2008年永福县早稻田稻纵卷叶螟发生动态及虫源性质

2008年通过调查和雌蛾卵巢解剖研究广西区永福县早稻田稻纵卷叶螟Cnaphalocrocis medinalis(Guenée)的发生动态和田间种群的虫源性质。结果表明,稻纵卷叶螟在永福县早稻田可发生4代。稻纵卷叶螟第1、2代属于基本迁入型;第3代性质较为复杂,属于本地繁殖型,既有迁入又有迁出;第4代为本地繁殖、大部分迁出型。对暴雨期间稻纵卷叶螟田间蛾量消长的研究表明,短时期的暴雨水淹对全县稻纵卷叶螟的田间蛾量消长总的影响不明显,但不同水淹情况的田块间虫量存在显著差异。还分析讨论2008年永福县早稻田稻纵卷叶螟暴发成灾的原因。     

2010年广西兴安地区稻纵卷叶螟发生动态及迁飞轨迹分析

稻纵卷叶螟是我国水稻上的重要害虫,近年来给我国水稻生产造成严重的损失。兴安地区位于广西东北部是每年稻纵卷叶螟在我国南北往返的必经之路,分析该地区稻纵卷叶螟的种群动态和迁飞规律,对全国稻纵卷叶螟的预测预报和防治工作意义重大。采用灯光诱捕、田间系统调查与雌蛾卵巢解剖的方法研究了2010年广西兴安地区稻纵卷叶螟的发生动态和世代虫源性质,并运用大气质点轨迹分析平台HYSPLIT和气象图形处理软件GrADS对2010年广西兴安地区稻纵卷叶螟迁飞高峰期进行了迁飞轨迹和气象背景分析。结果表明:(1)稻纵卷叶螟种群数量在广西兴安地区随季节变化明显,年发生6代,于4月底迁入,迁飞活动主要集中在5月下旬-8月中旬。在双季早稻田、单季中稻田和双季晚稻田均发生3代,且在不同类型田中重叠发生,其在双季早稻田的发生量明显高于单季中稻田和双季晚稻田。(2)明确了兴安地区稻纵卷叶螟各世代虫源性质。第2、3代主害双季早稻,均为迁入虫源;第4代数量最多,主害双季早稻,属于迁入虫源在本地繁殖世代;7月中下旬连续降雨天气阻碍第四代稻纵卷叶螟从本地迁出,滞留单季中稻为害。第5代主害单季中稻,虫源性质复杂,主要为本地虫源本地繁殖型,既有迁入,又有迁出;第6代前期主害单季中稻,后期主害双季晚稻,第7代为害双季晚稻,虫源性质均为本地虫源大部迁出型。(3)2010年广西兴安5月上旬稻纵卷叶螟迁入虫源地来自广东沿海阳江和湛江稻区,6月中旬大规模迁入虫源地主要来自广东沿海雷州半岛稻区。低空激流为稻纵卷叶螟的迁入提供了运载气流,而当时的降雨是迫使稻纵卷叶螟集中降落的主要原因。10月中旬从本地迁出的稻纵卷叶螟,随东北气流南下可到达广西沿海北海市。     

稻纵卷叶螟(Cnaphalocrocis medinalis(Güenée))在水稻品种上的半自然种群生命表参数及对植株含糖量的影响

在排除天敌情况下,用生命表方法比较了稻纵卷叶螟在5个常用栽培水稻品种扬粳9538、淮稻9号、扬辐粳8号、扬稻6号和汕优63上的半自然种群生命表。结果表明,取食淮稻9号的稻纵卷叶螟种群趋势指数最低,表现为较强的抗耐性;扬辐粳8号的稻纵卷叶螟种群趋势指数最高;各品种间稻纵卷叶螟不同虫期的存活率、♀/♂、蛹重、产卵量、卷叶率有一定差异;稻纵卷叶螟为害后,植株内可溶性糖含量品种间无明显差异,但不同品种与对照(未接虫)相比含量有增有减;还原糖含量品种间差异显著。     

