Secondary evolutionary escalation between brachiopods and enemies of other prey

The fossil record of predation indicates that attacks on Paleozoic brachiopods were very rare, especially compared to those on post-Paleozoic mollusks, yet stratigraphically and geographically widespread. Drilling frequencies were very low in the early Paleozoic (<1%) and went up slightly in the mid-to-late Paleozoic. Present-day brachiopods revealed frequencies only slightly higher. The persistent rarity of drilling suggests that brachiopods were the secondary casualties of mistaken or opportunistic attacks by the enemies of other taxa. Such sporadic attacks became slightly more frequent as trophic systems escalated and predators diversified. Some evolutionarily persistent biotic interactions may be incidental rather than coevolutionary or escalatory in nature.     

Predation in the paleozoic: gastropod-like drillholes in devonian brachiopods

Middle Devonian articulate brachiopods (Ludlowville and Moscow Formations, Hamilton Group, New York) have external tapered holes with a central boss that are indistinguishable from drillholes of naticid gastropods that are known from the Triassic and later. Drillholes are specific to prey (ribbed shells were avoided) and specific to sites on prey. Healed drillholes suggest penetration of live prey. As many as 44 percent of the preferred prey are drilled, indicating a level of predation that has been reported only from post-Paleozoic strata.     

黑缘红瓢虫个体间干扰反应的研究

本文研究了黑缘红瓢虫个体间的干扰作用对捕食作用率的影响。结果表明:黑缘红瓢虫对朝鲜球坚蚧的捕食作用率随捕食者个体间的相互干扰作用的增加而下降,两者之间的关系随黑缘红瓢虫数量的增加呈幂函数下降曲线。黑缘红瓢虫个体间存在明显的相互干扰效应。     

Tyrannosaur life tables: an example of nonavian dinosaur population biology

The size and age structures for four assemblages of North American tyrannosaurs-Albertosaurus, Tyrannosaurus, Gorgosaurus, and Daspletosaurus-reveal a pronounced, bootstrap-supported pattern of age-specific mortality characterized by relatively high juvenile survivorship and increased mortality at midlife and near the maximum life span. Such patterns are common today in wild populations of long-lived birds and mammals. Factors such as predation and entrance into the breeding population may have influenced tyrannosaur survivorship. This survivorship pattern can explain the rarity of juvenile specimens in museum collections.     

应用分子方法进行捕食者中肠分析的研究进展

捕食行为是生态学相互作用研究中最困难的问题之一。生态学者已经采用了多种方法来研究节肢动物的捕食行为。其中对田间收集的捕食者进行中肠分析成为获得关于捕食行为数据最清楚、有效的方法。文章综述了对捕食者进行中肠分析的主要方法,特别介绍了单克隆抗体技术和DNA技术的应用进展。     

Predatory fish select for coordinated collective motion in virtual prey

Movement in animal groups is highly varied and ranges from seemingly disordered motion in swarms to coordinated aligned motion in flocks and schools. These social interactions are often thought to reduce risk from predators, despite a lack of direct evidence. We investigated risk-related selection for collective motion by allowing real predators (bluegill sunfish) to hunt mobile virtual prey. By fusing simulated and real animal behavior, we isolated predator effects while controlling for confounding factors. Prey with a tendency to be attracted toward, and to align direction of travel with, near neighbors tended to form mobile coordinated groups and were rarely attacked. These results demonstrate that collective motion could evolve as a response to predation, without prey being able to detect and respond to predators.     

Predators accelerate nutrient cycling in a bromeliad ecosystem

Conventional ecological theory predicts that predators affect nutrient cycling by decreasing the abundance or activity of prey. By using a predator-detritivore-detritus food chain in bromeliads, we show that predators can increase nutrient cycling by a previously undescribed, but broadly applicable, mechanism: reducing nutrient export by prey emigration. Contrary to expectations, predation on detritivores increases detrital nitrogen uptake by bromeliads. Predation reduces detritivore emergence and hence export of nitrogen from the system. Detritivores therefore benefit their host plant, but only when predators are present. More generally, our results show that predator loss or extinction can dramatically and unexpectedly affect ecosystem functioning.     

