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Denise M Dearing - One of the best experts on this subject based on the ideXlab platform.
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beyond fermentation other important services provided to endothermic herbivores by their gut microbiota
Integrative and Comparative Biology, 2017Co-Authors: Denise M Dearing, Kevin D KohlAbstract:: For decades, comparative biologists have recognized the importance of microbial partners in facilitating herbivory as a successful feeding strategy. Most of this success is attributed to the ability of gut microbes to digest recalcitrant dietary fiber and provides usable nutrients to their hosts. Gut microbes can also provide numerous other functions, such as vitamin synthesis, nitrogen recycling, and the detoxification of Plant secondary compounds. Here, we review these microbial functions in herbivorous mammals and birds, highlighting studies that utilize recently developed metagenomic techniques. Several of these studies emphasize that microbial services are the product of interactions and exchanges within a complex microbial community, rather than the product of an individual member. Additionally, a number of these microbial functions are interdependent. For example, levels of dietary nitrogen or Plant Toxins can influence fiber digestibility. Further studies into the variety of microbial services provided to herbivorous hosts, and how these services might interact will broaden our understanding of host-microbe interactions.
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ambient temperature mediated changes in hepatic gene expression of a mammalian herbivore neotoma lepida
Molecular Ecology, 2017Co-Authors: Patrice Kurnath Connors, Jael R Malenke, Denise M DearingAbstract:Herbivores regularly ingest natural Toxins produced by Plants as a defence against herbivory. Recent work suggests that compound toxicity is exacerbated at higher ambient temperatures. This phenomenon, known as temperature-dependent toxicity (TDT), is the likely result of decreased liver function at warmer temperatures; however, the underlying cause of TDT remains speculative. In the present study, we compared the effects of temperature and dietary Plant Toxins on differential gene expression in the liver of an herbivorous rodent (Neotoma lepida), using species-specific microarrays. Expression profiles revealed a greater number of differentially expressed genes at an ambient temperature below the thermal neutral zone for N. lepida (22°C) compared to one within (27°C). Genes and pathways upregulated at 22°C were related to growth and biosynthesis, whereas those upregulated at 27°C were associated with gluconeogenesis, apoptosis and protein misfolding, suggestive of a stressed state for the liver. Additionally, few genes associated with xenobiotic metabolism were induced when woodrats ingested Plant Toxins compared to nontoxic diets, regardless of temperature. Taken together, the results highlight the important role of ambient temperature on gene expression profiles in the desert woodrat. Temperatures just below the thermal neutral zone might be a favourable state for liver metabolism. Furthermore, the reduction in the number of genes expressed at a temperature within the thermal neutral zone indicates that liver function may be reduced at temperatures that are not typically considered as thermally stressful. Understanding how herbivorous mammals will respond to ambient temperature is imperative to accurately predict the impacts of climate change.
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gut microbes of mammalian herbivores facilitate intake of Plant Toxins
Ecology Letters, 2014Co-Authors: Kevin D Kohl, Robert B Weiss, James C Cox, Colin Dale, Denise M DearingAbstract:The foraging ecology of mammalian herbivores is strongly shaped by Plant secondary compounds (PSCs) that defend Plants against herbivory. Conventional wisdom holds that gut microbes facilitate the ingestion of toxic Plants; however, this notion lacks empirical evidence. We investigated the gut microbiota of desert woodrats (Neotoma lepida), some populations of which specialise on highly toxic creosote bush (Larrea tridentata). Here, we demonstrate that gut microbes are crucial in allowing herbivores to consume toxic Plants. Creosote Toxins altered the population structure of the gut microbiome to facilitate an increase in abundance of genes that metabolise toxic compounds. In addition, woodrats were unable to consume creosote Toxins after the microbiota was disrupted with antibiotics. Last, ingestion of Toxins by naive hosts was increased through microbial transPlants from experienced donors. These results demonstrate that microbes can enhance the ability of hosts to consume PSCs and therefore expand the dietary niche breadth of mammalian herbivores.
