To sleep or not to sleep: the ecology of sleep in artificial organisms

Background  

All animals thus far studied sleep, but little is known about the ecological factors that generate differences in sleep characteristics across species, such as total sleep duration or division of sleep into multiple bouts across the 24-hour period (i.e., monophasic or polyphasic sleep activity). Here we address these questions using an evolutionary agent-based model. The model is spatially explicit, with food and sleep sites distributed in two clusters on the landscape. Agents acquire food and sleep energy based on an internal circadian clock coded by 24 traits (one for each hour of the day) that correspond to "genes" that evolve by means of a genetic algorithm. These traits can assume three different values that specify the agents' behavior: sleep (or search for a sleep site), eat (or search for a food site), or flexibly decide action based on relative levels of sleep energy and food energy. Individuals with higher fitness scores leave more offspring in the next generation of the simulation, and the model can therefore be used to identify evolutionarily adaptive circadian clock parameters under different ecological conditions.     

Weed management in maize using crop competition: A review

Weeds are a major constraint to crop production, and are responsible for considerable yield losses in maize production systems throughout the world. Herbicides are widely used for weed control in maize production systems, but can have negative environmental consequences. Researchers have evaluated the use of crop competition and suppression to manage weeds in various crop combinations, including maize-based systems. Crop competition in maize may involve techniques such as reduced row spacing, increased planting density, and the use of competitive cultivars that exhibit weed suppressive potential. In this review, examination of the literature has revealed the considerable value of using crop competition in integrated weed management programs. Research has demonstrated that narrowing row spacing to half the standard distance reduced weed biomass by 39–68%, depending on weed species. Researchers have also demonstrated that increasing maize planting density by up to twice the standard rate achieved a reduction in weed biomass of 26–99%. While little research has been conducted into the use of competitive maize cultivars for weed management, several studies have documented cultivars with potential to suppress weeds. Attributes of weed competitive cultivars include high leaf area index, and other elements of leaf architecture that improve light interception by the crop, so increasing the shading of weeds. Combining crop competition methods with other agronomic practices can increase their effectiveness in controlling weeds. For example, biomass of Setaria italica (L.) Beauv was reduced by 60% when maize planting density was increased by 1.5 times the recommended spacing, and this effect was more pronounced when fertilizer was banded rather than broadcast. In summary, the strategic use of crop competition to control weeds has been a success in many regions, and is an important tool in integrated weed management. The importance of crop competition methods has particular relevance where farmers are unable to afford herbicides, as making use of crop competition is more economical.     

Troublesome toxins: time to re-think plant-herbivore interactions in vertebrate ecology

Earlier models of plant-herbivore interactions relied on forms of functional response that related rates of ingestion by herbivores to mechanical or physical attributes such as bite size and rate. These models fail to predict a growing number of findings that implicate chemical toxins as important determinants of plant-herbivore dynamics. Specifically, considerable evidence suggests that toxins set upper limits on food intake for many species of herbivorous vertebrates. Herbivores feeding on toxin-containing plants must avoid saturating their detoxification systems, which often occurs before ingestion rates are limited by mechanical handling of food items. In light of the importance of plant toxins, a new approach is needed to link herbivores to their food base. We discuss necessary features of such an approach, note recent advances in herbivore functional response models that incorporate effects of plant toxins, and mention predictions that are consistent with observations in natural systems. Future ecological studies will need to address explicitly the importance of plant toxins in shaping plant and herbivore communities.     

从市场集中度角度考察国际茶叶市场竞争程度

本文利用市场集中度指标对国际茶叶市场竞争及垄断程度进行了实证分析.研究结果表明:国际茶叶市场属于高度垄断型市场,并且垄断程度逐步增强.这主要由于国际茶叶市场日益激烈的竞争导致茶叶出口国家中强者更强,弱者更弱的分化趋势.     

Visual ecology of the Australian lungfish (Neoceratodus forsteri)

Background

The transition from water to land was a key event in the evolution of vertebrates that occurred over a period of 15–20 million years towards the end of the Devonian. Tetrapods, including all land-living vertebrates, are thought to have evolved from lobe-finned (sarcopterygian) fish that developed adaptations for an amphibious existence. However, while many of the biomechanical and physiological modifications necessary to achieve this feat have been studied in detail, little is known about the sensory adaptations accompanying this transition. In this study, we investigated the visual system and visual ecology of the Australian lungfish Neoceratodus forsteri, which is the most primitive of all the lungfish and possibly the closest living relative to the ancestors of tetrapods.

