Diversity of natural enemies in Central Otago,New Zealand apple orchards: a practical measure of sustainability in pest management?

The diversity of the arthropod fauna in apple orchards in Central Otago was recorded from 1994 to 1999 using beating trays, pitfall traps, and sticky traps and the data analysed by the Shannon–Wiener Index. Three different fruit production systems were compared, conventional (CFP), integrated (IFP), and biological (BFP), to determine whether total arthropod diversity and/or the diversity of natural enemies (predators and parasitoids) could be used to measure the sustainability of their pest management practices. The contribution of natural enemies to the diversity indices was also examined to determine if they reflected the key species essential for sustainable pest management. The diversity of natural enemies in beating trays was found to be the measure most sensitive to changes in pest management. The diversity of both the total arthropod fauna and natural enemies was much lower under CFP than under either IFP or BFP, due to the use of broad-spectrum pesticides. This practice made the CFP programme unsustainable and it is no longer used. During the transition from CFP to IFP, the diversity indices rose to become similar to that in the BFP programme by the third season. The introduction of frequent applications of fungicides in BFP, including lime sulphur, appeared to reduce total arthropod and natural enemy diversity. Falls in the diversity indices for natural enemies were shown to reflect reduced numbers, range, and evenness of natural enemies but not necessarily the key species known to be critical for sustainable pest management. It is proposed that a Shannon–Wiener Index for natural enemies in beating trays of 0.2 or less in summer is strongly indicative of unsustainable pest management in Otago apple orchards. On the other hand, indices of 0.3–0.8, as found under IFP and BFP, do not give unequivocal or quantitative indications of the sustainability of pest management. A suite of other measures of sustainability are more useful, notably combining lower pesticide use, reduced pest damage and presence at harvest, the greater roles of key natural enemies, more effective plant resistance to pests and diseases, and higher profitability.     

Faecal pellets of lichenivorous mites contain viable cells of the lichen-forming ascomycete Xanthoria parietina and its green algal photobiont, Trebouxia arboricola

The bright yellow wall lichen, Xanthoria parietina , is usually inhabited by oribatid mites (Acari) which do not only find shelter, but also graze on selected areas of the thallus. As X. parietina does not produce symbiotic vegetative propagules and its compatible photobiont, unicellular green algae of the genus Trebouxia , are rare outside lichen thalli, we tested the hypothesis of dispersal of viable Trebouxia cells via acarine faeces. The lichenivorous mites, Trhypochtonius tectorum and Trichoribates trimaculatus , were isolated from thalli of X. parietina and cultured in the laboratory on a lichen diet. Light microscopic investigations of faecal pellets from mites that had been feeding on X. parietina indicated gut passage of intact ascospores and photobiont cells. In a series of experiments, viable algal and fungal cells contained in such faecal pellets were cultured. The taxonomic affiliation of these isolates was identified using molecular techniques, i.e. comparative investigations of nuclear ribosomal gene data (ITS 1 and 2, 5.8S rDNA) in the algal and fungal partners, and of the species-specific hydrophobin gene sequence in the fungal partner. Our culturing experiments demonstrated that the faecal pellets of both lichenivorous mites, upon feeding on X. parietina , contain viable ascospores and photobiont cells ( Trebouxia arboricola ) and thus might be a common and successful mode of vegetative short- and long-distance dispersal of this and numerous other lichen-forming ascomycetes and their photobionts. Future studies will have to elucidate the evolutionary significance of invertebrate interactions with lichens. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 259–268.     

林丹烟剂干扰下毛竹(Phyllostachys heterocycla cv.pubescens)林节肢动物群落的结构与组成

对林丹烟剂干扰下毛竹（Phyllostachys heterocycla cv.pubescens）林节肢动物群落结构与组成的系统定位观察与分析表明：长期使用林丹烟剂明显增加了群落主要物种（Pi≥0.05）的植食性种类及其优势度,显著降低群落总体的物种多样性,减少蜘蛛目、膜翅目、鞘翅目和双翅目或捕食性、寄生性和中性功能集团的物种数,削弱林冠层寄生性和捕食性物种在种类和数量上对植食性物种的制约潜能,引起叶部植食性害虫的暴发。因此,在毛竹害虫控制中应避免长期大量使用林丹烟剂。     

The molecular bases of plant resistance and defense responses to aphid feeding: current status

