稻纵卷叶螟种群系统动态模拟

本文组建了稻纵卷叶螟种群系统模似模型,它由系统亚模型和总模型二个部分组成.系统亚模型包括发育、死亡和繁殖三个子模块.系统总模型是作者提出的新模型,它综合了前人所提出的种群模型的优点,以差分方程形式给出,以生理时间为单位,考虑了种群内个体间发育速率的差异,不仅能模拟种群数量动态,而且能模拟种群年龄结构,同时能预测发生期.模型有效性检验表明,模拟结果基本上能吻合实测结果.文中还对5个影响因子进行了灵敏性分析.     

稻纵卷叶螟种群系统动态模拟

本文组建了稻纵卷叶螟种群系统模似模型,它由系统亚模型和总模型二个部分组成.系统亚模型包括发育、死亡和繁殖三个子模块.系统总模型是作者提出的新模型,它综合了前人所提出的种群模型的优点,以差分方程形式给出,以生理时间为单位,考虑了种群内个体间发育速率的差异,不仅能模拟种群数量动态,而且能模拟种群年龄结构,同时能预测发生期.模型有效性检验表明,模拟结果基本上能吻合实测结果.文中还对5个影响因子进行了灵敏性分析.     

昆虫种群动态模拟模型

昆虫是动物界中最大的类群,与人类有着密切的利害关系。对昆虫的数量预测与符合经济和生态规律的管理,一直都被国内外列入重点研究课题。种群动态模拟是害虫管理中重要的基础工作。近十年来,关于昆虫种群动态模型的理论和实验研究进展迅速。现分别从单种种群和多种种群两个方面对国内外近些年来昆虫种群动态模拟模型的研究进展进行了概括和总结。单种种群从两个方面阐述:一是最基本的种群动态模拟模型Log istic方程的研究成果,包括方程的修正、参数的拟合与最优捕获策略等;另一个方面是对种群动态模拟常用的矩阵模型的概述,主要介绍不等期年龄组、矩阵维数的变化、矩阵维数与历期的关系、个体之间的发育差异以及发育速率差异等等对昆虫种群动态模型的影响。多种群主要从建模和模型应用两个部分对国内外研究成果进行综述。最后,对种群动态模拟模型研究的发展方向做了深入地讨论,即在原有的数据采集工作的基础上,使用面向对象程序设计语言,把各种要素包括各种物种及各种环境条件抽象成类,用消息传递来表示昆虫种群内个体与个体、昆虫种群与环境之间的相互作用,再结合先进的数学算法,建立一个直观的、操作简单的昆虫种群动态模型库,使模型结构与现实世界有最大的相似性。这样就可以实现昆虫种群动态的可视化、立体化、实时化和精确化的监测及预测。     

粘虫种群动态模拟的研究

本文描述了一种计算种群动态和发育进度的新方法。以稍修改过的Ruesink(1976)的模型为基础,模拟了自然变温下粘虫的种群动态。 考虑到每天的最高温度(约14∶00)和最低温度(约5∶00)出现的时间间隔明显的不相等这一事实,我们提出了用不同周期的正弦函数计算有效积温,根据有效积温计算发育速率,然后根据发育速率计算粘虫推进的年龄级数。 把粘虫的一个世代分成10个不同的阶段(卵、1—6龄幼虫、预蛹、蛹和成虫各为一个阶段)。输入每天的最高、最低温度、相对湿度、各阶段的发育起点温度、有效积温和存活率,用计算机进行逐日动态模拟和预测的结果见图1、2和表4。除1、2龄幼虫由于个体小等原因调查时有遗漏外,模拟和预测的发生量和发生期与生命表数据、徐州农科所和驻马店农科所的实测值较为吻合。因此,我们认为该模型不仅可用于模拟自然变温下的种群动态,而且可较准确地预测发生期。     

恒温和变温对小菜蛾发育速率的影响

研究了小菜蛾的发育速率在恒温和自然变温下的变化规律。恒温下小菜蛾在 8～ 32℃内能完成整个幼期的发育 ,在 30～ 32℃下发育最快。幼虫能完成发育的温度范围宽于卵和蛹。在模拟恒温下发育速率和温度关系时 ,王 -兰 -丁模型效果较好 ,而 Logistic模型能较好地模拟适温区和低温区的发育速率 ,直线模型只能用于适温区内发育速率的模拟。恒温下的存活率和温度符合二次曲线关系。不同恒温下发育历期的分布符合“同形性质”。变温下 ,小菜蛾能够发育的温度范围比恒温下的广。在适温区 ,Logistic模型、直线模型和王 -兰 -丁模型均能较好地模拟变温下小菜蛾的羽化进度 ,但在低温区 ,Logistic模型和王 -兰 -丁模型模拟的效果优于直线模型。     

