不同培育模式胭脂虫产量评估

对云南禄丰两种培育模式下胭脂虫Dactylopius coccus Costa产量进行了调查与评估,结果表明:1)在大棚内培育近3年的梨果仙人掌植株上接种培育胭脂虫,每年每667 m2大棚约可产胭脂虫干虫32kg;2)在大棚内悬挂仙人掌茎片上接种培育胭脂虫,每667 m2仙人掌寄主林每年所产茎片约可产胭脂虫干虫9 kg。     

胭脂虫Dactylopius coccus Costa培育方法研究

【目的】为探索胭脂虫Dactylopius coccus高产培育新方法。【方法】胭脂虫的室内培养模式有采摘茎片培育模式和种植培育模式两种。本研究在采摘茎片模式下开展了培育环境构筑、平铺培育、接种方式、蔗糖培育等培育技术的研究;在种植模式下进行了接种方式、轮放培育和寄主高度控制的培育技术研究。【结果】探索出胭脂虫在两种模式下的新培育方法。【结论】在采摘茎片培育模式下,采用松针覆土保湿效果较好;平铺培育产量较高,值得推广;悬挂培育宜采用网兜内置谷草接种方式。蔗糖对胭脂虫有明显助食作用,喷洒适当浓度的蔗糖有助于提高胭脂虫的产量。在种植模式下,宜进行轮放培育,寄主植株高度控制在100 cm之内且茎片级数在4级之内,可避免植株倒伏及断离。采用纱网撒种方式,可节约接种环节中大量人力。     

胭脂虫寄生前后梨果仙人掌挥发性物质的变化

为了研究胭脂虫Dactylopius coccus Costa寄生前后梨果仙人掌(Opuntia ficus-indica Mill)挥发性物质的变化,以动态顶空密闭循环吸附捕集法捕集胭脂虫寄生前后梨果仙人掌的挥发物,并运用全自动热脱附-气相色谱/质谱(ATD-GC/MS)联用技术进行分析检测,用峰面积归一化法测定其相对含量。结果表明,无虫梨果仙人掌的挥发物中共检测到8种化合物,有虫的梨果仙人掌中共检测到9种化合物,化合物的种类和含量都有一定的变化;萜烯类是植食昆虫诱导的植物挥发性次生物质中的主要成分,本试验中,萜烯类在胭脂虫寄生前后的含量由23.12%降为6.98%。在无虫仙人掌的挥发物中检测出苯甲醛,含量约占1.73%,有虫的仙人掌中则未检测到;同样在有虫仙人掌挥发物中检出的其他物质如酯类(21.15%)、醇类(1.79%)和卤代芳烃类(1.51%)物质在无虫仙人掌植株中都未检测出。     

Volatile changes of Opuntia ficus-indica Mill before and after parasitizing by Dactylopius coccus Costa

为了研究胭脂虫Dactylopius coccus Costa寄生前后梨果仙人掌(Opuntia ficus-indica Mill)挥发性物质的变化,以动态顶空密闭循环吸附捕集法捕集胭脂虫寄生前后梨果仙人掌的挥发物,并运用全自动热脱附-气相色谱/质谱(ATD-GC/MS)联用技术进行分析检测,用峰面积归一化法测定其相对含量.结果表明,无虫梨果仙人掌的挥发物中共检测到8种化合物,有虫的梨果仙人掌中共检测到9种化合物,化合物的种类和含量都有一定的变化;萜烯类是植食昆虫诱导的植物挥发性次生物质中的主要成分,本试验中,萜烯类在胭脂虫寄生前后的含量由23.12％降为6.98％.在无虫仙人掌的挥发物中检测出苯甲醛,含量约占1.73％,有虫的仙人掌中则未检测到;同样在有虫仙人掌挥发物中检出的其他物质如酯类(21.15％)、醇类(1.79％)和卤代芳烃类(1.51％)物质在无虫仙人掌植株中都未检测出.     