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induced and constitutive responses of digestive enzymes to Plant Toxins in an herbivorous mammal
The Journal of Experimental Biology, 2011Co-Authors: Kevin D Kohl, Denise M DearingAbstract:SUMMARY Many Plants produce Plant secondary compounds (PSCs) that bind and inhibit the digestive enzymes of herbivores, thus limiting digestibility for the herbivore. Herbivorous insects employ several physiological responses to overcome the anti-nutritive effects of PSCs. However, studies in vertebrates have not shown such responses, perhaps stemming from the fact that previously studied vertebrates were not herbivorous. The responses of the digestive system to dietary PSCs in populations of Bryant9s woodrat (Neotoma bryanti) that vary in their ecological and evolutionary experience with the PSCs in creosote bush (Larrea tridentata) were compared. Individuals from naive and experienced populations were fed diets with and without added creosote resin. Animals fed diets with creosote resin had higher activities of pancreatic amylase, as well as luminal amylase and chymotrypsin, regardless of prior experience with creosote. The experienced population showed constitutively higher activities of intestinal maltase and sucrase. Additionally, the naive population produced an aminopeptidase-N enzyme that was less inhibited by creosote resin when feeding on the creosote resin diet, whereas the experienced population constitutively expressed this form of aminopeptidase-N. Thus, the digestive system of an herbivorous vertebrate responds significantly to dietary PSCs, which may be important for allowing herbivorous vertebrates to feed on PSC-rich diets.
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the manipulation of Plant Toxins by a food hoarding herbivore ochotona princeps
Ecology, 1997Co-Authors: Denise M DearingAbstract:Generalist mammalian herbivores typically avoid Plant species containing high levels of Plant secondary compounds because generalists are thought to lack the ability to process large quantities of these chemicals. Here I propose and test two hypotheses: (1) that food-hoarding herbivores behaviorally overcome consumption limits imposed by secondary compounds by storing food until the Toxins degrade; and (2) that the presence of secondary compounds in cached Plant material facilitates the preservation of these items, as well as other cached items that lack such compounds. To evaluate these hypotheses, I conducted a number of field and laboratory experiments using the North American pika, Ochotona princeps, a generalist herbivore that consumes low-phenolic vegetation in the summer while it simultaneously collects and stores high-phenolic vegetation for subsequent consumption during winter. In experiments investigating decomposition of summer and winter diets of pikas, after 10 mo of storage, the winter diet retained 20.5% more biomass, and was higher in energy, lower in fiber, and equal in nitrogen compared to the summer diet. Moreover, a common food item in the winter diet, Acomastylis rossii, which contains high levels of phenolics, was the only Plant extract to deter bacterial growth in a bioassay. Acomastylis rossii leaves with experimentally reduced phenolic levels retained significantly less biomass than leaves with natural phenolic concentrations. However, the presence of A. rossii in artificial caches containing a low-phenolic species, Trifolium parryi, did not facilitate the preservation of T. parryi. Approximately halfway through the typical storage period, phenolic concentrations of pika winter diet samples in artificial caches decreased to levels readily consumed by pikas in their summer diet. Examination of natural haypiles of pikas before and after storage revealed that pikas do increase their intake of A. rossii from the haypile sometime during the winter. In experiments with captive pikas, pikas preferred A. rossii with experimentally reduced phenolic concentrations over those with natural concentrations. Observations of pikas foraging from natural and artificial haypiles suggested that pikas do not increase their intake of A. rossii from the haypile until phenolics levels decrease. Taken together, the results support both of the hypotheses. Pikas manipulate Plant chemistry by storing Plants rich in allelochemicals and by delaying consumption of these Plants until the Toxins decay. Moreover, Plants with high levels of secondary compounds exhibit superior preservation qualities so that more biomass and nutrients are retained during storage. As food caching is a common strategy among several animal classes and many foods contain potentially deleterious compounds, the manipulation of food Toxins by storage may be a prevalent phenomenon.