稻纵卷叶螟(Cnaphalocrocis medinalis(Gene))在水稻品种上的半自然种群生命表参数及对植株含糖量的影响

在排除天敌情况下,用生命表方法比较了稻纵卷叶螟在5个常用栽培水稻品种扬粳9538、淮稻9号、扬辐粳8号、扬稻6号和汕优63上的半自然种群生命表。结果表明,取食淮稻9号的稻纵卷叶螟种群趋势指数最低,表现为较强的抗耐性;扬辐粳8号的稻纵卷叶螟种群趋势指数最高;各品种间稻纵卷叶螟不同虫期的存活率、♀/♂、蛹重、产卵量、卷叶率有一定差异;稻纵卷叶螟为害后,植株内可溶性糖含量品种间无明显差异,但不同品种与对照(未接虫)相比含量有增有减;还原糖含量品种间差异显著。     

寄主转换对稻纵卷叶螟寄主种群适合度及生命表参数的影响

【目的】稻纵卷叶螟Cnaphalocrocis medinalis是水稻的迁飞性害虫之一,同时也能在玉米上完成世代。本研究旨在探究寄主转换对稻纵卷叶螟寄主种群适合度的影响。【方法】稻纵卷叶螟玉米种群和水稻种群分别取食原寄主和转换寄主,形成取食玉米的稻纵卷叶螟玉米种群、取食水稻的稻纵卷叶螟玉米种群、取食玉米的稻纵卷叶螟水稻种群和取食水稻的稻纵卷叶螟水稻种群4个处理组合,构建这些处理组合的稻纵卷叶螟寄主种群年龄 龄期两性生命表,测定其适合度和生命表参数。【结果】稻纵卷叶螟幼期发育历期以取食水稻的稻纵卷叶螟水稻种群最长(29.2 d),以取食水稻的稻纵卷叶螟玉米种群最短(24.8 d);适合度指标(蛹重、化蛹率、羽化率、产卵量)、生命表参数(存活率、最大繁殖力、最高繁殖值、幼期寿命期望值)、种群参数(内禀增长率、周限增长率、净增殖率)均在两种群取食玉米时最大,在取食水稻的稻纵卷叶螟玉米种群中最小(除蛹重外),而且取食玉米的稻纵卷叶螟水稻种群又往往优于取食水稻的稻纵卷叶螟水稻种群。【结论】稻纵卷叶螟玉米种群在寄主转换后适合度和种群增长显著下降,而稻纵卷叶螟水稻种群在寄主转换后适合度和种群增长有所上升,表明玉米比水稻更有利于提高稻纵卷叶螟的适合度和种群增长,这一与自然条件下稻纵卷叶螟极少在玉米上发生为害相悖的现象值得深入研究。     

东亚夏季风进退对我国南方水稻主产区稻纵卷叶螟发生的影响

为了探明东亚季风对我国南方水稻主产区稻纵卷叶螟迁飞的影响,为中短期预警提供科学依据,利用2000—2016年中国稻纵卷叶螟赶蛾量数据,结合NECP气象再分析资料,分析了东亚夏季风进退与我国南方水稻主产区稻纵卷叶螟迁飞的关系,结果表明:(1)稻纵卷叶螟的初始迁入与东亚夏季风的向北推进密切相关,除华南稻区稻纵卷叶螟迁入始期提前于东亚夏季风北界经过该区的时间外,在其他稻区两者基本同步;东亚夏季风北边界在不同稻区首次和二次出现的早晚对该稻区稻纵卷叶螟的向北迁入的始期具有一定的指示意义。(2)各稻区北迁的高峰期一般都发生在东亚夏季风控制范围内,其中6月中旬—8月上旬东亚夏季风活动范围到达30°N以北地区,此时是我国南方稻区稻纵卷叶螟北迁峰次最多、迁入量最集中的时期;东亚夏季风北界在本30°N以北地区持续时间的长短与稻纵卷叶螟年发生程度呈显著的正相关。(3) 8月中下旬是东亚冬、夏季风的转换期,也是稻纵卷叶螟种群的"混合迁"发生期,此时,西南稻区和江淮稻区北部迎来初次南迁峰;9月后东亚夏季风开始南撤,东北冬季风快速南下,稻纵卷叶螟种群也随之不断向南迁飞。(4)2007年稻纵卷叶螟在江淮稻区特大爆发的大气背景是:6月末—7月的强西南季风使沿江稻区迁入虫量比常年显著增加,也为7月下旬至8月下旬稻纵卷叶螟大规模向江淮稻区迁入奠定了虫源基础;7月份江南、华南地区的降水异常偏少使喜湿的稻纵卷叶螟种群进一步向沿江和江淮地区聚集;8月份东亚夏季风的回撤偏晚以及9月份华北地区和江淮地区北部的相对偏暖,使江淮稻区稻纵卷叶螟种群在当地滞留时间偏长、南迁起始期和高峰期异常偏晚。     