紫胶蚧寄生对久树生长的影响

研究一个世代中紫胶蚧KerrialaccaKerr寄生对久树(Schleicheraoleosa(Lour)Oken)生长产生的影响。结果表明:紫胶蚧寄生对整株寄主植物(久树)的生长有促进作用,被寄生的植株与对照植株之间,树高、地径、胸径和冠幅增长比例相差2%～4%。紫胶蚧寄生对被寄生枝条的生长有抑制作用,被紫胶蚧寄生的枝条长度和枝径的增长小于未被紫胶蚧寄生的枝条,未被紫胶蚧寄生的枝条表面积增加的幅度比被紫胶蚧寄生的枝条的表面积增加幅度大17%。紫胶蚧寄生对枝条和整株植物的生长影响不一样,反应了紫胶蚧和寄主植物在长期的协同进化过程中采取的防御和反防御机制。对于寄主植物而言,被寄生的枝条合成的营养成分有部分被紫胶蚧吸收,生长受到影响,如果被寄生过量,甚至会死亡;而对于整株植物而言,在害虫侵袭下,会出现超补偿行为,生长量超过未被寄生的植株。对于紫胶蚧,寄主植物这种防御行为对种群繁衍有利,其他未被寄生的枝条的超补偿生长,为紫胶蚧后代提供了更广阔的生存空间。研究紫胶蚧寄生对久树生长的影响,为充分利用紫胶蚧种虫和寄主植物资源打下基础。     

空心莲子草叶甲对空心莲子草控制效果的定量评价

为了解空心莲子草叶甲Agasicles hygrophila被引入中国20多年后其取食行为与取食能力是否发生改变, 我们通过采集叶甲自然种群的成虫, 在室内用空心莲子草Alternanthera philoxeroides饲养获得检测用叶甲各虫态与虫量进行室内定量检测, 研究了空心莲子草叶甲自然种群各龄幼虫与成虫在不同密度下对空心莲子草的控害效果。结果显示： 1龄幼虫喜食顶芽嫩叶, 在每株接0.2和1头1龄幼虫密度下, 空心莲子草仍有新叶和侧芽生成, 生物量、 株高与茎节数仍在增加; 在5头/株的密度下, 空心莲子草的生物量、 叶片数和侧芽数均出现负增长; 在10头/株的密度下, 草的生物量、 株高、 叶片数、 侧芽数和茎节数均表现为负增长。2龄幼虫优先取食顶芽嫩叶, 也取食老叶与茎杆, 在每株10头2龄幼虫的密度下, 接虫7 d后, 40%的植株死亡。3龄幼虫取食叶片与茎秆, 后期钻入茎秆中化蛹,在10头/株密度下,7 d后, 已引起52%的植株死亡, 存活株的茎节数显著减少。成虫可24 h连续取食植株的任何组织, 0.2头/株的密度下,空心莲子草叶片与侧芽数量已呈现负增长; 5头/株的密度下,空心莲子草的生物量、 株高、 叶片数、 侧芽数与茎节数均呈现较大的负增长; 10头/株的控草效果更加显著。     

胭脂虫养殖方式初探

2003～2005年在四川凉山彝族自治州西昌市、宁南县,对胭脂虫进行大棚养殖试验、大棚仙人掌悬挂养殖试验和野外养殖试验,结果表明大棚养殖和大棚仙人掌悬挂养殖胭脂虫效果比较好;野外养殖受气候影响较大,胭脂虫难以成活.     

不同纬度地区互花米草生长性状及适应性研究

互花米草是我国沿海潮间带分布面积最广的入侵植物, 研究不同纬度地区间互花米草的生长特征和适应对策有助于揭示该植物对大范围异质生境的入侵适应机制。对我国沿海10 个省市26 个地区互花米草生长情况的调查发现:1)不同地区间互花米草的株高、节长、基茎、单株地上生物量、种群密度等性状特征均存在显著差异(P<0.01), 其变化规律与纬度密切相关: 随着纬度的升高, 互花米草的株高、节长、基茎、单株地上生物量、种群地上生物量总体呈现先升后降的规律, 而种群密度呈现为先降后升的规律。2)边缘区的互花米草种群密度优势明显: 植物个体矮小细密,种群密度最高达到2668 株·m–2, 是分布区中部的20 多倍, 较高的种群密度大幅度增加了个体或分株数量, 提高了生存概率, 降低了因种群面积过小带来的种群灭绝风险; 分布区中部的互花米草植株个体优势明显: 植株种群密度较低, 但植株个体高大粗壮, 单株地上生物量最高达到48.81 g, 是分布区边缘的30 倍; 表明中心区和边缘区的互花米草种群分别表现出“表现最大化”和“种群维持”的适应对策。3)温度是影响不同地区间互花米草生长差异的主要因素, 降水次之, 而pH 和盐度影响较小。     

布氏潜蝇茧蜂对橘小实蝇幼虫寄生作用的研究

在试验室条件下研究了布氏潜蝇茧蜂Fopius vandenboschi(Fullaway)的寄生习性。结果表明:该寄生蜂嗜好寄生低龄的橘小实蝇幼虫;橘小实蝇幼虫的密度对布氏潜蝇茧蜂的寄生有明显的影响;被寄生的幼虫数随寄主自身密度的增加而增加,当寄主幼虫密度达每果片30只以上时,寄生数量的增加幅度就趋于下降,用Holling圆盘方程模拟为Na=0.9051N/(1 0.0163N)。此外,布氏潜蝇茧蜂的自身密度对寄生作用也有影响,随着寄生蜂数量的增加,寄生蜂的发现域逐渐变小,用Hassell-Varley方程表示为α=0.4655P-0.5807。     

