草间小黑蛛对茶蚜的捕食功能反应

在实验室条件下研究了草间小黑蛛(Erigonidium graminicolum)对茶蚜(Toxoptera aurantii)的捕食作用。草间小黑蛛对茶蚜的捕食功能反应属于HollingⅡ型。草间小黑蛛有较强的种内干扰反应,随着捕食者密度的增大,草间小黑蛛的捕食率相应降低。猎物密度和天敌密度相互干扰会降低草间小黑蛛的寻找效应,但对捕食量没有影响。     

草间小黑蛛对棉铃虫幼虫的捕食作用及其模拟模型的研究——Ⅲ.模拟模型的进一步研究

根据实验室实验的结果,李超等(1982a、b)分别提出了草间小黑蛛-棉铃虫作用系统和草间小黑蛛-棉铃虫-棉蚜作用系统的模拟模型。本文通过大田中进行的笼罩实验结果,进一步完善了功能反应参数的修正方法,使模型的行为更接近于实际情形。在此基础上,对描述草间小黑蛛-棉铃虫-棉蚜作用系统的四种可能的模拟模型的行为,通过数值模拟的结果来进行初步的探讨。     

转Bt棉花对蜘蛛生长发育及捕食行为的影响

室内评价了取食转Bt棉叶的棉铃虫幼虫对草间钻头蛛和八斑鞘腹蛛生长发育的影响.并通过捕食功能反应评价了取食了Bt棉叶的棉铃虫幼虫对成熟草间钻头蛛捕食行为的影响.室内饲养实验结果表明草间钻头蛛、八斑鞘腹蛛取食用转Bt棉叶处理的棉铃虫幼虫与取食普通棉叶处理的棉铃虫幼虫的发育历期、成蛛体重都没有显著差异.捕食功能反应实验结果表明草间钻头蛛对棉铃虫幼虫的捕食功能反应符合HollingⅡ型圆盘方程,两组不同猎物饲养成熟的草间钻头蛛对同种处理的棉铃虫幼虫的捕食行为没有显著差异.综合考虑：转Bt棉对蜘蛛生长发育、捕食能力没有显著的负作用.     

转Bt基因棉田蜘蛛的时空动态及控害作用

1998-1999年在河北棉区系统调查转Bt基因棉棉田中的蜘蛛发生时空的研究结果表明,在转Bt基因棉田中,全年百株累计数量为3984头,占棉田总捕食性天敌数量的49.7%。其中优势蜘蛛温室希蛛,狼蛛和草间小黑蛛分别占53.6%,16.7%和18.6%。季节动态表现为棉田前期少,中,后期多,最高可达百株454头;棉株下部和地面的蜘蛛增加快,而上,中部蜘蛛增加慢,空间分布表现为下部和地面占优势,丰富度分别为0.464和0.303,而上部蜘蛛的丰富度仅为0.067。地面蜘蛛中以狼蛛和草间小黑蛛占优势,分别占52.6%和40.6%。基于蜘蛛的数量,时空动态及与棉铃虫的配合程度认为,对棉铃虫起主要控制作用的为草间小黑蛛,温室希蛛和卷叶蛛,分别占蜘蛛总控制指数的41.3%,25.2%和10.9%。其中2代棉铃虫发生期,草间小黑蛛贡献最大。占67.7%。3代棉铃虫发生期,温室希蛛和草间小黑蛛分别占29.0%和25.4%的贡献率,4代棉铃虫发生期温室希蛛起主要作用。占45.3%的贡献率。     

拟环纹狼蛛对褐飞虱的捕食作用及其模拟模型的研究Ⅲ.选择捕食作用

本文研究了拟环纹狼蛛雌成蛛对褐飞虱、稻纵卷叶螟的选择捕食作用。在不同猎物类型共存和不同总猎物密度下,测定了捕食者对猎物的喜好性和转换行为,分析了捕食者对猎物的功能反应形式,喜好性和转换行为与共存猎物种类、数量之间的关系;建立了在多种猎物类型共存时,雌成蛛对猎物的总捕食作用方程及对每一种猎物类型的捕食作用方程。室内验证实验表明:所建立的捕食作用方程具有一定的描述能力。     