Clare Mcarthur - One of the best experts on this subject based on the ideXlab platform.
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influences of Plant Toxins and their spatial distribution on foraging by the common brushtail possum a generalist mammalian herbivore
Journal of Chemical Ecology, 2012Co-Authors: Carolyn L. Nersesian, Peter B. Banks, Clare McarthurAbstract:Generalist herbivores forage on a variety of Plant species, allowing them to gain nutrients while limiting ingestion of harmful Toxins. As the capacity to mix diets appears important for maximizing intake, the spatial scale in heterogeneity of food resources should influence the foraging behavior of herbivores. Our aim was to identify how the feeding strategy of a generalist mammalian herbivore, the common brushtail possum, responds to foods within a spatially defined environment. We evaluated foraging responses against increasing spatial separation between pairs of artificial diets that differed in flavor and toxin profile, to determine how distance and diet affect intake and behavior. Foraging responses were influenced by the type of diet or the degree of spatial separation between foods but not by their interaction. Diet influenced intake, time spent feeding, and feeding rate, but had no effect on nightly foraging interval, number of feeding bouts, or bout length. The number of switches between paired food resources and foraging efficiency (intake per unit distance, which accounts for the energetic costs of travelling), were influenced only by distance. Titrating foraging against a range of distances demonstrated how quickly foraging efficiency can decline in response to the spatial separation of food resources, highlighting the importance of spatial heterogeneity of Plants within the home range of an herbivore.
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The foraging tightrope between predation risk and Plant Toxins: a matter of concentration
Functional Ecology, 2011Co-Authors: Clare Mcarthur, Peter B. Banks, Paul A. Orlando, Joel S. BrownAbstract:Summary 1. Plants defend and predators attack, provoking the foraging dilemma faced by herbivores and frugivores of how to eat enough without being eaten. High toxin concentration in leaves and fruits inhibits consumption, while predation risk reduces feeding opportunities, as prey forage to avoid encountering predators. Thus, both factors vary and define the quality of the landscape. How foraging animals directly quantify, compare and respond to these two costs has rarely been tested. 2. We show that free-ranging bushbabies – small, frugivorous primates – change their behaviour and use of artificial food patches based on the interplay between toxin concentration in food and patch safety. Using a titration experiment, we demonstrate that bushbabies quantify the relative costs of toxin and fear. We pinpoint where these costs are equivalent and show that animals seek food patches with the lower net cost. 3. We conclude that the ecological effectiveness of Plant Toxins as defence against consumers needs to be considered in the context of a landscape of fear – and the relative impact of antipredator tactics and Plant defence is strongly shaped by the concentration of these defences. 4. A corollary is that Plants may benefit from fear as a substitute for their own chemical defence, adding a new dimension to the concept of indirect Plant defence. Whether, from the Plant’s perspective, the benefits derived from fear can be considered evolutionarily adaptive rather than simply ecologically serendipitous remains to be tested.
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Titrating the cost of Plant Toxins against predators: determining the tipping point for foraging herbivores
The Journal of animal ecology, 2011Co-Authors: Carolyn L. Nersesian, Peter B. Banks, Clare McarthurAbstract:1. Foraging herbivores must deal with Plant characteristics that inhibit feeding and they must avoid being eaten. Principally, Toxins limit food intake, while predation risk alters how long animals are prepared to harvest resources. Each of these factors strongly affects how herbivores use food patches, and both constraints can pose immediate proximate costs and long-term consequences to fitness. 2. Using a generalist mammalian herbivore, the common brushtail possum (Trichosurus vulpecula), our aim was to quantitatively compare the influence of Plant toxin and predation risk on foraging decisions. 3. We performed a titration experiment by offering animals a choice between non-toxic food at a risky patch paired with food with one of five toxin concentrations at a safe patch. This allowed us to identify the tipping point, where the cost of toxin in the safe food patch was equivalent to the perceived predation risk in the alternative patch. 4. At low toxin concentration, animals ate more from the safe than the risky patch. As toxin concentration increased at the safe patch, intake shifted until animals ate mainly from the risky patch. This shift was associated with behavioural changes: animals spent more time and fed longer at the risky patch, while vigilance increased at both risky and safe patches. 5. Our results demonstrate that the variation in toxin concentration, which occurs intraspecifically among Plants, can critically influence the relative cost of predation risk on foraging. We show that herbivores quantify, compare and balance these two different but proximate costs, altering their foraging patterns in the process. This has potential ecological and evolutionary implications for the production of Plant defence compounds in relation to spatial variation in predation risk to herbivores.