Plant genes participating in the recognition of aphid herbivory in concert with plant genes involved in defense against herbivores mediate plant resistance to aphids. Several such genes involved in plant disease and nematode resistance have been characterized in detail, but their existence has only recently begun to be determined for arthropod resistance. Hundreds of different genes are typically involved and the disruption of plant cell wall tissues during aphid feeding has been shown to induce defense responses in Arabidopsis, Triticum, Sorghum, and Nicotiana species. Mi‐1.2, a tomato gene for resistance to the potato aphid, Macrosiphum euphorbiae (Thomas), is a member of the nucleotide‐binding site and leucine‐rich region Class II family of disease, nematode, and arthropod resistance genes. Recent studies into the differential expression of Pto‐ and Pti1‐like kinase genes in wheat plants resistant to the Russian wheat aphid, Diuraphis noxia (Mordvilko), provide evidence of the involvement of the Pto class of resistance genes in arthropod resistance. An analysis of available data suggests that aphid feeding may trigger multiple signaling pathways in plants. Early signaling includes gene‐for‐gene recognition and defense signaling in aphid‐resistant plants, and recognition of aphid‐inflicted cell damage in both resistant and susceptible plants. Furthermore, signaling is mediated by several compounds, including jasmonic acid, salicylic acid, ethylene, abscisic acid, giberellic acid, nitric oxide, and auxin. These signals lead to the development of direct chemical defenses against aphids and general stress‐related responses that are well characterized for a number of abiotic and biotic stresses. In spite of major plant taxonomic differences, similarities exist in the types of plant genes expressed in response to feeding by different species of aphids. However, numerous differences in plant signaling and defense responses unique to specific aphid–plant interactions have been identified and warrant further investigation.     

厚壳贻贝两种新型防御素的分子鉴定

贻贝是全球范围内具有重要经济价值和生态价值的双壳贝类。贻贝抗菌肽具有极强的分子多样性,也是当前抗菌肽研究的重要对象。防御素是贻贝抗菌肽的重要成员, 从厚壳贻贝中鉴定到2种新型防御素, 但其分子特性和免疫机制尚不清楚。为此, 对厚壳贻贝体内新发现的2种防御素开展研究。序列分析结果表明,2种新型防御素均具有节肢动物防御素结构特征,因而被命名为arthropod like defensin (ALD)。利用荧光定量PCR研究了2种防御素在贻贝不同组织及不同发育阶段的表达量差异。进一步分析了2种防御素在3种不同微生物诱导下的表达量时间曲线。利用固相化学合成技术对2种防御素的成熟肽区进行合成并开展了功能验证。研究结果表明, 2种ALD 主要表达部位在外套膜和消化腺, 且ALD-1具有雄性特异表达特征。此外, ALD-1和ALD-2在贻贝幼虫阶段均未表达; 在不同微生物刺激下, 2种ALD表现出不同的免疫反应模式, 显示出2种防御素具有不同的免疫调节机制。化学合成的2种ALD均具有抑菌活性, 其对不同微生物的抑制率在20%~80%之间。上述研究为深入了解贻贝免疫防御的分子机制,以及贻贝抗菌肽的免疫功能和后续的分子资源开发奠定了基础。     

冻融作用对大兴安岭多年冻土区土壤节肢动物的影响

利用室内模拟冻融试验,以5 ℃未冻融为对照,研究冻融强度(-5～5 ℃、-10～5 ℃)和冻融频次(1、5、10、15次)对我国大兴安岭多年冻土区土壤节肢动物群落结构的影响。结果表明: 试验共分离到土壤节肢动物4198只,隶属于4纲9目24 科 33属;强冻融(-10～5 ℃)显著降低了土壤节肢动物的个体数和类群数,而轻冻融(-5～5 ℃)尤其是短期(1次冻融循环)处理则使某些类群的个体数增加;在轻冻融处理中类群数、Margalef指数和Shannon指数随着冻融频次的增加显著降低,但在强冻融处理中并未表现出规律性变化;越冬虫态是土壤节肢动物抵御低温胁迫的生存策略之一,同时蜱螨亚纲具有较好的耐寒性。土壤节肢动物对冻融作用的差异性响应、物种间的协同作用以及土壤环境均是影响其群落组成的主要因素。本研究将为我国中高纬多年冻土区土壤节肢动物多样性研究和保护提供数据支持和理论依据。     

