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1,187 results for “herbivores”
Data from: Use of an exotic host plant affects mate choice in an insect herbivore
The colonization of exotic plants by herbivorous insects has provided opportunities for investigating causes and consequences associated with the evolution of niche breadth. The butterfly Lycaeides melissa utilizes exotic alfalfa, Medicago sativa, which is a relatively poor larval resource, and previous studies have found that caterpillars that consume M. sativa develop into smaller and less fecund adults. Here we investigate the effect of smaller female body size on male mate preference, a previously unexplored consequence of novel host use. Smaller females, which developed on the exotic host, were less likely to be visited by males. This result was confirmed with a second set of choice tests involving females reared on a single plant species, thus ruling out host-specific confounding factors. We suggest that an effect on mate choice be considered as part of the complex suite of factors determining persistence of herbivorous insects following colonization of new habitats or resources.
Data from: Relaxation of herbivore-mediated selection drives the evolution of genetic covariances between plant competitive and defense traits
Insect herbivores are important mediators of selection on traits that impact plant defense against herbivory and competitive ability. Although recent experiments demonstrate a central role for herbivory in driving rapid evolution of defense and competition-mediating traits, whether and how herbivory shapes heritable variation in these traits remains poorly understood. Here, we evaluate the structure and evolutionary stability of the G matrix for plant metabolites that are involved in defense and allelopathy in the tall goldenrod, Solidago altissima. We show that G has evolutionarily diverged between experimentally-replicated populations that evolved in the presence versus the absence of ambient herbivory, providing direct evidence for the evolution of G by natural selection. Specifically, evolution in an herbivore-free habitat altered the orientation of G, revealing a negative genetic covariation between defense- and competition-related metabolites that is typically masked in herbivore-exposed populations. Our results may be explained by predictions of classical quantitative genetic theory, as well as the theory of acquisition-allocation trade-offs. The study provides compelling evidence that herbivory drives the evolution of plant genetic architecture.
Data from: Interactions between C:N:P stoichiometry and soil macrofauna control dung decomposition of savanna herbivores
1. Although dung of mammalian herbivores is an important pathway for nutrient return in savanna ecosystems, differences in dung decomposition rates among species have been little studied. 2. We measured rates of dung deposition and decomposition for various herbivores in a moist Tanzanian savanna, and related differences among species to nutrient concentrations and the activities of soil macrofauna (e.g., different mesh sizes of decomposition bags, or presence and absence of dung beetles). 3. Dung C:N:P stoichiometry varied widely among species, which could in part be explained by differences in feeding strategy (browsers vs. grazers) and digestive physiology (ruminants vs. non-ruminants). Rates of both decomposition and nutrient release were influenced by the C:N:P stoichiometry of dung, with lower relative losses of the least abundant nutrient. Surprisingly, soil macrofauna increased relative losses of the least abundant nutrient, thereby stabilizing the ratio of N loss to P loss. Dung beetles increased rates of N and P release from wildebeest dung significantly and also increased N availability in the soil. 4. We conclude that rates of nutrient return in dung depend not only on where herbivores deposit their dung, but also on its C:N:P stoichiometry, the activity of soil macrofauna, and interactions between these factors. These factors may therefore influence the relative availabilities of N and P in the soil and hence the functioning of savanna ecosystems.
Data from: Preference for outbred host plants and positive effects of inbreeding on egg survival in a specialist herbivore
Inbreeding can profoundly affect the interactions of plants with herbivores as well as with the natural enemies of the herbivores. We studied how plant inbreeding affects herbivore oviposition preference, and whether inbreeding of both plants and herbivores alters the probability of predation or parasitism of herbivore eggs. In a laboratory preference test with the specialist herbivore moth Abrostola asclepiadis and inbred and outbred Vincetoxicum hirundinaria plants, we discovered that herbivores preferred to oviposit on outbred plants. A field experiment with inbred and outbred plants that bore inbred or outbred herbivore eggs revealed that the eggs of the outbred herbivores were more likely to be lost by predation, parasitism or plant hypersensitive responses than inbred eggs. This difference did not lead to differences in the realized fecundity as the number of hatched larvae did not differ between inbred and outbred herbivores. Thus, the strength of inbreeding depression in herbivores decreases when their natural enemies are involved. Plant inbreeding did not alter the attraction of natural enemies of the eggs. We conclude that inbreeding can significantly alter the interactions of plants and herbivores at different life-history stages, and that some of these alterations are mediated by the natural enemies of the herbivores.