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Integrating the costs of Plant Toxins and predation risk in foraging decisions of a mammalian herbivore
Oecologia, 2010Co-Authors: Sahar N. Kirmani, Peter B. Banks, Clare McarthurAbstract:Foraging herbivores must satisfy their nutrient requirements in a world of toxic Plants while also avoiding predators. Plant Toxins and perceived predation risk at food patches should both reduce patch residency time, but the relative strengths of these factors on feeding decisions has rarely been quantified. Using an arboreal generalist herbivore, the common brushtail possum Trichosurus vulpecula , we tested the effects on food intake of the Plant toxin, cineole, and regurgitated pellets from one of its predators, the powerful owl Ninox strenua at the small spatial scale of the food patch. We used the giving-up density (GUD) framework, with animals harvesting food items (sultanas) in an inedible matrix (small pebbles). We ran two consecutive field experiments in a eucalypt woodland in eastern Australia, 1 month apart in the same location. In experiment 1, there was a significant interaction between cineole [at 17% of dry matter (DM)] and owl pellets. The GUD was lowest in the absence of both cineole and owl pellet, intermediate in the presence of owl pellet; and highest with cineole ± owl pellet. The effect of owl pellet diminished over time. In experiment 2, only cineole (at 10% DM) increased the GUD significantly. The difference in effect of owl pellet was probably due to both habituation and freshness of the cue. Our study demonstrates the importance of synthesising predator–prey and Plant–herbivore ecology to better understand the complex set of constraints influencing foraging herbivores. The greater effect of toxin than fear on possums is likely to be due to its high, but ecologically relevant concentration. This highlights the need to explore the relative and net impacts of a range of concentrations of Plant Toxins and predation risks.
Vicent Yusa - One of the best experts on this subject based on the ideXlab platform.
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target analysis and retrospective screening of veterinary drugs ergot alkaloids Plant Toxins and other undesirable substances in feed using liquid chromatography high resolution mass spectrometry
Talanta, 2016Co-Authors: Nuria Leon, Agustin Pastor, Vicent YusaAbstract:Abstract A comprehensive strategy combining a quantitative method for 77 banned veterinary drugs, mycoToxins, ergot alkaloids and Plant Toxins, and a post-target screening for 425 substances including pesticides and environmental contaminants in feed were developed using a QuEChERS-based extraction and an ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC–HRMS). The quantitative method was validated after previous statistical optimisation of the main parameters governing ionisation, and presented recoveries ranging, in general, from 80 to 120%, with a precision in terms of Relative Standard Deviation (RSD) lower than 20%. The full-scan accurate mass data were acquired with a resolving power of 50000 FWHM and a mass accuracy lower than 5 ppm. The method LOQ was lower than 12.5 µg kg −1 for the majority of the veterinary drugs and Plant Toxins and 20 µg kg −1 for ergot alkaloids. For post-target screening a customised theoretical database including the exact mass, the polarity of acquisition and the expected adducts was built and used for post-run retrospective screening. The analytical strategy was applied to 32 feed samples collected from farms of the Valencia Region (Spain). Florfenicol, zearalenone and atropine were identified and quantified at concentrations around 10 µg kg −1 . In the post-target screening of the real samples, Sulfadiazine, Thrimetoprin and Pirimiphosmethyl were tentatively identified.
