变维矩阵模型在温室白粉虱种群动态模拟中的应用

自七十年代以来,温室白粉虱(Trialeurodes vaporariorum Westw.)已成为我国北部温室中的主要害虫。为了最经济地将害虫控制在经济允许水平以下,必须进行数量预报和最优管理。为此,建立种群动态的模拟模型是必不可少的一步。 当然,影响昆虫种群动态的因子是很多的。但作为变温动物,温度因子是最基本的因子之一。尤其对那些象温室白粉虱的昆虫,温室系统相对地简单,天敌从种类到数量上都很     

温室白粉虱的种群动态及其对黄瓜生理生化特性影响的研究

用种群生物量代替种群数量作为统计温室白粉虱种群,既能代表种群数量的多少,又能反映不同虫态白粉虱危害程度的大小。不同初始虫量处理的种群生物量变化动态均与时间呈Logistic曲线关系。初始种群大的处理,各个时间的种群生物量都大。 黄瓜叶片光合作用强度,糖、叶绿素、蛋白质含量与种群生物量的大小呈负相关。其中叶片含fos量的变化与种群危害的程度吻合较好;植株孕蓄——开花期是抗逆能力较弱的时期,也是温室白粉虱种群迅速上升的时期,白粉虱的累积危害效应一般在这个时期反映出来,这个时期应是综合防治的关键时期。     

黑龙江地区烟粉虱和温室白粉虱发生动态

本文报道了我国高纬度地区(黑龙江哈尔滨)烟粉虱和温室白粉虱的全年发生过程。连续2年调查结果显示,粉虱在哈尔滨地区只能在温室中越冬,于来年5月大棚的第一茬蔬菜上首先发生,至7月第二茬大棚作物时才在大田有少量(低于300头/百叶)出现,在7月末的部分保护地作物上,粉虱种群密度可达到6000头/百叶;而大棚蔬菜中则以番茄和黄瓜上发生最为严重,少量大棚因此绝收;入秋后又从大田消失。结果显示,我国高纬度省份的保护地(温室和大棚)粉虱为害仍然严重,迫切需要从切断源头和迁移扩散路线进行有效防治。     

保护地间作芹菜对温室粉虱的防治作用

温室白粉虱Trialeurodes vaporariorum(Westwood)和烟粉虱Bemisia tabaci(Gennadius)是严重危害葫芦科、茄科和豆科等多种蔬菜的主要害虫,具有分布范围广、种群数量大、繁殖力强等特性。作者通过田间试验研究了蔬菜保护地内间作温室粉虱非嗜食植物芹菜(Apium graveliens L.)对其的防治效果。结果表明:与空白处理和常规化学防治相比,在番茄和黄瓜保护地内间作芹菜对温室粉虱均具有显著的防治效果,驱避效果分别达到98.0%和84.5%。这些结果是初步的,但其为进一步研究温室粉虱的寄主选择机制和非化学防治方法提供了依据。     

B型烟粉虱和温室白粉虱在温度逆境下的生存特性比较

为了明确B型烟粉虱和温室白粉虱在温度逆境下的生存特性对其种群发展的影响,通过进行高温和低温暴露试验,研究了B型烟粉虱和温室白粉虱卵、伪蛹、成虫在37℃,39℃,41℃,43℃,45℃下暴露1～2 h后的存活率,以及这两种粉虱卵、2～3龄若虫、伪蛹和成虫在2℃下暴露1～12 d后的存活率。结果表明：两种粉虱的卵、伪蛹和成虫在37℃～45℃下暴露1～2 h,其存活率均随着温度的上升而降低;但在相同处理条件下B型烟粉虱3种供试虫态的存活率要高于温室白粉虱。B型烟粉虱在2℃下暴露2～12 d,各供试虫态的存活率迅速下降,卵、2～3龄若虫、伪蛹在2℃下暴露12 d后均不能存活,成虫在2℃下暴露4 d后也全部死亡;而温室白粉虱卵、伪蛹在2℃下暴露12 d后其存活率还能超过45%,成虫在2℃下暴露7 d后仍有80.9%能够存活。结果说明,B型烟粉虱和温室白粉虱对温度逆境的适应性存在差异,B型烟粉虱对高温的适应性要高于温室白粉虱;温室白粉虱对高温敏感,但对低温的适应性要显著高于B型烟粉虱。据此推测,两种粉虱对温度逆境适应性的差异是导致其种群发生存在差异的一个重要原因。     

