Host plants influence parasitism of forest caterpillars

Patterns of association between herbivores and host plants have been thought to reflect the quality of plants as food resources as influenced by plant nutrient composition, defences, and phenology. Host-plant-specific enemies, that is, the third trophic level, might also influence the distribution of herbivores across plant species. However, studies of the evolution of herbivore host range have generally not examined the third trophic level, leaving unclear the importance of this factor in the evolution of plant-insect herbivore interactions. Analysis of parasitoid rearings by the Canadian Forest Insect Survey shows that parasitism of particular Lepidoptera species is strongly host-plant-dependent, that the pattern of host-plant dependence varies among species of caterpillars, and that some parasitoid species are themselves specialized with respect to tree species. Host-plant-dependent parasitism suggests the possibility of top-down influence on host plant use. Differences in parasitism among particular caterpillar-host plant combinations could select for specialization of host plant ranges within caterpillar communities. Such specialization would ultimately promote the species diversification of Lepidoptera in temperate forests with respect to escape from enemies.     

Trophic cascades across ecosystems

Predation can be intense, creating strong direct and indirect effects throughout food webs. In addition, ecologists increasingly recognize that fluxes of organisms across ecosystem boundaries can have major consequences for community dynamics. Species with complex life histories often shift habitats during their life cycles and provide potent conduits coupling ecosystems. Thus, local interactions that affect predator abundance in one ecosystem (for example a larval habitat) may have reverberating effects in another (for example an adult habitat). Here we show that fish indirectly facilitate terrestrial plant reproduction through cascading trophic interactions across ecosystem boundaries. Fish reduce larval dragonfly abundances in ponds, leading to fewer adult dragonflies nearby. Adult dragonflies consume insect pollinators and alter their foraging behaviour. As a result, plants near ponds with fish receive more pollinator visits and are less pollen limited than plants near fish-free ponds. Our results confirm that strong species interactions can reverberate across ecosystems, and emphasize the importance of landscape-level processes in driving local species interactions.     

Universal scaling relations in food webs

The structure of ecological communities is usually represented by food webs. In these webs, we describe species by means of vertices connected by links representing the predations. We can therefore study different webs by considering the shape (topology) of these networks. Comparing food webs by searching for regularities is of fundamental importance, because universal patterns would reveal common principles underlying the organization of different ecosystems. However, features observed in small food webs are different from those found in large ones. Furthermore, food webs (except in isolated cases) do not share general features with other types of network (including the Internet, the World Wide Web and biological webs). These features are a small-world character and a scale-free (power-law) distribution of the degree (the number of links per vertex). Here we propose to describe food webs as transportation networks by extending to them the concept of allometric scaling (how branching properties change with network size). We then decompose food webs in spanning trees and loop-forming links. We show that, whereas the number of loops varies significantly across real webs, spanning trees are characterized by universal scaling relations.     

聚果榕小蜂群落在中国西双版纳和缅甸曼德勒之间的地理变异

榕树及其传粉榕小蜂之间的相互作用是互惠共生的经典例子，每种雌雄同株的榕树还庇护着多样的非传粉小蜂，并共生形成多营养级的榕小蜂群落，是研究群落生态学的有趣模型。区域的物种库、物种的生物地理特征及种间相互作用可能影响榕小蜂群落，但研究很少。本研究选择分布于中国西双版纳和缅甸曼德勒的雌雄同株聚果榕小蜂群落作为研究对象，比较地理分布差异对榕小蜂个体大小及共存网络的影响。结果显示：聚果榕小蜂群落在两地由相同的6个种组成，但分布于西双版纳的6种榕小蜂的个体均显著大于分布在曼德勒的同种榕小蜂。在两个分布地传粉榕小蜂均为优势种，然而在西双版纳传粉榕小蜂种群较大，而在曼德勒非传粉小蜂更丰富。在两地聚果榕有不同的榕小蜂群落结构和物种丰富度，且榕小蜂共存的网络也存在变异，在两地共存网络有相同的节点、边、连接度和全局聚类系数，但是在西双版纳的共存网络有较大的直径和较高的群落矩阵温度，这表明分布于西双版纳的聚果榕小蜂群落种间互作不太紧密，群落受到的干扰较大。由此，阐明了由地理分布所驱动的榕小蜂群落变异。     

