Interactions between phytophagous insects and their Opuntia hosts

Abstract.

• 1 The cactophagous insect community on opuntias is analysed to show the number of insect species in different taxa. An extension of this analysis gives the average species complement on large and small opuntias.
• 2 A highly significant positive correlation is found between the total number of phytophagous insect species on individual Opuntia species and a measure of the overall ‘architecture’ of their host plants.
• 3 The specificity of the phytophagous insects on opuntias is briefly considered and the community as a whole analysed by guilds. The co-evolution of the Opuntia-feeding insects and their hosts has culminated in a community of specialist insects to the exclusion of nearly all generalist phytophages.
• 4 The life history strategies of the Opuntia-feeding insects are reviewed. Common to all developmental stages are morphological and behavioural adaptations that reduce the risk of attack by natural enemies. This is clearly the consequence of living on structurally simple host plants where there is little place to hide.
• 5 The possible influence of insect herbivores on Opuntia evolution is discussed.
• 6 An understanding of the interactions between the phytophagous insect community and opuntias has clear implications for the biological control of alien Opuntia weeds.

     

Plant nutrient supply determines competition between phytophagous insects

Indirect competition is often mediated by plant responses to herbivore feeding damage and is common among phytophagous insect species. Plant-mediated responses may be altered by abiotic conditions such as nutrient supply, which can affect plant growth, morphology, and the concentration of primary and secondary metabolites. Nutrient supply can be manipulated by the type and amount of fertilizer applied to a plant. Brassica oleracea plants were grown in several types of fertilizer, including those commonly used in sustainable and conventional agricultural systems. The occurrence of indirect competition between two phytophagous species from different feeding guilds (a phloem-feeder and leaf-chewer) was assessed. The leaf-chewer reduced aphid populations on plants growing in most fertilizer treatments, but not on those in the ammonium nitrate fertilizer treatment, which caused the highest concentration of foliar nitrogen. The potential consequences of our findings are discussed for phytophagous species in conventional and sustainable agricultural systems.     

Transition rates between specialization and generalization in phytophagous insects

Although most species of animals exhibit specialized patterns of resource use, it is unclear whether specialization evolves at a faster rate than generalization. To test this hypothesis, transition rates toward specialization and toward generalization were estimated using phylogenies from 15 groups of phytophagous insects. Among the groups studied, maximum-likelihood analyses showed that the forward transition rate from generalization to specialization was significantly higher than the reverse transition rate from specialization to generalization (mean ratio of forward to reverse transition rate = 1.47 using uniform branch lengths and 1.76 using Grafen branch lengths). Although phylogenetic conservatism of host-plant use is common, the results suggest that the evolution of specialization is a highly dynamic process. For example, higher transitions rates both toward and away from specialization as well as equal transition rates were inferred. Collectively, the results reveal a tendency for directional evolution toward increased specialization but also indicate that specialization does not always represent an evolutionary dead-end that strongly limits further evolution.     

植食性昆虫的学习行为

学习是指因经历不同而导致的行为变化。在植食性昆虫中,学习主要包含习惯性反应、厌恶性学习、联系性学习、敏感性反应和嗜好性诱导等类型。昆虫在幼虫和成虫期都具有学习能力,但幼虫期食料和取食经历不会对成虫行为产生直接影响。昆虫学习行为的表现受其本身食性、寄主刺激物的类别及寄主植物时空分布动态等因子的影响。学习能力有助于植食性昆虫应对复杂多变的植物环境,提高对寄主植物的利用效率,有利于其生存繁衍。对害虫学习行为的了解可为栖境调控、行为调控等害虫治理方法提供重要     