Results

Juvenile Neoceratodus have five spectrally distinct retinal visual pigments. A single type of rod photoreceptor contains a visual pigment with a wavelength of maximum absorbance (λ_max) at 540 nm. Four spectrally distinct single cone photoreceptors contain visual pigments with λ_max at 366 (UVS), 479 (SWS), 558 (MWS) and 623 nm (LWS). No double cones were found. Adult lungfish do not possess UVS cones and, unlike juveniles, have ocular media that prevent ultraviolet light from reaching the retina. Yellow ellipsoidal/paraboloidal pigments in the MWS cones and red oil droplets in the LWS cones narrow the spectral sensitivity functions of these photoreceptors and shift their peak sensitivity to 584 nm and 656 nm, respectively. Modelling of the effects of these intracellular spectral filters on the photoreceptor colour space of Neoceratodus suggests that they enhance their ability to discriminate objects, such as plants and other lungfishes, on the basis of colour.

Conclusion

The presence of a complex colour vision system based on multiple cone types and intracellular spectral filters in lungfishes suggests that many of the ocular characteristics seen in terrestrial or secondarily aquatic vertebrates, such as birds and turtles, may have evolved in shallow water prior to the transition onto land. Moreover, the benefits of spectral filters for colour discrimination apply equally to purely aquatic species as well as semi-aquatic and terrestrial animals. The visual system of the Australian lungfish resembles that of terrestrial vertebrates far more closely than that of other sarcopterygian fish. This supports the idea that lungfishes, and not the coelacanth, are the closest living relatives of the ancestors of tetrapods.     

Application of image analysis for the varietal classification of barley:: Morphological features

This paper presents an exploratory investigation of the application of morphological features in image analysis for varietal classification of Polish spring barley. The objective of this study was to determine the utility of morphological features for classifying individual kernels of five varieties of barley. Furthermore, this study was performed to find the best method to classify kernels of barley with the lowest error of classification. Image processing consisted of several steps: image acquisition, segmentation, external and internal image feature extraction, classification and interpretation. Each barley kernel was described using 74 morphological features. The selection was carried out using three methods based on: Fisher's coefficient, probability of error and average correlation coefficient and mutual information. Principle component analysis (PCA), linear discriminant analysis (LDA), and non-linear discriminant analysis (NDA) were used throughout this paper as the classification methods. The results confirmed that the method using morphological features may be successfully employed in image analysis for preliminary varietal identification of barley kernels. Furthermore, LDA was found to be the method which best separated different varieties of objects.     

2017年中国玉米生物学研究进展

2017年我国玉米基础研究继续保持快速发展态势,在国内外主流学术期刊发表有重要影响的研究成果。2017年,我国科研人员在91个SCI收录期刊发表玉米生物学相关研究论文266篇,其中,在5年平均影响因子超过5.0的期刊发表高水平论文49篇,主要进展集中在基因编辑相关研究、玉米子粒发育遗传调控、玉米抗非生物胁迫基因挖掘和功能研究、玉米抗病基因挖掘及功能分析、玉米重要农艺性状基因/QTLs鉴定和克隆、玉米组学研究和玉米育种技术这7个方面。     

生境管理在茶树害虫生态控制中的作用

利用“生境管理”策略—间作植物增强天敌控害能力和利用植物挥发物的对害虫和天敌的行为进行调控已在茶树害虫生态控制系统中开展了一系列尝试。增加茶园“斑块”中的植物多样性能明显增加天敌类型和数量,罗勒、迷迭香以及某些豆科植物释放的挥发物在一定条件下可以对害虫产生引诱或驱避效应,仙鹤草的提取物能够用来增强天敌的捕食能力或寄生能力。源自茶树本身的系列挥发物例如顺-3-己烯醇、反-2-己烯醛、罗勒烯、芳樟醇、香叶醇和吲哚等能用于诱集和驱避害虫,聚集寄生性或捕食性天敌。水杨酸、茉莉酸、苯并噻二唑及β-氨基丁酸等诱导剂处理茶树可以增进茶树的直接抗虫性能,并促进茶树挥发物的释放以提高天敌定位能力。     

The relevance of marine chemical ecology to plankton and ecosystem function: an emerging field

Marine chemical ecology comprises the study of the production and interaction of bioactive molecules affecting organism behavior and function. Here we focus on bioactive compounds and interactions associated with phytoplankton, particularly bloom-forming diatoms, prymnesiophytes and dinoflagellates. Planktonic bioactive metabolites are structurally and functionally diverse and some may have multiple simultaneous functions including roles in chemical defense (antipredator, allelopathic and antibacterial compounds), and/or cell-to-cell signaling (e.g., polyunsaturated aldehydes (PUAs) of diatoms). Among inducible chemical defenses in response to grazing, there is high species-specific variability in the effects on grazers, ranging from severe physical incapacitation and/or death to no apparent physiological response, depending on predator susceptibility and detoxification capability. Most bioactive compounds are present in very low concentrations, in both the producing organism and the surrounding aqueous medium. Furthermore, bioactivity may be subject to synergistic interactions with other natural and anthropogenic environmental toxicants. Most, if not all phycotoxins are classic secondary metabolites, but many other bioactive metabolites are simple molecules derived from primary metabolism (e.g., PUAs in diatoms, dimethylsulfoniopropionate (DMSP) in prymnesiophytes). Producing cells do not seem to suffer physiological impact due to their synthesis. Functional genome sequence data and gene expression analysis will provide insights into regulatory and metabolic pathways in producer organisms, as well as identification of mechanisms of action in target organisms. Understanding chemical ecological responses to environmental triggers and chemically-mediated species interactions will help define crucial chemical and molecular processes that help maintain biodiversity and ecosystem functionality.     