Dimensionality of consumer search space drives trophic interaction strengths

Trophic interactions govern biomass fluxes in ecosystems, and stability in food webs. Knowledge of how trophic interaction strengths are affected by differences among habitats is crucial for understanding variation in ecological systems. Here we show how substantial variation in consumption-rate data, and hence trophic interaction strengths, arises because consumers tend to encounter resources more frequently in three dimensions (3D) (for example, arboreal and pelagic zones) than two dimensions (2D) (for example, terrestrial and benthic zones). By combining new theory with extensive data (376 species, with body masses ranging from 5.24 × 10(-14) kg to 800 kg), we find that consumption rates scale sublinearly with consumer body mass (exponent of approximately 0.85) for 2D interactions, but superlinearly (exponent of approximately 1.06) for 3D interactions. These results contradict the currently widespread assumption of a single exponent (of approximately 0.75) in consumer-resource and food-web research. Further analysis of 2,929 consumer-resource interactions shows that dimensionality of consumer search space is probably a major driver of species coexistence, and the stability and abundance of populations.     

稻田周围杂草上寄生蜂资源初步调查

用改装的吸虫器对福建省古田县稻田周围杂草上寄生蜂进行调查 ,采集到寄生蜂 19科 78种 (或类 )。其中 ,绝大多数寄生蜂是稻田害虫的寄生性天敌 ;少数为重寄生蜂 (如螟蛉折唇姬蜂等 ) ;还有极少数种类既是害虫寄生蜂又是重寄生蜂 (如大痣细蜂等 )。这表明稻田周围杂草上贮藏着丰富的寄生蜂资源 ,是稻田寄生蜂的重要种库。适当保留稻田田埂的杂草和稻田周围的杂草地 ,有利于保护稻田寄生蜂资源 ,提高寄生蜂对水稻害虫的自然控制作用     

Allometric degree distributions facilitate food-web stability

In natural ecosystems, species are linked by feeding interactions that determine energy fluxes and create complex food webs. The stability of these food webs enables many species to coexist and to form diverse ecosystems. Recent theory finds predator-prey body-mass ratios to be critically important for food-web stability. However, the mechanisms responsible for this stability are unclear. Here we use a bioenergetic consumer-resource model to explore how and why only particular predator-prey body-mass ratios promote stability in tri-trophic (three-species) food chains. We find that this 'persistence domain' of ratios is constrained by bottom-up energy availability when predators are much smaller than their prey and by enrichment-driven dynamics when predators are much larger. We also find that 97% of the tri-trophic food chains across five natural food webs exhibit body-mass ratios within the predicted persistence domain. Further analyses of randomly rewired food webs show that body mass and allometric degree distributions in natural food webs mediate this consistency. The allometric degree distributions hold that the diversity of species' predators and prey decreases and increases, respectively, with increasing species' body masses. Our results demonstrate how simple relationships between species' body masses and feeding interactions may promote the stability of complex food webs.     

云南省柑桔蚧虫的寄生蜂初报

报道从云南省柑桔蚧虫育出的寄生蜂３４种，隶属２个总科、６个科、２４个属；其中９种为云南省新记录，指出了常见蚧虫的主要寄生蜂，对３个我国未报道而在云南常见的种作了简要记述并附特征图。     

Reconciling complexity with stability in naturally assembling food webs

Understanding how complex food webs assemble through time is fundamental both for ecological theory and for the development of sustainable strategies of ecosystem conservation and restoration. The build-up of complexity in communities is theoretically difficult, because in random-pattern models complexity leads to instability. There is growing evidence, however, that nonrandom patterns in the strengths of the interactions between predators and prey strongly enhance system stability. Here we show how such patterns explain stability in naturally assembling communities. We present two series of below-ground food webs along natural productivity gradients in vegetation successions. The complexity of the food webs increased along the gradients. The stability of the food webs was captured by measuring the weight of feedback loops of three interacting 'species' locked in omnivory. Low predator-prey biomass ratios in these omnivorous loops were shown to have a crucial role in preserving stability as productivity and complexity increased during succession. Our results show the build-up of food-web complexity in natural productivity gradients and pin down the feedback loops that govern the stability of whole webs. They show that it is the heaviest three-link feedback loop in a network of predator-prey effects that limits its stability. Because the weight of these feedback loops is kept relatively low by the biomass build-up in the successional process, complexity does not lead to instability.     

An ecological and evolutionary perspective on human-microbe mutualism and disease

The microbial communities of humans are characteristic and complex mixtures of microorganisms that have co-evolved with their human hosts. The species that make up these communities vary between hosts as a result of restricted migration of microorganisms between hosts and strong ecological interactions within hosts, as well as host variability in terms of diet, genotype and colonization history. The shared evolutionary fate of humans and their symbiotic bacteria has selected for mutualistic interactions that are essential for human health, and ecological or genetic changes that uncouple this shared fate can result in disease. In this way, looking to ecological and evolutionary principles might provide new strategies for restoring and maintaining human health.     

