Alien plants have greater impact than habitat fragmentation on native insect flower visitation networks

Aim

Habitat fragmentation and alien species are among the leading causes of biodiversity loss. In an attempt to reduce the impact of forestry on natural systems, networks of natural corridors and patches of natural habitat are often maintained within the afforested matrix, yet these can be subject to degradation by invasion of non‐native species. Both habitat fragmentation and alien invasive species disrupt the complex interaction networks typical of native communities. This study examines whether an invasive plant and/or the fragmented nature of the forestry landscape influences natural flower visitation networks (FVNs), flower–visitor abundance and richness or flower/visitor species composition.

Location

The species rich and diverse grasslands in the KwaZulu‐Natal Midlands, South Africa is under threat from transformation, particularly by commercial forestry plantations, restricting much of the remaining untransformed grasslands into remnant grassland patches (RGPs). Remaining patches are under additional threat from the invasive Rubus cuneifolius Pursh (bramble). Sites were established in RGPs and in a nearby protected area (PA), with and without brambles present for both areas.

Results

Flower abundance and flower area of native plant species were greater within RGP than in PA, but only in the absence of R. cuneifolius. Flower–visitor assemblages differed between invaded and uninvaded sites and also differed between PA and RGP sites. Both areas lost specialist flower–visitor species in the presence of brambles. Network modularity was greatly reduced by the presence of bramble, indicating a reduction in complexity and organization. The structure of FVNs was otherwise unaffected by presence of bramble or being located in RGPs or the PA.

Main conclusions

The RPGs contribute to regional biodiversity conservation through additional compositional diversity and intact FVNs. Rubus cuneifolius reduces ecological complexity of both RGPs and PAs, however, and its removal must be prioritized to conserve FVNs.     

气候变化对中国农作物虫害发生的影响

基于1961—2010年全国农区527个气象站点气象资料、全国病虫害资料以及农作物种植面积等资料,对全国虫害发生面积与气象因子采用相关分析法,分析了气象要素变化对虫害发生的影响。结果表明:气候变化背景下,年平均温度、平均降水强度分别以0.27℃.10a-1、0.24mm.(d.10a)-1的速度增长,年日照时数以47.40h.10a-1的速度减小;年降水量增长速率为0.14mm.10a-1,但波动较大;虫害发生面积率距平与平均温度、平均降水强度距平呈显著正相关,平均温度、平均降水强度分别每增加1℃、1mm.d-1,虫害发生面积率增加0.648、0.713,虫害发生面积将增加0.96、1.06亿hm2次;虫害发生面积率距平与年日照时数距平呈显著负相关,其每降低100h,虫害发生面积率增加0.40,虫害发生面积将增加0.59亿hm2次;总体上,虫害发生面积率距平与年降水量距平的关系不明显。虫害发生面积率距平与年平均小雨量、微雨量雨日数、小雨量雨日数距平呈显著负相关,3个因子分别每减少1mm、1d、1d,虫害发生面积率增加0.014、0.066、0.052,发生面积将增加0.02、0.10、0.08亿hm2次。     

我国花椒害虫研究进展

危害我国花椒的害虫种类达190余种,隶属于16目82科。文章对我国广泛分布及危害严重的花椒害虫的危害特点、发生规律及防治技术进行综述,将我国花椒害虫分布及危害区分为北部、东部、西南部、华南部4个区域。北部地区的主要害虫包括5目24科30余种,危害严重的害虫为花椒窄吉丁甲、花椒桔啮跳甲、台湾狭天牛等;东部地区的主要害虫包括4目11科20余种,危害严重的害虫为台湾狭天牛、二斑黑绒天牛、吹棉蚧等;西南地区的主要害虫包括5目19科20余种,危害严重的害虫为棉蚜、桑拟轮蚧、花椒伪安瘿蚊等;华南地区的主要害虫包括3目16科20余种,危害严重的害虫为棉蚜、花椒桔啮跳甲、星天牛等。     

Diagnostic molecular markers of six lepidopteran insect pests infesting apples in Korea

