应用DNA条形码构建天敌-猎物食物网的方法

定量构建天敌-猎物食物网是有效开展害虫管理的基础。常用的食物网构建方法有单克隆抗体法、肠道内容物的PCR检测法、实时荧光定量PCR法等。这些方法灵敏度高、特异性强,但只能定性或定量检测天敌对已知猎物物种,即已明确捕食或寄生关系的物种的捕食情况,并不能检测未明确捕食或寄生关系的猎物种类和捕食量。而DNA条形码是一段具有物种特异性的DNA短片段,能够实现物种的快速鉴定。它最早应用于昆虫分类学,现随着高通量测序技术的发展,基于高通量测序的DNA复合条形码技术,对猎物的扩增范围更广,弥补了常规分子方法只能检测已知猎物的缺陷,可实现已知或未知猎物物种的迅速确定,构建相对完整的食物网。为了提高猎物的检测率,完善食物网结构,本文总结了DNA条形码在天敌-猎物昆虫食物网构建中的技术路线,介绍了条形码基因的选择原理、通用引物的设计及验证方法、以及高通量测序及数据分析的基本流程,并以一个实例展示了该方法的实现过程,叙述了该方法的优点及目前存在的争议,旨在为研究基于保护和利用天敌昆虫、增强食物网稳定性的害虫生态调控提供理论指导和方法支持。     

传统测序与高通量测序在稚鱼食性分析中的比较

对鱼类早期生长阶段的摄食研究有助于了解其饵料来源及其在食物网中的功能地位,而全面准确地获取其食物种类信息是关键,高通量测序技术的发展给动物食性研究带来了前所未有的机遇和挑战.本研究以大亚湾人工码头海域金钱鱼稚鱼为对象,以18S rDNA为靶标,分别使用传统Sanger测序和Illumina Solexa高通量测序对其食物组成进行分析,比较两种方法在稚鱼摄食研究中的适用性.结果表明: 金钱鱼稚鱼为杂食性,食物多样性高,纤毛虫和苔藓动物是最优势的食物类群.使用传统测序方法共获得67条有效食物序列,分属于8个类群,涵盖23个生物种类;使用高通量测序方法共获得17000多条有效食物序列,分属于9个类群,涵盖35个生物种类.两种方法检测到的食物类群基本相同,但高通量测序方法在反映食物多样性和覆盖范围上更具优势,且灵敏度更高,检测出传统测序方法未发现的甲藻和褐藻种类,说明高通量测序技术可以较全面而准确地覆盖稚鱼的食物谱.高通量测序获取的大量数据,可在一定程度上提供半定量信息,克服传统测序在定量研究方面的不足.高通量测序技术在稚鱼摄食研究上优势更明显,食谱覆盖更广,检测灵敏度更高,显著提升了数据与结果的可信度,可为海洋生物摄食生态学研究提供强有力的支撑.     

两种分析方法在豹猫食物构成中的应用比较

豹猫(Prionailurus bengalensis)作为北京地区的顶级食肉动物,对于维持食物网结构和生态系统稳定性起到重要的生态作用。对于捕食动物食物构成研究,较为简便的方法是粪样内容物检视法,而粪样残余物DNA鉴定技术具有更为准确细致的优势,但也存在不足,探索不同方法的优势互补,将有助于提高技术应用成效。本研究利用DNA宏条形码技术与粪样内容物分析法,对采集自北京市4个自然保护区的71份豹猫粪样进行食物构成分析,比较两种分析方法的特点,了解豹猫的食物资源利用状况。结果显示,DNA宏条形码技术共鉴别出36种猎物,来自10目22科,4个保护区的豹猫食性具有显著差异,百花山、松山、云蒙山保护区的豹猫食物种类的出现比率均以小型哺乳类为主,其中对鼠类的捕食比例最高,对鸟类的捕食次之,而分布于云峰山保护区的豹猫对鸟类捕食比例最高,对鼠类的捕食次之。粪样内容物分析法鉴别出9类猎物,其中包括昆虫和植物两种DNA宏条形码技术未检出的食物,4个保护区的豹猫食物均以鼠类和鸟类为主,且最多检测出鼠类数量为3只、鸟类2只,次要食物则为植物和昆虫。两种方法均显示北社鼠(Niviventer confucia...     