Ecosystem consequences of species richness and composition in pond food webs

Resolving current concerns about the role of biodiversity on ecosystems calls for understanding the separate roles of changes in species numbers and of composition. Recent work shows that primary productivity often, but not always, saturates with species richness within single trophic levels. However, any interpretation of such patterns must consider that variation in biodiversity is necessarily associated with changes in species composition (identity), and that changes in biodiversity often occur across multiple trophic levels. Here we present results from a mesocosm experiment in which we independently manipulated species richness and species composition across multiple trophic levels in pond food webs. In contrast to previous studies that focused on single trophic levels, we found that productivity is either idiosyncratic or increases with respect to species richness, and that richness influences trophic structure. However, the composition of species within richness levels can have equally or more marked effects on ecosystems than average effects of richness per se. Indirect evidence suggests that richness and associated changes in species composition affect ecosystem attributes through indirect effects and trophic interactions among species, features that are highly characteristic of natural, complex ecosystems.     

高温胁迫对植食性昆虫影响研究进展

昆虫作为变温动物类群,极易遭受高温胁迫的影响。研究高温胁迫对植食性昆虫的影响,可为气候变暖背景下农林害虫的种群动态监测及地理适生区预测提供重要理论依据。笔者从植食性昆虫个体、种间互作关系、种群及群落3个层面,综述了高温胁迫对植食性昆虫影响的国内外进展。研究发现,高温胁迫会对植食性昆虫个体的生长发育、繁殖及生理生化带来负面效应,但昆虫自身也会进化出一系列基于形态、行为及基因表达的热胁迫响应机制。高温胁迫对寄主植物、天敌、共生微生物的影响也能够通过种间互作传递给植食性昆虫,并导致寄主植物-植食性昆虫-天敌3级营养关系发生变化。同时,高温胁迫还能通过影响昆虫个体及种间关系,间接影响昆虫的种群动态、种群多样性及其生态功能,并可能导致植食性昆虫的种群大爆发或衰退。最后,笔者认为此领域未来研究方向为:在个体层面上,应优化高温胁迫处理方式并综合考虑干旱和降水等环境因子,开展农林害虫种群的长期野外监测,应注重高温胁迫对昆虫参与生长发育繁殖功能基因的影响;在种间关系层面上,应关注高温胁迫对昆虫关联的复杂多样的食物网及互作体系的影响;此外,应结合高温胁迫对不同昆虫种类自身生理特性和行为模式的影响,阐明温度升高对昆虫群落的影响。     

Simple rules yield complex food webs

Several of the most ambitious theories in ecology describe food webs that document the structure of strong and weak trophic links that is responsible for ecological dynamics among diverse assemblages of species. Early mechanism-based theory asserted that food webs have little omnivory and several properties that are independent of species richness. This theory was overturned by empirical studies that found food webs to be much more complex, but these studies did not provide mechanistic explanations for the complexity. Here we show that a remarkably simple model fills this scientific void by successfully predicting key structural properties of the most complex and comprehensive food webs in the primary literature. These properties include the fractions of species at top, intermediate and basal trophic levels, the means and variabilities of generality, vulnerability and food-chain length, and the degrees of cannibalism, omnivory, looping and trophic similarity. Using only two empirical parameters, species number and connectance, our 'niche model' extends the existing 'cascade model and improves its fit ten-fold by constraining species to consume a contiguous sequence of prey in a one-dimensional trophic niche.     

Geographic structure and dynamics of coevolutionary selection

Coevolution of species is one of the major processes organizing the Earth's biodiversity. Recent coevolutionary theory has indicated that the geographic structure of species has the potential to impose powerful and continuing effects on coevolutionary dynamics, if that structure creates selection mosaics and coevolutionary hotspots across landscapes. Here we confirm that current coevolutionary selection in interspecific interactions can be highly divergent across both narrow and broad geographic scales, thereby fueling continuing coevolution of taxa. Study of a widespread plant insect interaction across a broad range of habitats for several years showed that an insect functioning both as a pollinator and a floral parasite can be strongly mutualistic in some habitats but commensal or antagonistic in neighbouring habitats. The results for one of the habitats span seven years, demonstrating that the local structure of coevolutionary selection can remain stable across multiple generations. Conservation of the evolutionary processes maintaining long-term biological diversity may require preservation of the conditions that allow a long-term shifting geographic mosaic of coevolutionary hotspots and coldspots.     