Two molecular identification techniques for differentiating six lepidopteran pests infesting apples in Korea are presented. These six species include two internal fruit feeders (Grapholita molesta and Carposina sasakii), two leaf rollers (Adoxophyes sp. and Archips breviplicanus) and two leaf miners (Phyllonorycter ringoniella and Lyonetia prunifoliella). All species occur until near harvest and reduce apple production. A 489 bp fragment of mitochondrial cytochrome oxidase subunit I (COI) was sequenced in these six species. The sequence was used to select species-specific restriction enzyme sites and to design diagnostic polymerase chain reaction (PCR) primers, resulting in the development of restriction fragment length polymorphism (RFLP)-PCR and diagnostic PCR. These methods were reliable and rapid in the identification of these six species.     

Indirect effects of deer on insect pests and soybean plants

1. White-tailed deer (Odocoileus virginianus Zimmermann) and insect pests negatively affect soybean production; however, little is known about how these herbivores potentially interact to affect soybean yield. Previous studies have shown deer browse on non-crop plants affects insect density and insect-mediated leaf damage, which together reduce plant reproductive output. In soybeans, reproductive output is influenced by direct and indirect interactions of different herbivores.
2. Here, we quantified indirect interactions between two groups of herbivores (mammals and insects) and their effects on soybean growth and yield. We examined responses of insect pest communities along a gradient of deer herbivory (29% to 49% browsed stems) in soybean monocultures.
3. Structural equation models showed that deer browse had direct negative effects on soybean plant height and yield. Deer browse indirectly decreased insect-mediated leaf damage by reducing plant height. Deer browse also indirectly increased pest insect abundance through reductions in plant height. Similarly, deer herbivory had an indirect positive effect on leaf carbon: nitrogen ratios through changes in plant height, thereby decreasing leaf nutrition.
4. These results suggest that pest insect abundance may be greater on soybean plants in areas of higher deer browse, but deer browse may reduce insect herbivory through reduced leaf nutrition.

     

Genetic engineering of fungal biocontrol agents to achieve greater efficacy against insect pests

Molecular biology methods have elucidated pathogenic processes in several fungal biocontrol agents including two of the most commonly applied entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana. In this review, we describe how a combination of molecular techniques has: (1) identified and characterized genes involved in infection; (2) manipulated the genes of the pathogen to improve biocontrol performance; and (3) allowed expression of a neurotoxin from the scorpion Androctonus australis. The complete sequencing of four exemplar species of entomopathogenic fungi including B. bassiana and M. anisopliae will be completed in 2010. Coverage of these genomes will help determine the identity, origin, and evolution of traits needed for diverse lifestyles and host switching. Such knowledge combined with the precision and malleability of molecular techniques will allow design of multiple pathogens with different strategies to be used for different ecosystems and avoid the possibility of the host developing resistance.     

中国南方害虫生物防治50周年回顾

综述了中国南方50年来害虫生物防治的研究与应用概况,特别是大卵（蓖麻蚕卵）繁殖赤眼蜂防治甘蔗螟虫的成功先例,为后来国内应用柞蚕卵繁殖赤眼蜂提供了宝贵经验。应用平腹小蜂防治荔枝蝽,解决了荔枝生产的主要害虫问题;引进澳洲瓢虫、孟氏隐唇瓢虫、松突圆蚧花角蚜小蜂均是我国生物防治成功的例证;以生物防治为主的水稻害虫综合防治研究坚持了20多年,从生产实践和理论方面均取得显著的成绩;在昆虫病原微生物的研究与应用方面,利用苏云金杆菌以色列变种防治蚊虫、松毛虫质多角体病毒的发现和应用、斜纹夜蛾核多角体病毒的分离以及中试和工厂化生产、昆虫病原线虫的大量繁殖与应用,取得了一批有应用价值的成果;在分子生物学研究方面,利用基因重组扩大了病原微生物的毒力与杀虫谱。总结和继承我国乃至世界上最早的以虫治虫（黄蚁防治柑桔害虫）的经验,对促进我国生物防治事业的发展具有重要意义。     