竹叶眼子菜(POTAMOGETON MALAIANUS MIQ.)叶面积测定及与栽培密度的关系初探

通过人为控制种群密度的栽培实验 ,用叶特征度量估测单叶叶面积 ( AL)、用茎特征度量估测整株叶面积 ( AS) ,分析不同栽培密度对叶面积测定的影响。结果表明 :( 1 )叶长×叶宽 ( L× W)与单叶叶面积相关性最大 ;茎长×茎上叶片数 ( LS× NL)测定整株叶面积较为适宜。 ( 2 )随着栽培密度增大 ,叶片相对变长变窄 ,比叶面积则增加 ,平均整株叶面积相应减小。( 3)不同的栽培密度对叶片形状有明显影响 ,反映在不同密度处理条件下叶片的几何拟合图形不同。     

Indirect versus direct effects of grasses on growth of a cactus (Opuntia fragilis): insect herbivory versus competition

Variation in plant performance between microhabitats is usually attributed to direct mechanisms, such as plant physiological tolerances or competitive interactions. However, indirect mechanisms, such as differences in herbivore pressure mediated by microhabitat differences, could create the same pattern of variation. In this study, we investigated the effect of insect herbivore pressure on the growth of the grassland cactus Opuntia fragilis under different regimes of grassland canopy cover. Our purpose was to establish the extent to which canopy cover plays a direct, competitive role versus an indirect, mediatory role in cactus growth. We manipulated aboveground microhabitat, specifically the cover of adjacent grasses. The three treatments were: (1) open canopy, with grass pinned down away from the cactus; (2) shaded canopy, with a partial mesh cage staked over the cactus; and (3) ambient grass canopy. We measured seasonal plant growth and recorded changes in insect herbivore occurrence and damage in relation to cover. Cactus growth, defined as the change in number of live cladodes, was higher in the open than under either treatment where the plant was more shaded (P<0.05). However, allocation to new growth, measured as the proportion of new segments (cladodes) in a patch, did not differ among cover treatments. Thus, the hypothesis that physiological constraints, or competition for light, limited cactus performance in grass is rejected. Instead, we found that both cladode mortality, caused by the larvae of a cactus moth borer (Melitara dentata), and occurrence of the moth were lower in the open microhabitat than in either shaded microhabitat. Thus, higher net growth in the open, unshaded treatment, rather than representing a release from competition for light with grasses, was better explained as an indirect effect of grass cover on the activity and impact of the cactus moth. These results show that indirect effects can lead to a misinterpretation of experimental data on direct effects. These data also contribute to an improved understanding of mixed results in the biological control of weedy cacti. Clearly, future evaluations of the relative importance of physiology, competition, and insect herbivory in plant performance must be environmentally explicit.     

Population distributions of plant size and light environment of giant ragweed (Ambrosia trifida L.) at three densities

Summary Plots in a naturally occurring population of giant ragweed (Ambrosia trifida L.) near Ames, Iowa, USA were left unthinned (high density,=693 plants/m²) or were thinned in early June 1989 to create low and medium densities of 10 and 50 plants/m². Size and light environment of individual plants were measured at monthly intervals from June to September. By September, low density plants had 15 times greater biomass/plant and 30 times greater leaf area/plant than high density plants, although biomass and leaf area per unit land area decreased with decreasing density. Plants at high density allocated more biomass to stem growth, but plants at medium and low density had successively higher leaf area ratios, higher potential photosynthetic rates, higher allocation to leaves, and higher growth rates. Average light on leaves decreased with increasing density and also decreased over the growing season in the low and medium densities. The distribution of light environments of individual plants was non-normal and skewed to the left in most months, in contrast to the rightwards skew of distributions of plant size parameters. Inequality in the distributions, as measured by coefficient of variation and Gini coefficients, increased over most of the growing season. There was little effect of density on inequality of stem diameter, height, or estimated dry weight, but inequality in reproductive output greatly increased with density. There was greater inequality in number of staminate flowers produced than in number of pistillate flowers and seeds produced. Path analysis indicated that early plant size was the most important predictor of final plant size and reproductive output; photosynthesis, conductance, and light environment were also significantly correlated with size and reproduction but usually were of minor importance. Variation in growth rate apparently increased inequality in plant size at low density, whereas belowground competition and death of smaller plants may have limited increases in inequality at high density.     