温室白粉虱的性行为

温度白粉虱Trialeurodes vaporaricrum Westw。目前已成为我国北方、日本、欧洲及美国等地的重要温室蔬菜害虫。此虫虽可用丽蚜小蜂Encarsia formosa Gahan进行生物防治,但受到作物种类、温度等多种条件限制,特别是要求在种群密度低时方能奏效(Ekbom,1977),而目前尚没有对该虫早期低密度时的有效预报办法。H.Weber早在1931年描述该虫交配行为时就曾预测性信息素在该虫的求偶活动中也许起重要作用。时过半个世纪,对此问题仍不清楚。Vaishampayan、Kogan等(1975)曾对该虫在寻找寄主植物中视觉及嗅觉行为所起的作用进行初步研究。本文作者(Li和Macchwitz,1983)曾见到在它的性行为中,雄虫通过性信息素接近雌虫。本工作描述该虫的性行为,以作为上文的补充。     

温室白粉虱在温室内六种寄主植物上的生命表及其分析

温室白粉虱Trialeurodes Vaporariorum (Westwood)现已成为北方地区温室内的重要蔬菜害虫,主要为害黄瓜与番茄,芹菜也在某种程度上受害。在露地也为害架豆与茄子等。为了达到防治目的,首先必需对温室白粉虱在这些寄主上的生活规律有所了解,本文用两年时间对该虫在常见六种寄主上的历期及生命表进行调查研究与比较,现把初步结果整理如下:     

烟草品种和温度对B型烟粉虱和温室白粉虱生物学参数的影响

在室内20℃、26℃和30℃三个设定温度条件下,研究了CF-965、NC-89和NC-82三个烟草品种对B型烟粉虱和温室白粉虱生长发育和繁殖的影响.结果表明:26℃时两种粉虱在CF-965、NC-89和NC-82三个烟草品种上的发育历期没有明显差异,但温室白粉虱卵期和若虫期的发育历期较烟粉虱依次分别延长了1.32d、2.81d和 2.04d.在CF-965上,B型烟粉虱卵期和若虫期的总存活率和平均单雌产卵量分别为54.19%和55.17粒,温室白粉虱仅分别为31.99%和39.17粒;在NC-89上,B型烟粉虱卵期和若虫期的总存活率和平均单雌产卵量分别为23.47%和37.50粒,温室白粉虱仅分别为15.75%和17.25粒;两种粉虱在NC-82上卵期和若虫期的总存活率和平均单雌产卵量差异不大,表明B型烟粉虱对CF-965和NC-89的适应能力较温室白粉虱强.两种粉虱在20℃时的发育历期最长,32℃时最短,26℃时居中.20°C时烟粉虱卵期和若虫期的存活率20.96%为最低,26℃和32℃时分别达54.19% 和53.29%;而温室白粉虱在32℃条件下存活率11.66%为最低,20℃和 26℃时分别达31 34% 和31.99%.温室白粉虱在20℃时产卵量大于烟粉虱, 在26℃时的产卵量小于烟粉虱,30℃时则不能产卵,但烟粉虱成虫30℃时的产卵量仍可达21.06粒.由此说明烟粉虱在较高温度条件下的适应能力显著强于温室白粉虱.山东烟区烟草生长中期的田间平均温度多在22～30℃,适合B型烟粉虱的发生,应引起高度重视.     