植物与植食性昆虫化学互作研究进展

植物与植食性昆虫之间存在着复杂的化学相互作用。一方面,当遭受植食性昆虫为害时,植物能识别植食性昆虫相关分子模式,触发早期信号事件和激素信号转导途径,并由此引起转录组与代谢组重组、直接和间接防御化合物含量升高,最后提高对植食性昆虫的抗性。另一方面,植食性昆虫也能识别植物的防御反应,并能通过分泌效应子、选贮、解毒以及降低敏感性等反防御措施抑制或适应植物的化学防御。深入剖析植物与植食性昆虫的化学互作,不仅可在理论上丰富对昆虫与植物互作关系的理解,而且可在实践上为作物害虫防控新技术的开发提供重要的理论与技术指导。     

植物-植食性昆虫-天敌三营养层次的相互作用及其研究方法

根据国内外的最新研究成果,从他感化合物和植物的营养物质、有毒物质、形态特征、密度、多样性以及分布等化学和物理因子两方面阐述了植物、植食性昆虫及其天敌三营养层次间直接和间接的相互关系,揭示了植物在三者关系中的核心作用,并就目前在该领域中的一些常用的研究方法作了介绍.     

Vegetative responses to defoliation of two Chilean matorral shrubs

Summary This paper reports the results of experimental defoliation of two common matorral species: Lithraea caustica and Colliguaya odorifera. L. caustica and C. odorifera are the matorral species previously shown to exhibit the highest and lowest levels of natural defoliation by browsing. Experimental defoliation was performed at four levels: 0% (controls), 25%, 66%, and 100%. C. odorifera exhibited vegetative responses stronger than controls only in the two highest levels of defoliation (66% and 100%), whereas L. caustica responded vigorously at the 25% and 100% levels. The results are related to the observed position of both species in the matorral community and their relative defoliation risks by natural and introduced herbivores.     

植物与植食性昆虫的分子互作:基础与应用

植物与植食性昆虫之间存在着复杂的分子互作.首先,植食性昆虫会利用自身的嗅觉和味觉化学感觉系统,通过对植物挥发性和非挥发性信息化合物的编码与解析,结合对植物颜色、形状等物理信息的感觉与编码,定位及确定寄主植物.其次,植物可以通过位于细胞膜的受体识别植食性昆虫相关模式分子和损伤相关模式分子,启动由早期信号事件和植物激素信号...     

植物—植食性昆虫—天敌三营养层次的相互作用及其研究方法

根据国内外的最新研究成果 ,从他感化合物和植物的营养物质、有毒物质、形态特征、密度、多样性以及分布等化学和物理因子两方面阐述了植物、植食性昆虫及其天敌三营养层次间直接和间接的相互关系 ,揭示了植物在三者关系中的核心作用 ,并就目前在该领域中的一些常用的研究方法作了介绍 .     

Ecological speciation in phytophagous insects

Divergent natural selection has been shown to promote speciation in a wide range of taxa. For example, adaptation to different ecological environments, via divergent selection, can result in the evolution of reproductive incompatibility between populations. Phytophagous insects have been at the forefront of these investigations of 'ecological speciation' and it is clear that adaptation to different host plants can promote insect speciation. However, much remains unknown. For example, there is abundant variability in the extent to which divergent selection promotes speciation, the sources of divergent selection, the types of reproductive barriers involved, and the genetic basis of divergent adaptation. We review these factors here. Several findings emerge, including the observation that although numerous different sources of divergent selection and reproductive isolation can be involved in insect speciation, their order of evolution and relative importance are poorly understood. Another finding is that the genetic basis of host preference and performance can involve loci of major effect and opposing dominance, factors which might facilitate speciation in the face of gene flow. In addition, we raise a number of other recent issues relating to phytophagous insect speciation, such as alternatives to ecological speciation, the geography of speciation, and the molecular signatures of speciation. Throughout, we aim to both synthesize what is known, as well as highlight areas where future work is especially needed.     

