一类考虑外界干扰的生物进化模型的动力学研究

依据进化动力学的理论与方法,建立了考虑外界干扰因素的Lotka-Volterra食物链进化模型,研究了中间捕食者种群表型特征的进化问题,得到了进化稳定、收敛稳定及产生进化分支的条件.最后,通过数值模拟分析了外界干扰对奇异策略的稳定性和表型特征进化分支情况的影响.     

When fear is near: threat imminence elicits prefrontal-periaqueductal gray shifts in humans

Humans, like other animals, alter their behavior depending on whether a threat is close or distant. We investigated spatial imminence of threat by developing an active avoidance paradigm in which volunteers were pursued through a maze by a virtual predator endowed with an ability to chase, capture, and inflict pain. Using functional magnetic resonance imaging, we found that as the virtual predator grew closer, brain activity shifted from the ventromedial prefrontal cortex to the periaqueductal gray. This shift showed maximal expression when a high degree of pain was anticipated. Moreover, imminence-driven periaqueductal gray activity correlated with increased subjective degree of dread and decreased confidence of escape. Our findings cast light on the neural dynamics of threat anticipation and have implications for the neurobiology of human anxiety-related disorders.     

腹管食螨瓢虫对桔全爪螨种群空间数量及时间动态的反应

腹管食螨瓢虫对其猎物桔全爪螨种群空间,数量及时间动态有明显的反应。在空间上,捕食者集中分布于猎物密度高的外层树冠,除其幼虫集中分布于树冠的中上部外,其余各虫态及其猎物种群在树冠各位点皆无显著的差异。捕食者能在果园内有效地搜索并趋集于猎物密度高的树上,对猎物种群聚集扩散趋势显示出有规则的反应。在数量上,捕食者在田间建立种群后,其数量消长将随猎物种群数量而起伏。捕食者对猎物种群空间及数量动态的反应都有10天左右的时滞。腹管食螨瓢虫对桔全爪螨自然控制效能高,经人工大量繁殖释放和助迁引进,是桔全爪螨综合治理的一个重要途径。     

Destruction of Pacific Corals by the Sea Star Acanthaster planci

Acanthaster planci, a coral predator, is undergoing a population explosion in many areas of the Pacific Ocean. Data on feeding rates, population movements, and stages of infestation were collected along coral reefs of Guam and Palau. Direct observations on destruction of Guam's coral reefs indicate that narrow, fringing reefs may be killed as rapidly as 1 kilometer per month. In a 2(1/2)-year period, 90 percent of the coral was killed along 38 kilometers of Guam's shoreline.     

具有Allee效应的捕食者-食饵模型的进化动力系统

研究了具有Allee效应的捕食者-食饵种群显性特征的共同进化动力系统.得到了在对称作用下连续稳定策略和进化分支的生态条件和进化条件,食饵的分支能导致捕食者分支;证明了在对称作用下进化动力系统经历超临界Hopf分支和次临界Hopf分支,周期进化是随机突变和选择过程的可能结果.在对称作用下进化自杀不可能发生,然而,在非对称作用下当种群遭受Allee效应时,进化自杀可能发生.     

转Bt基因棉对棉铃虫及其天敌发生的影响

1999年和2000年对转基因棉田棉铃虫及天敌进行了定点调查。结果表明：转基因棉对棉铃虫成虫、卵无驱避作用和抗性表现，不影响棉铃虫在植株上的落卵量，但转基因棉第二、三代棉铃虫幼虫数量与常规棉相对显著减少，存在明显抗虫性。转基因棉不影响捕食性天敌的数量。     

Effects of predator hunting mode on grassland ecosystem function

The way predators control their prey populations is determined by the interplay between predator hunting mode and prey antipredator behavior. It is uncertain, however, how the effects of such interplay control ecosystem function. A 3-year experiment in grassland mesocosms revealed that actively hunting spiders reduced plant species diversity and enhanced aboveground net primary production and nitrogen mineralization rate, whereas sit-and-wait ambush spiders had opposite effects. These effects arise from the different responses to the two different predators by their grasshopper prey-the dominant herbivore species that controls plant species composition and accordingly ecosystem functioning. Predator hunting mode is thus a key functional trait that can help to explain variation in the nature of top-down control of ecosystems.     

