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1,186 results for “defensiveness”
Data from: Salicylate plant defenses reduce aphid nutritional quality and increase predator consumption
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Resource gradients create energy trade-offs in the inducible defense response of <em>Paramecium aurelia</em>
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Data from a test of female defense in male collared lizards
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Change in threespine stickleback defensive traits, following brook trout introduction
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Data from: Sick plants in grassland communities: a growth-defense trade-off is the main driver of fungal pathogen abundance
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Data from: What's that smell? Hummingbirds avoid foraging on resources with defensive insect compounds
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Plant volatiles induced by herbivore eggs prime defenses and mediate shifts in the reproductive strategy of receiving plants
<p>Plants can detect cues associated with the risk of future herbivory and modify defense phenotypes accordingly; however, our current understanding is limited both with respect to the range of early warning cues to which plants respond and the nature of the responses. Here we report that exposure to volatile emissions from plant tissues infested with herbivore eggs promotes stronger defense responses to subsequent herbivory in two Brassica species. Furthermore, exposure to these volatile cues elicited an apparent shift from growth to reproduction in Brassica nigra, with exposed plants exhibiting increased flower and seed production, but reduced leaf production, relative to unexposed controls. Our results thus document plant defense priming in response to a novel environmental cue, oviposition-induced plant volatiles, while also showing that plant responses to early warning cues can include changes in both defense and life-history traits.</p>
Date from: Top-down effects from parasitoids may mediate plant defense and plant fitness
<ol> <li>Plants face many environmental stresses that can impact the<span>ir </span><span><span>survival</span></span><span>, developm</span>ent, and fitness. Insects are the most diverse, abundant and threatening herbivores in nature. As a consequence, plants produce direct chemical and physical defenses to reduce herbivory. They also release volatiles to recruit natural enemies that indirectly protect them from herbivory. The recruitment of parasitic wasps can benefit plant fitness because they ultimately kill their insect hosts.</li> <li>Recently, studies showed that parasitoids can indirectly mediate plant defenses by modulating herbivore oral secretions. In addition to the direct benefits of parasitoids in terms of reducing herbivore survival, we tested if the reduction in induced defenses by parasitized caterpillars compared to non-parasitized caterpillars may reduce the costs associated with defense expression.</li> <li>We provide evidence that tomato plants treated with saliva from parasitized caterpillars have significantly higher fitness parameters including increased flower numbers (16.3%) and heavier fruit weight (15%), compared to plants treated with saliva from non-parasitized caterpillars. Since plants were grown without actual herbivores, the higher values for these fitness parameters were due to lower costs of induced defenses and not due to reduced herbivory by parasitized caterpillars. Furthermore, the resulting seed germination time was shorter and the germination rate was higher when the maternal plants were previously exposed to parasitized herbivore treatment compared to control (non-treated) plants.</li> <li>Overall, application of saliva did not result in transgenerational priming of offspring defense responses. However, offspring of parents exposed to caterpillar saliva had lower constitutive levels and higher induced levels of trypsin inhibitor than offspring from unexposed parents.</li> <li>This study shows that the saliva of parasitized caterpillars can modulate plant defenses and further demonstrates that the lower induction of plant defenses is associated with elevated plant fitnes<span>s </span><span><span>in the absence of herbivore feeding</span></span><span>, sugge</span>sting that induced plant defenses are costly. </li> </ol>
Data from: Evolutionary constraint on low elevation range expansion: defense-abiotic stress tolerance tradeoff in crosses of the ecological model Boechera stricta
Most transplant experiments across species geographic range boundaries indicate that adaptation to stressful environments outside the range is often constrained. However, the mechanisms of these constraints remain poorly understood. We used extended generation crosses from diverged high and low elevation populations. In experiments across low elevation range boundaries, there was selection on the parental lines for abiotic stress tolerance and resistance to herbivores. However, in support of a defense-tolerance tradeoff, extended generation crosses showed non-independent segregation of these traits in the lab across a drought-stress gradient and in the field across the low elevation range boundary. Genotypic variation in a marker from a region of the genome containing a candidate gene (MYC2) was associated with change in the genetic tradeoff. Thus, using crosses and forward genetics, we found experimental genetic and molecular evidence for a pleiotropic tradeoff that could constrain the evolution of range expansion.