小黑瓢虫与两种猎物作用系统研究:选择捕食作用

研究了小黑瓢虫与烟粉虱及红蜘蛛两种猎物作用系统中 ,小黑瓢虫雌成虫对两种猎物卵的选择捕食作用。结果表明 :当两种猎物共存时 ,小黑瓢虫雌成虫对烟粉虱卵在低密度下不表现喜好性 ,而在中等密度和高密度下表现正喜好性 ,对红蜘蛛卵在各密度下均不表现喜好性。对烟粉虱卵的转换效应会由于总猎物密度的不同而呈现不同的效应 ,即在低密度 (15 0粒 )时无转换行为 ,在中等密度 (30 0粒 )时有负转换行为 ,在高密度 (6 0 0粒 )时有正转换行为。而对红蜘蛛卵则在各总猎物密度下均呈现负转换效应。同时组建了两种猎物共存时 ,小黑瓢虫雌成虫对猎物的总捕食作用方程及对每一种猎物类型的捕食作用方程 ,分析了两种猎物共存时 ,小黑瓢虫雌成虫对各猎物寻找效应的变化情况。     

八斑鞘蛛对多种猎物的选择捕食作用研究

研究八斑鞘蛛在多种猎物共存时的日捕食量,功能反应,捕食作用率。在有棉铃虫和棉蚜共存且密度互补时,八斑鞘蛛对棉铃虫的功能反应属Holling Ⅲ型反应;一种猎物密度变化,其他种猎物密度固定时,功能反应呈Holling Ⅱ型反应。研究了捕食作用率与猎物共存种类,相对丰盛度,捕食者本身数量的关系。 计算机(IBM-PC)模拟结果表明:捕食者个体间的相互干扰、温度、猎物内禀增长率对系统稳定性有一定影响。     

草间钻头蛛(Hylyphantes graminicola)对果蝇(Drosophila melanogaster)捕食作用的研究

在实验室条件下,研究了草间钻头蛛Hylyphantes graminicola对果蝇Drosophila melanogaster的捕食功能反应.结果表明,在一定范围内,草间钻头蛛捕食效应随猎物密度增加而增加;随自身密度增加而减小;随着蜘蛛和果蝇密度的增加,相互干扰明显,捕食效率下降;雌蛛比雄蛛捕食量大.     

转Cry1Ac+Cry2Ab棉对棉铃虫的控制作用及对天敌捕食烟粉虱功能反应的影响

文章以转Cry1Ac基因棉(中棉所41)和常规棉(中棉所49)为对照,研究了转Cry1Ac+Cry2Ab基因棉(639020)在棉花生长的关键时期——蕾期(二代棉铃虫发生期)、花期(三代棉铃虫发生期)和花铃期(四代棉铃虫发生期)对棉铃虫的控制作用,同时研究了639020棉田主要捕食性天敌(中华草蛉幼虫、龟纹瓢虫、小花蝽和草间小黑蛛)对烟粉虱的捕食功能,明确了639020棉花在生长的关键时期对棉铃虫的控制效果及对棉田主要捕食性天敌捕食功能反应的影响。结果表明,639020棉花对二代和三代棉铃虫具有良好的控制作用,抗虫性分别比中棉所41提高了52.85%和16.22%,其中前者差异达显著水平,后者差异不显著。在棉花蕾期、花期和花铃期,639020棉田棉铃虫落卵量都比中棉所41棉田和中棉所49棉田低(除二代棉铃虫发生期);棉铃虫幼虫数量都极显著低于常规棉,且都低于防治指标,但与中棉所41棉田无显著差异。639020棉田中华草蛉、龟纹瓢虫、小花蝽和草间小黑蛛对烟粉虱的捕食功能与中棉所41棉田和常规棉田相比无显著变化。研究结果以期为新型转基因棉花环境安全性研究及其外源基因的抗虫遗传效应和生产应用前景进行安全性评价。     