Powdery mildew of mango: A review of ecology,biology, epidemiology and management

Powdery mildew of mango, incited by the fungus Pseudoidium anacardii (F. Noack) U. Braun & R.T.A. Cook 2012 (formerly known as Oidium mangiferae Berthet), is one of the most common, widespread and serious diseases throughout the world and causes significant yield losses. Symptomatology, biology, and etiology of powdery mildew and its control through fungicides have not been widely studied, and substantial information is still required on the inoculum potential, growth models and epidemiological parameters of powdery mildew, influence of changing climate, impact of extensive use of fungicides and disease resistance. These critical factors may influence the development and emergence of diverse isolates of O. mangiferae including fungicide-resistant strains. Mango varieties differ slightly in their reaction to powdery mildew but a source of resistance has not been identified. In view of the increasing demands of mangoes in the world, control of powdery mildew is gaining importance. The present review treats briefly different aspects of powdery mildew disease with major emphasis on its ecology, pathology, epidemiology and management. Some new approaches such as biological control, integrated management strategies and some other aspects which have not been highlighted in former reviews, are also discussed.     

第三届国际名茶评比—赴日本复评概况

2001年9月5日,笔者等3人赴日本参加"国际名茶日本品评大奖会".由中、日的茶叶专家组成"国际名茶日本大奖评选委员会",在日本金谷町对"第三届国际名茶评比"中部分获得金奖的茶叶,又进行了展示性的评比,共有38只茶叶获奖,其中获得"日本大奖"的茶叶10只,"准日本大奖"的20只,"中日新闻奖"3只,"日本粮食新闻奖"3只,"静冈新闻放送奖"2只.在获奖的茶叶中,中国茶有33只、日本茶5只.凡是获得奖级的茶叶,均由日方颁发奖状.     

森林资源可持续经营的景观生态学原理

随着人类社会对森林资源期望值的不断提高以及对其经营思想的不断进步,森林资源可持续经营理念已经被越来越多的人接受,并成为新时期森林经营的指导思想。本文基于国内外森林资源经营现状,尝试把景观生态学的基本原理应用于森林资源可持续经营中,既拓宽了景观生态学的应用领域,又丰富和发展了森林资源的经营理论,从而有效促进森林资源的可持续发展。     

Intra-specific competition in maize: early establishment of hierarchies among plants affects final kernel set

Reduced plant biomass and increased plant-to-plant variability are expected responses to crowding in monocultures, but the underlying processes that control the onset of interplant interference and the establishment of hierarchies among plants within a stand are poorly understood. We tested the hypothesis that early determined plant types (i.e. dominant and dominated individuals) are the cause of the large variability in final kernel number per plant (KNP) usually observed at low values of plant growth rate (PGR) around silking in maize (Zea mays L.). Two hybrids (DK696 and Exp980) of contrasting response to crowding were cropped at different stand densities (6, 9 and 12 plants m⁻²), row spacings (0.35 and 0.70 m), and water regimes (rainfed and irrigated) during 1999/2000 and 2001/2002 in Argentina. The onset of interplant competition started very early during the cycle, and significant differences (P<0.05) in estimated plant biomass between stand densities were detected as soon as V_4–6 (DK696) and V_6–7 (Exp980). Plant population and row spacing treatments did not modify the onset of the hierarchical growth among plants, but did affect (P<0.02–0.08) the dynamic of the process. For both hybrids, the rate of change in relative growth between plant types was larger at 9 and 12 plants m⁻² (ca. 0.12 g/g per 100 °C day) than at 6 plants m⁻² (ca. 0.07 g/g per 100 °C day). For all treatments, the largest difference in estimated shoot biomass between plant types took place between 350 (V₇) and 750 °C day (V₁₃) from sowing, and remained constant from V₁₃ onwards. Dominant plants always had more kernels per plant (P<0.05) than the dominated ones, but differences between plant types in PGR around silking were significant (P<0.05) only at 12 plants m⁻². Our research confirmed the significant (P<0.01) curvilinear response of KNP to PGR around silking, but also determined a differential response between plant types: the mean of residual values were significantly (P<0.01) larger for dominant than for dominated individuals. Estimated ear biomass at the onset of active kernel growth (R₃) reflected the variation in KNP (r²≥0.62), and was significantly (P<0.01) related to estimated plant biomass at the start of active ear growth (ca. V₁₃). This response suggested that the physiological state of each plant at the beginning of the critical period had conditioned its reproductive fate. This early effect of plant type on final KNP seemed to be exerted through current assimilate partitioning during the critical period.     