温室白粉虱对几种园艺植物的偏好性

温室白粉虱Trialeurodesvaporariorum是世界性害虫,每年都造成巨大的经济损失。研究了温室白粉虱在多种园艺植物混栽温室内对不同植物的选择性,结果表明在2 0种常见蔬菜和花卉中,可危害其中1 3种;温室白粉虱对其中6种寄主植物(旱金莲、一品红、菊花、番茄、小白菜和羽叶甘蓝)的选择性有显著差异,其种群数量为旱金莲和番茄显著多于小白菜、一品红和菊花,羽叶甘蓝显著少于其它5种植物;不同的虫态之间排序有小变动;温室白粉虱在番茄植株上部的垂直分布表现为卵和成虫在第3叶居多,若虫在第5叶居多,伪蛹在第9叶居多。     

烟粉虱及温室白粉虱为害后对后续粉虱种群的影响

【目的】分析烟粉虱Bemisia tabaci(Gennadius)或温室白粉虱Trialeurodes vaporariorum(Westwood)为害番茄后对后续温室白粉虱和烟粉虱生长、发育、成虫寿命和繁殖等产生的促进或抑制作用,可为明确寄主植物番茄介导的温室白粉虱-烟粉虱的种间互作,开展粉虱的科学防控提供科学依据。【方法】通过在寄主植物番茄叶片上先将B型烟粉虱或温室白粉虱按不同的顺序、时间间隔分开接种,再系统观察后续接上的两种粉虱生长、发育、繁殖等种群参数的变化。【结果】(1)先期接上烟粉虱对后续温室白粉虱的发育、寿命、产卵量有明显的促进作用;这种作用需烟粉虱的持续诱导,若去掉烟粉虱,其对温室白粉虱的促进作用即消失;先期接上温室白粉虱可缩短后续烟粉虱伪蛹期,但温室白粉虱的持续存在不利于烟粉虱的产卵,且明显降低烟粉虱的内禀增长率和净增殖率。(2)先后在番茄上同时接上温室白粉虱可降低后续烟粉虱的单雌产卵量和雌、雄虫的成虫寿命;先后同时接种烟粉虱却显著地增加了温室白粉虱的单雌产卵量;烟粉虱的提前存在降低了后续烟粉虱单雌产卵量。(3)但两种粉虱之间作用存在着一定的时间滞后性。烟粉虱对温室白粉虱的发育、寿命、产卵量产生的促进作用大约在其卵期后的一段时间才能显现出来;温室白粉虱对烟粉虱伪蛹期的缩短作用也需提前诱导;而温室白粉虱对温室白粉虱的促进作用相当滞后,直到成虫期才显现出来。【结论】B型烟粉虱和温室白粉虱之间可通过寄主番茄产生相互影响,前期烟粉虱为害可显著促进后续温室白粉虱卵和若虫的发育,而前期温室白粉虱为害对烟粉虱的发育不利。     

羊草叶片气体交换参数对温度和土壤水分的响应

 采用生长箱控制的方法研究了羊草(Leymus chinensis)幼苗叶片光合参数对5个温度和5个水分梯度的响应和适应。结果表明：轻度、中度土壤干旱并没有限制羊草叶片的生长,对气体交换参数亦无显著影响,反映了羊草幼苗对土壤水分胁迫的较高耐性。叶片生物量以26 ℃时最大,其它依次为23 ℃、20 ℃、29 ℃和32 ℃。温度升高使气孔导度和蒸腾速率增加, 却使光合速率和水分利用效率降低。水分和温度对叶片生物量、光合速率、气孔导度和蒸腾速率存在显著的交互作用,表明高温加强了干旱对叶片生长和气体交换的影响, 降低了羊草对土壤干旱的适应能力。高温和干旱的交互作用将显著减少我国半干旱地区草原的羊草生产力。     

