Growth and development of immature life stages ofPropylaea 14-punctata L. andCoccinella 7-punctata L. [Col.: Coccinellidae] simulated by the metabolic pool model

The conversion of aphid prey tissue (Acyrthosiphon pisum Harris) into predator biomass (immature life stages ofPropylaea 14-punctata L. andCoccinella 7-punctata L.) is calculated by plotting weight gain against assimilation (i.e. consumption minus egestion). This concept is added to the metabolic pool model byGutierrez et al. (1981) that enables the simulation of growth and development of a predator on a physiological basis. Physiological time is expressed in daydegrees above lower development thresholds for both species. Visual examination of observed and calculated values showed that the model satisfactorily describes the growth patterns of the above predators.      

Effects of the concurrent exclusion of ants and earwigs on aphid abundance in an organic citrus grove

Based on the well-known mutualism between ants (Hymenoptera: Formicidae) and aphids (Homoptera: Aphididae), we conducted a five-year experiment of ant-exclusion from the canopies of citrus trees as a possible method of biological control of aphids. However, our results showed that the exclusion of ants from the canopies increased, instead of reducing, aphid abundance. To explain this unexpected result, we reasoned that the exclusion of ants from the canopies might also have excluded crawling insects that prey on aphids, such as the European earwig (Forficula auricularia L., Dermaptera: Forficulidae). Such a possibility is supported by the negative relationship between aphid density and the abundance of earwigs, consistent with a top-down control of aphids by earwigs. In contrast, the abundance of other aphid predators (Coleoptera: Coccinellidae, and Heteroptera) had no such negative effect on aphid density but a positive one, suggesting a bottom-up control, and showed no differences between control and ant-excluded trees. Thus, the most likely explanation for the increase in aphid abundance in the ant-excluded trees is the absence of earwigs from the canopies of the experimental trees, providing further evidence of the major role that earwigs play as control agents of aphids in cultivated trees.     

Small-scale disturbances spread along trophic chains: leaf-cutting ant nests, plants, aphids, and tending ants

Small-scale disturbances caused by animals often modify soil resource availability and may also affect plant attributes. Changes in the phenotype of plants growing on disturbed, nutrient-enriched microsites may influence the distribution and abundance of associated insects. We evaluated how the high nutrient availability generated by leaf-cutting ant nests in a Patagonian desert steppe may spread along the trophic chain, affecting the phenotype of two thistle species, the abundance of a specialist aphid and the composition of the associated assemblage of tending ants. Plants of the thistle species Carduus nutans and Onopordum acanthium growing in piles of waste material generated by leaf-cutting ant nests (i.e., refuse dumps) had more leaves, inflorescences and higher foliar nitrogen content than those in non-nest soils. Overall, plants in refuse dumps showed higher abundance of aphids than plants in non-nest soils, and aphid colonies were of greater size on O. acanthium plants than on C. nutans plants. However, only C. nutans plants showed an increase in aphid abundance when growing on refuse dumps. This resulted in a similar aphid load in both thistle species when growing on refuse dumps. Accordingly, only C. nutans showed an increase in the number of ant species attending aphids when growing on refuse dumps. The increase of soil fertility generated by leaf-cutting ant nests can affect aphid abundance and their tending ant assemblage through its effect on plant size and quality. However, the propagation of small-scale soil disturbances through the trophic chain may depend on the identity of the species involved.     