Optimal Defense Theory in an ant‐plant mutualism: extrafloral nectar as an induced defense is maximized in the most valuable plant structures
<ol> <li class="Normal1">Optimal Defense Theory (ODT) predicts that to maximize the benefits of defense against herbivores while minimizing its costs, plants will <span><span>invest in defenses</span></span> to structures according to their value and to the likelihood that they will be attacked. Constitutive defenses are expected in structures of high value, whereas induced defenses are expected in structures of low value. Regarding the biotic defense mediated by extrafloral nectaries (EFNs) and based on ODT, we predicted that under control conditions EFNs on higher-value structures would produce more nectar than would EFNs on lower-value structures, attracting more ants; however, when damaged, EFNs on higher-value structures would not increase the production of extrafloral nectar (since constitutive defenses should be employed in this region), whereas EFNs on lower-value structures would so (since induced defenses should be employed in this region), at a level commensurate with the extent of damage. </li> <li class="Normal1">Here we test these predictions in a Brazilian ant-plant mutualism. <i>Qualea multiflora</i> (Vochysiaceae), a savanna tree, presents EFNs on both lower-value structures (leaves) and higher-value structures (inflorescences). We simulated herbivory by cutting 10% or 40% of the leaves, or 10% of the flowers, then monitoring extrafloral nectar production and ant attendance. </li> <li class="Normal1">Extrafloral nectar volume and calorie content, as well as ant abundance, were higher in EFNs of inflorescences compared to EFNs of leaves both before and after simulated herbivory, consistent with one of our predictions. However, EFNs on both leaves and inflorescences, not leaves only, were induced by simulated herbivory, a pattern opposite to our prediction. Plants subjected to higher levels of leaf damage (i.e., more damage to lower-value tissues) <span><span>produced more and higher-calorie extrafloral nectar, but showed similar ant abundance, partially consistent with our prediction</span></span>. </li> <li class="Normal1"><span><span><span><span><span><span><span><span><span><span><span>Our results show that extrafloral nectar production before and after simulated herbivory, as well as the ant recruitment, vary according to the plant structure on which EFNs are located. Our study is unique showing that ant recruitment via extrafloral nectar follows predictions from Optimal Defense Theory, and that the ant foraging patterns may be shaped by the level and region damaged in the plant.</span></span></span></span></span></span></span></span></span></span></span></li> </ol>
Reproduction affects immune defenses in the guinea pig even under ad libitum food
<p>Reproduction is one of the most costly processes in the life of an animal. Life history theory assumes that when resources are limiting allocation to reproduction will reduce allocation to other essential processes thereby inducing costs of reproduction. The immune system is vital for survival. If reproduction reduces investment in immune function, this could increase the risk of disease, morbidity and mortality. We here test in the guinea pig, if even under <i>ad libitum</i> food conditions, pregnancy and lactation reduce the activity of the adaptive and innate immune system compared to the reaction of non-reproducing animals. In response to a challenge with keyhole limpet haemocyanin the antibody-mediated adaptive immunity during pregnancy and lactation was reduced. Pregnant and lactating females showed higher levels of bacterial killing activity, an integrated measure of innate immunity, than non-reproducing females. However, two major effectors of the innate immunity, the natural antibody and the complement of pregnant and lactating females showed lower levels than in non-reproducing females. Pregnant and lactating females did not differ significantly in the expressed levels of innate immunity. Our results indicate that changes in the immune response during reproduction are physiological adjustments to predictable allocation problems, because they happen even under <i>ad libitum</i> food availability.</p>