Biological control of insect pests in apple orchards in China

Apple is one of the most important fruits in China, and both yield and quality are greatly affected by insect pests. According to surveys, there are more than 200 species of natural enemies in apple orchards. Few, however, have been closely studied. Major natural enemies including parasitoids, predators and pathogens are briefly described in this review, especially focusing on two parasitoids of Trichogramma dendrolimi Matsumura and Aphelinus mali Haldeman, predatory mites and a pathogenic fungus of Beauveria bassiana (Balsamo) Vuillemin as case studies. Augmentation, one important strategy of biological control, supplements the natural control provided by the existing natural enemy community in apple orchards, and greatly increases their efficiency in controlling pests. Conservation biological control is also widely applied in four major apple-producing areas. Based on habitat manipulation, the ground cover planting system helps regulate the microclimate and enhance the biodiversity of apple orchards, effectively conserving the richness and diversity of beneficial insect species. Certain achievements have been made in the main biological control strategies including successful introduction of some exotic natural enemies such as A. mali and Typhlodromus occidentalis Nesbitt, augmentative production and application of biological control agents such as T. dendrolimi, B. bassiana and Bacillus thuringiensis, and further research in conservation of establishing adaptive ground cover planting patterns to local environment. Challenges, however, still exist. Biological control of insect pests in apple orchards is an important part of integrated pest management programs, requiring more research and application in China.     

Biological control of insect pests in litchi orchards in China

This paper describes the current state of the biological control of insect pests in litchi orchards in China. Litchi is growing in importance as a fruit in China and the control of litchi stink bug, Tessaratoma papillosa (Drury) (Hemiptera: Pentatomidae) by the solitary egg endoparasitoid Anastatus japonicus (Ashmead) (Hymenoptera: Eulophidae) is an example of successful classical biological control. This review will cover the current economic status of litchi production in China, the challenges faced in litchi pest management, and possible solutions. The review will also focus on research activities and experiences drawn from many years of experimentation and field work by researchers in an attempt to promote biological control and reduce insecticide use to produce healthier food and a safer environment. Studies on the biology and ecology of T. papillosa and its egg parasitoid A. japonicas will be summarized. The adult longevity and long oviposition period, in combination with the short life cycle, high fecundity, and resistance to harsh environmental conditions make this parasitoid ideal for biological control. The straightforwardness of mass-rearing and easy access to high quality factitious host eggs have made it possible to control T. papillosa with this parasitoid in litchi orchards over large areas in China. Both pest and parasitoid have been thoroughly studied, and A. japonicus has been used in the field for control since late 1960s. The introduction of techniques for mass-rearing of A. japonicus and the parasitoid’s efficacy in controlling T. papillosa once released will be discussed. Finally, we will address the problems currently facing litchi pest management and the importance of conservation biological control in the development and implementation of integrated pest management (IPM).     

Forest defoliator outbreaks under climate change: effects on the frequency and severity of outbreaks of five pine insect pests

To identify general patterns in the effects of climate change on the outbreak dynamics of forest‐defoliating insect species, we examined a 212‐year record (1800–2011) of outbreaks of five pine‐defoliating species (Bupalus piniarius, Panolis flammea, Lymantria monacha, Dendrolimus pini, and Diprion pini) in Bavaria, Germany for the evidence of climate‐driven changes in the severity, cyclicity, and frequency of outbreaks. We also accounted for historical changes in forestry practices and examined effects of past insecticide use to suppress outbreaks. Analysis of relationships between severity or occurrence of outbreaks and detrended measures of temperature and precipitation revealed a mixture of positive and negative relationships between temperature and outbreak activity. Two moth species (P. flammea and Dendrolimus pini) exhibited lower outbreak activity following years or decades of unusually warm temperatures, whereas a sawfly (Diprion pini), for which voltinism is influenced by temperature, displayed increased outbreak occurrence in years of high summer temperatures. We detected only one apparent effect of precipitation, which showed Dendrolimus pini outbreaks tending to follow drought. Wavelet analysis of outbreak time series suggested climate change may be associated with collapse of L. monacha and Dendrolimus pini outbreak cycles (loss of cyclicity and discontinuation of outbreaks, respectively), but high‐frequency cycles for B. piniarius and P. flammea in the late 1900s. Regional outbreak severity was generally not related to past suppression efforts (area treated with insecticides). Recent shifts in forestry practices affecting tree species composition roughly coincided with high‐frequency outbreak cycles in B. piniarius and P. flammea but are unlikely to explain the detected relationships between climate and outbreak severity or collapses of outbreak cycles. Our results highlight both individualistic responses of different pine‐defoliating species to climate changes and some patterns that are consistent across defoliator species in this and other forest systems, including collapsing of population cycles.     