Data from: Climate and atmospheric change impacts on sap-feeding herbivores: a mechanistic explanation based on functional groups of primary metabolites
Global climate and atmospheric change are widely predicted to affect many ecosystems. Herbivorous insects account for 25% of the planet's species so their responses to environmental change are pivotal to how future ecosystems will function. Atmospheric change affects feeding guilds differently, however, with sap-feeding herbivores consistently identified as net beneficiaries of predicted increases in atmospheric carbon dioxide concentrations (eCO2). The mechanistic basis for these effects remains largely unknown, and our understanding about how multiple environmental changes, acting in tandem, shape plant–insect interactions is incomplete. This study investigated how increases in temperature (eT) and eCO2 affected the performance of the pea aphid (Acyrthosiphon pisum) via changes in amino acid concentrations in the model legume, lucerne (Medicago sativa). Aphid performance increased under eCO2 at ambient temperatures, whereby aphid fecundity, longevity, colonization success and rm increased by 42%, 30%, 25% and 21%, respectively. eT negated the positive effects of eCO2 on both fecundity and rm, however, and performance was similar to when aphids were reared at ambient CO2. We identified discrete functional groups of amino acids that underpinned the effects of climate and atmospheric change, in addition to plant genotype, on aphid performance. Effects of eT and eCO2 held true across five M. sativa genotypes, demonstrating the generality of their effects. Combining this knowledge with amino acid profiles of existing cultivars raises the possibility of predicting future susceptibility to aphids and preventing outbreaks of a global pest. Moreover, environmentally induced changes in the nutritional ecology of aphids have the capacity to change life-history strategies of aphids and their direct and indirect interactions with many other organisms, including mutualists and antagonists.
Data from: Grazer effects on soil carbon storage vary by herbivore assemblage in a semi-arid grassland
1. Accounting for 10-30% of global soil organic carbon, grassland soils potentially present a large reservoir for storing atmospheric CO2. Livestock grazing management can substantially affect grassland soil carbon (C) storage, but few controlled experiments have explored how herbivore assemblages (different herbivore species and combinations) affect soil C storage. 2. We examined effects of moderate grazing by different herbivore assemblages (no grazing; sheep grazing; cattle grazing; mixed grazing by sheep and cattle) on soil organic carbon storage in two types of grassland communities (high forbs/high diversity and low forbs/low diversity), within a semi-arid grassland with a five-year grazing history. 3. We found that herbivore assemblage generated varying effects on soil C storage and the effects were subject to grassland community types. In the low diversity community, none of three herbivore assemblages studied had obvious effects on soil C storage. In the high diversity community, however, sheep grazing significantly decreased soil C storage due to high selectivity for high quality forbs, and cattle grazing had no effects on soil C storage, while mixed grazing by sheep and cattle significantly increased soil C storage. Overall, soil C storage was highest in mixed-grazed grassland sites with high diversity. 4. Synthesis and applications. Our study suggests that explicitly incorporating grazer species and the combination of grazing livestock into grassland grazing management may help mitigate greenhouse gas emissions. Caution should be exercised when using grazer species with high food selectivity when grazing management is also aimed at climate mitigation, especially in grasslands with abundant high quality forbs and high plant diversity, as sheep grazing may reduce soil carbon (C) storage. Moreover, mixed grazing, including multiple herbivore species, may contribute to a reduction in foraging selectivity for a plant community by means of complementary foraging. It could therefore be considered as an optimal grazing management strategy to maintain and improve soil C storage.
