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Susanne Wurst - One of the best experts on this subject based on the ideXlab platform.
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Community- Weighted Mean Plant Traits Predict Small Scale Distribution of Insect Root Herbivore Abundance
PLOS ONE, 2015Co-Authors: Ilja Sonnemann, Hans Pfestorf, Florian Jeltsch, Susanne WurstAbstract:Small scale distribution of insect root Herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root Herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root Herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root Herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root Herbivores mainly comprised click beetle (Coleoptera, Elateridae) larvae (43%) in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive- and vegetative plant height), and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio). Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root Herbivores, insect root Herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of insect root Herbivores with large, fast growing plants may counteract dominance of those species, thus promoting plant diversity.
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Root herbivore identity matters in plant-mediated interactions between root and shoot Herbivores
Basic and Applied Ecology, 2007Co-Authors: Susanne Wurst, Wim H. Van Der PuttenAbstract:Summary Plants are simultaneously attacked by a multitude of Herbivores that affect plant responses and plant-mediated interactions in a variety of ways. So far, studies on indirect interactions between below- and aboveground Herbivores have almost exclusively focused on interactions between only one root and one shoot herbivore species at the same time. Since these studies show a variety of outcomes, we test the hypothesis that root herbivore identity matters in below-/aboveground interactions. We studied the combined effects root-feeding nematodes ( Pratylenchus penetrans ) and wireworms ( Agriotes lineatus larvae) on Plantago lanceolata and on the performance of aboveground phloem-feeding aphids ( Myzus persicae ) and chewing caterpillars ( Chrysodeixis chalcites larvae). Since root Herbivores may also affect resource availability and the microbial community in the rhizosphere, we examined resource utilization by soil microorganisms using BIOLOG EcoPlates™. Wireworms decreased root biomass by 13%, but led to compensatory shoot growth. Nematodes and the aboveground Herbivores did not affect the biomass of Plantago lanceolata . Feeding by C. chalcites larvae enhanced the concentration of aucubin in leaves, which might explain the high mortality of the caterpillars. Aphids and the belowground Herbivores did not change iridoid glycoside levels in the leaves. However, the number of aphid offspring was reduced by 44% when nematodes had been added to the soil, whereas wireworms had no effect. We observed higher utilization of BIOLOG carbon sources by the soil microorganisms only in the presence of Pratylenchus penetrans . Our results suggest that the outcome of below–aboveground interactions highly depends on herbivore identity.
Maren L Friesen - One of the best experts on this subject based on the ideXlab platform.
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rapid evolution of medicago polymorpha during invasion shifts interactions with the soybean looper
Ecology and Evolution, 2019Co-Authors: Chandra N Jack, Maren L FriesenAbstract:The Enemy Release Hypothesis posits that invasion of novel habitats can be facilitated by the absence of coevolved Herbivores. However, a new environment and interactions with unfamiliar Herbivores may impose selection on invading plants for traits that reduce their attractiveness to Herbivores or for enhanced defenses compared to native host plants, leading to a pattern similar to enemy release but driven by evolutionary change rather than ecological differences. The Shifting Defense Hypothesis posits that plants in novel habitats will shift from specialized defense mechanisms to defense mechanisms effective against generalist Herbivores in the new range. We tested these ideas by comparing herbivore preference and performance of native (Eurasia)- and invasive (New World)-range Medicago polymorpha, using a generalist herbivore, the soybean looper, that co-occurs with M. polymorpha in its New World invaded range. We found that soybean loopers varied in preference and performance depending on host genotype and that overall the herbivore preferred to consume plant genotypes from naive populations from Eurasia. This potentially suggests that range expansion of M. polymorpha into the New World has led to rapid evolution of a variety of traits that have helped multiple populations become established, including those that may allow invasive populations to resist herbivory. Thus, enemy release in a novel range can occur through rapid evolution by the plant during invasion, as predicted by the Shifting Defense Hypothesis, rather than via historical divergence.
Robert S. Fritz - One of the best experts on this subject based on the ideXlab platform.
