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1,186 results for “defensiveness”
Survey of aspen leaf mining and leaf defenses, including foliar phenolic glycosides and extrafloral nectaries
This dataset characterizes the insect damage levels and chemical defenses of aspen (Populus tremuloides) leaves collected from multiple sites near Fairbanks, Alaska in June 2007. The intent of the data set was to relate leaf mining damage by the aspen leaf miner, Phyllocnistis populiella, to the concentration of phenolic glycosides (secondary metabolites; putative defensive compounds) in leaves.
Induction of aspen chemical defense by leaf mining, tested experimentally in 2006
This dataset summarizes the result of a manipulative experiment designed to test whether natural levels of damage by the aspen leaf miner, Phllocnistis populiella, causes the induction of foliar phenolic glycosides in small aspen ramets in the field.
Induction of aspen chemical defense by leaf mining, tested experimentally in 2007.
This dataset summarizes the result of a manipulative experiment designed to test the time course of phenolic glycoside induction by small aspen (Populus tremuloides) in response to leaf mining by the aspen leaf miner, Phyllocnistis populiella.
Trichoderma atroviride P1 Colonization of Tomato Plants Enhances Both Direct and Indirect Defense Barriers Against Insects
<p><strong>FIGURE 1</strong> </p> <p>Survival rate of <em>S. littoralis</em> larvae, from 3rd instar (time 0) to pupation, reared on tomato leaves obtained from plants treated with <em>Trichoderma atroviride</em> P1 or untreated control plants. Asterisk indicates that the two survival curves are significantly different (LogRank test, <em>P</em> = 0.0027).</p> <p> </p> <p><strong>FIGURE 3</strong> </p> <p>Survival of <em>Macrosiphum euphorbiae</em> reared on tomato plants treated with <em>T. atroviride</em> P1 or untreated control plants. Asterisk indicates that the two survival curves are significantly different (LogRank test, <em>P</em> = 0.0012).</p> <p> </p> <p><strong>FIGURE 4</strong> </p> <p>Flight behavior of <em>Aphidius ervi</em> females (%) toward tomato plants inoculated with <em>T. atroviride</em> P1 and untreated controls. Asterisk indicates a significant difference, assigned by <em>G</em> test for independence (<em>P</em> < 0.001).</p> <p> </p> <p><strong>TABLE 1</strong></p> <p>GC-MS detection of VOCs released by tomato plants obtained from seeds untreated (Control) and treated with <em>Trichoderma atroviride</em> strain P1.</p> <p> </p>
Data from: Chemical defenses shift with the seasonal vertical migration of a Panamanian poison frog
Dendrobatid poison frogs sequester lipophilic alkaloids from their arthropod prey to use as a form of chemical defense. Some dendrobatid frogs seasonally migrate between the leaf litter of the forest floor in the dry season to the canopy in the wet season, which may yield differences in prey (arthropods) and therefore alkaloid availability over space and time. Here, we document a seasonal vertical migration of Andinobates fulguritus (the yellow-bellied poison frog) from ground to canopy between dry and wet seasons. We observed turnover in alkaloid composition between seasons and found that dry season frogs contained a lower relative quantity of alkaloids; however, there was no change in alkaloid richness between seasons. The 77 alkaloids of 13 structural classes identified in this population appear to be derived mostly from mites and ants, though the two most common alkaloids were mite derived. Our observed shifts in defensive profiles are consistent with well-documented turnover in mite and ant communities between seasons and vertical strata. As climate change is expected to lengthen and strengthen dry seasons in many tropical regions, our results suggest that arboreal poison frogs forced to the ground for longer periods of time may see a shift in the abundance of alkaloids, possibly decreasing their defensive potential. This study provides further predictions for the wide-reaching effects of climate change, even as nuanced as charismatic poison frogs losing their poisons.