棉蚜及其捕食性天敌时空生态位研究

研究结果表明,棉蚜的时间生态位宽度较小而空间生态位宽度较大,说明棉蚜种群的发生有高峰期明显和全株为害的特点．棉蚜的时动空间生态位宽度与种群密度无相关性,说明棉蚜的为害较复杂．捕食性天敌中草间小黑蛛和龟纹瓢虫的时空生态位宽度较大,说明它们发生期较长、分布范围较广．八斑球腹蛛和龟纹瓢虫与棉蚜的时间生态位重叠度较大,八斑球腹蛛和草间小黑蛛与棉蚜的空间生态位重量度较大．与棉蚜的时间×空间生态位重叠度,八斑球腹蛛＞龟纹瓢虫＞草间小黑蛛＞其它天敌合计＞三色长蝽＞三突花蛛＞小花蝽,这一结果同棉蚜与捕食性天敌数量的关联度大小排序相一致,表明捕食性天敌与棉蚜的时间同步和空间同线性与天敌的捕食作用密切相关．     

Intraguild predation: fiction or reality?

Intraguild predation has become a major research topic in biological control. Quantification of multipredator interactions and an understanding of the consequences on target prey populations are needed, which only highlights the importance of population dynamics models in this field. However, intraguild predation models are usually based on Lotka–Volterra equations, which have been shown not to be adequate for modeling population dynamics of aphidophagous insects and their prey. Here we use a simple model developed for simulation of population dynamics of aphidophagous insects, which is based on the type of egg distribution made by predatory females, to estimate the real strength of intraguild predation in the aphidophagous insects. The model consists of two components: random egg distribution among aphid colonies, and between-season population dynamics of the predatory species. The model is used to estimate the proportion of predatory individuals that face a conflict with a heterospecific competitor at least once during their life. Based on this, predictions are made on the population dynamics of both predatory species. The predictions are confronted with our data on intraguild predation in ladybirds.     

Complementary predation on metamorphosing species promotes stability in predator–prey systems

Functionally redundant predation and functionally complementary predation are both widespread phenomena in nature. Functional complementary predation can be found, for example, when predators feed on different life stages of their prey, while functional redundant predation occurs when different predators feed on all life stages of a shared prey. Both phenomena are common in nature, and the extent of differential life-stage predation depends mostly on prey life history; complementary predation is expected to be more common on metamorphosing prey species, while redundant predation is thought to be higher on non-metamorphosing species. We used an ordinary differential equation model to explore the effect of varying degree of complementary and redundant predation on the dynamic properties of a system with two predators that feed on an age-structured prey. Our main finding was that predation on one stage (adult or juvenile) resulted in a more stable system (i.e., it is stable for a wider range of parameters) compared to when the two predators mix the two prey developmental stages in their diet. Our results demonstrate that predator–prey dynamics depends strongly on predators' functionality when predator species richness is fixed. Results also suggest that systems with metamorphosing prey are expected to be more diverse compared to systems with non-metamorphosing prey.     

High reproductive rates result in high predation risks: a mechanism promoting the coexistence of competing prey in spatially structured populations

I tested the hypothesis that spatial structure provides a trade-off between reproduction and predation risk and thereby facilitates predator-mediated coexistence of competing prey species. I compared a cellular automata model to a mean-field model of two prey species and their common predator. In the mean-field model, the prey species with the higher reproductive rate (the superior competitor) always outcompeted the other species (the inferior competitor), both in the presence of and the absence of the predator. In the cellular automata model, both prey species, which differed only in their reproductive rates, coexisted for a long time in the presence of their common predator at intermediate levels of predation. At low predation rates, the superior competitor dominated, while high predation rates favored the inferior competitor. This discrepancy in the results of the different models was due to a trade-off that spontaneously emerged in spatially structured populations; that is, the more clustered distribution of the superior competitor made it more susceptible to predation. In addition, coexistence of competing prey species declined with increasing dispersal ranges of either prey or predator, which suggests that the trade-off that results from spatial structure becomes less important as either prey or predator disperse over a broader range.     