Opposite latitudinal patterns for bird and arthropod predation revealed in experiments with differently colored artificial prey

The strength of biotic interactions is generally thought to increase toward the equator, but support for this hypothesis is contradictory. We explored whether predator attacks on artificial prey of eight different colors vary among climates and whether this variation affects the detection of latitudinal patterns in predation. Bird attack rates negatively correlated with model luminance in cold and temperate environments, but not in tropical environments. Bird predation on black and on white (extremes in luminance) models demonstrated different latitudinal patterns, presumably due to differences in prey conspicuousness between habitats with different light regimes. When attacks on models of all colors were combined, arthropod predation decreased, whereas bird predation increased with increasing latitude. We conclude that selection for prey coloration may vary geographically and according to predator identity, and that the importance of different predators may show contrasting patterns, thus weakening the overall latitudinal trend in top‐down control of herbivorous insects.     

Isolation of Arthrobotrys oligospora from soil of the Chinese Northern Tianshan Mountain slope pasture show predatory ability against Haemonchus contortus larvae

To understand the biocontrol ability of Arthrobotrys oligospora isolated from the Northern Tianshan Mountain slope pasture, Xinjiang region, China, on livestock gastrointestinal nematode diseases, we acquired 68 soil samples and isolated 26 nematode-trapping fungi using Haemonchus contortus L₃. Eight isolates were identified based on their morphological and molecular identification. The predacious activity against H. contortus was detected before and after passage through the sheep gastrointestinal tract. As a result, these eight isolates were identified as A. oligospora. They displayed predacious activities ranging from 90% to 97%. Six of the isolates could pass through the sheep gastrointestinal tract significantly reducing the number of H. contortus larvae by 76–79%. This study shows that A. oligospora isolated from the northern slope pasture of Tianshan Mountain has high predacious activity against H. contortus larvae and partly passing through the sheep gastrointestinal tract. This study also shows that conidial suspensions have no toxic side-effects on the sheep, indicating that they have the potential for the development of oral biological agents which prevent and control livestock gastrointestinal nematode diseases.     

Differential resilience of invertebrates to fire

Fires are natural to ecosystems in many parts of the world, yet few studies have examined multi‐taxa invertebrate responses to these fires. We sampled a wide range of invertebrate taxa and feeding guilds at sites 3 months, 1 year and 3 years after fire, and in unburned control sites at the same time. A range of invertebrate sampling techniques was used on Table Mountain, in the Cape Floristic Region biodiversity hotspot, an area prone to natural and human‐induced fires. Sampling time differences strongly affected the composition of the whole assemblage, with fire having a major additional influence. Assemblages showed differential resilience to fire, especially in terms of species richness and abundance. One year after fire, the burned sites had the most compositional differences for the surface‐active species compared to control sites, while after 3 years, these sites were similar. Aerial assemblages were very different 3 years after burning, especially the pollination guild. Furthermore, these 3‐year‐old burned sites had the most unique species, suggesting that burning and longer‐term recovery is important for overall diversity. Some components of the invertebrate assemblage were remarkably resilient to fire (particularly ants), while others were far more conservative (pollinators). Nevertheless, fire allows new species to enter the ecosystem and can thus be used to promote local biodiversity if used appropriately. Ants alone should not be used to represent the whole invertebrate assemblage as they do not represent the more fire‐prone groups. A cross‐section of functional guilds is recommended in invertebrate recovery/fire management conservation programmes. These results have general significance in that a variety of feeding guilds need to be sampled when monitoring invertebrate responses to fire.     

Mid-Cretaceous charred fossil flowers reveal direct observation of arthropod feeding strategies

Although plant-arthropod relationships underpin the dramatic rise in diversity and ecological dominance of flowering plants and their associated arthropods, direct observations of such interactions in the fossil record are rare, as these ephemeral moments are difficult to preserve. Three-dimensionally preserved charred remains of Chloranthistemon flowers from the Late Albian to Early Cenomanian of Germany preserve scales of mosquitoes and an oribatid mite with mouthparts inserted into the pollen sac. Mosquitoes, which today are frequent nectar feeders, and the mite were feeding on pollen at the time wildfire consumed the flowers. These findings document directly arthropod feeding strategies and their role in decomposition.