Is insect defoliation in eucalypt forests greater than that in other temperate forests?

Claims have been made in the past that insect defoliation in eucalypt forests of Australia is both chronically high and greater than defoliation levels in northern temperate forests. Recent published data, however, indicate that some eucalypt forests may sustain low level defoliation. Careful reexamination of the literature on defoliation in eucalypt forests indicates that there are not enough data available to quantify defoliation on an Australian-wide basis. Therefore it cannot be claimed that insect defoliation in eucalypt forests is greater than that in other temperate forests. There are also insufficient data to claim that insects are a major factor responsible for the growth differential between indigenous and overseas plantation-grown eucalypts. The ecological impact of herbivorous insects in eucalypt and northern temperate forests is also discussed.     

我国苹果害虫(螨)的研究与防治:回顾与展望

20世纪后50年尤其是改革开放20年来,我国果业生产发展迅猛,成就举世瞩目。截止1998年全国果园面积863．55万hmz,果品总产量达54529亿kg,居世界之首。在落叶果树中苹果发展最快,1998年为283．8万hm’,产量达194．8亿kg,面积和产量在苹果生产国中均居首位,我国年人均占有苹果已达15kg,超出世界人均水平4kg左右。但若以单位面积产量衡量,我国与水果生产发达国家相比尚有较大差距。1998年我国苹果每667mz产量为405．Ikg,仅及发达国家的1／3－l／5。这在一定程度上反映了我国水果生产管理水平的差距,其中病虫为害是重要因素之一。本…     

Tea: Biological control of insect and mite pests in China

Tea is one of the most economically important crops in China. To secure its production and quality, biological control measures within the context of integrated pest management (IPM) has been widely popularized in China. IMP programs also provide better control of arthropod pests on tea with less chemical insecticide usage and minimal impact on the environment. More than 1100 species of natural enemies including about 80 species of viruses, 40 species of fungi, 240 species of parasitoids and 600 species of predators, as well as several species of bacteria have been recorded in tea ecosystems in China. Biological and ecological characteristics of some dominant natural enemies have been well documented. Several viral, bacterial, and fungal insecticides have been commercially utilized at large scale in China. Progress in biological control methods in conjunction with other pest control approaches for tea insect pest management is reviewed in this article. Knowledge gaps and future directions for tea pest management are also discussed.     

Reprint of: Biological control of rice insect pests in China

Rice is one of the most important food crops in the world. China has the second largest area of the rice growing in the world and the highest yield of rice produced. Infestation by insect pests, especially rice planthoppers, stem borers and leaf folders, is always a serious challenge to rice production in China. Current methods for controlling insect pests in China mainly include good farming practices, biological control, breeding and growing resistant varieties, and the use of chemical insecticides. However, for farmers, the favorite method for insect pest control is still the application of chemical insecticide, which not only causes severe environmental pollution and the resurgence of herbivores but also reduces populations of the natural enemies of herbivores. To control insect pests safely, effectively and sustainably, strategies encouraging biological control are currently demanded. Here we review the progress that has been made in the development and implementation of biological controls for rice in China since the 1970s. Such progress includes the species identification of the natural enemies of rice insect pests, the characterization of their biology, and the integration of biological controls in integrated pest management. To develop effective ecological engineering programs whose aim is to implement conservation biological controls, further research, including the evaluation of the roles of plants in non-crop habitats in conservation biological controls, volatiles in enhancing efficiency of natural enemies and natural enemies in manipulating insect pests, and education to increase farmers’ knowledge of biological controls, is proposed.     