动物的捕食行为

简要介绍了捕食行为研究的一些主要方向,如猎物选择、食物贮藏、捕食喂幼和捕食的节律性等,还讨论了动物的搜寻和捕食策略以及攻击方式等。     

高通量测序技术及其应用

高通量测序技术是DNA测序发展历程的一个里程碑,它为现代生命科学研究提供了前所未有的机遇。详细介绍了以454、Solexa和SOLiD为代表的第二代高通量测序技术,以HeliScope TIRM和Pacific Biosciences SMRT为代表的单分子测序技术,以及最近Life Science公司推出的Ion Personal Genome Machine (PGM)测序技术等高通量测序技术的最新进展。在此基础上,阐述了高通量测序技术在基因组测序、转录组测序、基因表达调控、转录因子结合位点的检测以及甲基化等研究领域的应用。最后,讨论了高通量测序技术在成本和后续数据分析等方面存在的问题及其未来的发展前景。     

昆虫与寄主植物营养关系的DNA分子追踪

农田生态系统中昆虫与寄主植物的食物营养关系错综复杂,利用田间直接观察法、肠道内含物形态学分析、同位素标记等方法都难于全面解析,常造成营养关系的缺失。近年来,DNA分子追踪技术迅速发展,利用一段较短的DNA序列能有效鉴别植食性昆虫取食寄主植物的种类,为这一领域研究提供了新方法。本文全面介绍了3种DNA分子追踪技术——诊断PCR技术、克隆测序技术和下一代测序技术(next generation sequencing,NGS)。其中诊断PCR技术包括单一PCR技术和多重PCR技术,适用于目标昆虫与已知寄主植物之间的营养关系分析;克隆测序技术能够在寄主植物种类未知的前提下,解析目标昆虫完整的寄主植物种类信息;下一代测序技术实现了短时间内对混合样品的测序,加之昆虫与植物DNA条形码序列数据库大量扩增,有效地提高寄主植物的鉴别能力。诊断PCR技术和克隆测序技术已在追踪地下害虫的取食行为、植食性昆虫取食范围及其在寄主植物间的转移与选择习性等方面被广泛应用,且进展明显。综合考虑各种技术的优缺点,本文提出将DNA分子追踪技术与同位素标记等其他方法相结合的研究策略,以便系统解析农田生态系统中昆虫与寄主植物之间的营养关系。     

动物食性分析在生态学中的应用研究进展——基于DNA宏条形码技术

动物食性分析是动物营养生态学的重要研究手段,可用于解析动物与环境因素的关联性、捕食者与猎物之间的关系,以及动物物种多样性等科学问题。近年来,基于新一代测序技术的DNA宏条形码技术被广泛应用到生态学多个研究领域,极大地促进了生命科学交叉学科的发展。其中,DNA宏条形码技术在动物食性分析中具有高分辨、高效率、低样本量等优势,具有重要的应用前景。综述了基于DNA宏条形码技术的动物食性分析在生态学中的应用研究进展,并进一步总结了DNA宏条形码技术原理和食性分析方法,着重探讨了基于DNA宏条形码技术的动物食性分析在珍稀濒危动物保护、生物多样性监测、农业害虫防治等生态学研究领域中的应用,并对DNA宏条形码技术在动物食性分析中存在的问题及应用前景进行小结与展望。     

动物觅食行为对捕食风险的反应

动物进行任何活动时均面临被捕食的风险 ,分析捕食风险与猎物觅食行为的关系 ,有助于揭示捕食者与猎物的协同进化机制。捕食风险具有限制或调节猎物种群数量的功能。在进化时间内 ,对猎物形态和行为特征的进化是潜在的选择压力之一 ,可利用环境因子作为信息源估测食物可利用性和捕食风险大小的动物 ,具有更大的适合度。信息源可分为包括视觉的、听觉的和化学的。动物进行觅食活动时 ,依据信息源的变化确定环境中捕食风险的大小 ,并根据自身的质量在捕食风险的大小之间做出权衡 ,通过食物选择、活动格局和栖息地利用等行为的变化降低捕食风险     

动物捕食性天敌摄食分析方法的研究进展

对动物捕食者的摄食进行分析是研究动物能量和营养需求、采食策略、生境利用及生态系统中种间关系的核心内容,因而是生态学的一个基本问题,几十年来一直受到生物学家的关注。在对农业害虫的生物防治过程中,既要明确天敌的食物谱,也要对其捕食量进行估算,这样才能真正实现利用捕食性天敌防治害虫的目的。如何获得某个捕食者准确的食物谱和捕食量一直是摄食分析领域的难点和生物防治领域中的研究焦点。为此,本文综述了迄今为止国内外有关捕食性天敌摄食分析方法研究的类型及其研究进展,并重点介绍了作者基于DNA条形码与数字PCR技术创建的一种蜘蛛摄食分析新方法,可对蜘蛛的摄食进行精确定量分析,突破了探究蜘蛛等捕食性天敌"吃什么"和"吃多少"的难题,为人们提供了充分认识和客观评价生态系统中自然控制力作用的科学信息。     