Effects of elevated CO2 on five plant-aphid interactions

We investigated interactions between five species of phloem-feeding aphids (Homoptera: Aphididae) and their host plants at elevated CO₂; Acyrthosiphon pisum (Harris) on Vicia faba L., Aphis nerii Boyer de Fonscolombe on Asclepias syriaca L., Aphis oenotherae Oestlund on Oenothera biennis L., Aulacorthum solani (Kaltenbach) on Nicotiana sylvestris Speg. & Comes and Myzus persicae (Sulzer) on Solanum dulcamara L. Host plants grown at elevated CO₂ generally had greater biomass, leaf area and C:N ratios than those grown at ambient CO₂, while plants with aphids had lower biomass and leaf area than those without aphids.The responses of aphid populations to elevated CO₂ were species-specific with one species increasing (M. persicae), one decreasing (A. pisum), and the other three being unaffected. CO₂ treatment did not affect the proportion of alate individuals produced. In general, aphid abundance was not significantly related to foliar nitrogen concentration.We performed separate analyses to test whether either aphid presence or aphid abundance modified the response of host plants to elevated CO₂. In terms of aphid presence, only three of the potential 15 interactions (five aphid species x three plant traits) were significant; A. solani slightly modified the response of the plant biomass to elevated CO₂ and M. persicae affected the response of leaf area and allocation. In terms of aphid abundance, only two of the potential 15 interactions were significant with A. nerii modifying the plant response to CO₂ in terms of total leaf area and allocation.We conclude that, in contrast to other insect groups such as leaf chewers, populations of most phloem-feeders may not be negatively affected by increased CO₂ concentrations in the future. The reasons for this difference include the possibility that aphids may be able to compensate for changes in host plant quality by altering feeding behaviour or by synthesizing amino acids. In addition, there is little evidence that aphid herbivory, even at high levels, will substantially modify the response of plants to elevated CO₂.     

Varying responses of insect herbivores to altered plant chemistry under organic and conventional treatments

The hypothesis that plants supplied with organic fertilizers are better defended against insect herbivores than those supplied with synthetic fertilizers was tested over two field seasons. Organic and synthetic fertilizer treatments at two nitrogen concentrations were supplied to Brassica plants, and their effects on the abundance of herbivore species and plant chemistry were assessed. The organic treatments also differed in fertilizer type: a green manure was used for the low-nitrogen treatment, while the high-nitrogen treatment contained green and animal manures. Two aphid species showed different responses to fertilizers: the Brassica specialist Brevicoryne brassicae was more abundant on organically fertilized plants, while the generalist Myzus persicae had higher populations on synthetically fertilized plants. The diamondback moth Plutella xylostella (a crucifer specialist) was more abundant on synthetically fertilized plants and preferred to oviposit on these plants. Glucosinolate concentrations were up to three times greater on plants grown in the organic treatments, while foliar nitrogen was maximized on plants under the higher of the synthetic fertilizer treatments. The varying response of herbivore species to these strong differences in plant chemistry demonstrates that hypotheses on defence in organically grown crops have over-simplified the response of phytophagous insects.     

Aphelinus albipodus(Hymenoptera: Aphelinidae) andDiaeretiella rapae(Hymenoptera: Braconidae) Parasitism onDiuraphis noxia(Homoptera: Aphididae) Infesting Barley Plants Differing in Plant Resistance to Aphids

Russian wheat aphid,Diuraphis noxia(Mordvilko), as a pest of small grains, has prompted research into biological control and host plant resistance. In the presence of Russian wheat aphid, leaves of a susceptible barley (Morex) are curled and chlorotic and sustain large densities of this aphid, while leaves of a resistant barley (STARS-9301B) remain flat and green and sustain fewer aphids. Might parasitism of Russian wheat aphid byAphelinus albipodusHayat & Fatima andDiaeretiella rapaeMcIntosh be affected differently by these plant types? When presented the plants separately and based on parasitism rate relative to aphid density, the largerD. rapaewas more effective in parasitizing relatively high densities of aphids within curled leaves of Morex than relatively low densities of aphids on uncurled leaves of STARS-9301B. Parasitism byA. albipodusdid not significantly differ among the plants. When given a choice of plants, approximately equal rates of parasitism occurred on the two plant lines for both parasitoid species, and parasitism byD. rapaewas greater thanA. albipodus.These data indicate that using parasitoid size as an indicator of success in a physically restricted environment may be misleading, when considered in a plant environment responsive in several manners to aphids (chlorosis, curling, and ability to sustain Russian wheat aphid). We expect that use of resistant barley will result in decreased parasitoid abundance as aphid densities decrease. However, parasitism rates are expected to be approximately equal on resistant and susceptible barley. In this system, plant resistance and biocontrol are compatible management strategies.     