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Genetic architecture of susceptibility to Herbivores in hybrid willows
Journal of evolutionary biology, 2003Co-Authors: Robert S. Fritz, Cris G. Hochwender, Steven J. Brunsfeld, B. M. RocheAbstract:We performed a common garden experiment using parental, F1, F2, and backcross willow hybrids to test the hypothesis that hybrid willows experience breakdown of resistance to Herbivores. After exposing plants to Herbivores in the field, we measured the densities/damage caused by 13 insect Herbivores and one herbivorous mite. Using joint-scaling tests, we determined the contribution of additive, dominance, and epistasis to variation in susceptibility to Herbivores (measured either as density or damage level) among the six genetic classes. We found the genetic architecture of susceptibility/resistance in the parental species to be complex, involving additive, dominance, and epistasis for each herbivore species. Although genic interactions altered plant susceptibility for each of the 14 Herbivores, three distinct patterns of response of Herbivores to hybrids were expressed. One pattern, observed in four herbivore species, supported the hypothesis of breakdown of resistance genes in recombinant hybrids. A second pattern, shown by six other herbivore species, supported the hypothesis of hybrid breakdown of host recognition genes. In other words, epistatic interactions for host recognition traits (probably oviposition/feeding stimulants or attractants) appeared to be important in determining herbivore abundance for those six species. The final patterns supported a structure of dominance, either for host recognition traits (in the case of three herbivore species) or for host resistance traits (for one herbivore species). The combination of differing responses of herbivore species, including members of the same genus and tribe, and the ubiquitous importance of epistasis suggests that many genes affect herbivore resistance in this hybrid willow system.
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GENETICS OF RESISTANCE OF SALIX SERICEA TO A DIVERSE COMMUNITY OF Herbivores
Evolution; international journal of organic evolution, 1997Co-Authors: Bernadette M. Roche, Robert S. FritzAbstract:We measured resistance of Salix sericea, the silky willow, to a diverse assemblage of 12 Herbivores. We investigated the potential for multispecies coevolution among these Herbivores by measuring genetic correlations between pairs of Herbivores interacting within the component community. After measuring herbivore attack on half-sib families of potted S. sericea during three years, we found significant narrow-sense heritabilities of resistance to Phyllonorycter salicifoliella and Phyllocnistis sp. in 1991. Thus, there is the potential for selection on resistance to these two Herbivores. Despite the many significant phenotypic correlations between herbivore abundances within a year, most genetic correlations between herbivore abundances within a year were not significant. The genetic and phenotypic correlation structure varied from year to year in this three-year study. Thus, it appears that there is the potential for evolution of resistance to the two Herbivores for which we found significant heritabilities, but multispecies coevolution seems unlikely.
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Genetic and soil-nutrient effects on the abundance of Herbivores on willow
Oecologia, 1996Co-Authors: Colin M. Orians, Robert S. FritzAbstract:The effects of soil-nutrient environment, plant genotype, and the interaction between the two on the resistance of the willow, Salix sericea, to insect species in a diverse herbivore community was measured. We found that soil-nutrient environment influenced plant growth and the abundance of most Herbivores of S. sericea. However, environmental effects on herbivore abundance were often modified by plant genetics; the abundance of four of seven Herbivores exhibited significant genotypeby-environment interaction effects. Pure genotype effects were mostly small and non-significant. The effects of fertilization differed among Herbivores. Several Herbivores were more abundant on fertilized plants, one was less abundant, and the abundance of others did not change. We found that feeding guild was a poor predictor of herbivore response. Finally we found significant phenotypic and genetic correlations among growth rate, internode length, and the abundances of several Herbivores.
Marc T J Johnson - One of the best experts on this subject based on the ideXlab platform.
