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Herbivore Feeding (herbivore + feeding)
Selected AbstractsBeing a generalist herbivore in a diverse world: how do diets from different grasslands influence food plant selection and fitness of the grasshopper Chorthippus parallelus?ECOLOGICAL ENTOMOLOGY, Issue 2 2010ALEXANDRA FRANZKE 1. Generalist insect herbivores occupy a variety of habitats that differ in food plant composition. Dietary mixing has been proposed as a possibility for generalists to overcome nutritional deficiencies of single plant species, but only a few studies have investigated herbivore feeding and fitness for diets that resemble natural scenarios. We studied feeding behaviour, survival, and reproduction of the generalist grasshopper Chorthippus parallelus raised on food plants of four typical habitats. 2. Grasshopper diet consisted of grasses (92.5%), legumes (6.7%) and, in small quantities, other forbs (0.8%). Diet selection differed between the four food plant mixtures, and depended on grasshopper sex and developmental stage. There was no correlation between the relative abundance of plant species in the field and the fraction of these species in the grasshopper diet. 3. Grasshoppers survived on average for 40.4 ± 1.0 days before maturity, grew 106.8 mg until maturity moult, and females laid 4.1 ± 0.4 egg pods, each of which contained 8.5 ± 0.4 eggs. However, despite the differences in feeding behaviour, grasshopper fitness was the same in all of the four food plant mixtures. While the digestibility of ingested food was similar in the four different treatments, indices indicated differences in the conversion efficiency to body mass. 4. Our results show that C. parallelus is a plastic feeder with no fixed preferences in diet composition. The results emphasise that generalist herbivores can counteract putative quality deficiencies of single food plants by selective dietary mixing. [source] Herbivores and pathogens on willow: do they affect each other?AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2003Matthias Simon Abstract 1,Willows often need to cope with attack by both rust fungi and herbivores. We studied whether rust infection on willow affects the herbivore, and vice versa, whether herbivore feeding affects the fungal infection. The system investigated by laboratory bioassays and greenhouse experiments consisted of the willow hybrid Salix × cuspidata, the rust Melampsora allii-fragilis and the willow leaf beetle Plagiodera versicolora. Effects were studied both on a local scale (rust infection and feeding on the same leaf) and systemically (rust infection and feeding on different, but adjacent leaves). 2,Rust infection was not affected by herbivore feeding on a local scale. Systemically, however, the willow's susceptibility towards rust infection was increased by herbivore feeding, as indicated by a higher number of rust sori on leaves adjacent to feeding-damaged leaves. The herbivore's performance was detrimentally affected by rust infection: increase of mortality (systemically), decrease of larval weight (locally and systemically) and prolonging of developmental time (locally and systemically). 3,Previous rust infection enhanced systemically the willow's susceptibility towards subsequent fungal infection. Previous herbivore feeding on the willow had no effects on the herbivore's developmental time and mortality. However, feeding upon previously feeding-damaged willow leaves significantly reduced larval weight. [source] Silicon-augmented resistance of plants to herbivorous insects: a reviewANNALS OF APPLIED BIOLOGY, Issue 2 2009O.L. Reynolds Abstract Silicon (Si) is one of the most abundant elements in the earth's crust, although its essentiality in plant growth is not clearly established. However, the importance of Si as an element that is particularly beneficial for plants under a range of abiotic and biotic stresses is now beyond doubt. This paper reviews progress in exploring the benefits at two- and three-trophic levels and the underlying mechanism of Si in enhancing the resistance of host plants to herbivorous insects. Numerous studies have shown an enhanced resistance of plants to insect herbivores including folivores, borers, and phloem and xylem feeders. Silicon may act directly on insect herbivores leading to a reduction in insect performance and plant damage. Various indirect effects may also be caused, for example, by delaying herbivore establishment and thus an increased chance of exposure to natural enemies, adverse weather events or control measures that target exposed insects. A further indirect effect of Si may be to increase tolerance of plants to abiotic stresses, notably water stress, which can in turn lead to a reduction in insect numbers and plant damage. There are two mechanisms by which Si is likely to increase resistance to herbivore feeding. Increased physical resistance (constitutive), based on solid amorphous silica, has long been considered the major mechanism of Si-mediated defences of plants, although there is recent evidence for induced physical defence. Physical resistance involves reduced digestibility and/or increased hardness and abrasiveness of plant tissues because of silica deposition, mainly as opaline phytoliths, in various tissues, including epidermal silica cells. Further, there is now evidence that soluble Si is involved in induced chemical defences to insect herbivore attack through the enhanced production of defensive enzymes or possibly the enhanced release of plant volatiles. However, only two studies have tested for the effect of Si on an insect herbivore and third trophic level effects on the herbivore's predators and parasitoids. One study showed no effect of Si on natural enemies, but the methods used were not favourable for the detection of semiochemical-mediated effects. Work recently commenced in Australia is methodologically and conceptually more advanced and an effect of Si on the plants' ability to generate an induced response by acting at the third trophic level was observed. This paper provides the first overview of Si in insect herbivore resistance studies, and highlights novel, recent hypotheses and findings in this area of research. Finally, we make suggestions for future research efforts in the use of Si to enhance plant resistance to insect herbivores. [source] Foraging efficiency of a parasitoid of a leaf herbivore is influenced by root herbivory on neighbouring plantsFUNCTIONAL ECOLOGY, Issue 5 2007R. SOLER Summary 1Root feeding insects can influence foliar quality of the host plant, which can affect the development and behaviour of leaf herbivores and parasitoids. Thus far, such interactions have been reported in situations where root and leaf associated organisms share a host-plant. We tested whether root herbivory influences searching behaviour of an above-ground parasitoid when the foliar feeding host of the parasitoid and the root herbivore are feeding on different plants. 2We manipulated the proportion of 25 plants (ranging from 0 to 1) exposed to root herbivory by Delia radicum (neighbouring-plants). Five additional plants were infested above-ground with Pieris brassicae larvae (host-infested plants) and were placed in-between the neighbouring plants. We then released females of the parasitoid Cotesia glomerata which attacks P. brassicae and studied foraging efficiency of the parasitoid. 3Overall, parasitoids located more host-infested plants during the maximum allowed searching time, and found their hosts about three times faster when neighbouring plants were exposed to root herbivory, than when neighbouring plants were not infested with D. radicum. Similar results were found when the host-infested plants were also exposed to root herbivory. 4Our results show that the interaction between an above-ground foliar feeding insect and its parasitoid can be influenced by the presence of non-host herbivores feeding on the roots of neighbouring conspecific plants. [source] | ||||||||||