Intra-specific competition in maize: Early established hierarchies differ in plant growth and biomass partitioning to the ear around silking

Early interferences among plants within a maize stand determine the establishment of extreme plant types (i.e. dominant and dominated individuals). The development of these hierarchies takes place well before [from the seventh leaf stage (V₇) onwards] the start of the critical period for kernel set (i.e. a 30-day period centered in silking). Kernel number per plant (KNP) is significantly related to plant growth rate around silking (PGR_S) and biomass partitioning to the ear during this period. Previous evidence has demonstrated that at high stand densities, extreme plant types may exhibit similar PGR_S values but set different KNP. We tested the hypothesis that early established plant hierarchies differ in biomass allocation to the ears during the period around silking. Two hybrids of contrasting tolerance to crowding (DK752 and DK765 as the tolerant and the intolerant hybrid, respectively) were cropped at different interplant competition intensities (6, 12, 12 pl m⁻² thinned to 6 pl m⁻² at V₉ and 6 pl m⁻² shading from V₉ onwards) during 2003/2004 and 2004/2005 in Argentina. For all treatments, the coefficient of variation (CV) of plant biomass increased from V₃ (ca. 1.2%) to V_9-10 (ca. 22%). From V₇ onwards, plant growth rate of dominant individuals was higher (P < 0.05) than that of the dominated plants. Hence, dominant plants exhibited higher (P < 0.05) PGR_S (ca. 4.5 g pl day⁻¹) than dominated individuals (ca. 3.7 g pl day⁻¹). As PGR_S declined in response to increased plant population density (ca. 5.1 and 2.8 for 6 and 12 pl m⁻², respectively), biomass partitioning to the ear was reduced (ca. 0.44 and 0.33 for 6 and 12 pl m⁻², respectively). For all treatments, however, dominant plants exhibited a greater biomass partitioning to the ear (ca. 0.41) than the dominated individuals (ca. 0.36). Consequently, the former were the individuals with the highest ear growth rate (ca. 1.9 and 1.4 g per ear per day for the dominant and dominated plant, respectively) and KNP (ca. 623 and 490 kernels per plant for the dominant and dominated plant, respectively) of the stand. We identified three traits on DK765 related to the low tolerance to high-density stress of this genotype: (i) a higher plant-to-plant variability (CV ca. 26% and 19%, for DK765 and DK752, respectively), (ii) a lower biomass partitioning to the ear around silking (ca. 0.26 and 0.39 for DK765 and DK752, respectively), and (iii) a higher response rate of KNP to ear growth rate around silking (ca. 370–738 and 360–414 kernels per g, for DK765 and DK752, respectively). Hence, as stand density was increased, KNP of DK765 was sharply reduced, especially in the dominated individuals of the stand.     

Azaspiracid shellfish poisoning: a review on the chemistry, ecology, and toxicology with an emphasis on human health impacts

Azaspiracids (AZA) are polyether marine toxins that accumulate in various shellfish species and have been associated with severe gastrointestinal human intoxications since 1995. This toxin class has since been reported from several countries, including Morocco and much of western Europe. A regulatory limit of 160 microg AZA/kg whole shellfish flesh was established by the EU in order to protect human health; however, in some cases, AZA concentrations far exceed the action level. Herein we discuss recent advances on the chemistry of various AZA analogs, review the ecology of AZAs, including the putative progenitor algal species, collectively interpret the in vitro and in vivo data on the toxicology of AZAs relating to human health issues, and outline the European legislature associated with AZAs.     

影响我国茶业国际竞争力的主要因素研究(续)

1. 优势因素①区域与资源优势自然资源属于初级要素。我国是茶树原产地,茶区地域跨暖温带、亚热带和边缘热带,而其他几个主要产茶国均位于热带地区。我国茶区广阔,有丰富的生态资源和茶树种质资源,从自然资源因素这类初级生产要素来看我国茶业有自然垄断优势。②科研与人力资源优势我国现有专业从事茶叶研究的机构15个,另有10所高等农业院校中设有茶学专业,每年可为国家培养数量众多的硕士、博士研究生和本科毕业生,这是其他几个主要产茶国所不具备的。几十年来,我国茶叶科技工作者在茶树良种选育、茶树栽培、茶叶加工、茶叶机械、茶叶综合…