Small variations in climate and soil conditions may have greater influence on multitaxon species occurrences than past and present human activities in temperate mountain forests

Aim

Human activity is known to greatly influence species occurrences. In forest ecosystems, biodiversity is often believed to be influenced by two habitat characteristics: (1) forest continuity, related to a minimum length of time in a wooded state since a threshold date; and (2) stand maturity, related to the availability of late‐developmental‐forest attributes. In a context of ongoing global biodiversity loss, qualifying the effect of past and present human activity on forest ecosystems while taking into account variations in abiotic factors is of primary importance for conservation.

Location

Temperate mountain forests in the Northern Alps.

Method

Based upon a sampling design crossing forest continuity (ancient vs. Recent) and stand maturity (mature vs. overmature), and while controlling for the effect of two major environmental factors, soil and climate, we explored the individual response of saproxylic beetle, springtail, herbaceous plant and epiphytic macrolichen species to past and present human activity.

Results

Forest continuity influenced the occurrence of relatively few species, indicating that past land use had almost no legacy effect on the species occurring in the study forests today. In contrast, stand maturity had an overall positive effect on species occurrences. However, our results showed that species occurrences were more obviously influenced by abiotic conditions. Indeed, beyond the effect of continuity and maturity factors, the probability of presence of numerous species was best explained by climate and soil.

Main conclusions

Overall, we show that species occurrence was more influenced by stand maturity than by forest continuity, but also that site‐specific characteristics were of great importance in explaining the probability of presence for numerous species. In the ecological context of alpine forests, these findings emphasize the need to better control for climatic and edaphic conditions in order to (1) improve accuracy in predicting species occurrence and (2) better design areas of conservation interest.

     

Invasive clonal plant species have a greater root-foraging plasticity than non-invasive ones

Clonality is frequently positively correlated with plant invasiveness, but which aspects of clonality make some clonal species more invasive than others is not known. Due to their spreading growth form, clonal plants are likely to experience spatial heterogeneity in nutrient availability. Plasticity in allocation of biomass to clonal growth organs and roots may allow these plants to forage for high-nutrient patches. We investigated whether this foraging response is stronger in species that have become invasive than in species that have not. We used six confamilial pairs of native European clonal plant species differing in invasion success in the USA. We grew all species in large pots under homogeneous or heterogeneous nutrient conditions in a greenhouse, and compared their nutrient-foraging response and performance. Neither invasive nor non-invasive species showed significant foraging responses to heterogeneity in clonal growth organ biomass or in aboveground biomass of clonal offspring. Invasive species had, however, a greater positive foraging response in terms of root and belowground biomass than non-invasive species. Invasive species also produced more total biomass. Our results suggest that the ability for strong root foraging is among the characteristics promoting invasiveness in clonal plants.     

Increased temperature variation poses a greater risk to species than climate warming

Increases in the frequency, severity and duration of temperature extremes are anticipated in the near future. Although recent work suggests that changes in temperature variation will have disproportionately greater effects on species than changes to the mean, much of climate change research in ecology has focused on the impacts of mean temperature change. Here, we couple fine-grained climate projections (2050–2059) to thermal performance data from 38 ectothermic invertebrate species and contrast projections with those of a simple model. We show that projections based on mean temperature change alone differ substantially from those incorporating changes to the variation, and to the mean and variation in concert. Although most species show increases in performance at greater mean temperatures, the effect of mean and variance change together yields a range of responses, with temperate species at greatest risk of performance declines. Our work highlights the importance of using fine-grained temporal data to incorporate the full extent of temperature variation when assessing and projecting performance.