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Ellagitannins from the Onagraceae Decrease the Performance of Generalist and Specialist Herbivores
Journal of Chemical Ecology, 2019Co-Authors: Daniel N. Anstett, Iris Cheval, Caitlyn D’souza, Juha-pekka Salminen, Marc T J JohnsonAbstract:Phenolics have a role in defenses against Herbivores, but the defensive functions of specific groups of phenolics are still poorly understood. For example, ellagitannins (a type of hydrolyzable tannin) are predicted to decrease insect herbivore performance, but the effect of different types of ellagitannins on generalist and specialist Herbivores has rarely been assessed. Here, we test the effects of the dominant oligomeric ellagitannins of Oenothera biennis and other Onagraceae on herbivore performance. We fed artificial diets containing between 1 and 100 mg/g of polyphenol fractions comprised of varying amounts and compositions of dimeric oenothein B, the trimeric oenothein A and larger oligomers, to one generalist ( Spodoptera exigua) and one specialist ( Schinia florida ) insect herbivore species. We compared the effects of these ellagitannin fractions on herbivore performance to the effects of artificial diet containing total phenolic extracts from O. biennis , which contained these ellagitannins as well as many additional phenolic metabolites including flavonoid glycosides and caffeic acid derivatives. Both the ellagitannin fractions and O. biennis phenolic extracts had strong negative effects on S. exigua and S. florida performance, with stronger effects on the generalist herbivore. Differences between the effects of the various ellagitannin fractions were small and depended on insect life stage. The defensive effects of these ellagitannins were large, with lethal concentrations as low as 0.1% of the diet. These results highlight the important defensive function of ellagitannins against specialist and generalist Herbivores and the need to characterize the effects of these understudied phenolics.
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Plant traits that predict resistance to Herbivores
Functional Ecology, 2010Co-Authors: Diego Carmona, Marc J Lajeunesse, Marc T J JohnsonAbstract:Summary 1. Although secondary metabolites are recognized as fundamental to the defence of plants against insect and mammalian Herbivores, their relative importance compared to other potential defensive plant traits (e.g. physical resistance, gross morphology, life-history, primary chemistry and physiology) are not well understood. 2. We conducted a meta-analysis to answer the question: What types of genetically variable plant traits most strongly predict resistance against Herbivores? We performed a comprehensive literature search and obtained 499 separate measurements of the strength of covariation (measured as genetic correlations) between plant traits and herbivore susceptibility – these were extracted from 72 studies involving 19 plant families. 3. Surprisingly, we found no overall association between the concentrations of secondary metabolites and herbivore susceptibility – plant traits other than secondary metabolites most strongly predicted herbivore susceptibility. Specifically, genetic variation in life-history traits (e.g. flowering time, growth rate) consistently exhibited the strongest genetic correlations with susceptibility. Genetic variation in gross morphological traits (e.g. no. branches, plant size) and physical resistance traits (e.g. latex, trichomes) were also frequently correlated with variation in herbivore susceptibility, but these relationships depended on attributes of the Herbivores (e.g. feeding guild) and plants (e.g. longevity). 4. These results call into question the conventional wisdom that secondary metabolites are the most important anti-herbivore defence of plants. We propose the hypothesis that Herbivores select most strongly on genetic variation in life-history, morphological and physical resistance traits, but the greater pleiotropic effects of genes controlling these traits impose strong constraints on their evolution. Meanwhile, secondary metabolites could have evolved to be important defensive mechanisms not because they have the largest effect on Herbivores, but because the constraints on their evolution are the weakest.
Chandra N Jack - One of the best experts on this subject based on the ideXlab platform.
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rapid evolution of medicago polymorpha during invasion shifts interactions with the soybean looper
Ecology and Evolution, 2019Co-Authors: Chandra N Jack, Maren L FriesenAbstract:The Enemy Release Hypothesis posits that invasion of novel habitats can be facilitated by the absence of coevolved Herbivores. However, a new environment and interactions with unfamiliar Herbivores may impose selection on invading plants for traits that reduce their attractiveness to Herbivores or for enhanced defenses compared to native host plants, leading to a pattern similar to enemy release but driven by evolutionary change rather than ecological differences. The Shifting Defense Hypothesis posits that plants in novel habitats will shift from specialized defense mechanisms to defense mechanisms effective against generalist Herbivores in the new range. We tested these ideas by comparing herbivore preference and performance of native (Eurasia)- and invasive (New World)-range Medicago polymorpha, using a generalist herbivore, the soybean looper, that co-occurs with M. polymorpha in its New World invaded range. We found that soybean loopers varied in preference and performance depending on host genotype and that overall the herbivore preferred to consume plant genotypes from naive populations from Eurasia. This potentially suggests that range expansion of M. polymorpha into the New World has led to rapid evolution of a variety of traits that have helped multiple populations become established, including those that may allow invasive populations to resist herbivory. Thus, enemy release in a novel range can occur through rapid evolution by the plant during invasion, as predicted by the Shifting Defense Hypothesis, rather than via historical divergence.