模拟轮伐期长短对杉木人工林氮动态的影响

近年来由于杉木Cunninghamia lanceolata连栽造成生产力日趋下降,已严重影响了杉木人工林的持续经营。运用FORECAST模型模拟杉木人工林在200 a间的生长情况,从而揭示其在不同轮伐期下氮循环的特点。模拟分好、中、差3种立地条件和10,25,50 a等3个不同的轮伐期长度。预测结果显示：杉木人工林氮的吸收量和归还量都随着轮伐期的增长而增加;叶片氮的含量也随着轮伐期的增长而增大;土壤有效氮在25 a轮伐期时下降,而后随着轮伐期变长又有所回升。以中等立地为例,10,25,50 a轮伐期土壤有效氮的200 a的平均值分别为96.24,86.87和96.07 kg.hm-2;吸收氮的平均值分别为49.22,58.44和69.07 kg.hm-2;凋落物形式归还氮的平均值分别为26.75,44.76和60.74 kg.hm-2。随着轮伐期增长,氮的循环系数增大,不同轮伐期的前4个轮伐期（前4代）氮的循环系数分别为0.544,0.766,0.847和0.879。模型预测的氮的吸收量与实测值具有很高的拟合度,达到显著水平。     

Peal-Reed模型在捕食性昆虫功能反应研究中的应用

根据昆虫功能反应数据 ,采用非线性回归分析方法 ,建立了描述昆虫功能反应的Peal -Reed模型。实例研究结果表明 :Peal-Reed模型是捕食者 -猎物功能反应研究中拟合精度最高的一种方法 ,为昆虫功能反应和生物防治的精确开展提供了新的研究方法。     

Precessional forcing of nutricline dynamics in the equatorial atlantic

Climate control of nutricline depth in the equatorial Atlantic can be monitored by variations in the abundance of the phytoplankton species Florisphaera profunda. A conceptual model, based on in situ evidence, associates high abundances of F. profunda with a deep nutricline and low abundances with a shallow nutricline. A 200,000-year record of F. profunda relative abundances, obtained from a deep-sea core sited beneath the region of maximum equatorial divergence at 10 degrees W, has 52 percent of its variance centered on the 23,000-year precessional band. Cross-spectral analysis between the signals of F. profunda and sea-surface temperature, independently derived from zooplankton species, shows their 23,000-year cycles to be coherent and nearly in phase. Abundance minima of F. profunda coincide with times of December perihelion, whereas abundance maxima coincide with June perihelion. These relations indicate that nutricline dynamics in the divergence region of the equatorial Atlantic are controlled by variations in the tropical easterlies, forced by the precessional component of orbital insolation, on time scales greater than 10,000 years.     

一类舌状绦虫传染病模型及其性态分析

以舌状绦虫病的传播为背景,建立并分析了一类含有S,I传染病仓室的食饵—捕食者系统模型.首先,证明了系统解的正性和有界性;其次,计算出了模型的基本再生数和分析了平衡点存在的条件;然后,证明了种群灭绝平衡点是不稳定的,并给出了仅易感食饵种群存在平衡点局部渐近稳定的条件和易感食饵和捕食者种群共存平衡点局部渐近稳定的条件;最后,通过构造Lyapunov函数,得出了仅易感食饵种群存在平衡点和易感食饵与捕食者种群共存平衡点的全局渐近稳定性.     

一类具有功能性反应的三种群食物链系统的稳定性

建立了具功能性反应的三种群食物链系统的模型,该系统是一个食饵种群被第一类捕食者种群捕食,而第二类捕食者种群仅捕食第一类捕食者种群．当给定参数满足一定条件下,应用微分方程理论和构造Liapunov函数的方法,讨论了平衡点的存在性,证明了平衡点的全局渐近稳定性和局部渐近稳定性．     

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。     

Strong top-down control in southern California kelp forest ecosystems

Global-scale changes in anthropogenic nutrient input into marine ecosystems via terrestrial runoff, coupled with widespread predator removal via fishing, have created greater urgency for understanding the relative role of top-down versus bottom-up control of food web dynamics. Yet recent large-scale studies of community regulation in marine ecosystems have shown dramatically different results that leave this issue largely unresolved. We combined a multiyear, large-scale data set of species abundances for 46 species in kelp forests from the California Channel Islands with satellite-derived primary production and found that top-down control explains 7- to 10-fold more of the variance in abundance of bottom and mid-trophic levels than does bottom-up control. This top-down control was propagated via a variety of species-level direct and indirect responses to predator abundance. Management of top-down influences such as fishing may be more important in coastal marine ecosystems, particularly in kelp forest systems, than is commonly thought.     