水生生态环境中捕食信息素的生态学效应

捕食信息素是捕食者释放的,能够引发猎物反捕食反应的化学信号。在水生生态系统中,捕食信息素在捕食者和猎物之间信息传递及协同进化过程中发挥着重要的作用,其生态学效应在国际上受到广泛关注。捕食信息素的来源有多种形式,研究中常使用养殖过捕食者的水溶液作为捕食信息素的来源。捕食信息素的作用效果受到捕食者和猎物的种类、信息素的浓度、观察的指标等多方面因素的影响。捕食信息素可以对水生生物的行为、形态和生活史特征等方面造成影响。水生生物通过感知捕食信息素来提前预知潜在的被捕食风险,并作出适应性调整,以降低被捕食的风险。在某些情况下,捕食信息素可以与污染物产生交互作用,从而干扰污染物对水生生物的毒性。对水生环境中捕食信息素的研究现状做了综述,介绍了当前对捕食信息素来源和理化性质等本质问题的认识,总结捕食信息素对水生生物行为、形态和生活史特征的影响,以及捕食信息素对污染物毒性的干扰,并分析了这一研究领域尚存在的困难和今后的研究方向。加强对捕食信息素的研究,将为解析水生环境中捕食者和猎物的生态关系提供新依据。     

Non-consumptive effects of predatory mites on thrips and its host plant

Recent reviews on trait-mediated interactions in food webs suggest that trait-mediated effects are as important in triggering top–down trophic cascades as are density-mediated effects. Trait-mediated interactions between predator and prey result from non-consumptive predator effects changing behavioural and/or life history traits of prey. However, in biological control the occurrence of trait-mediated interactions between predators, prey and plants has been largely ignored. Here, we show that non-consumptive predator effects on prey cascade down to the plant in an agro-ecological food chain. The study system consisted of the predatory mites P. persimilis and N. californicus , the herbivorous non-target prey western flower thrips F. occidentalis and the host plant bean. Irrespective of predator species and risk posed to prey, the presence of predator eggs led to increased ambulation, increased mortality and decreased oviposition of thrips. Furthermore, the presence of predator eggs reduced leaf damage caused by thrips. To our knowledge this is the first experimental evidence suggesting a positive trophic cascade triggered by non-consumptive predator effects on non-target prey in an augmentative biological control system.     

Effects of global environmental changes on parasitoid–host food webs and biological control

Global environmental changes threaten biodiversity and the interactions between species, and food-web approaches are being used increasingly to measure their community-wide impacts. Here we review how parasitoid–host food webs affect biological control, and how their structure responds to environmental change. We find that land-use intensification tends to produce webs with low complexity and uneven interaction strengths. Dispersal, spatial arrangement of habitats, the species pool and community differences across habitats have all been found to determine how webs respond to landscape structure, though clear effects of landscape complexity on web structure remain elusive. The invasibility of web structures and response of food webs to invasion have been the subject of theoretical and empirical work respectively, and nutrient enrichment has been widely studied in the food-web literature, potentially driving dynamic instability and altering biomass ratios of different trophic levels. Combined with food-web changes observed under climate change, these responses of food webs could signal changes to biological control, though there have been surprisingly few studies linking food-web structure to pest control, and these have produced mixed results. However, there is strong potential for food-web approaches to add value to biological control research, as parasitoid–host webs have been used to predict indirect effects among hosts that share enemies, to study non-target effects of biological control agents and to quantify the use of alternative prey resources by enemies. Future work is needed to link food-web interactions with evolutionary responses to the environment and predator–prey interactions, while incorporating recent advances in predator biodiversity research. This holistic understanding of agroecosystem responses and functioning, made possible by food-web approaches, may hold the key to better management of biological control in changing environments.     