温度对二斑叶螨实验种群生长的影响

采用大樱桃叶片饲养二斑叶螨Tetranychus urticae Koch,组建其在15,20,25,30和35℃下的实验种群生命表,分析温度对二斑叶螨种群动态的影响。结果表明:在试验的温度范围内,二斑叶螨的发育速率随着温度的升高而加快,并符合Logistic模型。二斑叶螨全世代的发育起点温度和有效积温分别为11.85℃和170.39日.度。计算出在不同温度下的实验种群的内禀增长率(rm)、净增殖率(R0)、周限增长率(λ)、世代平均周期(T)和种群加倍时间(t)等种群参数。     

桃蚜被寄生龄期与受寄生蜂影响大小的关系

在两个温度下将桃蚜Myzus perstcae无翅型不同龄期个体供菜蚜茧蜂Diaeretiella rapae产卵寄生,然后观察寄主蚜虫的发育、存活和生殖情况.结果表明,寄主蚜虫的发育速率不受影响,而从接受寄生蜂产卵到生殖率明显下降、产幼蚜终止、死亡三种症状出现的时间间隔分别为寄生蜂完成整个幼期发育所需时间的30%、40%、60%左右,这一规律不依寄主接受产卵的龄期和温度条件而变化,从而导致寄主所受影响随着接受产卵时龄期的增大而迅速下降.当蚜虫在1—2龄接受产卵时,一般不能产幼蚜,从二龄后期起,随着接受产卵龄期的推迟,所表现的内禀增长能力迅速增加,至羽化为成蚜时接受产卵,内禀增长能力已与未被寄生蚜虫的接近.由此可见,寄主不同龄期被产卵寄生的相对机率是影响蚜虫-蚜茧蜂混合种群动态关系的决定性因子之一,蚜茧蜂必须产卵于大量的1—3龄若蚜,才有可能对蚜虫种群的增长有明显的抑制作用.     

新型杀螨剂丁氟螨酯对土耳其斯坦叶螨亚致死效应

为了解新型杀螨剂丁氟螨酯Tetranychus turkestani对土耳其斯坦叶螨实验种群的亚致死效应,本研究采用叶碟法研究了其亚致死剂量对土耳其斯坦叶螨实验种群成螨和卵生命表参数的影响。结果表明:经丁氟螨酯LC20、LC10亚致死剂量处理成螨后,成螨的平均寿命、产卵量和次代卵的孵化率均显著降低;次代种群除了卵期、LC20幼螨期和LC10若螨期显著延长外,所有处理次代种群成螨期和雌螨寿命均显著缩短,其余处理次代种群幼螨期、若螨期和产卵前期均无显著差异;次代种群的净生殖率(Ro)和平均世代历期(T)均显著降低,内禀增长率(rm)和周限增长率(λ)增加;存活率和平均每雌日产卵率显著降低。丁氟螨酯LC20、LC10亚致死剂量处理卵后,次代种群除了LC10处理卵期明显延长和幼螨期显著缩短外,所有处理次代种群若螨期、成螨期和雌螨寿命均显著缩短,其余处理卵期、幼螨期和产卵前期均无显著差异;净生殖率(Ro)和平均世代历期(T)均显著降低,内禀增长率(rm)和周限增长率(λ)增加;存活率和平均每雌日产卵率显著降低。这些结果表明,新型杀螨剂丁氟螨酯亚致死剂量可以降低土耳其斯坦叶螨种群的发育速率,这对土耳其斯坦叶螨的综合防治策略的制定有积极意义。     

稻纵卷叶螟地理种群的比较研究

本文应用实验种群生命表技术,比较了三个地区不同世代(南宁五代、衡阳四代、南京三代,三地各相距4—6个纬度)和同是第二世代稻纵卷叶螟(Cnaphalocrocis medinalis Guenee)种群的发育、存活、繁殖、内禀增长力等参数的差异.结果表明,三个地区不同世代的种群,除个别温度外,南京种群的存活率、平均产卵量、内禀增长力、繁殖价大于衡阳种群;衡阳种群大于南宁种群,形成明显的纬度梯度.而同是第二世代,则三个地区种群这些参数差异不显著.对发育历期进行裂区试验的方差分析,种群间均无显著差异.可以用一个公共的发育速率模型.文中分析和讨论了形成种群间这些差异的原因,可能是种群的同型交配效应或迁飞的自然选择效应.     