Interpretation of metameric architecture in dominant shrubs of the Chilean matorral

Summary The seasonal progression of phenophases in 21 shrub species of the Chilean matorral was analyzed. Five modules or basic units that are responsible for the aboveground architecture of the plants were characterized. These modules appear to be organized in seven different spatial arrangements. In drought-deciduous species a module type with an absolute short shoot with limited apical growth, leafy or spiny, predominated. In evergreen species long shoot and temporal leafy short shoot module types were more frequent. The spatial arrangement of morphologically different modules and the temporal sequence of their formation allow a dynamic interpretation of the modular architecture of the plants.     

Host marking behavior in phytophagous insects and parasitoids

Oviposition behavior in phytophagous insects and entomophagous parasitoids is often modified by the presence of conspecific brood (eggs and larvae). Often, females avoid laying eggs on or in hosts bearing brood, a behavior that acts to reduce the level of competition suffered by their offspring. Avoidance of occupied hosts is typically mediated by cues and/or signals associated with brood. In this article, we review the role of Marking Pheromones (MPs) as signals of brood presence in both phytophagous and entomophagous insects. We place information about the function and evolution of MPs in the context of recent theory in the field of animal communication. We highlight the dynamics of host-marking systems and discuss how effects of MPs vary according to factors such as female experience and egg load. We also examine variation in the form and function of MP communication across a variety of insect taxa. While studies of MP communication in phytophagous insects have focused on the underlying behavioral mechanisms and chemistry of MP communication, studies in entomophagous insects have focused on the functional aspects of MPs and their role in decision-making in insects. We argue that an approach that incorporates the important contributions of both of these somewhat independent, but complementary areas of research will lead to a more complete understanding of MPs in insects. Finally, we suggest that MP systems are model systems for the study of animal signaling and its evolution.     

Hosts as habitats: faunal similarity of phytophagous insects between host plants

1. Published lists on the phytophages recorded on 86 cabbage plant species (Brassicaceae) and 30 thistle species (Cynaroideae) were used to investigate patterns in the faunal similarity of phytophages. This was done by calculating the Jaccard index and a standardised index of similarity between pairs of host species using presence/absence data. 2. The faunal similarity measured as Jaccard indices indicated that pairs of cabbage hosts share on average 36% of phytophagous species whereas pairs of thistle hosts share only 10%. 3. The faunal similarity between two host species increased with the taxonomic affinity of hosts. This increase was more pronounced in thistles than in cabbage plants. 4. Irrespective of the taxonomic affinity of hosts, in the cabbage plants the faunal similarity of endophages was lower than in ectophages. In contrast, in the thistles faunal similarity differed only between endophages and ectophages for hosts of the same genera. 5. Differences in the patterns of faunal similarity between the two host taxa may be due to idiosyncratic characteristics of the plant taxa, e.g. the unique chemical properties of the cabbage plants and the resource‐rich flower heads of thistles.     

Effects of hostplant age on phytophagous insects

In Colorado beetle females fed with physiologically aged potato leaves, an inhibition or even a standstill of reproduction occurs, followed by diapause.In such beetles, the volume of the corpora allata is reduced and the medial cerebral neurosecretory cells do not transport their neurosecretory material. In feeding tests, it is shown that the beetle can detect the age of its hostplant.

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Zusammenfassung Wenn weiblichen Kartoffelkäfern zwei Arten bevorzugter Wirtspflanzen zur Verfügung stehen, ändert sich ihr Wirtswahlverhalten mit dem Ansteigen der Temperatur, während das nicht der Fall ist, wenn abgelehnte mit angenommenen Pflanzen verglichen werden.Die Käfer können zwischen alten und jungen Blättern bevorzugter Wirtspflanzen unterscheiden.Bei Kartoffelkäfern, die mit physiologisch gealtertem Laub gefüttert werden, tritt eine Hemmung oder sogar ein völliger Stillstand der Reproduktion ein, worauf eine Diapause folgt. Es scheint, daß die Corpora allata beeinflußt werden und aufhören zu arbeiten; die Käfer zeigen histologisch die charakteristischen Anzeichen diapausierender Käfer genauso wie hungernde Käfer: einen völligen Stillstand des Transportes von Neurosekret und eine dichte Anhäufung neurosekretorischen Materials innerhalb der Zellen. Nachfolgende Nahrungsaufnahme der hungernden Käfer bewirkt den Transport neurosekretorischen Materials entlang der Neurosekretbahnen und die Dispersion desselben innerhalb des Zellplasmas.Es scheint also, daß die jahreszeitlichen Veränderungen im Zustand der Wirtspflanze dem neuro-endokrinen System angezeigt werden und für die Nahrungswahl sowie für die Synchronisation von Bedeutung sind.