Data from: Temperature dependence of predation stress and the nutritional ecology of a generalist herbivore
Prey at risk of predation may experience stress and respond physiologically by altering their metabolic rates. Theory predicts that such physiological changes should alter prey nutrient demands from N-rich to C-rich macronutrients and shift the balance between maintenance and growth/reproduction. Theory further suggests that for ectotherms, temperature stands to exacerbate this stress. Yet, the interactive effects of predation stress and temperature stress on diet, metabolism, and survival of ectotherms are not well known. This knowledge gap was addressed with a laboratory study in which wild juvenile grasshoppers were collected, assigned to one of three groups, and raised at three different temperatures. All grasshoppers had access to equal quantities of two diets composed of opposite carbohydrate:protein ratios. Half of the individuals in each temperature group were exposed to predation risk cues from spider predators, while the other half were kept in risk free conditions. Grasshoppers consumed more carbohydrates when exposed to predation risk, but consumption favored greater protein intake as temperature increased. Moreover, the difference in carbohydrate intake between risk cue and risk free treatments diminished as temperature increased. Furthermore, variability between individual consumption patterns both within and between treatments decreased markedly as temperature increased, suggesting that higher temperatures promote more consistent individual consumption behaviors. Grasshoppers grew faster and larger as temperature increased, which translated into higher survival rates at higher temperatures. Warmer grasshoppers also did not alter their metabolic rates in response to predation risk cues, in contrast to colder grasshoppers. Digestive efficiency increased with temperature as well, further indicating that lower temperatures were much more stressful than higher temperatures for grasshoppers. The study shows that physiological responses of ectothermic herbivores to predation stress are highly plastic and temperature dependent, with higher temperatures promoting increased protein intake, growth, development, survival, and digestive efficiency relative to colder temperatures. These findings help to reconcile why dietary responses (proportion of protein vs. carbohydrate intake) to predation stress may vary among different prey taxa studied previously.
Data from: When resistance is futile, tolerate instead: silicon promotes plant compensatory growth when attacked by above- and belowground herbivores
Plants have evolved numerous herbivore defences which are resistance- or tolerance-based. Resistance involves physical and chemical traits that deter and/or harm herbivores whereas tolerance minimises fitness costs of herbivory, often via compensatory growth. The Poaceae frequently accumulate large amounts of silicon (Si) which can be used for herbivore resistance, including biomechanical and (indirectly) biochemical defences. To date, it is unclear whether Si improves tolerance of herbivory. Here we report how Si enabled a cereal (Triticum aestivum) to tolerate damage inflicted by above- and belowground herbivores. Leaf herbivory increased Si concentrations in the leaves by >50% relative to herbivore-free plants, indicating it was an inducible defensive response. In plants without Si supplementation, leaf herbivory reduced shoot biomass by 52% and root herbivory reduced root biomass by 68%. Si supplementation, however, facilitated compensatory growth such that shoot losses were more than compensated for (+14% greater than herbivore-free plants) and root losses were minimised to -16%. Si supplementation did not improve plant resistance since Si did not enhance biomechanical resistance (i.e. force of fracture) or reduce leaf consumption and herbivore relative growth rates. We propose that Si-based defence operates in wheat via tolerance either in addition, or as an alternative, to resistance-based defence.
Data from: Temperature-dependent, behavioral, and transcriptional variability of a tritrophic interaction consisting of bean, herbivorous mite, and predator
Different organisms compensate for, and adapt to, environmental changes in different ways and therefore environmental changes affect animal–plant interactions. We consequently assessed the effect of temperature on a tritrophic system of the lima bean, the spider mite Tetranychus urticae, and the predatory mite Phytoseiulus persimilis. In this system the plant defends itself against T. urticae by emitting volatiles that attract P. persimilis. Over a range of 20 40°C the emission of volatiles by infested plants and the attraction of P. persimilis, peaked at 30°C but the number of eggs laid by T. urticae adults and the number of eggs consumed by P. persimilis, peaked at 35°C. This indicates that the spider mites and predatory mites performed best at a higher temperature than that at which most volatile attractants were produced. We used data from transcriptome pyrosequencing of the mites and found that P. persimilis up-regulated gene families for heat shock proteins (HSPs) and ubiquitin-associated proteins, whereas T. urticae did not. RNA interference-mediated gene suppression in P. persimilis, developed in the current study, revealed that predation on T. urticae eggs by P. persimilis fed with PpHsp70-1 dsRNA was reduced at 35°C, when the expression level of PpHsp70-1 was greatly increased but not at 25°C. Overall, our molecular and behavioral approaches revealed that the mode and tolerance of lima bean, T. urticae, and the predatory mite P. persimilis are distinctly affected by temperature variability, thereby making their tritrophic interactions temperature dependent.