亚洲玉米螟性体型二型性及幼虫发育历期与蛹重的关系

【目的】探明亚洲玉米螟不同地理种群性体型二型性及幼虫发育历期与蛹重的关系。【方法】在26℃,L︰D=16︰8条件下,详细记录了来自热带地区的海南省三亚种群,来自亚热带地区的广东省广州和江西省永修种群,及来自温带地区的河北廊坊种群的雌雄幼虫发育历期、蛹重、成虫重,并计算幼虫发育速率。【结果】不同地理种群的雌性个体均显著大于雄性个体。三亚种群雌雄个体的发育历期没有差异,但雌性的生长速率显著大于雄性个体;广州种群、永修种群及廊坊种群,雌雄的生长速率没有差异,但雌性幼虫的发育历期显著长于雄性幼虫。各地理种群蛹重随幼虫发育历期的延长呈下降趋势。【结论】亚洲玉米螟存在明显的性体型二型性,雌雄个体发育历期和生长速率存在地理差异。     

Life history traits of Aedes caspius (Diptera: Culicidae): a laboratory study of larval stages

The larval survival and development times of Aedes caspius (Diptera: Culicidae) were examined in the laboratory. These life history traits were estimated using life tables constructed for two populations, one of which had been subjected to a long-term larvicide control program. Traits were evaluated for eight different population densities. The effects of population, larval stage and larval density were investigated using a general linear model. Density was positively correlated with larval survival but did not affect development time. The fourth instar and pupae had the lowest larval survival rates. First and fourth instar larvae had the longest development times. These traits were not significantly different between the two populations. The effect of larvicide control on these traits is discussed.     

LARVAL ECOLOGY OF MARINE BENTHIC INVERTEBRATES: PALEOBIOLOGICAL IMPLICATIONS

1. Modes of larval development play important roles in the ecology, biogeography, and evolution of marine benthic organisms. Studies of the larval ecology of fossil organisms can contribute greatly to our understanding of such roles by allowing us to race effects on evolutionary time scales. 2. Modes of development can be inferred for well preserved molluscan fossils because the size of the initial larval shell (Protoconch I in gastropods, Prodissoconch I in bivalves) reflects egg size. Other morphological criteria are also available, and a comparative approach based on related taxa with known development may be the most reliable method. By combining larval and adult traits, it is possible to recognize modes of larval development in at least some fossil bryozoans, brachiopods, and echinoderms as well. (a) Planktotrophic larvae arise from small eggs, are released in enormous numbers with little parental investment per offspring, and suffer tremendous mortality during and shortly after a planktic existence. These larvae feed on the plankton during development, and are commonly capable of a prolonged free-swimming existence, and thus wide dispersal. (b) Nonplanktotrophic larvae (which include both planktic lecithotrophic forms and ‘direct developers’) generally arise from large eggs, with relatively few young produced per parent. Relative to planktotrophic larvae, nonplanktotrophic larvae generally receive greater parental investment per larva, and larval mortality is generally lower. These larvae rely on yolk for nutrition during development, and planktic durations are generally much briefer than for species with planktotrophic larvae, so that dispersal capability is considerably less. Energetic investment per egg is generally higher than in planktotrophs, but as there are lower fecundities as well it is difficult to generalize about the total energetic cost of one mode of reproduction against the other. 3. Owing to the high dispersal capability of planktotrophic larvae, it has been suggested that species with such larvae will be geographically widespread, geologically long-ranging, and exhibit low speciation and extinction rates. Species with nonplanktotrophic larvae will tend to be geographically more restricted, geologically short-ranging, and exhibit high speciation and extinction rates (again, as a consequence of their characteristically low larval dispersal capabilities). 4. Recognition of differential dispersal capabilities can play a role in paleobiogeo-graphic analyses. Concurrent study of the distribution of groups with contrasting modes of development will permit testing of hypotheses concerning timing, magnitudes and frequencies of migration and vicariance events. 5. Larval types are not randomly distributed in the oceans, but relationships with other aspects of the organisms' biology and habitats are very complex. Mode of development varies with: (a) Ecology. A simple r–––K model of adaptive strategies is clearly insufficient to explain the observed relationships: while many ‘equilibrium’ species have nonplanktotrophic larvae, and organisms living in less prdictable environments often have planktotrophic larvae, some of the most opportunistic marine species have nonplanktotrophic larvae. Nonetheless, planktotrophic development seems most suited for exploitation of patchy but widespread habitats. (b) Latitude. At shelf depths, planktotrophy is predominant in the tropics, and decreases sharply at high latitudes. (c) Depth. Incidence of planktotrophy decreases with depth across the continental shelf, at least in some taxa. Beyond the shelf, many deep-sea organisms are nonplanktotrophic (e.g. most bivalves, peracarid crustaceans), but planktotrophic development appears to be present in other groups (prosobranch gastropods, ophiuroids, and bivalves inhabiting transient habitats such as sunken wood and hydrothermal vents). These trends in developmental types will be accompanied by trends in evolutionary rates and patterns as outlined above. The study of larval ecology by paleobiologists will yield insights into the processes that gave rise to ancient evolutionary and biogeographic patterns, and will permit the development and testing of hypotheses on the origins of the patterns observed in modern seas.     

