致倦库蚊实验种群动态研究

本文应用考虑年龄——龄期及雌雄性的生命表方法和传统的生命表方法计算,分析了致倦库蚊实验种群在温度为25℃条件下的种群增长参数,稳定年龄——龄期分布情况。在生命表分析的基础上,用转移矩阵模拟了致倦库蚁数量变动的规律。     

珍稀濒危植物桫椤种群生命过程及谱分析

根据种群生命表和生存分析理论,以高度级为基础编制了桫椤种群特定时间生命表,绘制了生存函数曲线,分析了种群的生命过程.结果表明:桫椤种群结构为前期增长、后期稳定类型.生命期望在第4龄级最大,此阶段种群生存质量相对较高.种群存活曲线属于典型的Deevey-Ⅲ型.种群生命过程有3个死亡高峰期,分别是第2龄级向第3龄级、第10龄级向第11龄级和第12龄级向第13龄级生长阶段.种群存活率随龄级增加呈单调减少,相应的积累死亡率呈单调增加,变动幅度为前期大、后期小;死亡密度函数曲线呈现前期下降、后期平缓稳定的特点,凹点出现于第4龄级.谱分析结果显示,桫椤种群数量波动性是大周期内有小周期的多谐波迭加,各周期作用基本上随周期的缩短而减小,基波的影响最显著.     

运用年龄-龄期两性生命表模拟昆虫种群动态及其在害虫治理中的应用

计算机模拟昆虫的种群数量动态变化对于昆虫种群预测和害虫治理十分重要。本文介绍以年龄-龄期两性生命表(age-stage, two-sex life table)为基础，利用计算机模拟预测昆虫的种群动态、种群捕食、寄生和取食的波动、害虫防治时机以及模拟的变异性。利用年龄-龄期两性生命表软件(程式)TWOSEX-MSChart与捕食率软件CONSUME-MSChart分析生命表与捕食率数据，再将分析结果用模拟软件TIMING-MSChart模拟预测种群增长过程中龄期结构以及捕食能力、寄生能力和取食能力的变化。依据种群动态可以预测害虫危害、天敌捕食、寄生蜂寄生能力，再用这些数据确定杀虫剂的施药时机和施药次数，预测生物防治中天敌释放的适当时机、释放数量和释放次数等；同时还可以依据生命表的变异性，利用自我重复取样(bootstrap)技术得到的2.5和97.5百分位(percentiles)或其他百分位的生命表预测种群增长的不确定性。借助基于两性生命表理论的计算机模拟可以预测害虫种群增长以及化学防治和生物防治的最佳时期，以达到经济有效的害虫综合治理，并为农业可持续性提供理论与技术支撑。     

年龄-龄期两性生命表及其在种群生态学与害虫综合治理中的应用

生命表是种群生态学与害虫治理的重要工具,由于传统雌性生命表无法正确描述昆虫的变态且忽略雄性个体,近年来国内外学者普遍采用年龄-龄期两性生命表。本文首先从昆虫种群的龄期分化、性比对种群增长的影响、总产卵前期与成虫产卵前期的差异、产卵期与产卵日数的差异4个方面概述了年龄-龄期两性生命表(age-stage, two-sex life table)的基本原理,进而阐明了基于bootstrap技术的生命表分析技术及其主要优点,然后介绍了年龄-龄期两性生命表各软件(TWOSEX-MSChart, CONSUME-MSChart, TIMING-MSChart)的主要用途,即预测种群的增长与防治适期、正确分析天敌的捕食率与害虫的取食量、预测天敌的种群增长与捕食潜能以及指导天敌的大量繁育。昆虫生命表作为一种强有力的分析技术,不仅在研究种群生态学和害虫治理方面已有广泛的应用,展望未来,这项技术还可以用于昆虫生理、抗药性、亚致死剂量、共生菌等方面的研究。     