Data from: Generation and maintenance of predation hotspots of a functionally important herbivore in a patchy habitat mosaic
1. By modifying how critical ecosystem functions are distributed across the landscape, the spatial configuration and characteristics of patches can play a strong role in structuring communities. In strongly predator-controlled ecosystems, this patchy distribution of function can have complex downstream consequences, subjecting some areas to disproportionately high rates of predation, leaving other areas susceptible to herbivore outbreaks. 2. In this study we assess how spatial attributes at patch and landscape scales potentially influence the spatial and temporal distribution of predation on a functionally important herbivore in a patchy Mediterranean marine macrophyte community characterized by strong top-down control. 3. We experimentally tracked how predation risk of tethered sea urchins varied across space over a 10-day period in a patchy seagrass meadow. We related these patterns with patch and landscape-level attributes across the habitat mosaic. 4. At the level of the patch, predation risk was highest in seagrass patches with low canopies, without access to sheltering rocks. Scaling up to the landscape mosaic however, predation risk increased in dense aggregations of patches with high perimeter-to-area ratios close to rocky habitats. Predation aggregated in spatially-explicit hotspots and coldspots that were maintained through time. Interestingly, this pattern of predation risk correlated well with the natural abundance of sea urchins. 5. Our results show that spatial patch configuration can be a strong mediator of top trophic functions in marine ecosystems, causing significant clumping in the way predation – and therefore herbivory – are distributed across space. Given the importance of top-down control for these shallow marine ecosystems, it is crucial to incorporate landscape attributes in understanding the impact of functionally important herbivores on highly fragmented habitats.
Data from: Spatial heterogeneity in the strength of plant-herbivore interactions under predation risk: the tale of bison foraging in wolf country
Spatial heterogeneity in the strength of trophic interactions is a fundamental property of food web spatial dynamics. The feeding effort of herbivores should reflect adaptive decisions that only become rewarding when foraging gains exceed 1) the metabolic costs, 2) the missed opportunity costs of not foraging elsewhere, and 3) the foraging costs of anti-predator behaviour. Two aspects of these costs remain largely unexplored: the link between the strength of plant-herbivore interactions and the spatial scale of food-quality assessment, and the predator-prey spatial game. We modeled the foraging effort of free-ranging plains bison (Bison bison bison) in winter, within a mosaic of discrete meadows. Spatial patterns of bison herbivory were largely driven by a search for high net energy gains and, to a lesser degree, by the spatial game with grey wolves (Canis lupus). Bison decreased local feeding effort with increasing metabolic and missed opportunity costs. Bison herbivory was most consistent with a broad-scale assessment of food patch quality, i.e., bison grazed more intensively in patches with a low missed opportunity cost relative to other patches available in the landscape. Bison and wolves had a higher probability of using the same meadows than expected randomly. This co-occurrence indicates wolves are ahead in the spatial game they play with bison. Wolves influenced bison foraging at fine scale, as bison tended to consume less biomass at each feeding station when in meadows where the risk of a wolf's arrival was relatively high. Also, bison left more high-quality vegetation in large than small meadows. This behavior does not maximize their energy intake rate, but is consistent with bison playing a shell game with wolves. Our assessment of bison foraging in a natural setting clarifies the complex nature of plant-herbivore interactions under predation risk, and reveals how spatial patterns in herbivory emerge from multi-scale landscape heterogeneity.
Data from: Transcriptome sequencing and microarray development for the woodrat (Neotoma spp.): custom genetic tools for exploring herbivore ecology
Massively parallel sequencing has enabled the creation of novel, in-depth genetic tools for nonmodel, ecologically important organisms. We present the de novo transcriptome sequencing, analysis and microarray development for a vertebrate herbivore, the woodrat (Neotoma spp.). This genus is of ecological and evolutionary interest, especially with respect to ingestion and hepatic metabolism of potentially toxic plant secondary compounds. We generated a liver transcriptome of the desert woodrat (Neotoma lepida) using the Roche 454 platform. The assembled contigs were well annotated using rodent references (99.7% annotation), and biotransformation function was reflected in the gene ontology. The transcriptome was used to develop a custom microarray (eArray, Agilent). We tested the microarray with three experiments: one across species with similar habitat (thus, dietary) niches, one across species with different habitat niches and one across populations within a species. The resulting one-colour arrays had high technical and biological quality. Probes designed from the woodrat transcriptome performed significantly better than functionally similar probes from the Norway rat (Rattus norvegicus). There were a multitude of expression differences across the woodrat treatments, many of which related to biotransformation processes and activities. The pattern and function of the differences indicate shared ecological pressures, and not merely phylogenetic distance, play an important role in shaping gene expression profiles of woodrat species and populations. The quality and functionality of the woodrat transcriptome and custom microarray suggest these tools will be valuable for expanding the scope of herbivore biology, as well as the exploration of conceptual topics in ecology.