我国新发现一种外来蚜虫——刺槐附毛斑蚜Appendiseta robiniae

记述了采自北京刺槐上的1种中国的记录外来蚜虫——刺槐附毛斑蚜,它原产于北美,寄主为刺槐,在当地一些地区较为常见,并已扩散到欧洲等地。描述了有翅孤雌蚜、无翅雌性蚜和有翅雄性蚜的鉴别特征,并提供了生态图片。最后讨论了它的潜在危害性及蚜虫寄主植物、蚜群生活状及生态照片在蚜虫识别上的重要性。     

Effects of aphid-tending Argentine ants, nitrogen enrichment and early-season herbivory on insects hosted by a coastal shrub

The presence of the exotic Argentine ant, Linepithema humile Mayr (Hymenoptera: Dolichoderinae), nitrogen enrichment, and early-season herbivory by the specialist beetle Trirhabda bacharidis (Coleoptera: Chrysomelidae) have been shown, through separate experiments, to affect the densities of insect herbivores of the coastal shrub Baccharis halimifolia (Asteraceae), in Florida. Using a fully-factorial field experiment, we examined the relative importance of all three of these factors to the six most common insect herbivore species utilizing this host plant in a West Central Florida coastal habitat. The presence of ants affected more herbivore species than either early-season herbivory by larval T. bacharidis or nitrogen enrichment. Experimental reductions of L. humile resulted in reductions of an aphid, its coccinellid predators, and adult T. bacharidis, and increases of two species of leafminers and one species of stemborer. Due to the strong negative effects of stemborer herbivory on host plant survival, the increase in stemborer abundance led to increased host plant mortality. Early-season herbivory by larval T. bacharidis only affected the abundance of aphids and their predators, both of which were more abundant on trees with reduced early-season herbivory. Nitrogen fertilization had the most limited effects and only T. bacharidis larvae achieved higher densities on fertilized trees. Our results indicate that aphid tending by the exotic L. humile affects other insects on B. halimifolia more so than herbivory by the exploitative competitor T. bacharidis or nitrogen as a limiting nutrient.     

Hyperpredation by generalist predatory mites disrupts biological control of aphids by the aphidophagous gall midge Aphidoletes aphidimyza

Biological control of different species of pest with various species of generalist predators can potentially disrupt the control of pests through predator-predator interactions. We evaluate the impact of three species of generalist predatory mites on the biological control of green peach aphids, Myzus persicae (Sulzer) with the aphidophagous gall midge Aphidoletes aphidimyza (Rondani). The predatory mites tested were Neoseiulus cucumeris (Oudemans), Iphiseius degenerans (Berlese) and Amblyseius swirskii Athias–Henriot, which are all commonly used for pest control in greenhouse sweet pepper. All three species of predatory mites were found to feed on eggs of A. aphidimyza, even in the presence of abundant sweet pepper pollen, an alternative food source for the predatory mites. In a greenhouse experiment on sweet pepper, all three predators significantly reduced population densities of A. aphidimyza, but aphid densities only increased significantly in the presence of A. swirskii when compared to the treatment with A. aphidimyza only. This stronger effect of A. swirskii can be explained by the higher population densities that this predator reached on sweet pepper plants compared to the other two predator species. An additional experiment showed that female predatory midges do not avoid oviposition sites with the predator A. swirskii. On the contrary, they even deposited more eggs on plants with predatory mites than on plants without. Hence, this study shows that disruption of aphid control by predatory mites is a realistic scenario in sweet pepper, and needs to be considered when optimizing biological control strategies.     