干旱胁迫对红松幼苗针叶超微结构的影响

在土壤逐渐失水和PEG溶液模拟的两种不同形式的干旱胁迫下,红松幼苗针叶细胞中叶绿体和线粒体超微结构的变化呈现出显著的差异。在土壤干旱胁迫下,叶绿体的片层结构发生严重的扭曲并在中央部分形成电子密度较高的黑色团块物质。PEG模拟的干旱胁迫下,叶绿体肿胀,空泡化明显,但在叶绿体的中央没有黑色团块物质的形成。在土壤干旱胁迫后,线粒体的膜结构仍然完整清晰,基质比胁迫前更为浓厚,而PEG溶液的干旱胁迫下,线粒体的数量增多,嵴明显减少,基质变得十分稀薄。可见两种不同方式的干旱胁迫处理下,细胞结构的损伤机制及损伤后产生的生理意义并不完全相同。     

POPULATION VARIABILITY IN DANTHONIA CAESPITOSA (GRAMINEAE) IN RESPONSES TO INCREASING DENSITY UNDER THREE TEMPERATURE REGIMES

The objective of this research was to compare the responses to increasing density of different natural populations of Danthonia caespitosa, a perennial grass of southern Australia, under different temperature regimes. Seeds were collected from four populations along a 167-km N–S transect beginning north of Deniliquin, N.S.W., and ending near Heathcote, Victoria. Seedlings from each population were planted in loamy sand at three densities and grown under day/night temperature regimes of 15/10, 24/19, and 33/28 C in the Canberra Ceres Phytotron. Results indicate that one natural population (or one temperature regime) can not be used to characterize this species' responses to increasing density. The effects of density and temperature on tillering, plant height, leaf length, and leaf width varied significantly among populations, so that populations achieved comparable shoot weights by different relative responses to density. Variability in biomass among individuals (as indicated by coefficients of variation) increased from low to intermediate density; however, size variability at the highest density was either greater, lesser, or approximately the same as that of plants at the intermediate density, depending upon the population and the temperature regime. The combinations of density and temperature which produced the maximum shoot growth per pot varied markedly among populations; at 24/19 C, populations from frequently disturbed areas of low perennial plant cover had greater shoot weights per pot at the intermediate density, while those populations from more stable grassland sites had their greatest shoot weights at the highest density. Flowering occurred in all populations at the low density in 15/10 C; however, only for the population from the ungrazed grassland was there any flowering in the other temperature regimes or at higher densities. It is concluded that a “response to density stress” could be differentially described for each population at each temperature regime, even though the four study populations represented only 1/10 of the latitudinal range of D. caespitosa.     

Luminometric and differential scanning calorimetry (DSC) studies on heat- and radiation inactivation of Bacillus subtilis luxAB spores

A bioluminescent derivative of Bacillus subtilis containing a plasmid encoding a luxAB fusion under control of a vegetative promoter and gives bioluminescence upon addition of an exogenous long-chain aldehyde has been used as test organism. Its spore populations have been produced and their heat- and radiation survival curves established. Heat-sensitization effect of pre-irradiation of spores was proven not only by colony counting but also with differential scanning calorimetry. Under a linearly programmed temperature increase, the heat destruction of spores surviving 2.5 kGy gamma irradiation resulted in at a few centigrade lower temperature than that of untreated spores. Heat denaturation endotherms in the DSC-thermogram of irradiated spores were shifted to lower temperatures as well. Comparative turbidimetric, luminometric and phase-contrast microscopic studies of untreated, heat-treated and irradiated spore populations showed that the kinetics of germination and the light emission during germination of radiation-inactivated spores were the same as those of untreated spores, revealing that the pre-formed luciferase enzyme packaged into the spores during sporulation remained intact after an irradiation dose causing 90% decrease in number of colony forming spores. Therefore, in contrast to heat-treated spores, the initial bioluminescence reading upon germination of irradiated spores does not reflect the viable count of their population.     