长瓣杓兰（Cypripedium lentiginosum）种群数量动态与生殖行为的相关性

尽管种群数量动态分析已广泛应用于濒危物种,但很少应用于中国兰科植物.根据中国云南特有的兰科物种长瓣杓兰(Cypnpedium lentiginosum)的生物学特征调查和生殖行为观察,计算出其各龄级的存活数、出现频率和子代数,描述其生殖行为和机制.利用基株出现频率计算其空间分布格局;利用其各龄级的存活数和平均生产子代数编制种群静态生命表和生殖力表、绘制存活曲线和年龄锥体,构建Leslie矩阵模型和连续增长模型N1=658e0.211t对种群数量动态过程进行预测;利用物候特征和传粉生物学观察结果分析其生殖行为和繁殖策略.在此基础上分析其生殖行为与其空间格局、年龄锥体和种群数量动态的关系.结果表明:长瓣杓兰的空间结构为成群分布,种群的年龄锥体属于金字塔-钟型锥体,种群存活表现为Deevey Ⅰ型;其种群的净增长率、内禀增长率和周限增长率较高,为增长型种群;种群增长受自身密度影响,连续增长模型不适用该种群的动态预测;引入密度制约因子构建的预测模型Nt=6000/(1 e2.094-0.211t)适用于其种群数量动态预测.长瓣杓兰的生殖行为表现在兼具无性繁殖和有性繁殖,无性繁殖不增加种群的个体数量,仅延续基株的寿命以维持现行种群数量和为有性生殖积累营养.有性繁殖通过花模拟繁殖地欺骗食蚜蝇进入唇瓣而传粉,致使54.37%±6.08%的花产生果实,果实产生充足幼龄植株并多数能进入有性繁殖阶段.有性繁殖在很长的一段时期多次生殖后代而成为种群发展的基础,显示出繁殖方式是影响种群数量动态变化的主要因素.其成功的生殖对策和这种对策在空间格局、年龄锥体上对种群数量动态的影响具有密切的相关性,表明长瓣杓兰的种群发展与其生物学特性相吻合,适生地的生长空间不连续性和狭窄成为其种群发展的制约因素,但该物种现在不需要也不适宜进行迁地保护.     

基于特定时间调查数据组建的白蜡窄吉丁种群生命表

为了探明影响白蜡窄吉丁Agrilus planipennis Fairmaire自然种群变化的关键因子, 本研究于2010-2011年采用当年秋季和翌年春季两个特定时间调查取样的方法, 组建了天津、 北京和辽宁3个地区白蜡窄吉丁的自然种群生命表。结果显示, 这3个地区白蜡窄吉丁的自然种群数量在今后几年均将呈增长趋势, 但不同地区的增长速率存在较大差异。北京地区白蜡窄吉丁的种群数量增长速率最快（种群趋势指数I=12.9997）, 其次是天津地区（I=12.4388）, 这两个地区的寄主植物相同, 均为绒毛白蜡。增长最慢的是辽宁地区（I=3.6394）, 其寄主植物为水曲柳。另外, 通过3个地区白蜡窄吉丁生命表和排除控制指数可以看出, 天津地区白蜡窄吉丁最主要的致死因子是白蜡吉丁柄腹茧蜂Spathius agrili Yang（种群数量排除控制指数EIPC=1.5382）, 对种群数量变动的贡献最大; 北京地区的是啄木鸟（EIPC=1.4515）, 而辽宁地区白蜡窄吉丁最主要的致死因子是白蜡吉丁卵跳小蜂Oobius agrili Zhang et Huang的寄生作用（EIPC=1.4701）。这些研究结果表明, 寄主植物的差异是影响白蜡窄吉丁自然种群数量变动的主要因素, 同时寄生性天敌白蜡吉丁柄腹茧蜂对种群数量的影响作用也比较大。因此, 实际应用中可以通过培育抗性树种和人工繁育优势天敌等方法对该虫进行有效防治。     

天目山自然保护区银杏天然种群生命表

以种群生命表和生存分析理论为基础,采用空间代替时间法和分段匀滑技术,编制浙江天目山自然保护区银杏天然种群特定时间生命表,绘制其死亡率曲线、消失率曲线、存活曲线和生存函数曲线,分析种群数量动态变化.结果表明:银杏种群结构存在波动性,趋于Deevey Ⅱ型,其成年阶段的个体较丰富;银杏种群死亡率和消失率曲线变化趋势基本一致...     

三化螟生命表的初报

<正> 生命表作为昆虫种群数量动态的研究,近年来已成为一种有效的手段。近年来由于水稻改制和品种等关系,三化螟Tryporyza incertulas(Walker)危害日益严重,有必要深入地掌握其种群数量动态,分析其主导因素,以便准确地进行数量预测,并提出合理可行的防治策略。为此,作者(黄)于1965、1966两年在广东湛江地区遂溪城月观察了三化螟的种群数量变动,共得生命表9个;1979年又在广东四会县大旺华侨农场观察了一年,又得生命表2个,现作如下初步报道。 一、第一代生命表的初步分析 1965、1966两年所得第一代生命表见表1。     