稻纵卷叶螟（Cnaphalocrocis medinalis（Güenée））在水稻品种上的半自然种群生命表参数及对植株含糖量的影响

在排除天敌情况下,用生命表方法比较了稻纵卷叶螟在5个常用栽培水稻品种扬粳9538、淮稻9号、扬辐粳8号、扬稻6号和汕优63上的半自然种群生命表。结果表明,取食淮稻9号的稻纵卷叶螟种群趋势指数最低,表现为较强的抗耐性;扬辐粳8号的稻纵卷叶螟种群趋势指数最高;各品种间稻纵卷叶螟不同虫期的存活率、♀／♂、蛹重、产卵量、卷叶率有一定差异;稻纵卷叶螟为害后,植株内可溶性糖含量品种间无明显差异,但不同品种与对照（未接虫）相比含量有增有减;还原糖含量品种间差异显著。     

两种组建稻纵卷叶螟种群生命表方法的比较

本文从1987～1988年在江苏句容,1988年在广东阳江海陵对稻纵卷叶螟自然种群采用系统调查法和分段接虫法比较了各组分的种群控制指数(Index of Population Control,IPC),初步的结果认为分段接虫法对捕食作用的估计明显偏大。在稻纵卷叶螟自然种群数量动态研究中拟采用系统调查法辅以天敌排除法测定自然存活率组建生命表为好。     

迁飞性害虫稻纵卷叶螟成虫的卵巢发育与性诱剂诱捕

【目的】迁飞性昆虫的生理发育比较复杂,这影响了其对性诱剂的行为反应,造成了田间性诱效果的较大波动。本研究旨在明确性诱剂诱捕对不同迁飞时期田间稻纵卷叶螟Cnaphalocrocis medinalis种群的监测效果以及性诱剂诱捕与雌蛾卵巢发育之间的关系。【方法】从2015年9月开始,在浙江宁波和温州、广西宾阳及江西宁都4地,利用性诱剂和网捕法监测稻纵卷叶螟田间种群动态。解剖雌性卵巢并拍摄卵巢分级特征图。利用双变量相关性分析性诱剂诱集和雌蛾卵巢发育之间的相关性。【结果】2016年6月下旬-7月中旬宾阳县稻纵卷叶螟为迁出代和本地繁殖代的混合种群,各级别卵巢均能解剖到,但是Ⅰ-Ⅱ级卵巢的比例最高;7月上旬宁都县稻纵卷叶螟为迁入代,卵巢以Ⅳ级为主(70%),雌蛾交配率达91.3%;9月下旬宁波北仑稻纵卷叶螟为迁出代,虫量逐渐减少至消失,卵巢处于未成熟状态,无交配发生;10月上旬温州市瓯海区稻纵卷叶螟为宁波南迁代的过境代,卵巢以Ⅱ和Ⅲ级为主,部分雌蛾完成交配,但未见雌蛾产卵。对于迁入代、过境代和本地繁殖代,网捕法和性诱法对种群动态的监测结果类似。对于迁出代,由于成虫未性成熟,性诱法不能引诱到雄蛾,但能网捕到大量成虫。相关性分析表明,对于迁入代、过境代和本地繁殖代性诱剂引诱的雄蛾数量与网捕成虫数量、网捕性成熟雌蛾数量之间均存在显著相关(P0.05),其中与后者之间的相关性达到极显著水平(P0.001)。【结论】性诱集可以用于准确监测迁入代、过境代和本地繁殖代田间稻纵卷叶螟种群动态。由于性诱剂监测的种群数量与稻纵卷叶螟的卵巢发育级别极显著相关,在进行防治适期或发生量预测时,性诱法可能比田间赶蛾法更有利于指导防治措施的实施。     