Gas exchange and growth responses to elevated CO2 and light levels in the CAM species Opuntia ficus-indica

Gas exchange and dry-weight production in Opuntia ficus-indica, a CAM species cultivated worldwide for its fruit and cladodes, were studied in 370 and 750 μmol mol⁻¹ CO₂ at three photosynthetic photon flux densities (PPFD: 5, 13 and 20 mol m⁻² d⁻¹). Elevated CO₂ and PPFD enhanced the growth of basal cladodes and roots during the 12-week study. A rise in the PPFD increased the growth of daughter cladodes; elevated CO₂ enhanced the growth of first-daughter cladodes but decreased the growth of the second-daughter cladodes produced on them. CO₂ enrichment enhanced daily net CO₂ uptake during the initial 8 weeks after planting for both basal and first-daughter cladodes. Water vapour conductance was 9 to 15% lower in 750 than in 370 μmol mol⁻¹ CO₂. Cladode chlorophyll content was lower in elevated CO₂ and at higher PPFD. Soluble sugar and starch contents increased with time and were higher in elevated CO₂ and at higher PPFD. The total plant nitrogen content was lower in elevated CO₂. The effect of elevated CO₂ on net CO₂ uptake disappeared at 12 weeks after planting, possibly due to acclimation or feedback inhibition, which in turn could reflect decreases in the sink strength of roots. Despite this decreased effect on net CO₂ uptake, the total plant dry weight at 12 weeks averaged 32% higher in 750 than in 370 μmol mol⁻¹ CO₂. Averaged for the two CO₂ treatments, the total plant dry weight increased by 66% from low to medium PPFD and by 37% from medium to high PPFD.     

Beetle and plant density as cues initiating dispersal in two species of adult predaceous diving beetles

Dispersal can influence population dynamics, species distributions, and community assembly, but few studies have attempted to determine the factors that affect dispersal of insects in natural populations. Consequently, little is known about how proximate factors affect the dispersal behavior of individuals or populations, or how an organism’s behavior may change in light of such factors. Adult predaceous diving beetles are active dispersers and are important predators in isolated aquatic habitats. We conducted interrelated studies to determine how several factors affected dispersal in two common pond-inhabiting species in southern Alberta, Canada: Graphoderus occidentalis and Rhantus sericans. Specifically, we (1) experimentally tested the effect of plant and beetle densities on dispersal probabilities in ponds; (2) surveyed ponds and determined the relationships among beetle densities and plant densities and water depth; and (3) conducted laboratory trials to determine how beetle behavior changed in response to variation in plant densities, conspecific densities, food, and water depth. Our field experiment determined that both species exhibited density dependence, with higher beetle densities leading to higher dispersal probabilities. Low plant density also appeared to increase beetle dispersal. Consistent with our experimental results, densities of R. sericans in ponds were significantly related to plant density and varied also with water depth; G. occidentalis densities did not vary with either factor. In the laboratory, behavior varied with plant density only for R. sericans, which swam at low density but were sedentary at high density. Both species responded to depth, with high beetle densities eliciting beetles to spend more time in deeper water. The presence of food caused opposite responses for G. occidentalis between experiments. Behavioral changes in response to patch-level heterogeneity likely influence dispersal in natural populations and are expected to be important for observed patterns of individuals in nature. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Population Structure and Growth Patterns of Opuntia echios var. gigantea along an Elevational Gradient in the Galípagos Islands1

Cacti growing in forests potentially experience growth limitation due to reduced light availability. To test this hypothesis, we studied the population structure of Opuntia echios var. gigantea at 15 sites on the south side of Isla Santa Cruz, Galípagos Islands, Ecuador. Populations were located in communities ranging from arid scrub at low elevations to closed‐canopy tropical dry forest at higher elevations. Ordination confirmed the existence of a strong elevation‐vegetation gradient. Opuntia abundance peaked at lower elevations (ca 30 m), with lower densities in closed‐canopy sites. For populations in scrub vegetation, density declined fairly regularly with plant height. Populations in forested sites had few plants of intermediate height, suggesting periodic recruitment. Scrub populations had random dispersion, while those in forests were aggregated. The change in spatial pattern may be related to a change in primary reproductive mode from asexual propagation via fallen fruits to propagation via fallen cladodes. Height was significantly correlated with stem diameter. Intercepts of these relationships increased toward higher elevations, probably in response to the increasing height of the surrounding canopy.     