The Relationship of Plant Age,Soil Temperature,and Population Density of Heterodera schachtii on the Growth of Sugarbeet

There were direct relationships between inoculum density of Heterodera schachtii Schm. (nematode population density), initial soil temperature, the growth of sugarbeets in the greenhouse under controlled temperatures, and nematode populations. Heterodera schachtii was least pathogenic on plants inoculated at 6 wk of age and most pathogenic on plants grown from inoculated germinated seed (0 wk of age). In the field, H. schachtii was least pathogenic on sugarbeets grown at an initial soil temperature of 6 C and most pathogenic on those grown at an initial soil temperature of 24 C. The growth period for sugarbeets at the different soil temperatures was determined by heat units; since penetration of sugarbeet roots by H. schachtii larvae is accelerated at soil temperatures above 10 C, each hour-degree ahove 10 C was counted as one effective heat unit (HU). Using this guideline it was determined that root weight depressions in the greenhouse, for each degree-unit population (HU-UP) where unit population = one larvae/g soil, were 0.052, 0.09, 0.12, and 0.17 mg at initial soil temperatures of 6, 12, 18, and 24 C, respectively. Root weight depressions were 0.28, 0.23, 0.15, and 0.086 mg when plants were inoculated at 0, 2, 4, and 6 wk of age.     

Size and growth relationships in juvenile steelhead: The advantage of large relative size diminishes with increasing water temperatures

In territorial stream salmonids, asymmetric competition can perpetuate individual size differences over time, but the extent to which this is manifested can be environmentally mediated. Here we study the variation in juvenile steelhead (Oncorhynchus mykiss) growth rates to identify the conditions (population density and water temperature) under which an individual’s size relative to its conspecifics conferred an advantage. Among steelhead rearing in the same stream section we found that relatively larger individuals on average grew faster than smaller conspecifics. However, comparing across stream sections there was a negative interaction between relative size and water temperature. The effect of an individual’s relative size on its growth rate decreased as temperatures were increasing, indicating that the advantages of being large diminished during periods of high temperatures or in locations with relatively higher temperatures. Compared to temperature, the effects of population density on the growth rate were less substantial. The results suggest that larger individuals on average acquire more resources than smaller individuals, and demonstrate that water temperature exerts an important, modulating control over growth performance in heterogeneous environments.     

Ecotypic differentiation and phenotypic plasticity in reproductive traits of Armadillidium vulgare (Isopoda: Oniscidea)

Armadillidium vulgare differed in growth and survivorship on two field sites. Growth rates were higher at a site with consistently higher quality food than at the other site where less high-quality food was produced and which was less predictably accessible. Survivorship was higher at the second site where temperature fluctuations were consistently smaller. Individuals from the two populations were kept for 6 months under the same food and temperature conditions and patterns of resource allocation to reproductive traits analysed. Members of the population from the site with good growth conditions had significantly higher reproductive allocation, by 13.5%, and larger broods, by 9.1%, than those from the site with poor growth conditions. Contrary to theoretical predictions, they also had significantly larger offspring, by 7.5% dry mass. Larger offspring survived better than small ones. This differential survivorship, by 20% for a 3.4% difference in live mass, was much more pronounced under conditions of moisture stress and under fluctuating temperature regimes. Larger offspring would therefore be at a selective advantage on the site with more severe temperature fluctuations. Phenotypic plasticity in reproductive traits in response to experimental changes in food quality, temperature and crowding were monitored. Reproductive allocation was increased by 20.8% under conditions of higher food quality, by 14.7% at higher temperatures, and by 12.5% under less crowded conditions. Brood size, but not offspring dry mass, increased when food quality increased. When crowding increased by 25.0%, the size of broods remained the same but the dry mass of individual offspring decreased by 11.2%. Members of the population from the site with more variable access to high-quality food showed more plasticity in reproductive traits in response to changes in food supply than members of the population from the site with the more predictable food supply. Members of the population from the site with more stable temperatures showed less plasticity to temperature changes than members of the population from the site with greater temperature fluctuations. It is concluded that the observed microevolutionary processes and phenotypic plasticity have adaptative value as responses to spatial and temporal heterogeneity in environmental conditions.     