Methods to identify the prey of invertebrate predators in terrestrial field studies

Predation is an interaction during which an organism kills and feeds on another organism. Past and current interest in studying predation in terrestrial habitats has yielded a number of methods to assess invertebrate predation events in terrestrial ecosystems. We provide a decision tree to select appropriate methods for individual studies. For each method, we then present a short introduction, key examples for applications, advantages and disadvantages, and an outlook to future refinements. Video and, to a lesser extent, live observations are recommended in studies that address behavioral aspects of predator–prey interactions or focus on per capita predation rates. Cage studies are only appropriate for small predator species, but often suffer from a bias via cage effects. The use of prey baits or analyses of prey remains are cheaper than other methods and have the potential to provide per capita predation estimates. These advantages often come at the cost of low taxonomic specificity. Molecular methods provide reliable estimates at a fine level of taxonomic resolution and are free of observer bias for predator species of any size. However, the current PCR‐based methods lack the ability to estimate predation rates for individual predators and are more expensive than other methods. Molecular and stable isotope analyses are best suited to address systems that include a range of predator and prey species. Our review of methods strongly suggests that while in many cases individual methods are sufficient to study specific questions, combinations of methods hold a high potential to provide more holistic insights into predation events. This review presents an overview of methods to researchers that are new to the field or to particular aspects of predation ecology and provides recommendations toward the subset of suitable methods to identify the prey of invertebrate predators in terrestrial field research.     

Estimating predation rates from molecular gut content analysis

Several methods have been published to estimate per capita predation rates from molecular gut content analysis relying on intuitive understanding of predation, but none have been formally derived. We provide a theoretical framework for estimating predation rates to identify an accurate method and lay bare its assumptions. Per capita predation can be estimated by multiplying the prey decay rate and the prey quantity in the predators. This assumes that variation in per capita predation rate is approximately normally distributed, prey decay occurs exponentially, and predation is in steady state. We described several ways to estimate steady state predation, including using only qualitative presence-absence data to estimate the decay rate and in addition, we provided a method for estimating per capita predation rate when predation is not in steady state. We used previously published data on aphid consumption by a ladybird beetle in a feeding trial to calculate the predation rate and compare published methods with this theoretically derived method. The estimated predation rate (3.29 ± 0.27 aphids/h) using our derived method was not significantly different from the actual predation rate, 3.11 aphids/h. In contrast, previously published methods were less accurate, underestimating the predation rate (0.33 ± 0.02 to 1.66 ± 0.8 aphids/h) or overestimating it (3.64 ± 0.30 aphids/h). In summary, we provide methods to estimate predation rates even when variation in predation rates is not exactly normally distributed and not in steady state and demonstrate that the prey decay rate, and not the prey detection period, is required.     

Predation and the evolutionary dynamics of species ranges

Gene flow that hampers local adaptation can constrain species distributions and slow invasions. Predation as an ecological factor mainly limits prey species ranges, but a richer array of possibilities arises once one accounts for how predation alters the interplay of gene flow and selection. We extend previous single-species theory on the interplay of demography, gene flow, and selection by investigating how predation modifies the coupled demographic-evolutionary dynamics of the range and habitat use of prey. We consider a model for two discrete patches and a complementary model for species along continuous environmental gradients. We show that predation can strongly influence the evolutionary stability of prey habitat specialization and range limits. Predators can permit prey to expand in habitat or geographical range or, conversely, cause range collapses. Transient increases in predation can induce shifts in prey ranges that persist even if the predator itself later becomes extinct. Whether a predator tightens or loosens evolutionary constraints on the invasion speed and ultimate size of a prey range depends on the predator effectiveness, its mobility relative to its prey, and the prey's intraspecific density dependence, as well as the magnitude of environmental heterogeneity. Our results potentially provide a novel explanation for lags and reversals in invasions.     