The development and mortality of the free-living stages of Haemonchus contortus in laboratory culture.

Haemonchus contortus eggs were cultured in intact fecal pellets at various temperatures (5-35 degrees C) for 22 days. Temperature and relative humidity were kept constant throughout the incubation period. Nl larval development occurred at 5 degrees C; peak third-stage larval recovery occurred at 20 degrees C. Egg mortality was an age-dependent phenomenon, whereas larval mortality remained constant irrespective of larval age. Development was characterized by a minimum development time followed by a transition to the next stage which occurred at a constant rate. All rates were temperature dependent. The minimum development times reported here are much less than those previously reported. Based on these results a mathematical model was used to describe the demography of the free-living stages of H. contortus at various temperatures.     

DEVELOPMENTAL CONSEQUENCES OF AN EVOLUTIONARY CHANGE IN EGG SIZE: AN EXPERIMENTAL TEST

Larvae of two species of sea urchins (Strongylocentrotus droebachiensis and S. purpuratus) differ in initial form and in the rate of development. To determine whether these differences are attributable to the large interspecific difference in egg size, we experimentally reduced egg size by isolating blastomeres from embryos. The rate of development of feeding larvae derived from isolated blastomeres was quantified using a novel morphometric method. If the differences early in the life histories of these two species are due strictly to differences in egg size, then experimental reduction of the size of S. droebachiensis eggs should yield an initial larval form and rate of development similar to that of S. purpuratus. Our experimental manipulations of egg size produced three clear results: 1) smaller eggs yielded larvae that were smaller and had simpler body forms, 2) smaller eggs resulted in slower development through the early feeding larval stages, and 3) effects of egg size were restricted to early larval stages. Larvae from experimentally reduced eggs of the larger species had rates of development similar to those of the smaller species. Thus, cytoplasmic volumes of the eggs, not genetic differences expressed during development, account for differences in larval form and the rate of form change. This is the first definitive demonstration of the causal relationship between egg size (parental investment per offspring) and life-history characteristics in marine benthic invertebrates. Because larval form influences feeding capability, the epigenetic effects of egg size on larval form are likely to have important functional consequences. Adaptive evolution of egg size may be constrained by the developmental relationships between egg size and larval form: evolutionary changes in egg size alone can result in concerted changes in larval form and function; likewise evolutionary changes in larval form and function can be achieved through changes in egg size. These findings may have broader implications for other taxa in which larval morphology and, consequently, performance may be influenced by changes in egg size.     

Density‐dependent natural selection in Drosophila: correlations between feeding rate,development time and viability

We have previously hypothesized that density‐dependent natural selection is responsible for a genetic polymorphism in crowded cultures of Drosophila. This genetic polymorphism entails two alternative phenotypes for dealing with crowded Drosophila larval cultures. The first phenotype is associated with rapid development, fast larval feeding rates but reduced absolute viability, especially in the presence of nitrogenous wastes like ammonia. The second phenotype has associated with it the opposite set of traits, slow development, slow feeding rates and higher viability. We suggested that these traits are associated due to genetic correlations and that an important selective agent in crowded larval cultures was high levels of ammonia. To test this hypothesis we have examined viability and larval feeding rates in populations kept at low larval densities but selected directly for (i) rapid egg‐to‐adult development, (ii) tolerance of ammonia in the larval environment and (iii) tolerance of urea in the larval environment. Consistent with our hypothesis we found that (i) larvae selected for rapid development exhibited increased feeding rates, and decreased viability in food laced with ammonia or urea relative to controls, and (ii) larvae selected to tolerate either ammonia or urea in their larval environment show reduced feeding rates but elevated survival in toxin‐laced food relative to controls. It would appear that development time and larval feeding rate are important characters for larvae adapting to crowded cultures. The correlated fitness effects of these characters provide important insights into the nature of density‐dependent natural selection.     