Honeydew collection by the invasive garden ant Lasius neglectus versus the native ant L. grandis

Honeydew collection performed by the invasive ant Lasius neglectus and by the native ant L. grandis was compared. The invasive ant collected 2.09 kg of honeydew per tree while the native ant collected 0.82 kg. The aphid Lachnus roboris was visited by both ant species. In holm oaks colonized by L. neglectus, aphid abundance tended to increase and its honeydew production increased twofold. The percentage of untended aphids was lower in holm trees occupied by L. neglectus. As tending ants also prey on insects, we estimated the percentage of carried insects. The native ant workers carried more insects than the invasive ant. Both ant species preyed mainly on Psocoptera and the rarely tended aphid, Hoplocallis picta. We conclude that the higher honeydew collection achieved by L. neglectus was the consequence of (1) its greater abundance, which enabled this ant to tend more Lachnus roboris and (2) its greater level of attention towards promoting an increase of honeydew production. Handling editor: Heikki Hokkanen     

Tomato-aphid-hoverfly: a tritrophic interaction incompatible for pest management

Trichome-based tomato resistance offers the potential to reduce pesticide use, but its compatibility with biological control remains poorly understood. We evaluated Episyrphus balteatus De Geer (Diptera, Syrphidae), an efficient aphidophagous predator, as a potential biological control agent of Myzus persicae Sulzer (Hemiptera, Aphididae) on trichome-bearing tomato cultivars. Episyrphus balteatus’ foraging and oviposition behavior, as well as larval mobility and aphid accessibility, were compared between two tomato cultivars (Lycopersicon esculentum Mill. ‘Moneymaker’ and ‘Roma’) and two other crop plants; broad bean (Vicia faba L.) and potato (Solanum tuberosum L.). Hoverfly adults landed and laid more eggs on broad beans than on three species of Solanaceae. Hoverfly larval movement was drastically reduced on tomato, and a high proportion of hoverfly larvae fell from the plant before reaching aphid prey. After quantifying trichome abundance on each of these four plants, we suggest that proprieties of the plant surface, specifically trichomes, are a key factor contributing to reduced efficacy of E. balteatus as a biological agent for aphid control on tomatoes. Handling editor: Stanislaw Gorb     

Ectopic expression of mitochondrial gamma carbonic anhydrase 2 causes male sterility by anther indehiscence

Plant mitochondria include gamma-type carbonic anhydrases (γCAs) of unknown function. In Arabidopsis, the γCAs form a gene family of five members which all are attached to the NADH dehydrogenase complex (complex I) of the respiratory chain. Here we report a functional analysis of gamma carbonic anhydrase 2 (CA2). The gene encoding CA2 is constitutively expressed in all plant organs investigated but it is ten fold induced in flowers, particularly in tapetal tissue. Ectopic expression of CA2 in Arabidopsis causes male sterility in transgenic plants. In normal anther development, secondary thickenings of the endothecial cell wall cause anthers to open upon dehydration. Histological analyses revealed that abnormal secondary thickening prevents anther opening in 35S::CA2 transgenic plants. CA2 abundance in transgenic plants is increased 2–3 fold compared to wild-type plants as revealed by Western blotting analyses. Moreover, abundance of other members of the CA family, termed CA3 and CAL2, is increased in transgenic plants. Oxygen uptake measurements revealed that respiration in transgenic plants is mainly based on NADH reduction by the alternative NADH dehydrogenases present in plant mitochondria. Furthermore, the formation of reactive oxygen species (ROS) is very low in transgenic plants. We propose that reduction in ROS inhibits H₂O₂ dependent lignin polymerization in CA2 over-expressing plants, thereby causing male sterility. Gene bank accession number: AY085025 (At1g47260).     