Is arthropod predation exclusively satiation‐driven?

Functional response models differ in which factors limit predation (e.g. searching efficiency, prey handling time, digestion) and whether predation behaviour is governed by an internal physiological state (e.g. satiation). There is now much evidence that satiation is a key factor in understanding changes in foraging behaviour, and that many predators are effectively digestion limited. Here, we ask if predation in a predatory arthropod can be explained from satiation-driven behaviour alone, or if behaviour is also influenced by the density of prey other than via the effect of prey ingestion on satiation. To address this question a satiation-based predation model is formulated, for which parameters are estimated on the basis of observations on digestion rate, satiation-related prey searching rate and prey capture behaviour, basically under high prey density conditions. The model predictions are subsequently tested against longer term predation experiments carried out at high and low prey densities. Since satiation can easily be linked with egg production, these tests are carried out both for predation and oviposition.
The predator–prey systems under study consist of females of two predatory mite species ( Neoseiulus barkeri and N. cucumeris ) and the larvae of two thrips species ( Thrips tabaci and Frankliniella occidentalis ) as their prey. For N. barkeri foraging on T. tabaci , the model gives good predictions at both high (4 larvae cm⁻¹) and low (0.1–1 larvae cm⁻²) prey densities. For N. cucumeris foraging on F. occidentalis , the predictions hold at the high prey density, but are too low at low prey densities. Thus our analysis indicates that we cannot fully explain density-dependent predation rates from satiation-driven behaviour alone. Different mechanisms are suggested on how prey density may affect foraging efficiency other than via satiation.     

Effects of habitat destruction and resource supplementation in a predator-prey metapopulation model

We developed a mean field, metapopulation model to study the consequences of habitat destruction on a predator-prey interaction. The model complements and extends earlier work published by Bascompte and Solé (1998, J. theor. Biol.195, 383-393) in that it also permits use of alternative prey (i.e., resource supplementation) by predators. The current model is stable whenever coexistence occurs, whereas the earlier model is not stable over the entire domain of coexistence. More importantly, the current model permits an assessment of the effect of a generalist predator on the trophic interaction. Habitat destruction negatively affects the equilibrium fraction of patches occupied by predators, but the effect is most pronounced for specialists. The effect of habitat destruction on prey coexisting with predators is dependent on the ratio of extinction risk due to predation and prey colonization rate. When this ratio is less than unity, equilibrial prey occupancy of patches declines as habitat destruction increases. When the ratio exceeds one, equilibrial prey occupancy increases even as habitat destruction increases; i.e., prey "escape" from predation is facilitated by habitat loss. Resource supplementation reduces the threshold colonization rate of predators necessary for their regional persistence, and the benefit derived from resource supplementation increases in a nonlinear fashion as habitat destruction increases. We also compared the analytical results to those from a stochastic, spatially explicit simulation model. The simulation model was a discrete time analog of our analytical model, with one exception. Colonization was restricted locally in the simulation, whereas colonization was a global process in the analytical model. After correcting for differences between nominal and effective colonization rates, most of the main conclusions of the two types of models were similar. Some important differences did emerge, however, and we discuss these in relation to the need to develop fully spatially explicit analytical models. Finally, we comment on the implications of our results for community structure and for the conservation of prey species interacting with generalist predators.     

A mathematical model with young predation

We generalise the model of [21] in which the author considered a predator-prey system with predators eating only the young ones (or eggs) of the prey species. The prime assumption of the present paper is that the birth rate (per unit individual per unit time) of predators depends not only on the current prey egg-level but also on all previous prey egg-levels. It is seen that under this assumption an otherwise stable system may be stable as well as unstable leading to the conclusion that young predation with time delay is less stable than without it. Finally for the model of [21] we prove a result which shows that large predation rates help in the co-existence of both predator and prey species.