Modelling the germination of Stellaria media using the concept of hydrothermal time

The germination characteristics of Stellaria media (common chickweed) were investigated over a range of constant temperatures and degrees of moisture stress in order to assess the suitability of hydrothermal time as a basis for modelling germination under field conditions. Maximum percentage germination occurred over a much narrower temperature range around the optimum temperature than previously seen for cultivated crop seed. The entire final percentage germination response to temperature in water was well described by two probit curves, and this model was extended to describe the data at all water potentials at a temperature close to the optimum. The implications of the reduction in germination at nonoptimal temperatures are discussed with respect to the interpretation of germination progress curves and conditional dormancy. After adjusting for maximum percentage germination, a hydrothermal time model was found to fit the data set well within the conditions normally encountered in horticultural seedbeds. This separation of the final percentage germination presents a flexible modelling approach that allows for the different levels of dormancy typically expressed within weed populations. By contrast with many previously reported species, S. media had a synchronous germination rate within the population at any given temperature/water potential combination. This synchronous germination of at least a proportion of the population over a wide range of temperature and water potentials might have ecological significance for the opportunistic germination behaviour of this weed species.     

PHENOTYPIC PLASTICITY AND REACTION NORMS IN TEMPERATE AND TROPICAL POPULATIONS OF DROSOPHILA MELANOGASTER: OVARIAN SIZE AND DEVELOPMENTAL TEMPERATURE

The plasticity of ovariole number relative to developmental temperature was studied in three populations of Drosophila melanogaster at both ends of the cline: a temperate French population and two equatorial Congolese. Ovary size was much greater in the French flies, in agreement with an already known latitudinal cline. Among isofemale lines, significant differences in genetic variability were observed between populations with a maximum variability at intermediate temperatures. Parameters of phenotypic variability (CV and FA) were not statistically different among lines or populations, but a significant increase at low temperature was demonstrated for both. The shapes of the response curves (i.e., the norm of reaction) were analyzed by adjusting the data to a quadratic equation. The parameters of the equation were highly variable among lines. On the other hand, the temperature for maximum value of ovarioles (TMV) was much less variable and exhibited only a slightly significant difference between temperate and tropical flies (22.2°C vs. 22.7°C). During its geographic extension toward colder places, D. melanogaster underwent a large, presumably adaptative, increase in ovariole number but very little change in the norm of reaction of that trait.     

Intra- and interspecific density dependence mediates weather effects on the population dynamics of a plant–insect herbivore system

Temperature and precipitation are two major factors determining arthropod population densities, but the effects from these climate variables are seldom evaluated in the same study system and in combination with inter- and intraspecific density dependence. In this study, I used a 19 year time series on plant variables (shoot height and flowering incidence) and insect density in order to understand direct and indirect effects of climatic fluctuations on insect population densities. The study system includes two closely related leaf beetle species (Galerucella spp.) and a flower feeding weevil Nanophyes marmoratus attacking the plant purple loosestrife Lythrum salicaria. Results suggest that both intraspecific density dependence and weather variables affected Galerucella population densities, with interactive effects of rain and temperature on insect densities that depended on the timing relative to insect life cycles. In spring, high temperatures increased Galerucella densities only when combined with high rain, as low rain implies a high drought risk. Low temperatures are only beneficial if combined with little rain, as high rain cause chilly and wet conditions that are bad for insects. In summer, interactive effects of rain and temperature are different because high temperatures and little rain cause drought that induce wilting in plants, thus reducing food availability for the leaf feeding larvae. In contrast, the density of the flower feeding weevil was less affected by temperature and precipitation directly, and more indirectly interspecific density dependent effects through reduced resource availability caused by previous Galerucella damage.