武夷山米槠种群结构及谱分析

在武夷山自然保护区对米槠种群数量动态进行了系统研究,编制了静态生命表,分析了存活曲线和死亡曲线,同时应用谱分析方法分析种群数量的动态变化。结果表明,武夷山自然保护区米槠种群基本属于进展型或稳定型,幼龄级个体多,中老龄级个体少。不同海拔的种群密度存在差异,其中C种群密度最大;静态生命表显示,种群在Ⅰ、Ⅱ径级时死亡率较高,随着年龄增加,死亡率逐渐降低,但到了Ⅳ、Ⅴ径级,由于生理衰老死亡率又上升;种群期望寿命在Ⅰ、Ⅱ径级较高,随着年龄增加,期望寿命逐渐下降;不同海拔的米槠种群的存活曲线均接近于Deevey Ⅲ 型。米槠种群自然更新过程存在明显的周期。     

濒危植物连香树种群结构与动态研究

以空间代替时间的方法调查了喇叭河自然保护区和宝兴县两个地区连香树种群的结构.绘制大小结构图,编制静态生命表,绘制存活曲线、消失率曲线和死亡率曲线,并进行种群动态谱分析.结果表明:两个地区连香树种群幼苗个体比例都比较大,但死亡率很高;存活曲线介于Deevey Ⅰ型和DeeveyⅡ型之间;消失率和死亡率曲线变化趋势一致;种群动态过程存在周期性,种群数量动态不仅受基波的影响,而且还显示出了小周期的波动.     

Population dynamics as related to rate of increase per generation

Summary Inflection points in animal population growth curves (expressed as a fraction of equilibrium population levels) are correlated with rates of increase per generation. The inflection point declines with increasing rates of increase per generation. This apparent unifying principle of population dynamics is independent of phenomena related to body size since the rate of increase per generation is not correlated with body size. Species as diverse as whales and bacteria appear to conform to the pattern. More studies of the observed relationships are to be encouraged.     

Generalized aphid population growth models with immigration and cumulative-size dependent dynamics

Mechanistic models in which the per-capita death rate of a population is proportional to cumulative past size have been shown to describe adequately the population size curves for a number of aphid species. Such previous cumulative-sized based models have not included immigration. The inclusion of immigration is suggested biologically as local aphid populations are initiated by migration of winged aphids and as reproduction is temperature-dependent. This paper investigates two models with constant immigration, one with continuous immigration and the other with restricted immigration. Cases of the latter are relatively simple to fit to data. The results from these two immigration models are compared for data sets on the mustard aphid in India.     

Direct estimates of multi-mesh gillnet selectivity to Oreochromis shiranus chilwae

The selectivity of multi-mesh monofilament nylon gillnets to Oreochromis shiranus chilwae was estimated directly by gillnetting in a small reservoir containing a population marked by size class. Numbers in each size class were estimated using the adjusted Petersen estimate. Pearson Type I curves were fitted to plots of selectivity against the fish length/mesh perimeter ratio, for two modes of capture: wedging and tangling. The generality of the selectivity curves is tested and discussed. The tangling component of the selectivity was unimportant, and for many applications the selectivity curves may be approximated by normal curves obtainable through indirect methods. However, the increase in the amplitude of the curves with mesh size, deserves further study.     

Cell population dynamics during the differentiative phase of tissue development

The dynamics of a cell population whose numbers are growing exponentially have been described well by a mathematical model based on the theory of age-dependent branching processes. Such a model, however, does not cover the period following exponential growth when cell differentiation curtails population size. This paper offers an extension to the branching process model to remedy this deficiency. The extended model is ideal for describing embryonic growth; its use is illustrated with data from embryonic retina. The model offers a better computational framework for the interpretation of a variety of data (growth curves of cell numbers, DNA histograms, thymidine labelling indices, FLM curves, BUdR-labelled mitoses curves) because age-distributions can be calculated at any stage of development, not just during exponential growth. Proportions of cells in the various phases of the cell cycle can be computed as growth slows. Such calculations show the gradual transition from a population dominated by cells which are young with respect to cell cycle age to one dominated by those which are old, and the effects such biases have on the proportions of cells in each phase.     

Inferring number of populations and changes in connectivity under the n-island model

Inferring the demographic history of species is one of the greatest challenges in populations genetics. This history is often represented as a history of size changes, ignoring population structure. Alternatively, when structure is assumed, it is defined a priori as a population tree and not inferred. Here we propose a framework based on the IICR (Inverse Instantaneous Coalescence Rate). The IICR can be estimated for a single diploid individual using the PSMC method of Li and Durbin (2011). For an isolated panmictic population, the IICR matches the population size history, and this is how the PSMC outputs are generally interpreted. However, it is increasingly acknowledged that the IICR is a function of the demographic model and sampling scheme with limited connection to population size changes. Our method fits observed IICR curves of diploid individuals with IICR curves obtained under piecewise stationary symmetrical island models. In our models we assume a fixed number of time periods during which gene flow is constant, but gene flow is allowed to change between time periods. We infer the number of islands, their sizes, the periods at which connectivity changes and the corresponding rates of connectivity. Validation with simulated data showed that the method can accurately recover most of the scenario parameters. Our application to a set of five human PSMCs yielded demographic histories that are in agreement with previous studies using similar methods and with recent research suggesting ancient human structure. They are in contrast with the view of human evolution consisting of one ancestral population branching into three large continental and panmictic populations with varying degrees of connectivity and no population structure within each continent.Subject terms: Population genetics, Biological models, Population genetics     