The Predatory Function of Three Spiders to Two Insect Pests in Rice Within a Multi-species Co-existence System

The prey-seeking behavior of three spiders (X1-Pirata subpiraticus, X2-Clubiona japonicola and X3-Tetragnatha japonica ) for brown plant hopper (X4-Nilaparvata lugens ) and rice spittle bug (Xs-Callitettix versicolor) was investigated, as well as how interference between and within species occurred, by using a quadratic regression rotational composite design. Six predation models derived from the analysis of interactions among and within predators and preys were developed. The total predatory capacity of spiders on rice insect pests after coexistence for one day can be expressed as follows: Y3 = 32. 795 + 2.25X1 + 1.083X2 + 0.5X3 + 10.167X4 + 3.167X5 - 1.67X12 - 2.42X22 - 3. 295X32 - 0. 045X42 + 0. 455X52 - 3. 125X1X2 + 0.375X1X3-0.625X1X4 - 0.375X1X5 + 0.375X2X3 - 0.875X2X4 + 0.125X2X5 + 0.375X3X4 - 0.375X3X5 + 0.125X4X5. The principal efficiency analysis using this model indicated that increases in insect pest density significantly increased predation by predators; this was much greater than the effect of any single predator. X4 had a greater effect than X5; however, X4 and X5 demonstrated little interspecific interference and even promoted each other and increased predation rates as the densities of the two pests increased. Among the three predators, an increase in the density of X1 had the greatest effect on the increase in predation, X3 had the second, X2 the third greatest effect. As predator density increased inter- and intra-species interference occurred, which were largely related to the size, activity, niche breadth, niche overlap and searching efficiency of the predators. X2 produced the greatest interference between different individuals and between any other predator species. X3 had the second greatest, which reduced predation levels at high predator densities. Because of these factors, the highest predation rate was obtained at a prey density of 120 per 4 rice-hills. The optimal proportion of the three predators in the multi-predator prey system was X1: X2: X3= 5.6:1.3: 4.1.     

剑毛帕厉螨与黔下盾螨种间相残的研究

【目的】研究食用菌害虫2种天敌剑毛帕厉螨(Stratiolaelaps scimitus)和黔下盾螨(Hyposipis chianensis)的种间相残特性,为开展两者的协调应用提供理论依据。【方法】在有或无自然猎物(腐食酪螨Tyrophagus putrescentiae)条件下,观察2种捕食螨不同螨态间的相残程度及相残后若螨的发育和雌成螨的产卵量。【结果】有自然猎物腐食酪螨时,2种螨较少发生相残。无自然猎物时,2种螨发生相残,相残程度与捕食者螨态和猎物螨态密切相关,但黔下盾螨若螨不捕食剑毛帕厉螨幼螨。捕食黔下盾螨卵或幼螨的剑毛帕厉螨若螨80%和100%发育到成螨,若螨期分别为7.88d和7.30d;捕食剑毛帕厉螨卵的黔下盾螨若螨仅有30%发育至成螨;缺乏自然猎物时,2种捕食螨相残后雌成螨的产卵量均显著低于存在腐食酪螨时的产卵量,一种捕食螨仅通过捕食另一种捕食螨,无法维持种群正常增长速度。【结论】剑毛帕厉螨与黔下盾螨不适合作为相互的猎物,存在其它更为适合的猎物时,不优先选择相残,在害虫密度较大的条件下可以同时应用。     