扬州邗江地区稻纵卷叶螟发生动态及影响因素分析

稻纵卷叶螟Cnaphalocrocis medinalis是扬州邗江地区重要的水稻害虫之一,具有远距离迁飞特性,且长期以来给本地区水稻安全生产带来了巨大威胁.为了明确扬州邗江地区稻纵卷叶螟的田间种群动态,本研究通过田间系统调查发现2010-2020年间稻纵卷叶螟四(2)代为害较轻,五(3)代和六(4)代仍是主害代.四(2)代只有在2010年和2013年形成了明显的高峰,而五(3)代和六(4)代可以形成明显的蛾蜂,且蛾高峰期持续天数均达到了 23 d及以上.五(3)代稻纵卷叶螟产卵高峰期田间虫(卵)量与发生程度正相关,但六(4)代稻纵卷叶螟的相关性较差.对本地区影响稻纵卷叶螟发生原因进行分析发现:月平均温度与五(3)代稻纵卷叶螟的发生程度有着密切的关联,但月平均温度与六(4)代种群的数量没有相关性.同时,田间降雨量与稻纵卷叶螟的发生情况无明显的相关性.此外,不同栽培方式也对稻纵卷叶螟的发生有关系,例如,在手栽稻田和机插稻田中六(4)代稻纵卷叶螟的蛾量要高于直播稻田.     

Sex ratio under the haystack model

This paper investigates the evolution of the sex ratio under an extension of the haystack model of Maynard Smith (1964). At the beginning of each season a stack is colonized by a number of fertilized females, and their offspring breed there for several generations until new haystacks are available for colonization. We intend this as a model for populations which undergo periodical population explosions and crashes. With mating before dispersal, the number of generations in the stack has little effect on the equilibrium sex ratio, but it has a marked effect with mating after dispersal. This model is then used to investigate the evolutionary stability of the mechanism of sex determination found in the wood lemming which leads to a population sex ratio of three females to one male.     

Population structure and the spread of disease

A common assumption of many mathematical models for the spread of disease is that there is random mixing among all individuals in the host population. This paper analyzes and develops a model for the spread of disease in a population consisting of several interacting subpopulations. The model considers 2 different types of interactions between individuals: 1) within a subpopulation because of geographic proximity, and 2) of the same or different subpopulations because of attendance at common social functions. A stability analysis performed on the equilibria of the model shows 2 stable states: 1) a population composed solely of susceptible individuals with no disease present, and 2) an interior point where there are susceptible, infective, and recovered individuals present at all times. The analysis shows that the threshold for disease maintenance is more easily exceed in centers that are members of a small local cluster than in randomly mixing centers, but that the spread of the disease throughout the population occurs more rapidly when the initial case attends a randomly mixing center. The conditions under which a disease will become established are dependent upon the transmission rate for the disease, the birth and death rate in each neighborhood, the recovery rate from the disease in each neighborhood, and the movement patterns of the individuals in the population. The study of the spread of disease in a population by means of mathematical models provides a valuable addition to the statistical data analyzed by epidemiologists. This model is relevant any time there is a division of the population into several interacting groups in which the probability of disease spread is a function both of neighborhood contact because of geographic proximity and of social interactions between groups.     

Pair-edge approximation for heterogeneous lattice population models

To increase the analytical tractability of lattice stochastic spatial population models, several approximations have been developed. The pair-edge approximation is a moment-closure method that is effective in predicting persistence criteria and invasion speeds on a homogeneous lattice. Here we evaluate the effectiveness of the pair-edge approximation on a spatially heterogeneous lattice in which some sites are unoccupiable, or "dead". This model has several possible interpretations, including a spatial SIS epidemic model, in which some sites are occupied by immobile host-species individuals while others are empty. We find that, as in the homogeneous model, the pair-edge approximation is significantly more accurate than the ordinary pair approximation in determining conditions for persistence. However, habitat heterogeneity decreases invasion speed more than is predicted by the pair-edge approximation, and the discrepancy increases with greater clustering of "dead" sites. The accuracy of the approximation validates the underlying heuristic picture of population spread and therefore provides qualitative insight into the dynamics of lattice models. Conversely, the situations where the approximation is less accurate reveals limitations of pair approximation in the presence of spatial heterogeneity.     