United we stand: evolution of increased competitive response and defense in response to crowding in an invasive plant
<p>1. The evolution of increased competitive ability (EICA) hypothesis predicts that invasive plant could evolve to be more competitive but be less defended as a result of releasing from their natural enemies, yet this hypothesis has rarely been addressed in density-dependence.</p> <p>2. Here, we grew five native (Argentina) and five introduced (USA) genotypes of perennial herb invasive plant <i>Alternanthera philoxeroides</i>, using an experimental setup that simulated different levels of neighbours heights and densities.</p> <p>3. Our results showed that introduced and native genotypes responded differently to changes in density: when neighbours were denser, introduced genotypes showed increases in total biomass, trichome density and triterpenoid saponins than native genotypes, but constants in shade-avoidance-related traits.</p> <p>4. Contrary to the predictions of EICA hypothesis, our findings contribute to a new pattern of both increased competitive response and defense in introduced populations in response to crowding, and highlight the importance of positive density-dependence in understanding invasive plant–plant interactions.</p>
Invasive earthworms reduce chemical defense and increase herbivory and pathogen infection in native trees
<ol> <li>Recent research shows that earthworms can alter defense traits of plants against herbivores and pathogens by affecting soil biochemistry. Yet, the effects of invasive earthworms on defense traits of native plants from previously earthworm-free ecosystems as well as the consequences for multitrophic interactions are virtually unknown.</li> <li>Here we use a combination of an observational study and a complementary experimental study to investigate the effects of invasive earthworms on leaf defense traits, herbivore damage, and pathogen infection in two poplar tree species (<i>Populus balsamifera </i>and <i>Populus tremuloides</i>) native to North American boreal forests.</li> <li>Our observational study showed that earthworm invasion was associated with enhanced leaf herbivory in saplings of both tree species. However, we only detected significant shifts in the concentration of chemical defense compounds in response to earthworm invasion for <i>P. balsamifera</i>. Specifically, leaf phenolic concentrations, including salicinoids and catechin, were lower in <i>P. balsamifera </i>from earthworm-invaded sites.</li> <li>Our experimental study confirmed an earthworm-induced reduction in leaf defense levels in <i>P. balsamifera</i> for one of the defense compounds, tremulacin. The experimental study additionally showed that invasive earthworms reduced leaf dry matter content, potentially increasing leaf palatability, and enhanced susceptibility of trees to infection by a fungal pathogen, but not to aphids, in the same tree species.</li> <li> <i>Synthesis. </i>Our results show that invasive earthworms can decrease the concentrations of some chemical defense compounds in <i>P. balsamifera</i>, which could make them susceptible to leaf-chewing insects. Such potential impacts of invasive earthworms are likely to have implications for tree survival and competition, native tree biodiversity, and ecosystem functioning.</li> </ol>
Visual contagion in prey defense signals can enhance honest defense
<p>The co-evolutionary arms race between predators and their prey has led to complex signaling, especially in groups that benefit from the social transmission of alarm signals. In particular, pursuit deterrence signals can allow individuals and groups to indicate, at relatively low cost, that a predator’s further approach is futile. Pursuit deterrence signals are usually more effective if amplified by becoming contagious and rapidly spreading among prey without requiring individual prey to confirm predator presence. However, this can also lead to runaway false signaling. We provide the first evidence of a contagious pursuit deterrence signal in social insects. The Asian honey bee, <em>Apis cerana</em>, performs an I See You (ISY) signal that deters attacking hornets. We show that these signals also attract guard bees to enhance defensive signaling and that the visual movements of appropriate stimuli alone (hornets and ISY signaling bees, but not harmless butterflies) provide sufficient stimuli. Olfaction and other potential cues are not necessary. The ISY signal is visually contagious and is buffered from runaway false signalsbecause it is specifically triggered and, likely, by selection for honesty within the highly cooperative bee colony. These results expand our understanding of contagious signals and how they can be honestly maintained in highly cooperative collectives.</p>