Data from: Tradeoffs affect the adaptive value of plasticity: Stronger cannibal-induced defenses incur greater costs in toad larvae
<p>Adaptive developmental plasticity allows individuals to match their phenotype with their environment, which can increase fitness where threats are inconsistently present. Because adaptive traits are not ubiquitously nor infinitely plastic, tradeoffs between benefits and costs or limits are theoretically necessary to constrain plastic responses. Systems in which extreme risk can be reliably detected are ideal for investigating mechanisms that constrain plasticity, as even costly responses may be adaptive where risk is severe. Cane toads (<em>Rhinella marina</em>) are abundant in Australia and produce large clutches (frequently >10,000 eggs), but asynchronous breeding and rapid development result in variable larval densities within breeding pools. In the field, we found that cannibalism by older cohorts often reduces the survival of conspecific eggs and newly hatched pre-feeding larvae ("hatchlings") by >99%, as feeding larvae ("tadpoles") use chemical cues from the relatively immobile hatchlings to locate and consume them. After hatchlings become free-swimming, however, they are safe from cannibalism. Hatchlings can reduce this period of vulnerability by accelerating development when they detect conspecific tadpole cues. However, this developmental acceleration decreases initial tadpole mass, reduces subsequent survival, growth, and development, affects behavior, and compromises feeding structures. Reaction norms differ among clutches, and greater developmental acceleration is followed by greater impairment of larval function in plastic clutches, whereas nonresponsive clutches are unaffected by exposure to cannibal cues. More plastic clutches ultimately exhibit both poorer performance and greater variation among siblings in exposed and (to a lesser degree) control treatments. Variation among clutches in tadpole viability is driven by differences in plasticity rather than phenotype; fitness reductions are linked to developmental acceleration, not rapid development <em>per se</em>. Clutches with intrinsically slow pre-feeding developmental rates exhibit stronger acceleration (i.e., steeper reaction norms), but clutches with intrinsically rapid development reach invulnerable stages more quickly than those that accelerate development. As a result, high cannibalism risk may favor canalized rapid development rather than facultative developmental acceleration. Cannibalism plays an important role in the recruitment of this invasive species, and hatchling defenses against this threat demonstrate how the limits and tradeoffs associated with an inducible defense can favor canalized defenses over phenotypic plasticity.</p>
Data from - Secondary metabolites in a neotropical shrub: spatiotemporal allocation and role in fruit defense and dispersal
<p>Data from "Secondary metabolites in a neotropical shrub: spatiotemporal allocation and role in fruit defense and dispersal" published in <em>Ecology </em>in 2020. doi.org/10.1002/ecy.3192</p>
Swimming and defense - competing needs across ontogeny in armored fishes (Agonidae)
<p>Biological armors are potent model systems for understanding the complex series of competing demands on protective exoskeletons; after all, armored organisms are the product of millions of years of refined engineering under the harshest conditions. Fishes are no strangers to armor, with various types of armor plating common to the 400 million years of evolution in both jawed and jawless fishes. Here we focus on the poachers (Agonidae), a family of armored fishes native to temperate waters of the Pacific rim. We examined armor morphology, body stiffness, and swimming performance in the Northern Spearnose Poacher (<i>Agonopsis vulsa</i>) over ontogeny. As juveniles, these fishes make frequent nocturnal forays into the water column in search of food, while heavily armored adults are bound to the benthos. Most armor dimensions and density increase with body length, as does body stiffness. Juvenile poachers have enlarged spines on their armor whereas adults invest more mineral in armor plate bases. Adults are stiffer and accelerate faster than juveniles with an anguilliform swimming mode. Subadults more closely approximate adults more than smaller juveniles, with regards to both swimming and armor mechanics. Poacher armor serves multiple functions over ontogeny, from facilitating locomotion, slowing sinking, and providing defense.</p>
Data from: The genetic architecture of plant defense tradeoffs in a common monkeyflower