Trophic interactions in an ant nest microcosm: a combined experimental and stable isotope (δ13C/δ15N) approach

Living in close association with other organisms has proven to be a widespread and successful strategy in nature. Some communities are completely driven by symbiotic associations and therefore, intimate relationships among the partners can be expected. Here, we analyzed in‐depth the food web of a particularly rich community of arthropods found in strict association with European red wood ants (Formica rufa group). We studied the trophic links between different ant‐associated myrmecophiles and food sources associated with the host ant, but also tested predator–prey links among myrmecophiles themselves. Our approach combined direct feeding tests and stable carbon and nitrogen isotope analyses for a large number of myrmecophiles. The results of the direct feeding tests reveal a complex food web. Most myrmecophiles were found to parasitize on ant brood. Moreover, we encountered multiple trophic predator– prey links among the myrmecophiles. The results of the stable isotope analyses complement these findings and indicate the existence of multiple trophic levels and trophic isotopic niche compartmentalization. δ¹⁵N values were strongly correlated with the trophic levels based on the direct tests, reflecting that δ¹⁵N values of myrmecophiles increased with higher trophic levels. This strong correlation underlines the strength of stable isotopes as a powerful tool to assess trophic levels. In addition, the stable isotope data suggest that most species only facultatively prey on ant brood. The presence of numerous trophic interactions among symbionts clearly contrasts with the traditional view of social insects nests as offering an enemy‐free space for symbionts. Interestingly, the ant host can indirectly benefit from these interactions because brood predators are also preyed upon by other myrmecophiles. Overall, this study provides unique insights into the complex interactions in a small symbiont microcosm system and suggests that the interactions between host and symbiont might be mediated by other symbionts in the same community.     

Molecular gut content analysis indicates the inter‐ and intra‐guild predation patterns of spiders in conventionally managed vegetable fields

Inter‐ and intra‐guild interactions are important in the coexistence of predators and their prey, especially in highly disturbed vegetable cropping systems with sporadic food resources. Assessing the dietary range of a predator taxon characterized by diverse foraging behavior using conventional approaches, such as visual observation and conventional molecular approaches for prey detection, has serious logistical problems. In this study, we assessed the prey compositions and compare the dietary spectrum of a functionally diverge group of predators—spiders—to characterize their trophic interactions and assess biological control potential in Brassica vegetable fields. We used high‐throughput sequencing (HTS) and biotic interaction networks to precisely annotate the predation spectrum and highlight the predator–predator and predator–prey interactions. The prey taxa in the gut of all spider families were mainly enriched with insects (including dipterans, coleopterans, orthopterans, hemipterans, and lepidopterans) with lower proportions of arachnids (such as Araneae) along with a wide range of other prey factions. Despite the generalist foraging behavior of spiders, the community structure analysis and interaction networks highlighted the overrepresentation of particular prey taxa in the gut of each spider family, as well as showing the extent of interfamily predation by spiders. Identifying the diverse trophic niche proportions underpins the importance of spiders as predators of pests in highly disturbed agroecosystems. More specifically, combining HTS with advanced ecological community analysis reveals the preferences and biological control potential of particular spider taxa (such as Salticidae against lepidopterans and Pisauridae against dipterans), and so provides a valuable evidence base for targeted conservation biological control efforts in complex trophic networks.     

Understanding and Manipulating Plant Attributes to Enhance Biological Control

This paper demonstrates the necessity to consider plants as an essential and interactive component of biological control practices. Plants not only possess direct chemical and morphological defenses against herbivores but also benefit from indirect defenses provided by parasitoids and predators, which use herbivores as hosts or prey. Plants play an active role in the interplay between entomophagous arthropods and herbivores and actually mediate many of the interactions, thereby influencing the intensity of protection received. Herein, we review how plant attributes influence natural enemy efficiency by providing shelter, mediating host/prey accessibility, providing host/prey finding cues, influencing host/prey suitability, mediating host/prey availability, and providing supplemental food sources for natural enemies. In light of this crucial role, we suggest ways of manipulating morphological and chemical attributes of crop plants for a more sustainable and balanced control of insect pests in agro-ecosystems.     

The underrated importance of predation in transmission ecology of direct lifecycle parasites

Most parasites with complex life cycles exploit trophic webs to pass from host to host in order to develop and, eventually, reproduce. Thus predation constitutes the necessary route for transmission. Conversely, the transmission of parasites that use a single host to develop and reproduce should be, in principle, not particularly affected by host trophic ecology. Here I challenge this view, showing that predation may be relevant also for direct lifecycle parasites. I used a large dataset of fish trophic interactions to investigate if the degree of monogenean species overlap in predators and prey deviated from randomness. I demonstrated that predators and prey often share more monogenean parasite genera than explained by host habitat ecology, geographical distribution and phylogeny. This suggests that predation may play an important role in promoting monogenean host range expansion. In addition, a non‐negligible proportion of considered prey–predator pairs showed a significantly high overlap in their monogenean parasites at the species level. This may indicate a tendency of some monogenean parasites to evolve transmission strategies targeted towards host interactions. If this hypothesis is true, these monogenean parasites would be much more vulnerable to co‐extinction than previously thought. Synthesis Predation is not expected to play an important role in the ecology and evolution of simple life cycle parasites. Yet, several predator fish tend to share with their prey more monogenean parasites than one would expect predicted from their geographical distribution, habitat preference, and or phylogenetic relationships. This suggests that some monogenean parasites have evolved transmission strategies more targeted towards host interactions than towards species‐specific traits. If this hypothesis is supported, it would have strong implications on host–parasite evolutionary ecology, primarily, suggesting the existence of peculiar situations where some parasites have evolved high specialized host finding behaviors to expand their host range.     