晋西北丘陵风沙区柠条林下草本植物群落组成和种群生态位变化特征

晋西北丘陵风沙区生态环境脆弱,是我国风沙活动危害最为严重的地区之一。为探究晋西北丘陵风沙区人工柠条林林下草本植物群落组成和种群生态位变化规律,以不同种植年限（撂荒地CK、6、12、18、40、50 a）人工柠条林林下天然草本植物群落作为研究对象,对其群落组成、重要值及种群生态位变化特征进行分析。研究结果表明：（1）不同年限柠条林下天然草本植物组成共记录到22科41属52种,其中,种植前期（0-6 a）林下草本植物以一年生草本植物为优势类群,伴有少数多年生草本植物（3种）;种植中期（12-18 a）林下草本植物主要由多年生草本植物（12种）为主,伴生有一年生草本植物（6种）及天然灌木（2种）组成;在种植后期（40-50 a）,林下草本植物依然以多年生草本植物（12种）为主。（2）在不同年限柠条林下,草本植物生态位宽度和生态位重叠发生明显变化,种植前期（0-12 a）的优势类群为一年生先锋物种（米蒿和野燕麦）,其生态位宽度最宽（9.46、9.34）,且与其他物种的生态位重叠程度最大（0.3、0.29）;而种植中后期（18-50 a）优势类群变为多年生草本植物,优势种披碱草与其他物种的生态位重叠程度最大（0.42）,说明其为林下植物群落主要的优势种和泛化种。（3）柠条林种植后期（50 a）,多数草本植物主要集中分布在生态位重叠系数DCA排序图的中心位置,说明在种植后期草本植物对相同环境的资源竞争激烈,林下草本植物群落处于演替过渡阶段。综上,人工种植柠条林相较于天然恢复（CK）,更有利于增加草本植物群落的多样性,但林下植物群落对资源的竞争更为激烈。这些研究结果对干旱半干旱地区风沙区植被恢复和生态重建具有重要的参考价值,对人工林生态恢复具有重要意义。     

Seasonal abundance of Allothrombium monochaetum and Allothrombium pulvinum in Navarra-Nafarroa (northern Spain), with notes on larval host preference and rate of parasitism

In this paper we report on the seasonal abundance of velvet mite larvae of Allothrombium pulvinum Ewing and Allothrombium monochaetum Goldarazena and Zhang in a meadow located in the mediterranean Navarra-Nafarroa region (northern Spain). Larvae of A. monochaetum peaked in numbers on Aphis fabae in mid-June while larvae of A. pulvinum peaked in the third week of July. Both species preferred the aphid thorax as attachment site. We also provide a list of aphid hosts of both mites and observed density of parasites on the hosts.     

Food web structure of aphids and their parasitoids in Belgian fruit agroecosystems

Community structures of aphids and their parasitoids were studied in fruit crop habitats of eastern Belgium in 2014 and 2015. Quantitative food webs of these insects were constructed separately for each year, and divided into subwebs on three host‐plant categories, fruit crop plants, non‐crop woody and shrub plants and non‐crop herbaceous plants. The webs were analyzed using the standard food web statistics designed for binary data. During the whole study period, 78 plant species were recorded as host plants of 71 aphid species, from which 48 parasitoid species emerged. The community structure, aphid / parasitoid species‐richness ratio and trophic link number varied between the two years, whereas the realized connectance between parasitoids and aphids was relatively constant. A new plant–aphid–parasitoid association for Europe was recorded. Dominant parasitoid species in the study sites were Ephedrus persicae, Binodoxys angelicae and Praon volucre: the first species was frequently observed on non‐crop trees and shrubs, but the other two on non‐crop herbaceous plants. The potential influence, through indirect interactions, of parasitoids on aphid communities was assessed with quantitative parasitoid‐overlap diagrams. Symmetrical links were uncommon, and abundant aphid species seemed to have large indirect effects on less abundant species. These results show that trophic indirect interactions through parasitoids may govern aphid populations in fruit crop habitats with various non‐crop plants, implying the importance for landscape management and biological control of aphid pests in fruit agroecosystems.     