<p>Determining how adaptive combinations of traits arose requires understanding the prevalence and scope of genetic constraints. Frequently observed phenotypic correlations between plant growth, defenses, and/or reproductive timing have led researchers to suggest that pleiotropy or strong genetic linkage between variants affecting independent traits is pervasive. Alternatively, these correlations could arise via independent mutations in different genes for each trait and extensive correlational selection. Here we evaluate these alternatives by conducting a QTL mapping experiment involving a cross between two populations of common monkeyflower (<em>Mimulus guttatus</em>) that differ in growth rate as well as total concentration and arsenal composition of plant defense compounds, phenylpropanoid glycosides (PPGs). We find no evidence that pleiotropy underlies correlations between defense and growth rate. However, there is a strong genetic correlation between levels of total PPGs and flowering time that is largely attributable to a single shared QTL. While this result suggests a role for pleiotropy/close linkage, several other QTLs also contribute to variation in total PPGs. Additionally, divergent PPG arsenals are influenced by a number of smaller-effect QTLs that each underlie variation in one or two PPGs. This result indicates that chemical defense arsenals can be finely-adapted to biotic environments despite sharing a common biochemical precursor. Together, our results show correlations between defense and life history traits are influenced by pleiotropy or genetic linkage, but genetic constraints may have limited impact on future evolutionary responses, as a substantial proportion of variation in each trait is controlled by independent loci.</p>
Data from: A growth-defense trade-off is general across native and exotic grasses
High-resource environments typically favor quick-growing, poorly-defended plants, while resource-poor environments typically favor slow-growing, well-defended plants. The prevailing hypothesis explaining this pattern states that, as resource availability increases, well-defended, slow-growing species are replaced by poorly defended, fast-growing species. A second hypothesis states that greater resource availability increases allocation to growth at the expense of defense, within species. Regardless of mechanism, if exotic species are released from enemies relative to natives, shifts in allocation to growth and defense both within and among species could differ by geographic provenance. To test whether resource availability alters growth or defense, within and among species, and whether any such effects differ between natives and exotics, we manipulated soil nutrient supply and access of aboveground insect herbivores and fungal pathogens under field conditions to individuals of six native and six exotic grass species that co-occurred in a North Carolina old field. The prevailing hypothesis' prediction—that species-level enemy impact increases with species' nutrient responsiveness—was confirmed. Moreover, this relationship did not differ between native and exotic species. The second hypothesis' prediction—that individual-level enemy impact increases with nutrient supply, after accounting for species-level variation in performance—was not supported. Together, these results support the idea, across native and exotic species, that plant species turnover is the primary mechanism underlying effects of nutrient enrichment on allocation to growth and defense in plant communities.
Data for "Elephant Genomes Reveal Insights into Differences in Disease Defense Mechanisms between Species".
<p>Data for "Elephant Genomes Reveal Insights into Differences in Disease Defense Mechanisms between Species".</p>
Defensive structures influence fighting outcomes
<ol> <li>In many animal species, individuals engage in fights with conspecifics over access to limited resources (e.g. mates, food, or shelter). Most theory about these intraspecific fights assumes that damage has an important role in determining the contest winner. Thus, defensive structures that reduce the amount of damage an individual accrues during intraspecific competition should provide a fighting advantage. </li> <li>Examples of such damage-reducing structures include the dermal shields of goats, the dorsal osteoderms of crocodiles, and the armored telsons of mantis shrimps. Although numerous studies have identified these defensive structures, no study has investigated whether they influence the outcomes of intraspecific fights. </li> <li>Here, we investigated whether inhibiting damage by enhancing an individual's armor influenced fighting behavior and success in the giant mesquite bug, <i>Thasus neocalifornicus</i> (Insecta: Hemiptera: Coreidae)<i>. </i> </li> <li>We found that experimentally manipulated individuals (i.e. those provided with additional armor) were 1.6 times more likely to win a fight when compared to the control. These results demonstrate that damage, and damage-reducing structures, can influence fighting success.</li> <li>The implications of these results are twofold. First, our results experimentally support a fundamental assumption of most theoretical fighting models: that damage is a fighting cost that can influence contest outcomes. Second, these results highlight the importance of an individual's defensive capacity, and why defense should not be ignored. </li> </ol>