M. D. Dearing - One of the best experts on this subject based on the ideXlab platform.
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experience matters prior exposure to Plant Toxins enhances diversity of gut microbes in herbivores
Ecology Letters, 2012Co-Authors: Kevin D Kohl, M. D. DearingAbstract:For decades, ecologists have hypothesised that exposure to Plant secondary compounds (PSCs) modifies herbivore-associated microbial community composition. This notion has not been critically evaluated in wild mammalian herbivores on evolutionary timescales. We investigated responses of the microbial communities of two woodrat species (Neotoma bryanti and N. lepida). For each species, we compared experienced populations that independently converged to feed on the same toxic Plant (creosote bush, Larrea tridentata)
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A specialist herbivore (Neotoma stephensi) absorbs fewer Plant Toxins than does a generalist (Neotoma albigula).
Physiological and biochemical zoology : PBZ, 2004Co-Authors: Jennifer S. Sorensen, Colin Turnbull, M. D. DearingAbstract:Detoxification capacity of enzymes in the liver is thought to be the primary factor governing dietary toxin intake by mammalian herbivores. Recently, toxin absorption in the gut was proposed as an alternative process that also influences toxin intake. We examined the role of the gut in regulating toxin absorption by quantifying excretion of a Plant secondary compound in the feces. We hypothesized that specialists have a greater capacity to reduce intestinal absorption of Toxins than do generalists. To test this hypothesis, we compared fecal excretion of alpha-pinene in specialist (Neotoma stephensi) and generalist (Neotoma albigula) woodrats. Alpha-pinene is the most abundant monoterpene in Juniperus monosperma, which occurs in the natural diet of both woodrat species. Woodrats were fed alpha-pinene in diets containing juniper foliage for 3 wk and, in a separate experiment, were given a single oral dose of alpha-pinene. Feces were collected from animals at the end of each experiment and analyzed for alpha-pinene concentration using gas chromatography. Both woodrat species excreted unchanged alpha-pinene in the feces. However, specialist woodrats excreted 40% more alpha-pinene per unit ingested from a juniper diet and excreted nearly four times a greater percentage of an oral dose of alpha-pinene compared with generalists.
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Elimination of Plant Toxins by herbivorous woodrats: revisiting an explanation for dietary specialization in mammalian herbivores.
Oecologia, 2002Co-Authors: Jennifer S. Sorensen, M. D. DearingAbstract:Constraints on rates of detoxification and elimination of Plant Toxins are thought to be responsible for limiting dietary specialization in mammalian herbi- vores. This hypothesis, known as the detoxification limitations hypothesis, suggests that most mammalian herbivores are generalists to avoid overdosing on Toxins from a single Plant species. The hypothesis also predicts that the few mammalian specialists that exist should have adaptations for rapid detoxification and elimination of Plant secondary compounds. We took a pharmacological approach to test whether specialists eliminate Toxins from the bloodstream faster than generalists. We compared elimination rate and total exposure of alpha-pinene in closely related dietary specialist and generalist woodrats, Neotoma stephensi and N. albigula, respectively. Animals were orally gavaged with alpha-pinene, a Plant secondary compound present in the natural diets of both woodrat species. We collected venous blood at 3, 6, 10, 15, and 20 min post-ingestion of alpha-pinene. Blood was analyzed for alpha-pinene concentration using gas chro- matography. We found that specialist and generalist woodrats did not differ in elimination rates of alpha- pinene. However, specialists had lower exposure levels of alpha-pinene than generalists due to lower initial delivery of alpha-pinene to the general circulation. The levels of alpha-pinene detected in the bloodstream of specialists were 4.7-5.3� lower over all time intervals than gener- alists. Thus, specialists encounter a functionally lower dose of toxin than generalists. We suggest that the lower exposure level of specialist woodrats may be due to mechanisms in the gut that decrease toxin absorption. Regardless of mechanism, lower exposure to Plant Toxins may allow specialists to forage on diets with high toxin concentrations thereby facilitating dietary specialization.