     

Long-term effects of ungulates on phytophagous insects

Abstract.  1. Most plants interact with a diverse suite of herbivores, allowing the opportunity for the existence of positive and negative interactions between highly dissimilar organisms. However, most studies on herbivorous interactions have been performed under the assumption that they occur mainly between similar species. Consequently, ecologists are still far from a full understanding of the ecological factors that determine insect population dynamics.
2. In this study, a 7-year field experiment was conducted that manipulated the presence of ungulates to evaluate their effects on the abundance, attack rate, and survival of four guilds of co-occurring herbivorous insects living on the same host plant: seed predators, stem borers, gall makers and sap suckers. These four guilds differed in habits and behaviour, the first three being sessile and endophytic and the last being free-living.
3. This study shows that the abundance of all four guilds was negatively affected by ungulates. However, the effect on attack rate differed among guilds, as mammals do not affect the seed predator attack rate. Ungulates also differentially affected insect survival, ingesting only seed predators and gall makers.
4. In summary, this study suggests that diverse mechanisms may affect different insect guilds in different ways. Therefore, competition between disparate herbivores appears to be complex and can be provoked by multiple mechanisms.     

On optimal oviposition behavior in phytophagous insects

A model is developed that predicts when an insect should oviposit on a potential larval host plant when it is encountered. Optimal behavior depends upon the suitability of this plant for larval development and on the probability of finding a more suitable host in the available time. This behavior is modeled for conditions in which the host either does or does not fluctuate in density.     

丛枝菌根真菌与植食性昆虫的相互作用

丛枝菌根(arbuscular mycorrhizal AM)真菌与昆虫均是陆地生态系统中的重要组分,同植物关系密切,对植物的影响和作用是巨大的。生态系统中则以AM真菌-植物-昆虫互作体系参预食物网与生态过程。早在20世纪80年代,人们已开始研究AM真菌对昆虫的影响。进入21世纪人们越来越重视AM真菌与昆虫的相互作用。总结了AM真菌对昆虫取食偏好、生长、繁殖和对植物危害等方面的影响、以及昆虫对AM真菌侵染、扩展和产孢的影响;分析了植物营养状况、昆虫性别、昆虫龄期和AM真菌种类等对AM真菌与昆虫相互作用的影响特点;探讨了AM真菌与昆虫相互作用的机制;展望了利用AM真菌抑制植食性害虫、及促进天敌昆虫和部分传粉昆虫作用的可能性,旨在丰富菌根学研究内容、促进AM真菌与昆虫互作领域的深入研究、为探索生物防控农林业害虫的新途径提供依据。     

Characterization of nativeFrankia strains isolated from chilean shrubs (Rhamnaceae)

Nine nativeFrankia strains were isolated from root nodules of four chilean actinorhizal plants (Rhamnaceae). The strains were designated as ChI1, ChI2, ChI3 and ChI4 fromColletia hystrix; ReI4 and ReI6 fromRetanilla ephedra; TqI12 and TqI15 fromTalguenea quinquinervis and TtI42 fromTrevoa trinervis. By scanning electron microscopy, all the strains exhibited similar actinomycetal structures: hyphae, sporangia and vesicles. The growth patterns of the isolates in BAP medium were similar. All showed a lag phase of approximately 6–7 days, then exhibited a logarithmic phase, except the ReI4 strain which seems to follow a linear growth pattern. A common feature of all the strains was a rapid loss of biomass at the end of the growth phase. All native strains grew on BAP medium supplemented with glucose. In six out of nine strains, the glucose was the best of the carbon sources tested. However, the strains differed in their ability to use other carbon sources such as arabinose, mannitol, maltose, succinate, sucrose, pyruvate, propionate and galactose. The isolates were sensitive to six antibiotics assayed (ampicillin, penicillin G, rifampicin, chloramphenicol, erythromycin and kanamycin). Using the acetylene reduction assay, the nitrogenase activity of the strains was determined. All strains grown in BAP medium lacking a combined nitrogen source were able to reduce acetylene ‘in vitro’.     