Growth regulation of the interstitial cell population in hydra. III. Interstitial cell density does not control stem cell proliferation

The interstitial cells of hydra contain a stem cell population which produces several classes of differentiated cell types. A model has been proposed which governs the growth rate of the interstitial cell population. This model, based on the density of interstitial cells in the tissue, makes specific predictions about the relationships among this density, the proportion of stem cells in the interstitial cell population, the growth rate of the interstitial cell population, and the amount of nematocyte differentiation. Hydroxyurea treatments were used to experimentally reduce interstitial cell numbers, and the validity of these expected correlations was tested. The results demonstrate that the predictions of the interstitial cell density model were not upheld. Furthermore, the findings suggest that the interstitial cells are a heterogeneous population, containing some cells which are no longer stem cells but which do retain a limited capacity for proliferation. In the following paper (S. Heimfeld and H.R. Bode, 1986, Dev. Biol. 115, 59-68) we have proposed an alternative mechanism to explain the observed correlations, which incorporates this heterogeneity into amplification divisions of interstitial cells already committed to differentiation.     

Population dynamics of lymphocystis disease in estuarine flounder, Platichthys flesus (L.)

The population dynamics of viral lymphocystis disease in an age-structured population of flounder, Plarichthys flesus (Linnaeus 1758), is studied with a mathematical model. For a single cohort the model illustrates the influence of host density and acquired immunity on length-prevalence profiles. This case corresponds to a host population at demographic equilibrium. When the model is extended to several cohorts, seasonal recruitment of susceptible hosts is shown to drive seasonality in disease prevalence. In both cases, there is good qualitative agreement between model predictions and field data from the Elbe estuary, Germany.     

A hierarchical Bayesian model for next-generation population genomics

The demography of populations and natural selection shape genetic variation across the genome and understanding the genomic consequences of these evolutionary processes is a fundamental aim of population genetics. We have developed a hierarchical Bayesian model to quantify genome-wide population structure and identify candidate genetic regions affected by selection. This model improves on existing methods by accounting for stochastic sampling of sequences inherent in next-generation sequencing (with pooled or indexed individual samples) and by incorporating genetic distances among haplotypes in measures of genetic differentiation. Using simulations we demonstrate that this model has a low false-positive rate for classifying neutral genetic regions as selected genes (i.e., Φ(ST) outliers), but can detect recent selective sweeps, particularly when genetic regions in multiple populations are affected by selection. Nonetheless, selection affecting just a single population was difficult to detect and resulted in a high false-negative rate under certain conditions. We applied the Bayesian model to two large sets of human population genetic data. We found evidence of widespread positive and balancing selection among worldwide human populations, including many genetic regions previously thought to be under selection. Additionally, we identified novel candidate genes for selection, several of which have been linked to human diseases. This model will facilitate the population genetic analysis of a wide range of organisms on the basis of next-generation sequence data.     

demoniche – an R‐package for simulating spatially‐explicit population dynamics

demoniche is a freely available R‐package which simulates stochastic population dynamics in multiple populations of a species. A demographic model projects population sizes utilizing several transition matrices that can represent impacts on species growth. The demoniche model offers options for setting demographic stochasticity, carrying capacity, and dispersal. The demographic projection in each population is linked to spatially‐explicit niche values, which affect the species growth. With the demoniche package it is possible to compare the influence of scenarios of environmental changes on future population sizes, extinction probabilities, and range shifts of species.     

一个具选择、突变、迁移的群体的遗传差分模型

假设一个群体是由“单位点—双基因”的个体所组成的,在该群体内存在选择、突变、迁移、生死等效应的作用。本文给出了在上述假设下并满足:(1)世代重叠,选择、突变、迁移、生死等效应的作用均在世代遗传之间完成;(2)群体适当大,个体间交配随机,符合孟德尔式遗传;(3)没有任何意外的灾祸等约定的群体遗传的数学模型。通过模型分析,我们能够进一步用数学语言来解释一些生命现象。模型分析指出:虽然某些群体不满足Hardy-Weinberg定律所叙述的条件,但可能具有和Hardy-Weinberg定律的结论相似的结果。该文中还就几个主要参数的变化讨论了群体遗传和进化的某些性质,如平衡等。最后,我们给出了该模型的一个数值例子。     

Survival in continuous structured populations models

The extended McKendrick-von Foerster structured population model is employed to derive a nonautonomous ordinary differential equation model of a population. The derivation assumes that the individual life history can be delineated into several physiological stages. We study the persistence of the population when the model is autonomous and base the nonautonomous survival analysis on the autonomous case and a comparison principle. A brief excursion into alternate life history strategies is presented.This work was supported in part by the U.S. Environmental Protection Agency under cooperative agreement CR 813353010