辽东栎的繁殖体及其与种群更新的关系

就辽东栎的种子雨及其传播动力、种子传播后的命运、种子萌发、幼苗建立、实生更新对动物捕食的适应和萌生特性等方面进行了简要综述,并对未来研究的发展方向进行了展望。辽东栎种子是多种脊椎动物和鸟类的食物资源,种子萌发和幼苗形成期间的捕食压力导致其实生更新困难,但捕食动物对种子的搬运和埋藏对辽东栎种群更新和扩散具有重要意义;光照和水分对辽东栎的种子萌发和幼苗建立都具有重要影响,在森林管理工作中,适当干扰 (例如择伐) 对辽东栎的种子萌发、幼苗生长与存活以及种群更新都是有利的。较强的萌生能力对维持辽东栎的遗传多样性和种群活力具有重要的生态学意义;在强干扰条件下,萌生作为辽东栎通过从种子、幼苗、幼树到成年植株过程中的更新瓶颈的途径,是辽东栎实现种群更新的主要对策。     

Predator-prey role reversal in a marine benthic ecosystem

Two closely located islands on the west coast of South Africa support widely different benthic communities. The biota at Malgas Island is dominated by seaweeds and by rock lobsters that consume settling mussels, thereby preventing the establishment of the mussels. They also prey on whelks, although one speces, Burnupena papyracea, is protected from predation by a commensal bryozoan that covers its shell. Marcus Island has extensive mussel beds, but rock lobsters and seaweeds are virtually absent; whelks (mostly Burnupena spp.) occur at high densities. Rock lobsters transferred to Marcus Island were overwhelmed and consumed by the whelks, reversing the normal predatorprey relation between the two species. These two contrasting communities persisted during 4 years and may represent multiple states of the same ecosystem. This effective change of roles between a prey species and its chief predator may provide an intrinsic mechanism to maintain these states following the initial exclusion of the predator.     

云南扁萤幼虫捕食功能研究

为了解云南扁萤幼虫捕食效能,本文从温度、捕食者密度、猎物种类三个方面对云南扁萤幼虫的捕食功能进行了研究。结果表明:四龄幼虫在不同梯度温度下的捕食效果为35℃30℃25℃20℃;捕食率随着捕食者密度的增加而降低,当捕食者密度从1增加到5时捕食率下降相对较快,而当捕食者密度从5增加到7时,捕食率下降却较为平缓;云南扁萤幼虫对灰巴蜗牛具有正喜好性和负转换行为,对野蛞蝓表现为负喜好性和正转换行为。     

A Sheep in Wolf's Clothing: Tephritid Flies Mimic Spider Predators

Mimicry where prey resemble predators to avoid predation is unusual. Snowberry flies, Rhagoletis zephyria Snow, possess striped wing patterns that resemble the legs of jumping spiders. Observations and comparisons of responses of the jumping spider Salticus scenicus (Clerck) to conspecifics, snowberry flies, and other prey flies showed that snowberry flies can avoid predation by jumping spiders through spider mimicry. The mimicry effect was decreased by obliterating snowberry fly wing stripes.     

多物种共存系统中蜘蛛对菜田害虫的控制作用

运用二次通用旋转组合设计统计方法,研究菜田生态系统中天敌优势种蜘蛛星豹蛛(X1)、草间黑蛛(X2)及主要害虫菜蚜(X3)、小菜蛾(X4)组成的多物种共存系统,探讨蜘蛛对菜田主要害虫的控制作用,分析天敌之间、害虫之间及天敌和害虫之间的相互作用关系,获得4个天敌对害虫的捕食量模型。对模型进行主效分析表明,害虫密度的大小对天敌的总捕食量影响较大,其中又以菜蚜密度对天敌的总捕食量的影响较大。天敌中对捕食量作用最大的是星豹蛛,其次是小狼逍遥蛛。分析天敌间的交互作用表明,2种天敌蜘蛛的种间和星豹蛛的种内干扰较大,主要原因是生态位重叠较大,种间、种内残杀较严重。而小狼逍遥蛛种内的干扰却不是很明显。最后讨论了天敌蜘蛛能有效控制害虫的最大密度,以及在该害虫密度下各种天敌密度的最佳组合。     

Predator-induced defense in a marine bryozoan

Laboratory experiments showed that predation by both trophically specialized and generalized nudibranch species triggers rapid induction of defensive spines in the bryozoan Membranipora membranacea. Spines effectively control the pattern and extent of intracolony mortality caused by nudibranch predation. Previously found only in plants, rotifers, and cladocerans, consumer-induced defenses may be widespread among clone-forming or colonial taxa exposed to nonfatal encounters with predators.     