Networks of physiological adjustments and defenses, and their synergy with sodium (Na+) homeostasis explain the hidden variation for salinity tolerance across the cultivated Gossypium hirsutum germplasm
<p>The abilities to mobilize and/or sequester excess ions within and outside the plant cell are important components of salt-tolerance mechanisms. Mobilization and sequestration of Na<sup>+</sup> involves three transport systems facilitated by the plasma membrane H<sup>+</sup>/Na<sup>+</sup> antiporter (SOS1), vacuolar<i> </i>H<sup>+</sup>/Na<sup>+</sup> antiporter (NHX1), and Na<sup>+</sup>/K<sup>+</sup> transporter<i> </i>in vascular tissues (HKT1). Many of these mechanisms are conserved across the plant kingdom. While <i>Gossypium hirsutum</i> (upland cotton) is significantly more salt-tolerant relative to other crops, the critical factors contributing to the phenotypic variation hidden across the germplasm have not been fully unraveled. In this study, the spatio-temporal patterns of Na<sup>+</sup> accumulation along with other physiological and biochemical interactions were investigated at different severities of salinity across a meaningful genetic diversity panel across cultivated upland <i>Gossypium. </i>The aim was to define the importance of holistic or integrated effects relative to the direct effects of Na<sup>+</sup> homeostasis mechanisms mediated by <i>GhHKT1, GhSOS1,</i> and <i>GhNHX1. </i>Multi-dimensional physio-morphometric attributes were investigated in a systems-level context using univariate and multivariate statistics, <i>randomForest,</i> and path analysis. Results showed that mobilized or sequestered Na<sup>+</sup> contributes significantly to the baseline tolerance mechanisms. However, the observed variance in overall tolerance potential across a meaningful diversity panel were more significantly attributed to antioxidant capacity, maintenance of stomatal conductance, chlorophyll content, and divalent cation (Mg<sup>2+</sup>) contents other than Ca<sup>2+</sup> through a complex interaction with Na<sup>+</sup> homeostasis. The multi-tier macro-physiological, biochemical and molecular data generated in this study, and the networks of interactions uncovered strongly suggest that a complex physiological and biochemical synergy beyond the first-line-of defense (Na<sup>+</sup> sequestration and mobilization) accounts for the total phenotypic variance across the primary germplasm of <i>Gossypium hirsutum</i>. These findings are consistent with the recently proposed Omnigenic Theory for quantitative traits and should contribute to a modern look at phenotypic selection for salt tolerance in cotton breeding.</p>
Antipredator tactics: a kin-selection benefit for defensive spines in coral catfish?
Morphological features that impair a predator's ability to consume a prey item may benefit individual prey; but what of features that prolong prey-handling but do not enhance prey survival? For example, a Striped Eel Catfish (Plotosus lineatus) will be fatally envenomated if struck by its specialist predator, the Greater Sea Snake (Hydrophis major). Nonetheless, the catfish typically erects long, toxic pectoral and dorsal spines that increase prey-handling times for the snake by around eightfold. Because the catfish travel in swarms of closely-related individuals, the delay enforced by spines may enable the victim's swarm-mates to disperse before the snake is able to search for another meal. In keeping with that hypothesis, defensive spines tend to be longer in catfish from regions where the Greater Sea Snake occurs, than from areas where the snake does not occur. Our data thus suggest that defensive weaponry in catfish, as in some eusocial insects, can evolve via kin selection as well as natural selection.