Leaf vibrations produced by chewing provide a consistent acoustic target for plant recognition of herbivores
<p>Plant defenses that respond to the threat of herbivory require accurate sensing of the presence of herbivores. Herbivory cues include mechanical damage, elicitors from insect saliva or eggs, and airborne volatiles emitted by wounded plants. Plants can also respond to the leaf vibrations produced by chewing herbivores. However, previous studies of the influence of feeding vibrations on plant defenses have been limited to single species pairs. In this study we test the hypothesis that chewing vibrations differ among herbivore species, both in their acoustic features and in their effect on plant defense responses. We first compare the acoustic traits of larval feeding vibrations in ten species from six families of Lepidoptera and one family of Hymenoptera. We then test responses of <i>A. thaliana</i> plants to variation among feeding vibrations of different individuals of one species, and to feeding vibrations of two species, including a pierid butterfly and a noctuid moth. All feeding vibrations consisted of repetitive pulses of vibration associated with leaf tissue removal, although chewing rates varied between species and between large and small individuals within species. The frequency spectra of the vibrations generated by leaf feeding were similar across all ten species. Induced defenses of <i>A. thaliana</i> did not differ when plants were played vibrations from different individuals, or vibrations of two species of herbivores with different chewing rates, when amplitude was held constant. These results suggest that feeding vibrations provide a consistent set of cues for plant recognition of herbivores.</p>
Data from: Removal of an apex predator initiates a trophic cascade that extends from herbivores to vegetation and the soil nutrient pool
It is widely assumed that organisms at low trophic levels, particularly microbes and plants, are essential to basic services in ecosystems, such as nutrient cycling. In theory, apex predators' effects on ecosystems could extend to nutrient cycling and the soil nutrient pool by influencing the intensity and spatial organization of herbivory. Here, we take advantage of a long-term manipulation of dingo abundance across Australia's dingo-proof fence in the Strzelecki Desert to investigate the effects that removal of an apex predator has on herbivore abundance, vegetation and the soil nutrient pool. Results showed that kangaroos were more abundant where dingoes were rare, and effects of kangaroo exclusion on vegetation, and total carbon, total nitrogen and available phosphorus in the soil were marked where dingoes were rare, but negligible where dingoes were common. By showing that a trophic cascade resulting from an apex predator's lethal effects on herbivores extends to the soil nutrient pool, we demonstrate a hitherto unappreciated pathway via which predators can influence nutrient dynamics. A key implication of our study is the vast spatial scale across which apex predators' effects on herbivore populations operate and, in turn, effects on the soil nutrient pool and ecosystem productivity could become manifest.
Data from: Fire frequency drives habitat selection by a diverse herbivore guild impacting top–down control of plant communities in an African savanna
In areas with diverse herbivore communities such as African savannas, the frequency of disturbance by fire may alter the top–down role of different herbivore species on plant community dynamics. In a seven year experiment in the Kruger National Park, South Africa, we examined the habitat use of nine common herbivore species across annually burned, triennially burned and unburned areas. We also used two types of exclosures (plus open access controls) to examine the impacts of different herbivores on plant community dynamics across fire disturbance regimes. Full exclosures excluded all herbivores > 0.5 kg (e.g. elephant, zebra, impala) while partial exclosures allowed access only to animals with shoulder heights ≤ 0.85 m (e.g. impala, steenbok). Annual burns attracted a diverse suite of herbivores, and exclusion of larger herbivores (e.g. elephant, zebra, wildebeest) increased plant abundance. When smaller species, mainly impala, were also excluded there were declines in plant diversity, likely mediated by a decline in open space available for colonization of uncommon plant species. Unburned areas attracted the least diverse suite of herbivores, dominated by impala. Here, herbivore exclusion, especially of impala, led to strong declines in plant richness and diversity. With no fire disturbance, herbivore exclusion led to competitive exclusion via increases in plant dominance and light limitation. In contrast, on triennial burns, herbivore exclusion had no effect on plant richness or diversity, potentially due to relatively little open space for colonization across exclosure treatments but also little competitive exclusion due to the intermediate fire disturbance. Further, the diverse suite of grazers and browsers on triennial burns may have had a compensating effect of on the diversity of grasses and forbs. Ultimately, our work shows that differential disturbance regimes can result in differential consumer pressure across a landscape and result in heterogeneous patterns in top–down control of community dynamics.
