 ,它们显然可以归入Ｐａｒｅｌａｓｍｏｔｈｅｒｉｕｍ这个属 ,但与上述已知的两个种都不相同。临夏副板齿犀 (新种 )Ｐａｒｅｌａｓｍｏｔｈｅｒｉｕｍｌｉｎｘｉａｅｎｓｅｓｐ .ｎｏ…     

马占相思林冠蜘蛛群落的结构分析

用杀灭菊酯喷洒林冠,收集得蜘蛛２６种,１９９只。群落组成以不结网为为主,全年均保持较高数量水平。结网类从４月至１０月成指数曲数下降。４个相似样地上的群落结构显著差异。以ＭａｃＡｒｔｈａｒ分布模型为基础,求出每个种在群落中的数量－时间－空间的重要值。结果以斜蛛的ＮＴＤ为最,斑络新妇幼体为次。蜘蛛－昆虫群落的营养结构在各样地上是一致的。蜘蛛作为捕食者,占总数１２－１５％。     

Day-to-day variation in phytoplankton assemblages during spring blooming in a fixed station along the Lebanese coastline

Day-to-day variations in coastal marine phytoplanktonic assemblageswere studied over a 45 day period and related to changing environmentalconditions. Water temperature increased from 17.5 to 23C. Importantfluctuations in water salinity, which normally ranges between37.5 and 39, were recorded. The phytoplankton community sampledwas composed mainly of diatoms, whose numbers increased regularlyover several days. Leptocylindrus danicus was dominant and waspositively correlated to total phytoplankton and total diatomconcentrations. Dinoflagellates did not show regular net variations.Some peaks were recorded which may have been caused by sporadicproliferation of well-known coastal species. Variations in chlorophylla concentration did not parallel increases in total cell numbers,which may have been caused by the introduction of new populationsand contamination of samples by benthic diatoms. In the absenceof thermal stability, changes in meteorological conditions directlyinfluenced phytoplankton populations. Large daily fluctuationsin population numbers and composition were recorded over a shortperiod. Fluctuations were highly significant in successive days.This emphasizes the importance of daily sampling of planktoncommunities. Changes in meteorological conditions appear todisturb the correlation between parameters. Consequently, frequentsampling may be useful in elucidating many secondary phenomenawhich could interfere.     

Screening of traditional Lebanese medicinal plants as antioxidants and inhibitors of key enzymes linked to type 2 diabetes

Abstract

This study aimed to investigate the inhibitory activity of key enzymes linked to type 2 diabetes (α-amylase and α-glucosidase) and the antioxidant properties of non polar (n-hexane) extracts from Coffea arabica, Citrus lanatus, Cucumis melo, Cuminum cyminum, Cocos nucifera, Coriandrum sativum, Foeniculum vulgare, Nigella sativa, Rhus coriaria, Pimpinella anisum, Syzygium aromaticum and Sesamum indicum collected in Lebanon. Extracts were analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The antioxidant activity was investigated by using different in vitro methods namely 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric Reducing Ability Power (FRAP) and β-carotene bleaching tests. C. melo showed the highest α-glucosidase inhibitory activity with an IC₅₀ value of 25.55?μg/ml, followed by C. lanatus white seeds and S. indicum (IC₅₀ of 34.41 and 38.78?μg/ml, respectively). S. indicum exhibited also the highest protection of lipid peroxidation with IC₅₀ values of 0.07 and 0.06?mg/ml after 30 and 60?min of incubation, respectively.     

A Role for Calcium-Permeable AMPA Receptors in Synaptic Plasticity and Learning

A central concept in the field of learning and memory is that NMDARs are essential for synaptic plasticity and memory formation. Surprisingly then, multiple studies have found that behavioral experience can reduce or eliminate the contribution of these receptors to learning. The cellular mechanisms that mediate learning in the absence of NMDAR activation are currently unknown. To address this issue, we examined the contribution of Ca²⁺-permeable AMPARs to learning and plasticity in the hippocampus. Mutant mice were engineered with a conditional genetic deletion of GluR2 in the CA1 region of the hippocampus (GluR2-cKO mice). Electrophysiology experiments in these animals revealed a novel form of long-term potentiation (LTP) that was independent of NMDARs and mediated by GluR2-lacking Ca²⁺-permeable AMPARs. Behavioral analyses found that GluR2-cKO mice were impaired on multiple hippocampus-dependent learning tasks that required NMDAR activation. This suggests that AMPAR-mediated LTP interferes with NMDAR-dependent plasticity. In contrast, NMDAR-independent learning was normal in knockout mice and required the activation of Ca²⁺-permeable AMPARs. These results suggest that GluR2-lacking AMPARs play a functional and previously unidentified role in learning; they appear to mediate changes in synaptic strength that occur after plasticity has been established by NMDARs.     

Recent advances in development of marker-free transgenic plants: Regulation and biosafety concern

During the efficient genetic transformation of plants with the gene of interest, some selectable marker genes are also used in order to identify the transgenic plant cells or tissues. Usually, antibiotic- or herbicide-selective agents and their corresponding resistance genes are used to introduce economically valuable genes into crop plants. From the biosafety authority and consumer viewpoints, the presence of selectable marker genes in released transgenic crops may be transferred to weeds or pathogenic microorganisms in the gastrointestinal tract or soil, making them resistant to treatment with herbicides or antibiotics, respectively. Sexual crossing also raises the problem of transgene expression because redundancy of transgenes in the genome may trigger homology-dependent gene silencing. The future potential of transgenic technologies for crop improvement depends greatly on our abilities to engineer stable expression of multiple transgenic traits in a predictable fashion and to prevent the transfer of undesirable transgenic material to non-transgenic crops and related species. Therefore, it is now essential to develop an efficient marker-free transgenic system. These considerations underline the development of various approaches designed to facilitate timely elimination of transgenes when their function is no longer needed. Due to the limiting number of available selectable marker genes, in future the stacking of transgenes will be increasingly desirable. The production of marker-free transgenic plants is now a critical requisite for their commercial deployment and also for engineering multiple and complex trait. Here we describe the current technologies to eliminate the selectable marker genes (SMG) in order to develop marker-free transgenic plants and also discuss the regulation and biosafety concern of genetically modified (GM) crops.