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"Chemical ecology"
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Chemical cues linked to risk
Chemical cues are essential for many ecological interactions. Previous studies of chemically mediated multitrophic interactions have typically focused on responses to cues from plants or herbivores above‐ground. It is increasingly clear, however, that below‐ground cues and those produced by organisms at higher trophic levels also have ecological importance. Prey animals often avoid predator odours to improve survival, and previous research has documented enhanced plant resistance following contact with below‐ground natural enemies, though the ecological basis was unknown. Here, we investigated plant and insect responses to chemical cues from below‐ground natural enemies and explored the ecological significance of these cues for multitrophic interactions. More specifically, we examined the influence of odours emitted by entomopathogenic nematodes (EPNs), a natural enemy of insect herbivores, on the performance and behaviour of their insect prey and the defence responses of nearby plants. Our findings revealed that EPN‐infected insect cadavers emit a characteristic blend of volatile compounds with bioactivity in plants and insects. EPN chemical cues influenced both performance and preference of a specialist herbivore, Colorado potato beetle (CPB, Leptinotarsa decemlineata), feeding on its host plant, potato (Solanum tuberosum). CPB larvae consumed less leaf tissue and gained less mass feeding on plants exposed to EPN cues compared to control plants. Female CPBs laid fewer eggs on plants with EPN cues than on controls, indicating deterrence by EPN cues or EPN‐altered plant defences. Plant defences were enhanced by exposure to live EPNs or EPN chemical cues. Potato plants exposed to EPN infective juveniles induced higher amounts of the defence hormone salicylic acid (SA) and had higher expression of the pathogenisis‐related gene PR‐1(PR4) in foliar tissue. Exposing plants to EPN cues primed induction of SA and jasmonic acid in response to feeding damage by CPB larvae. These findings suggest that herbivores avoid cues from their EPN natural enemies and plants respond to the beneficial nematodes by enhancing systemic defences that reduce herbivore performance. This work has important implications for the chemical ecology of tritrophic interactions as we report that the third trophic level can play direct and indirect roles in plant defence. A plain language summary is available for this article. Plain Language Summary
Journal Article
The hidden company that trees keep : life from treetops to root tips
James Nardi guides you through the innermost unseen world that trees share with a wondrous array of creatures. With their elaborate immune responses, trees recruit a host of allies as predators and parasites to defend against uninvited advances from organisms that chew on leaves, drain sap, and bore into wood. Microbial life thrives in the hidden spaces of leaf scales, twigs, and bark, while birds, mammals, and insects benefit from the more visible resources trees provide. In return, animals help with pollination, seed dispersal, and recycling of nutrients. 'The Hidden Company That Trees Keep' blends storytelling with illustrations and science to reveal how the lives of trees are intertwined with those of their diverse companions.
Book
Impact of Marine Chemical Ecology Research on the Discovery and Development of New Pharmaceuticals
Diverse ecologically important metabolites, such as allelochemicals, infochemicals and volatile organic chemicals, are involved in marine organismal interactions. Chemically mediated interactions between intra- and interspecific organisms can have a significant impact on community organization, population structure and ecosystem functioning. Advances in analytical techniques, microscopy and genomics are providing insights on the chemistry and functional roles of the metabolites involved in such interactions. This review highlights the targeted translational value of several marine chemical ecology-driven research studies and their impact on the sustainable discovery of novel therapeutic agents. These chemical ecology-based approaches include activated defense, allelochemicals arising from organismal interactions, spatio-temporal variations of allelochemicals and phylogeny-based approaches. In addition, innovative analytical techniques used in the mapping of surface metabolites as well as in metabolite translocation within marine holobionts are summarized. Chemical information related to the maintenance of the marine symbioses and biosyntheses of specialized compounds can be harnessed for biomedical applications, particularly in microbial fermentation and compound production. Furthermore, the impact of climate change on the chemical ecology of marine organisms—especially on the production, functionality and perception of allelochemicals—and its implications on drug discovery efforts will be presented.