Data from: Does plant diversity increase top–down control of herbivorous insects in tropical forest?
Higher trophic level interactions are key mediators of ecosystem functioning in tropical forests. A rich body of theory has been developed to predict the effects of plant diversity on communities at higher trophic levels and the mechanisms underlying such effects. The 'enemies hypothesis' states that predators exert more effective top–down control of herbivorous insects with increasing plant diversity. Support for this hypothesis has been found in temperate forests and agroecosystems, but remains understudied in tropical forests. We compared incidence of attacks of different natural enemies using artificial caterpillars in a tropical forest landscape and investigated the role of plant community structure (i.e. species richness, composition and density), and the role of forest fragmentation (i.e. patch size, edge distance and canopy openness) on predation intensity. Plant community effects were tested with respect to three vegetation strata: trees, saplings and herbs. Observed predation was substantially due to ants. Predation rates increased with plant species richness for trees and herbs. Density of saplings, herb cover and herb species composition were important factors for predation. No significant patterns were found for fragmentation parameters, suggesting that forest fragmentation has not altered predation intensity. We conclude that in tropical forests, top–down control of herbivorous insects in the understory vegetation is affected by a combination of plant diversity, plant species composition and structural features of the plant community.
Data from: Cascading reproductive isolation: plant phenology drives temporal isolation among populations of a host-specific herbivore
All organisms exist within a complex network of interacting species, thus evolutionary change may have reciprocal effects on multiple taxa. Here, we demonstrate "cascading reproductive isolation," whereby ecological differences that reduce gene flow between populations at one trophic level affect reproductive isolation (RI) among interacting species at the next trophic level. Using a combination of field, laboratory and common-garden studies and long-term herbaria records, we estimate and evaluate the relative contribution of temporal RI to overall prezygotic RI between populations of Belonocnema treatae, a specialist gall-forming wasp adapted to sister species of live oak (Quercus virginiana and Q. geminata). We link strong temporal RI between host-associated insect populations to differences between host plant budbreak phenology. Budbreak initiates flowering and the production of new leaves, which are an ephemeral resource critical to insect reproduction. As flowering time is implicated in RI between plant species, budbreak acts as a "multitrophic multi-effect trait," whereby differences in budbreak phenology contribute to RI in plants and insects. These sister oak species share a diverse community of host-specific gall-formers and insect natural enemies similarly dependent on ephemeral plant tissues. Thus, our results set the stage for testing for parallelism in a role of plant phenology in driving temporal cascading RI across multiple species and trophic levels.
Data from: Mammalian herbivores affect leafhoppers associated with specific plant functional types at different timescales
1. Theory predicts that mammalian herbivores affect the quantity and quality of plants on which they preferentially feed in the short term. In the longer term, they can promote either preferred or less preferred plants, depending on whether preferred plants are adapted or sensitive to grazing. Less clear are the short- and long-term responses of herbivorous insects to mammalian herbivory, and how these responses depend on the specific plants or plant functional types on which the insects feed. 2. We progressively excluded large, medium, and small mammals for five growing seasons in two subalpine vegetation types with long-term differences in mammalian grazing intensity. Short-grass vegetation has a history of intensive grazing, while tall-grass vegetation has been grazed less intensively. We tested whether mammals altered the abundance and body size of leafhoppers specialized on specific plant functional types (grasses, sedges, forbs, or legumes/forbs), distinguishing between short-term (exclosures) and long-term (vegetation types) differences in mammalian grazing pressure. Furthermore, we assessed whether leafhoppers' responses were explained by changes in biomass or quality of the plant functional types on which they feed. 3. In the short term, mammal exclosures increased the abundance of grass- and forb-feeding leafhoppers via increases in the biomass of grasses and forbs, regardless of vegetation type. Both grasses and forbs are preferred food plants of mammals. In the long term, the biomass of sedges, which are less preferred by mammals, increased in the less intensively grazed tall-grass vegetation. This resulted in a higher abundance of sedge-feeding leafhoppers. The small size of these sedge feeders lowered the average leafhopper body size in the tall-grass vegetation. Plant nutritional quality did not explain any effects of exclusions or vegetation types. 4. Our results demonstrate that both short- and long-term effects of mammalian herbivores on the biomass of specific plant functional types caused concurrent changes in the abundance of specialized herbivorous insects, which scaled up to community-wide shifts in insect body size, a key life-history trait. A plant-functional-type approach can thus help to predict how overabundance or extinction of mammalian herbivores impacts on other components of the food web at various timescales.