Feeding inhibitors and food preference in chewing phytophagous insects

Experiments carried out on chewing phytophagous insects showed that both the slightly and the more highly specialized species are very sensitive to deterrents, but it seems that narrower host specialization is connected with greater sensitivity of the chemoreceptors to feeding inhibitors. As the chemosensory influence of specific phagostimulants can be simulated by other substances, it seems that the sensitivity to deterrents is more important in determining the host range, than the adaptation to specific phagostimulants. Thus the evolution of oligophagy is mainly due to the specialization of chemoreceptors to deterrents. It is suggested that there is a fundamental difference in the function of chemoreceptors reacting upon phagostimulants, and upon deterrents, respectively. The narrow negative specialization to deterrent factors makes possible the use of feeding inhibitors for plant protection purposes.

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Zusammenfassung In letzter Zeit wurde von verschiedenen Verfassern die Bedeutung vergällend wirkender Stoffe für die Nahrungsspezialisation beissender phytophager Insekten betont. Die Häufigkeit des Vorkommens solcher Stoffe im Pflanzenreich, bezogen auf eine Insektenart, war jedoch nur in wenigen Fällen bekannt. Um weitere diesbezügliche Angaben zu erhalten, wurden Versuche mit Hilfe des Blattscheiben-Tests und des Sandwich-Tests an verschieden stark spezialisierten Insektenarten durchgeführt.Es zeigte sich, dass sowohl bei den weniger als auch bei den stärker spezialisierten Arten die überwiegende Mehrzahl der nicht oder nur mässig verzehrbaren Pflanzenarten Vergällungsstoffe enthält. Mit steigender Nahrungsspezialisation ist aber auch eine gewisse Tendenz der Zunahme an Empfindlichkeit gegen Vergällungsstoffe zu verzeichnen. Es scheint also, dass je enger die Spezialisation der Chemorezeptoren auf Fraßstoffe ist, umso enger die negative Spezialisation vermutlich anderer Rezeptoren gegen Inhibitorstoffe ist.Da die Reizwirkung der in den Hauptwirtspflanzen eines oligophagen Insekts enthaltenen spezifischen Frassstoffe auch durch gewisse andere, in nicht verwandten Pflanzen vorkommenden Stoffe ausgelöst werden kann, muss die negative Spezialisation der Rezeptoren gegen Inhibitoren als der wichtigere Faktor der Nahrungsspezialisation betrachtet werden. Es ist also anzunehmen, dass die Evolution der Nahrungsspezialisation im wesentlichen durch letztere Art der Rezeptorenspezialisation bedingt ist.Die Tatsache, dass Stoffe verschiedenster chemischer Beschaffenheit vergällend wirken können, während als Frassstoffe nur gewisse Gruppen von Verbindungen in Betracht kommen, weist darauf hin, dass zwischen den auf Frassinhibitoren und den auf Frasstoffe ansprechenden Chemorezeptoren ein grundlegender funktioneller Unterschied besteht.Die enge negative Spezialisation gegen Vergällungsstoffe ermöglicht die Anwendung derselben gegen beissende Insekten, wie es im Falle des Kartoffelkäfers bereits bewiesen wurde. Diese Möglichkeit ist desto bemerkenswerter, als sie den Weg für die Entwicklung hochspezifischer Pflanzenschutzverfahren eröffnet.