The introduction ofMimorista pulchellalis [Lepidoptera: Pyraustidae] into South Africa for the biological control of jointed cactus,Opuntia aurantiaca 1. Biology and mass-rearing techniques

A laboratory investigation was conducted on a pyraustid moth imported from South America for jointed cactus control. It was found that the moths were crepuscular, with females laying an average of 48±3.5 eggs over a period of 4–8 days. Larvae hatched out at night and usually tunnelled into the terminal ends of cactus cladodes at a site where young cactus growth occurred. The lifecycle was completed inside the cactus, pupation typically occurring in the dry husk of the cladode on which the egg was laid. Mass-rearing of the moth was easy if plants with young cactus growth were used.      

Behavioral evolution accompanying host shifts in cactophilic Drosophila larvae

For plant utilizing insects, the shift to a novel host is generally accompanied by a complex set of phenotypic adaptations. Many such adaptations arise in response to differences in plant chemistry, competitive environment, or abiotic conditions. One less well‐understood factor in the evolution of phytophagous insects is the selective environment provided by plant shape and volume. Does the physical structure of a new plant host favor certain phenotypes? Here, we use cactophilic Drosophila, which have colonized the necrotic tissues of cacti with dramatically different shapes and volumes, to examine this question. Specifically, we analyzed two behavioral traits in larvae, pupation height, and activity that we predicted might be related to the ability to utilize variably shaped hosts. We found that populations of D. mojavensis living on lengthy columnar or barrel cactus hosts have greater activity and pupate higher in a laboratory environment than populations living on small and flat prickly pear cactus cladodes. Crosses between the most phenotypically extreme populations suggest that the genetic architectures of these behaviors are distinct. A comparison of activity in additional cactophilic species that are specialized on small and large cactus hosts shows a consistent trend. Thus, we suggest that greater motility and an associated tendency to pupate higher in the laboratory are potential larval adaptations for life on a large plant where space is more abundant and resources may be more sparsely distributed.     

Growth characteristics of newly initiated cladodes of Opuntia ficusindica as affected by shading, drought and elevated CO2

Biomass accumulation and area expansion of newly initiated cladodes of Opuntia ficus-indica were studied to help understand the high productivity of this Crassulacean acid metabolism species. In a glasshouse, both dry weight and area increased more and more rapidly for about 30 days and then increased linearly with time up to 63 days. The relative growth rate averaged 0. 12 day^-1, comparable to values for productive C₃ and C₄ plants. New cladodes initiated on basal cladodes with 2-fold higher initial dry weight grew twice as fast. Drought reduced biomass accumulation and area expansion of new cladodes by 62 and 52%, respectively. A 70% reduction in irradiation decreased biomass accumulation of new cladodes by 17% and their thickness by 11%. In a growth chamber containing 720 μmol Co₂ (mol air)^-1, biomass of newly initiated cladodes was 7% higher, area was 8% less, specific mass was 16% higher and less carbohydrate was translocated from basal cladodes than for 360 μmol Co₂ mol^-1. The large capacity for storage of carbohydrate and water in basal cladodes of O. ficus-indica apparently buffered environmental stresses, thereby reducing their effects on growth of daughter cladodes     

Effects of competition,herbivory and substrate disturbance on growth and size structure in pin cherry (Prunus pensylvanica L.) seedlings

We examined separate and interactive effects of intraspecific competition, vertebrate browsing and substrate disturbance on the growth and size structure of pin cherry (Prunus pensylvanica L.) in the first two seasons of growth after clearcutting, in a hardwoods forest in New Hampshire, United States. Over the 15-month study period, 97.5% of 1801 individuals survived, and mean plant height increased from 4-fold at high density to 5-fold at low density. Relative height growth was significantly lower at higher plant densities in two of the three growth periods examined. Vertebrate browsers (moose and deer) significantly preferred taller plants. Browsed plants had higher relative height growth following browsing than unbrowsed plants (compensatory growth) at low and intermediate densities. The degree of compensation declined with density and compensation was not significant at the highest density level. At low and intermediate densities, plants browsed early in life regained height dominance through compensatory growth; they failed to regain dominance at high density. Because compensatory growth tended to offset the effects of size-selective browsing, there was no difference in the degree of size inequality between browsed and unbrowsed plots. However, size inequality increased with plant density. Substrate disturbance caused by logging had no significant effects on either relative height growth or size inequality. The slope of the relationship between relative height growth and initial height increased significantly with density and time, and was higher in unbrowsed than in browsed plots, suggesting that competition among plants was size-asymmetric. Despite the preference of browsers for large plants, there was a clear net growth advantage for plants of large initial size, when the effects of competition, browsing and compensatory growth were combined. The interactive effects of density and browsing demonstrate the importance of a multifactorial approach to the analysis of individual plant performance and population structure.