Georg Petschenka - One of the best experts on this subject based on the ideXlab platform.
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how herbivores coopt Plant defenses natural selection specialization and sequestration
Current opinion in insect science, 2016Co-Authors: Georg Petschenka, Anurag A. AgrawalAbstract:We review progress in understanding sequestration by herbivorous insects, the use of Plant chemical defenses for their own defense. We incorporate sequestration into the framework of Plant–insect coevolution by integrating three hierarchical issues: (1) the relationship between dietary specialization and sequestration of Plant defenses, (2) the physiological mechanisms involved in sequestration, and (3) how sequestration evolves via interactions between trophic levels. Sequestration is often associated with specialization, but even specialized sequestration is not an evolutionary dead-end. Despite considerable progress in understanding physiological mechanisms, detailed knowledge of how Plant Toxins cross the insect gut epithelium is still largely lacking. Sequestration is likely a major vehicle for coevolutionary escalation in speciose Plant–insect–predator interactions, suggesting that a strictly bitrophic view is untenable.
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Milkweed butterfly resistance to Plant Toxins is linked to sequestration, not coping with a toxic diet.
Proceedings. Biological sciences, 2015Co-Authors: Georg Petschenka, Anurag A. AgrawalAbstract:Insect resistance to Plant Toxins is widely assumed to have evolved in response to using defended Plants as a dietary resource. We tested this hypothesis in the milkweed butterflies (Danaini) which have progressively evolved higher levels of resistance to cardenolide Toxins based on amino acid substitutions of their cellular sodium-potassium pump (Na(+)/K(+)-ATPase). Using chemical, physiological and caterpillar growth assays on diverse milkweeds (Asclepias spp.) and isolated cardenolides, we show that resistant Na(+)/K(+)-ATPases are not necessary to cope with dietary cardenolides. By contrast, sequestration of cardenolides in the body (as a defence against predators) is associated with the three levels of Na(+)/K(+)-ATPase resistance. To estimate the potential physiological burden of cardenolide sequestration without Na(+)/K(+)-ATPase adaptations, we applied haemolymph of sequestering species on isolated Na(+)/K(+)-ATPase of sequestering and non-sequestering species. Haemolymph cardenolides dramatically impair non-adapted Na(+)/K(+)-ATPase, but had systematically reduced effects on Na(+)/K(+)-ATPase of sequestering species. Our data indicate that major adaptations to Plant Toxins may be evolutionarily linked to sequestration, and may not necessarily be a means to eat toxic Plants. Na(+)/K(+)-ATPase adaptations thus were a potential mechanism through which predators spurred the coevolutionary arms race between Plants and insects.
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na k atpase resistance and cardenolide sequestration basal adaptations to host Plant Toxins in the milkweed bugs hemiptera lygaeidae lygaeinae
Proceedings of The Royal Society B: Biological Sciences, 2015Co-Authors: Christiane Bramer, Jürgen Deckert, Susanne Dobler, Michael Stemmer, Georg PetschenkaAbstract:Despite sequestration of Toxins being a common coevolutionary response to Plant defence in phytophagous insects, the macroevolution of the traits involved is largely unaddressed. Using a phylogenetic approach comprising species from four continents, we analysed the ability to sequester toxic cardenolides in the hemipteran subfamily Lygaeinae, which is widely associated with cardenolide-producing Apocynaceae. In addition, we analysed cardenolide resistance of their Na+/K+-ATPases, the molecular target of cardenolides. Our data indicate that cardenolide sequestration and cardenolide-resistant Na+/K+-ATPase are basal adaptations in the Lygaeinae. In two species that shifted to non-apocynaceous hosts, the ability to sequester was secondarily reduced, yet Na+/K+-ATPase resistance was maintained. We suggest that both traits evolved together and represent major coevolutionary adaptations responsible for the evolutionary success of lygaeine bugs. Moreover, specialization on cardenolides was not an evolutionary dead end, but enabled this insect lineage to host shift to cardenolide-producing Plants from distantly related families.