SOIL AERATION AND THE EMERGENCE OF LARVAE FROM CYSTS OF THE BEET EELWORM, HETERODERA SCHACHTII SCHM

Moisture content, pore size, depth and oxygen consumption in the soil, which influence soil aeration, have been studied in relation to larval emergence from cysts of the beet eelworm. Experiments show that the rate of larval emergence increases with aeration. In studies of larval emergence in the field emphasis should be laid on soil structure rather than on a mechanical analysis. Those factors associated with good soil tilth favour high rates of larval emergence.     

THE EVOLUTION OF DEVELOPMENT IN DROSOPHILA MELANOGASTER SELECTED FOR POSTPONED SENESCENCE

The role of development in the evolution of postponed senescence is poorly understood despite the existence of a major gerontological theory connecting developmental rate to aging. We investigate the role of developmental rate in the laboratory evolution of aging using 24 distinct populations of Drosophila melanogaster. We have found a significant difference between the larval developmental rates of our Drosophila stocks selected for early (B) and late-life (O) fertility. This larval developmental time difference of approximately 12% (O > B) has been stable for at least 5 yr, occurs under a wide variety of rearing conditions, responds to reverse selection, and is shown for two other O-like selection treatments. Emerging adults from lines with different larval developmental rates show no significant differences in weight at emergence, thorax length, or starvation resistance. Long-developing lines (O, CO, and CB) have greater survivorship from egg to pupa and from pupa to adult, with and without strong larval competition. Crosses between slower developing populations, and a variety of other lines of evidence, indicate that neither mutation accumulation nor inbreeding depression are responsible for the extended development of our late-reproduced selection treatments. These results stand in striking contrast to other recent studies. We argue that inbreeding depression and inadvertent direct selection in other laboratories' culture regimes explain their results. We demonstrate antagonistic pleiotropy between developmental rate and preadult viability. The absence of any correlation between longevity and developmental time in our stocks refutes the developmental theory of aging.     

EVOLUTIONARY LOSS OF LARVAL FEEDING: DEVELOPMENT,FORM AND FUNCTION IN A FACULTATIVELY FEEDING LARVA,BRISASTER LATIFRONS

Species with large eggs and nonfeeding larvae have evolved many times from ancestors with smaller eggs and feeding larvae in numerous groups of aquatic invertebrates and amphibians. This change in reproductive allocation and larval form is often accompanied by dramatic changes in development. Little is known of this transformation because the intermediate form (a facultatively feeding larva) is rare. Knowledge of facultatively feeding larvae may help explain the conditions under which nonfeeding larvae evolve. Two hypotheses concerning the evolutionary loss of larval feeding are as follows: (1) large eggs evolve before modifications in larval development, and (2) the intermediate form (facultatively feeding larva) is evolutionarily short-lived. I show that larvae of a heart urchin, Brisaster latifrons, are capable of feeding but do not require food to complete larval development. Food for larvae appears to have little effect on larval growth and development. The development, form, and suspension feeding mechanism of these larvae are similar to those of obligate-feeding larvae of other echinoids. Feeding rates of Brisaster larvae are similar to cooccurring, obligate-feeding echinoid larvae but are low relative to the large size of Brisaster larvae. The comparison shows that in Brisaster large egg size, independence from larval food, and relatively low feeding rate have evolved before the heterochronies and modified developmental mechanisms common in nonfeeding echinoid larvae. If it is general, the result suggests that hypotheses concerning the origin of nonfeeding larval development should be based on ecological factors that affect natural selection for large eggs, rather than on the evolution of heterochronies and developmental novelties in particular clades. I also discuss alternative hypotheses concerning the evolutionary persistence of facultative larval feeding as a reproductive strategy. These hypotheses could be tested against a phylogenetic hypothesis.     

Modeling the effects of environmental variability on Balanus glandula larval development

Planktonic larvae encounter variability in the marine environmentas they develop, and rates of larval development are affectedby changes in certain environmental variables. We examine theeffects of variation in environmental parameters on the durationof the naupliar period of Balanus glandula larvae. Naupliardevelopment rate is modeled as a function of temperature andfood concentration. Simulations of the time course of developmentwere driven by time series of temperature and food concentrationcollected at two locations on the US west coast. Predicted naupliardurations are reasonable in comparison to previous observations.Simulations of larval development and dispersal were drivenby output of a three-dimensional physical circulation modeland remotely sensed chlorophyll. These simulations demonstratethe impact of spatial variation in current velocity, temperatureand chlorophyll on the duration of the larval period, the dispersaltrajectory of these organisms and ultimately on recruitmentsuccess. Our naupliar development model coupled with a physicalcirculation model is a useful tool for addressing questionsof intertidal population ecology.