棉田叶螨亚群落营养结构初步研究

本文报道了新疆棉田螨类群落中的叶螨科（Ｔｅｔｒａｎｙｃｈｉｄａｅ）亚群落营养结构。从采到的标本中已鉴定出棉叶螨５种，天敌２６种。初步探索了叶螨亚群落的食物网络关系，比较了棉田不同施药水平与天敌数量关系。     

长春市南湖公园两栖类的生境选择和营养生态的初步研究

本文研究了1997年4-7月吉林省长春市南湖公园五种两栖类的生境和食性特点．结果表明：五种两栖类生境及食物多样性指数不同,生境及食物相似性指数亦有较大差异．食物多样性和相似性差异与栖息生境有关．研究结果为公园规划提供科学依据．     

Unified spatial scaling of species and their trophic interactions

Two largely independent bodies of scaling theory address the quantitative relationships between habitat area, species diversity and trophic interactions. Spatial theory within macroecology addresses how species richness scales with area in landscapes, while typically ignoring interspecific interactions. Complexity theory within community ecology addresses how trophic links scale with species richness in food webs, while typically ignoring spatial considerations. Recent studies suggest unifying these theories by demonstrating how spatial patterns influence food-web structure and vice versa. Here, we follow this suggestion by developing and empirically testing a more unified scaling theory. On the basis of power-law species-area relationships, we develop link-area and non-power-law link-species models that accurately predict how trophic links scale with area and species richness of microcosms, lakes and streams from community to metacommunity levels. In contrast to previous models that assume that species richness alone determines the number of trophic links, these models include the species' spatial distribution, and hence extend the domain of complexity theory to metacommunity scales. This generality and predictive success shows how complexity theory and spatial theory can be unified into a much more general theory addressing new domains of ecology.     

饥饿对中华倒刺鲃和慈鲷鱼群觅食行为的影响

探究种类和饥饿对不同生境和集群特征鱼类的群体觅食行为的影响。选取群体互动特征不同、生境和食物资源状况迥异的鲤科(Cyprinidae)鱼类中华倒刺鲃(Spinibarbus sinensis)和慈鲷科(Cichlidae)鱼类斑马拟丽鱼(Pseudotropheus zebra)(后简称慈鲷)幼鱼作为实验对象,采用六臂迷宫来设置觅食情景,分析比较了前期经历饥饿或维持日粮摄食(对照组)鱼群的探索强度、凝聚力指标(IC)、首次到达食物臂速度、食物臂时间占比等行为学参数。与中华倒刺鲃相比,慈鲷有更高的探索强度和更低的IC值。饥饿导致慈鲷探索强度下降、首次到达食物臂速度加快和食物臂时间占比上升;中华倒刺鲃经历饥饿后食物臂时间占比略有下降。慈鲷和中华倒刺鲃群体觅食行为存在种间差异,且仅有慈鲷在群体觅食行为上表现出对食物匮乏的适应性变化,这可能与2种鱼类生境、食物资源等条件不同有关。     

Coral communities are regionally enriched along an oceanic biodiversity gradient

Ecological communities are influenced by processes operating at multiple scales. Thus, a better understanding of how broad- as well as local-scale processes affect species diversity and richness is increasingly becoming a central focus in modern community ecology. Here, in a study of unprecedented geographical scope, we show significant regional and local variation in the species richness of coral assemblages across an oceanic biodiversity gradient. The gradient that we sampled extends 10,000 km eastwards from the world's richest coral biodiversity hotspot in the central Indo-Pacific. Local richness and the size of regional species pools decline significantly across 15 islands spanning the gradient. In addition, richness declines across three adjacent habitats (reef slopes, crests and flats). In each habitat, a highly consistent linear relationship between local and regional species richness indicates strong regional enrichment. Thus, even on the most diverse coral reefs in the world, local coral assemblages are profoundly affected by regional-scale processes. Understanding these historical and biogeographical influences is essential for the effective management and preservation of these endangered communities.     

榕树传粉生物学的特性

榕树传粉生物学是当今植物生殖生物学研究的一个热点 .榕树为榕小蜂提供具生态保护作用的栖息场所和生长发育必须的营养物质 ,榕小蜂为榕树传粉 ,二者是植物和昆虫间高度专一化的互惠共生伙伴 .榕树和榕小蜂各具独特的生物学特性 ,共生双方在形态结构、生理生态和生物学行为上高度特化和互适 ,在物候生活史链上环环衔接 ,构成一个十分复杂而精确的传粉生态系统 .