Data from: Tolerance to deer herbivory and resistance to insect herbivores in the common evening primrose (Oenothera biennis)
The evolution of plant defence in response to herbivory will depend on the fitness effects of damage, availability of genetic variation, and potential ecological and genetic constraints on defence. Here we examine the potential for evolution of tolerance to deer herbivory in Oenothera biennis while simultaneously considering resistance to natural insect herbivores. We examined: i) the effects of deer damage on fitness; ii) the presence of genetic variation in tolerance and resistance; iii) selection on tolerance; iv) genetic correlations with resistance that could constrain evolution of tolerance; and v) plant traits that might predict defence. In a field experiment, we simulated deer damage occurring early and late in the season, recorded arthropod abundances, flowering phenology, and measured growth rate and lifetime reproduction. Our study showed that deer herbivory has a negative effect on fitness, with effects being more pronounced for late-season damage. Selection acted to increase tolerance to deer damage, yet there was low and non-significant genetic variation in this trait. In contrast, there was substantial genetic variation in resistance to insect herbivores. Resistance was genetically uncorrelated with tolerance, whereas positive genetic correlations in resistance to insect herbivores suggest there exists diffuse selection on resistance traits. In addition, growth rate and flowering time did not predict variation in tolerance, but flowering phenology was genetically correlated with resistance. Our results suggest that deer damage has the potential to exert selection because browsing reduces plant fitness, but limited standing genetic variation in tolerance is expected to constrain adaptive evolution in O. biennis.
Data from: Phylogenetic composition of host plant communities drives plant-herbivore food web structure
1. Insects tend to feed on related hosts. The phylogenetic composition of host plant communities thus plays a prominent role in determining insect specialization, food web structure, and diversity. Previous studies showed a high preference of insect herbivores for congeneric and confamilial hosts suggesting that some levels of host plant relationships may play more prominent role that others. 2. We aim to quantify the effects of host phylogeny on the structure of quantitative plant-herbivore food webs. Further, we identify specific patterns in three insect guilds with different life histories and discuss the role of host plant phylogeny in maintaining their diversity. 3. We studied herbivore assemblages in three temperate forests in Japan and the Czech Republic. Sampling from a canopy crane, a cherry picker and felled trees allowed a complete census of plant-herbivore interactions within three 0.1 ha plots for leaf chewing larvae, miners, and gallers. We analyzed the effects of host phylogeny by comparing the observed food webs with randomized models of host selection. 4. Larval leaf chewers exhibited high generality at all three sites, whereas gallers and miners were almost exclusively monophagous. Leaf chewer generality dropped rapidly when older host lineages (5-80 myr) were collated into a single lineage but only decreased slightly when the most closely related congeneric hosts were collated. This shows that leaf chewer generality has been maintained by feeding on confamilial hosts while only a few herbivores were shared between more distant plant lineages and, surprisingly, between some congeneric hosts. In contrast, miner and galler generality was maintained mainly by the terminal nodes of the host phylogeny and dropped immediately after collating congeneric hosts into single lineages. 5. We show that not all levels of host plant phylogeny are equal in their effect on structuring plant-herbivore food webs. In the case of generalist guilds, it is the phylogeny of deeper plant lineages that drives the food web structure whereas the terminal relationships play minor roles. In contrast, the specialization and abundance of monophagous guilds is affected mainly by the terminal parts of the plant phylogeny and does not generally reflect deeper host phylogeny.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
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