Plant volatiles mediate evolutionary interactions between plants and tephritid flies and are evolutionarily more labile than non-volatile defenses
<p><span><span><span><span><span><span><span><span><span><span><span>1. Studies show that plant defenses influence the host-use of herbivores and tend to be evolutionarily more labile than herbivore traits (e.g., feeding preferences). However, all previous studies have focused exclusively on non-volatile plant defenses thereby overlooking the roles of plant volatiles.</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>2. We hypothesized that volatiles are equally important determinants of herbivore host-use and are evolutionarily more labile than herbivore traits. To test these hypotheses, the following experiments were conducted.</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>3. We identified the volatiles and non-volatiles of 17 Asteraceae species and measured their relative contents. We also used a highly resolved bipartite trophic network of the 17 host species and 20 herbivorous (pre-dispersal seed predator) tephritid fly species to determine the evolutionary interactions between plants and herbivores. </span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>4. The chemical data showed that interspecific similarity in volatiles—but not non-volatiles and phylogenetic distance—significantly accounted for the herbivore community across the plant species; this implies that plant volatiles—but not non-volatile compounds and species identity—dictate plant-tephritid fly interactions. Moreover, we observed phylogenetic signal for non-volatiles but not for volatiles; therefore closely related herbivores do not necessarily use closely related host species with similar non-volatiles, but do tend to attack plants producing similar volatiles. Thus, plant volatiles are evolutionarily more labile than non-volatiles and herbivore traits associate with host use. </span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>5. These results show that the interactions between plants and herbivores are evolutionary asymmetric, shed light on the role of plant volatiles in plant-herbivore interactions, and highlight the need to include data for both volatiles and non-volatiles when investigating plant-animal interactions.</span></span></span></span></span></span></span></span></span></span></span></p>
Preference, performance, and chemical defense in an endangered butterfly using novel and ancestral host plants
<p>Adoption of novel host plants by herbivorous insects can require new adaptations and may entail loss of adaptation to ancestral hosts. We examined relationships between an endangered subspecies of the butterfly <i>Euphydryas editha </i>(Taylor's checkerspot) and three host plant species. Two of the hosts (<i>Castilleja hispida, Castilleja levisecta</i>) were used ancestrally while the other, <i>Plantago lanceolata</i>, is exotic and was adopted more recently. We measured oviposition preference, neonate preference, larval growth, and secondary chemical uptake on all three hosts. Adult females readily laid eggs on all hosts but favored <i>Plantago </i>and tended to avoid <i>C. levisecta. </i>Oviposition preference changed over time.<i> </i>Neonates had no preference among host species, but consistently chose bracts over leaves within both <i>Castilleja </i>species. Larvae developed successfully on all species and grew to similar size on all of them unless they ate only <i>Castilleja </i>leaves (rather than bracts) which limited their growth. Diet strongly influenced secondary chemical uptake by larvae. Larvae that ate <i>Plantago </i>or <i>C. hispida </i>leaves contained the highest concentrations of iridoid glycosides, and iridoid glycoside composition varied with host species and tissue type. Despite having largely switched to a novel exotic host and generally performing better on it, this population has retained breadth in preference and ability to use other hosts.</p>
Tomato Plants Treated with Systemin Peptide Show Enhanced Levels of Direct and Indirect Defense Associated with Increased Expression of Defense-Related Genes
<p>Numerical data that underlies tables, graphs and statistics of the Plants article from Coppola et al., 2019: "Tomato Plants Treated with Systemin Peptide Show Enhanced Levels of Direct and Indirect Defense Associated with Increased Expression of Defense-Related Genes".</p>
Dynamics of transposable elements in recently diverged fungal pathogens: lineage-specific transposable element content and efficiency of genome defenses
<p>Transposable elements (TEs) impact genome plasticity, architecture and evolution in fungal plant pathogens. The wide range of TE content observed in fungal genomes reflects diverse efficacy of host-genome defence mechanisms that can counter-balance TE expansion and spread. Closely related species can harbour drastically different TE repertoires. The evolution of fungal effectors, which are crucial determinants of pathogenicity, has been linked to the activity of TEs in pathogen genomes. Here we describe how TEs have shaped genome evolution of the fungal wheat pathogen <em>Zymoseptoria tritici</em> and four closely related species. We compared <em>de novo</em> TE annotations and Repeat-Induced Point mutation signatures in twenty-six genomes from the <em>Zymoseptoria</em> species-complex. Then, we assessed the relative insertion ages of TEs using a comparative genomics approach. Finally, we explored the impact of TE insertions on genome architecture and plasticity. The twenty-six genomes of <em>Zymoseptoria</em> species reflect different TE dynamics with a majority of recent insertions. TEs associate with accessory genome compartments, with chromosomal rearrangements, with gene presence/absence variation and with effectors in all <em>Zymoseptoria </em>species. We find that the extent of RIP-like signatures varies among <em>Z. tritici</em> genomes compared to genomes of the sister species. The detection of a reduction of RIP-like signatures and TE recent insertions in <em>Z. tritici</em> reflects ongoing but still moderate TE mobility. </p>
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