Journal Article
Indian ocean biogeochemical processes and ecological variability
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 185.Indian Ocean Biogeochemical Processes and Ecological Variability provides a synthesis of current knowledge on Indian Ocean biogeochemistry and ecology and an introduction to new concepts and topical paradigm challenges. It also reports on the development of more extensive/frequent observational capacity being deployed in the Indian Ocean. This represents the first collection of syntheses that emphasize a basin-wide perspective, and the contributing authors include some of the most esteemed oceanographers and Indian Ocean experts in the world. The volume is derived from invited plenary talks that were presented at the initial Sustained Indian Ocean Biogeochemistry and Ecosystem Research (SIBER) workshop held at the National Institute of Oceanography (NIO) in Goa, India, in October 2006. The volume discusses The overlying physical processes set by monsoonal forcing and how these control biological production and variability Nutrient cycling and limitation Pelagic carbon cycling and air-sea exchange Benthic biogeochemistry and ecology The impact of climate and human activities on biogeochemistry and ecosystems. The readership for this book will consist of academic and governmental researchers interested in exploring how oceanographic, atmospheric, and hydrological processes combine to establish the environmental setting that supports and drives the pelagic system and which are especially relevant to understanding the complex biogeochemical and ecological interactions in the Indian Ocean.
eBook
Chemical Cues from Entomopathogenic Nematodes Vary Across Three Species with Different Foraging Strategies, Triggering Different Behavioral Responses in Prey and Competitors
Chemical cues play important roles in predator–prey interactions. Semiochemicals can aid predator foraging and alert prey organisms to the presence of predators. Previous work suggests that predator traits differentially influence prey behavior, however, empirical data on how prey organisms respond to chemical cues from predator species with different hunting strategies, and how foraging predators react to cues from potential competitors, is lacking. Furthermore, most research in this area has focused on aquatic and aboveground terrestrial systems, while interactions among belowground, soiling-dwelling organisms have received relatively little attention. Here, we assessed how chemical cues from three species of entomopathogenic nematodes (EPNs), each with a different foraging strategy, influenced herbivore (cucumber beetle) and natural enemy (EPN) foraging behavior. We predicted these cues could serve as chemical indicators of increased predation risk, prey availability, or competition. Our findings revealed that foraging cucumber beetle larvae avoided chemical cues from Heterorhabditis bacteriophora (active-foraging cruiser EPNs), but not Steinernema carpocapsae (ambusher EPNs) or Steinernema riobrave (intermediate-foraging EPNs). In contrast, foraging H. bacteriophora EPNs were attracted to cues produced by the two Steinernema species but not conspecific cues. Notably, the three EPN species produced distinct blends of olfactory cues, with only a few semi-conserved compounds across species. These results indicate that a belowground insect herbivore responds differently to chemical cues from different EPN species, with some EPN species avoiding prey detection. Moreover, the active-hunting EPNs were attracted to heterospecific cues, suggesting these cues indicate a greater probability of available prey, rather than strong interspecific competition.
Journal Article
Environmental contamination : health risks and ecological restoration
\"Drawn from presentations made during the Croucher Advanced Study Institute workshop held in 2010, this volume covers all the fundamentals necessary for contaminated site assessment and remediation. It discusses historical and emerging contaminants, human health, risk assessment and bioremediation. It contains numerous case studies, many of them from the Asia-Pacific region, that look at the effects of rapid industrialization. It also examines both historical and emerging contaminants such as persistent organic pollutants and electronic waste\"-- Provided by publisher.
Book
Toxicity of Milkweed Leaves and Latex: Chromatographic Quantification Versus Biological Activity of Cardenolides in 16 Asclepias Species
Cardenolides are classically studied steroidal defenses in chemical ecology and plant-herbivore coevolution. Although milkweed plants (Asclepias spp.) produce up to 200 structurally different cardenolides, all compounds seemingly share the same well-characterized mode of action, inhibition of the ubiquitous Na+/K+ ATPase in animal cells. Over their evolutionary radiation, milkweeds show a quantitative decline of cardenolide production and diversity. This reduction is contrary to coevolutionary predictions and could represent a cost-saving strategy, i.e. production of fewer but more toxic cardenolides. Here we test this hypothesis by tandem cardenolide quantification using HPLC (UV absorption of the unsaturated lactone) and a pharmacological assay (in vitro inhibition of a sensitive Na+/K+ ATPase) in a comparative study of 16 species of Asclepias. We contrast cardenolide concentrations in leaf tissue to the subset of cardenolides present in exuding latex. Results from the two quantification methods were strongly correlated, but the enzymatic assay revealed that milkweed cardenolide mixtures often cause stronger inhibition than equal amounts of a non-milkweed reference cardenolide, ouabain. Cardenolide concentrations in latex and leaves were positively correlated across species, yet latex caused 27% stronger enzyme inhibition than equimolar amounts of leaf cardenolides. Using a novel multiple regression approach, we found three highly potent cardenolides (identified as calactin, calotropin, and voruscharin) to be primarily responsible for the increased pharmacological activity of milkweed cardenolide mixtures. However, contrary to an expected trade-off between concentration and toxicity, later-diverging milkweeds had the lowest amounts of these potent cardenolides, perhaps indicating an evolutionary response to milkweed’s diverse community of specialist cardenolide-sequestering insect herbivores.
Journal Article