Numerical Equilibrium Analysis for Structured Consumer Resource Models

In this paper, we present methods for a numerical equilibrium and stability analysis for models of a size structured population competing for an unstructured resource. We concentrate on cases where two model parameters are free, and thus existence boundaries for equilibria and stability boundaries can be defined in the (two-parameter) plane. We numerically trace these implicitly defined curves using alternatingly tangent prediction and Newton correction. Evaluation of the maps defining the curves involves integration over individual size and individual survival probability (and their derivatives) as functions of individual age. Such ingredients are often defined as solutions of ODE, i.e., in general only implicitly. In our case, the right-hand sides of these ODE feature discontinuities that are caused by an abrupt change of behavior at the size where juveniles are assumed to turn adult. So, we combine the numerical solution of these ODE with curve tracing methods. We have implemented the algorithms for “Daphnia consuming algae” models in C-code. The results obtained by way of this implementation are shown in the form of graphs.     

Inference of past population expansion from the timing of coalescence events in a gene genealogy

We investigate the expected coalescent in populations growing exponentially. The distribution of expected times to coalescence events may show a linear relationship with a number of ancestral lineages, when the latter is subjected to the "epidemic transformation". However, in a number of viral populations, upward curves are created when the epidemically transformed number of ancestral lineages is plotted against time. We consider possible causes of such upward curves. These include the possibility that a curved line is created through a transformation failure due to a sample size that is too large. We suggest a new formula for predicting such failure. The second cause is a population size increasing at an accelerating rate. However, the combination of recent coalescent events and an upward curve is created by an accelerating population increase only under restricted conditions. Specifically, such a pattern is expected only when, were population growth not to have accelerated, the transformation would have failed anyway. The third cause of nonlinearity arises in the estimated coalescent, as distinct from the real coalescent, if the mutation rate is small. However, coalescence times estimated from data typically give a straight line following epidemic transformation, but the rate of exponential increase, or r value, will be underestimated.     

小陇山国家级自然保护区华山松种群更新动态分析

以种群生命表及生存分析理论为基础,将林木依胸径大小分级,以林木径级结构代替年龄结构,采用分段匀滑技术编制小陇山国家级自然保护区华山松种群静态生命表,对其种群年龄结构、死亡率曲线、损失度曲线、存活曲线、生存函数曲线及其幼苗的更新动态、死亡率和原因进行分析。结果表明:该种群属于增长型,表现出前期增长,中期稳定,后期衰退的特点;该种群的整个生命过程,显示了三次死亡高峰,其中幼苗死亡率较高,以后的死亡率低而平缓,符合种群的自然动态规律,也指出"天保工程"实施的意义和效果;该研究指示了华山松的动态以及种群的变化趋势,对保护区已经实施的生态监测和森林保护有着十分重要的意义。     

Survey of elephant damage to baobabs in Tanzania's Lake Manyara National Park

This 1981 survey assesses elephant-induced bark damage and mortality in the population of baobab trees at Lake Manyara National Park. Comparisons are made with a similar survey conducted there in 1969. The age structure of the baobab population is estimated and linear and exponential survivorship curves are calculated. Damage and mortality increased over the 11 year interval but the basic form of the population age structure remained unchanged. Damage was found to increase while mortality decreased with tree size. Both damage and mortality are lower in the southern part of the park where the trees are less accessible to elephants. The recorded mortality was higher than expected values taken from the calculated survivorship curves but lower than mortalities in other parks where baobabs and elephants have been found together at high densities.     

黄山松种群结构与动态研究

以“空间代替时间”的方法,以种群径级结构代替年龄结构,采用静态生命表和生存分析的方法,探讨了天柱山国家森林公园黄山松种群结构和动态规律。结果表明,随海拔升高,黄山松种群密度增大,径级分布范围减小,种群存活曲线由Deevey-Ⅱ型之间过渡到Deevey—Ⅰ型,种群由稳定型过渡为增长型。表明由低海拔向高海拔,黄山松种群处于不同的演替和发展阶段。