Predicting the outcomes of a tri‐trophic interaction between an indigenous parasitoid and an exotic herbivorous pest and its host plants

Understanding the novel ecological interactions that result from biological invasions is a critical issue in modern ecology and evolution as well as pest management. Introduced herbivorous insects may interact with native plants and indigenous natural enemies, creating novel tri‐trophic interactions. To help predict the potential outcomes of novel interactions, we investigated the behavioural and physiological responses of an indigenous generalist parasitoid (Habrobracon gelechiae) to an introduced generalist herbivore (the light brown apple moth, Epiphyas postvittana) and its new host plants in California. We first examined the parasitoid's host location and acceptance on a range of nine common host plants of the moth representing distinctly different geographic origins and morphologies (to examine the effect of a known toxic plant on the parasitoid's performance, an additional toxic plant species was also tested that the moth consumes in the laboratory but does not naturally attack). The parasitoid was able to locate the host larvae on all plants equally well, although clutch size was affected by host plant. We then determined fitness of the moth and the parasitoid on four representative plants. The moth larvae suffered higher mortality and a slower developmental rate on the known toxic plant than on the other three plants, but the parasitoid's fitness correlates did not differ between the host food plants. These results show a high level of plasticity in the indigenous generalist parasitoid in its ability to exploit the exotic host on a wide range of host plants, generating an invasion‐driven novel tri‐trophic interaction.     

Intra- and interspecific variation in trophic ecology of ‘predatory’ ants in the subfamily Ponerinae

1. The characterisation of energy flow through communities is a primary goal of ecology. Furthermore, predator–prey interactions can influence both species abundance and community composition. The ant subfamily Ponerinae includes many predatory species that range from generalist insectivores to highly specialised hunters that target a single prey type. Given their high diversity and ubiquity in tropical ecosystems, measuring intra- and interspecific variation in their trophic ecology is essential for understanding the role of ants as predators of insect communities. 2. The stable isotopic composition of nitrogen of 22 species from the ant subfamily Ponerinae was measured, relative to plants and other predatory and herbivorous insects at two Atlantic Forest sites in Argentina. The study tested the general assumption that ponerine ants are all predatory, and examined intra- and interspecific variation in trophic ecology relative to habitat, body size and cytochrome c oxidase subunit 1 sequences (DNA barcoding). 3. Stable isotope analysis revealed that most ponerines occupy high trophic levels (primary and secondary predators), but some species overlapped with known insect herbivores. Species residing at low trophic levels were primarily arboreal and may rely heavily on nectar or other plant-based resources in their diet. In addition, larger species tend to occupy lower trophic positions than smaller species. 4. Although some of the species were divided into two or more genetic clusters by DNA barcoding analysis, these clusters did not correspond to intraspecific variation in trophic position; therefore, colony dietary flexibility most probably explains species that inhabit more than one trophic level.     

No evidence for the uptake of Cry1Ab Bt-endotoxins by the generalist predator Scarites subterraneus (Coleoptera: Carabidae) in laboratory and field experiments

Many generalist predators are abundant in transgenic crops but the uptake of Bt-endotoxins could affect their role in biological control. We tested the hypothesis that small, but detectable, quantities of Cry1Ab-Bt-endotoxin would flow along the corn-slug-carabid food chain but concentrations would be small and have no effect on carabid fecundity. In addition to controlled laboratory feeding trials, it was predicted that elevated concentrations of Bt-endotoxin would be found in field-collected gut-samples of Scarites subterraneus from transgenic corn due to predation on Bt-containing prey. Despite the uptake of Bt-endotoxins by the slug Deroceras laeve, the hypothesis that movement occurred throughout the corn-slug-carabid food chain was rejected. No Bt-endotoxins were found in laboratory or field-collected Scarites. This explained the insignificant differences in egg production between carabids exposed to Bt-containing versus non-Bt-containing prey. However, laboratory and field analyses with other predators are required to identify trophic linkages through which Bt-endotoxins flow.