Interaction of endophytic diazotrophic bacteria and Fusarium oxysporum f. sp. cubense on plantlets of banana ‘Maça’

The objective of this work was to evaluate the effect of endophytic diazotrophic bacteria Herbaspirillum and Burkholderia on the Fusarium oxysporum f. sp. cubense (Foc) establishment and on the plantlets growth of the ‘Maçã’ banana (Musa spp., group ABB). Two assays were carried out in a greenhouse at the National Center of Tropical Agroindustry in Fortaleza city, Ceará State (Brazil), using randomized block designs in the factorial arrangements 4?×?2 and 8?×?2. On the first trial plantlets were inoculated with the Burkholderia sp. AB202; Herbaspirillum sp., BA227, both of strains and controls bacteria, with and without Foc and cultivated in pots filled with an autoclaved mixture of washed sand and vermiculite (ratio 3:2 v v^?1), during 4 months. On a second assay, plants were subjected to following conditions: absence and presence of strains AB202, AB213 (Burkholderia spp.), BA227, BA234 (Herbaspirillum-like), AB202 plus BA227, AB213 plus BA234, the mixture of the four bacterial strain, absence and presence of the Foc; and cultivated in pots filled with autoclaved Haplic Arenosol, during 2 months. The plant association with diazotrophs and the Foc was confirmed, and factors interacted significantly on the most probable number of bacteria and the colony forming units of the pathogen on roots and plant rhizomes. The potential of the endophytes on the inhibition of Foc propagate units and on the plant growth promotion was demonstrated. The higher biomass was observed four and 2 months after plant inoculation with AB202 and BA234. Results showed that these endophytes may be used as potential biofertilizer and biocontrol agents.     

常绿阔叶林植物叶片N、P化学计量特征对毛竹扩张的响应

为从生态化学计量内平衡角度解释常绿阔叶林不同层次植物对毛竹(Phyllostachys edulis)扩张的生存响应差异性,该研究采用空间代替时间的方法,在江西井冈山国家级自然保护区沿毛竹扩张方向选取典型毛竹-常绿阔叶林界面,依次设置毛竹林、竹阔混交林和常绿阔叶林样地,比较分析了毛竹扩张方向上样地内不同乔木层、灌木层、草本层植物叶片及土壤N、P含量及比例。结果表明:(1)从毛竹林到阔叶林,土壤N含量上升,P含量下降,N:P上升(P<0.05); 乔木层树种 [红楠(Machilus thunbergii)、赤杨叶(Alniphyllum fortunei)及交让木(Daphniphyllum macropodum)]叶片P含量下降,N:P上升(P<0.05); 除灌木层的红果山胡椒(Lindera erythrocarpa)外,各林分中的灌木层和草本层植物N、P含量及比例变化较小。(2)土壤N:P与乔木层、草本层和灌木层植物叶片N:P分布呈显著正相关、负相关与不相关。(3)在各林分中,毛竹叶片N、P含量及比例较稳定。综上认为,毛竹通过改变土壤N、P化学计量特征进行扩张,引起植物体N、P元素化学计量特征发生变化。灌木及草本植物受土壤异质性影响较小,但是乔木层植物N、P元素化学计量特征却因此失衡,这可能是阔叶林乔木层树种存亡受威胁的重要原因。     

Revision of the genus Clibadium (Asteraceae, Heliantheae)

Clibadium L. (Asteraceae, Heliantheae) is a genus of 29 species distributed throughout latin America, from Mexico to Peru, and in the West Indies, with high numbers of species in Costa Rica, Colombia, and Ecuador.Clibadium includes shrubs and small trees; usually with loosely aggregated capitula; herbaceous phyllaries arranged in 1–5 series; receptacles usually paleaceous throughout; corollas of pistillate florets 2–4-lobed; corollas of the staminate florets 4–5-lobed; purple to black anthers; and chromosome numbers alln=16. Two sections of species previously recognized are here considered as subgenera (subg.Paleata and subg.Clibadium) containing two and four sections, respectively.Clibadium subg.Paleata contains five species distributed in sects.Eggersia (3 spp.) andTrixidium (2 spp.), and subg.Clibadium has 24 species distributed among sects.Clibadium (6 spp.),Glomerata (9 spp.),Grandifolia (5 spp.), andOswalda (4 spp.).