Climate change, keystone predation, and biodiversity loss

Climate change can affect organisms both directly via physiological stress and indirectly via changing relationships among species. However, we do not fully understand how changing interspecific relationships contribute to community- and ecosystem-level responses to environmental forcing. I used experiments and spatial and temporal comparisons to demonstrate that warming substantially reduces predator-free space on rocky shores. The vertical extent of mussel beds decreased by 51% in 52 years, and reproductive populations of mussels disappeared at several sites. Prey species were able to occupy a hot, extralimital site if predation pressure was experimentally reduced, and local species richness more than doubled as a result. These results suggest that anthropogenic climate change can alter interspecific interactions and produce unexpected changes in species distributions, community structure, and diversity.     

Fear of predation slows plant-litter decomposition

Aboveground consumers are believed to affect ecosystem functioning by regulating the quantity and quality of plant litter entering the soil. We uncovered a pathway whereby terrestrial predators regulate ecosystem processes via indirect control over soil community function. Grasshopper herbivores stressed by spider predators have a higher body carbon-to-nitrogen ratio than do grasshoppers raised without spiders. This change in elemental content does not slow grasshopper decomposition but perturbs belowground community function, decelerating the subsequent decomposition of plant litter. This legacy effect of predation on soil community function appears to be regulated by the amount of herbivore protein entering the soil.     

Brachiopods: biomechanical interdependences governing their origin and phylogeny

The adaptive advantage of epibenthic articulate brachiopods over inarticulate forms resulted from a modification of the mechanics of shell opening from an indirect hydraulic system to a direct muscular one. As a consequence, the articulate brachiopods were able to reduce the complex muscular system of the ancestral inarticulates, freeing two-thirds of the space within the shell for enlargement of the feeding apparatus. The original hydraulic mechanism of the inarticulate brachiopods most likely evolved from the hydrostatic skeleton of metameric lower invertebrates, probably polychaete-like annelids, as shown by a biomechanical analysis. The transitional stages between such annelids and inarticulate brachiopods are presented and explained as adaptive improvements in body construction.     

江苏侧隆螽对马尾松毛虫的捕食作用

江苏侧隆螽具有个体大,食量大,活动范围广,发生早,捕食作用时间长等特点,是马尾松毛虫的有效天敌之一。1984～1986年,在室内进行了捕食者对不同虫态(龄期),马尾松毛虫的功能反应,测定了捕食者个体间的相互干扰作用及其对功能反应的影响,并建立了参数方程,能在一定程度上描述螽斯对马尾松毛虫卵,幼小幼虫及老龄幼虫的捕食作用。     

星豹蛛(Pardosa astrigera L. Koch)对菜蚜的捕食作用及模拟模型的研究

研究了星豹蛛对菜蚜的日捕食量、捕食功能反应, 构建了捕食模拟模型。室内测定结果表明, 星豹蛛成蛛与亚成蛛对成熟菜蚜的日捕食量上限为42头/天, 对该虫的捕食量随猎物密度的增加而增加, 随自身密度的增加而减少。用Holling圆盘方程进行模拟, 其功能反应属于HollingⅡ型; 对自身密度的功能反应可以用Hassell-Varley提出的方程进行拟和。星豹蛛对自身密度与猎物密度的联合反应方程已被构建。经卡方检验, 以上各方程理论值与实际值误差均不显著。