脉冲存放食饵连续捕获捕食者阶段结构数学模型

根据生物资源管理的实际,改进了原有捕食者-食饵模型,研究了一个连续收获捕食者与脉冲存放食饵的阶段结构时滞捕食-食饵模型,得到了捕食者灭绝周期解全局吸引和系统持久的充分条件.结论说明了脉冲存放食饵对系统的持久起到了重要作用,并且为生物资源管理中的捕食-食饵系统的开发提供了策略基础.     

Impact of food and predation on the snowshoe hare cycle

Snowshoe hare populations in the boreal forests of North America go through 10-year cycles. Supplemental food and mammalian predator abundance were manipulated in a factorial design on 1-square-kilometer areas for 8 years in the Yukon. Two blocks of forest were fertilized to test for nutrient effects. Predator exclosure doubled and food addition tripled hare density during the cyclic peak and decline. Predator exclosure combined with food addition increased density 11-fold. Added nutrients increased plant growth but not hare density. Food and predation together had a more than additive effect, which suggests that a three-trophic-level interaction generates hare cycles.     

Perceived predation risk reduces the number of offspring songbirds produce per year

Predator effects on prey demography have traditionally been ascribed solely to direct killing in studies of population ecology and wildlife management. Predators also affect the prey's perception of predation risk, but this has not been thought to meaningfully affect prey demography. We isolated the effects of perceived predation risk in a free-living population of song sparrows by actively eliminating direct predation and used playbacks of predator calls and sounds to manipulate perceived risk. We found that the perception of predation risk alone reduced the number of offspring produced per year by 40%. Our results suggest that the perception of predation risk is itself powerful enough to affect wildlife population dynamics, and should thus be given greater consideration in vertebrate conservation and management.     

Lupinus arcticus Wats. Grown from Seeds of Pleistocene Age

Seeds of the arctic tundra lupine (Lupinus arcticus) at least 10,000 years old were found in lemming burrows deeply buried in permanently frozen silt of Pleistocene age in unglaciated central Yukon. They readily germinated in the laboratory and have since grown into normal, healthy plants.     

Thrips-mediated impacts from transgenic rice expressing Cry1Ab on ecological fitness of non-target predator Orius tantilus(Hemiptera:Anthocoridae)

Various rice lines have been genetically modified with genes from Bacillus thuringiensis(Bt) to continuously produce Bt insecticidal proteins against lepidopteran larvae. The Bt insecticidal protein constantly expresses in the plants to create an opportunity for non-target herbivores to acquire and convey the protein to their predators or parasitoids across trophic levels. This paper evaluates the effects of Bt rice(namely, Kemindao 1(KMD1) and Kemindao 2(KMD2)) expressing Cry1 Ab as compared to its non-Bt control line, Xiushui 11 on non-target predator Orius tantilus(a generalist predatory anthocorid of thrips) under laboratory and field conditions. To measure several biological parameters such as total nymphal duration and fecundity of this bug, it was reared on thrips and pollens of KMD1 and KMD2 as compared to their control under laboratory conditions. By comparison with the control, Bt rice did not significantly affect main life-history characteristics(total nymphal duration, female adult longevity, oviposition period and fecundity) of this anthocorid preying on Bt rice-fed thrips along with Bt rice pollens, except that the fecundity of this predator for KMD1 was distinctly lower as compared with KMD2 or the control. Enzyme-linked immunosorbent assay(ELISA) results showed that no Cry1 Ab protein was detected in this predator fed on thrips or rice pollen from Bt rice but was in Bt rice pollens. With the beat plate, plastic bag and color trap sampling methods, two-year field monitoring of O. tantilus abundance demonstrated that Bt rice had no significant detrimental effects on the population dynamics and seasonal average densities of this predatory anthocorid as compared with the control. Thus, it is suggested that growing our tested Bt rice(KMD1 and KMD2) producing Cry1 Ab will pose a negligible risk to the anthocorid, O. tantilus.     

多种群共存系统中天敌对稻纵卷叶螟控制作用的数学模拟

本文应用二次回归旋转组合设计的方法,建立了在拟水狼蛛、拟环纹狼蛛、食虫瘤胸蛛、粽管巢蛛、青翅蚊形隐翅虫及稻纵卷叶螟六个种群共存系统中稻纵卷叶螟各龄幼虫被捕食量的数学模型。检验表明,所建立的五个模型均能较好地模拟稻纵卷叶螟各龄幼虫被捕食量与供试的六个群之间的关系,文中还应用多年大田系统调查的资料来对模型进行较正。