Hemipteran defensive odors trigger predictable color biases in jumping spider predators
<p>Multimodal warning displays often pair one signal modality (odor) with a second modality (color) to avoid predation. Experiments with bird predators suggest these signal components interact synergistically, with aversive odors triggering otherwise hidden aversions to particular prey colors. In a recent study, this phenomenon was found in a jumping spider (<em>Habronattus trimaculatus</em>), with the defensive odor from a coreid bug (<em>Acanthocephala femorata</em>) triggering an aversion to red. Here, we explore how generalizable this phenomenon is by giving <em>H. trimaculatus</em> the choice between red or black prey in the presence or absence of defensive odors secreted from (1) eastern leaf-footed bugs (<em>Leptoglossus phyllopus</em>, Hemiptera), (2) grass stinkbugs (<em>Mormidea pama</em>, Hemiptera), (3) Asian ladybird beetles (<em>Harmonia axyridis</em>, Coleoptera), and (4) eastern lubber grasshoppers (<em>Romalea microptera</em>, Orthoptera). As expected, in the presence of the hemipteran odors, spiders were less likely to attack red prey (compared to no odor). Unexpectedly, the beetle and grasshopper odors did not bias spiders away from red. Our results with the hemipteran odors were unique to red; follow-up experiments indicated that these odors did not affect biases for/against green prey. We discuss our findings in the context of generalized predator foraging behavior and the functions of multimodal warning displays. </p>
Public Defense of Doctoral Thesis: "Improving the Resilience of the Constrained Internet of Things" (raw video)
<p>This is the raw video footage of Renzo E. Navas' public PhD Thesis Defense: "Improving the Resilience of the Constrained Internet of Things". Original date: Wednesday 9th of December 2020.</p>
Securing the IoT through Moving Target Defense (short film)
<p>Short film by Renzo E. Navas, presented in the Festival de sciences en cour[t]s 2019 (scientific vulgarisation)</p> <p><a href="https://www.youtube.com/channel/UCUY4_X-KClXAxmdbg_VCfDA">Festival Sciences en Courts (Youtube)</a> -- <a href="http://sciences-en-courts.fr/">http://sciences-en-courts.fr/</a></p> <p>** Mention spéciale du jury **</p> <p>Teaser:</p> <p>Une lampe... connecté? OUI. Parce que l'Internet des Objets (IdO) est arrivé. Mais l'IdO n'est pas limité à la maison. Il est partout. L'IdO ouvre la possibilité à nouvelles façons de faire interagir le monde physique et numérique. Malheureusement, les cyber-attaques ne sont pas exclus de ces nouvelles interactions. Je travaille pour faire la vie des cyber-attaquants plus difficile, et par conséquence cela des nos objets connectés (... et la notre) plus tranquille. Mon travail est basé sur le paradigme "Moving Target Defense" (MTD) [En français: Défense du Cible en Mouvement], qui propose faire que certaines propriétés de nos systèmes soient en changement perpétuel. Avec le MTD, la réussite des attaquants -assuré auparavant- sera en échec. Par : Renzo Navas</p>
Data from: Induced phenological avoidance: a neglected defense mechanism against seed predation in plants
<p>1. Flowering phenology is an important life history trait affecting plant reproductive performance and is influenced by various abiotic and biotic factors. Pre-dispersal seed predation and pollination are expected to impose counteracting selection pressure on flowering phenology, with pre-dispersal seed predation expected to favor off-peak flowering and pollination to favor synchronous flowering. <br> 2. Here we studied the effect of pre-dispersal seed predation by the beetle Byturus ochraceus, a specialist seed herbivore, on the flowering phenology of Geum urbanum. This forest understorey plant species is self-pollinating, so that the influence of seed predation can be studied independent from pollination. We measured in detail the timing and predation rate of individual flowers during two consecutive years in more than 60 individuals. We tested the hypotheses that pre-dispersal seed predation exerts selection for within-season compensatory flowering as well as for induced phenological avoidance in the following season.<br> 3. We found no indication for compensatory flowering within a growing season, but plants that experienced predation shifted their flowers to the end of the flowering season the subsequent year. This induced phenological avoidance points to a plastic response to pre-dispersal seed predation that may be adaptive. Importantly, the delay in flower production came at a cost, since flowers later in the season had a reduced seed output, presumably because of increasing light limitation following forest canopy closure. <br> 4. Synthesis: Herbivory by specialist enemies can cause serious fitness decline in hosts. We here show that induced shifts in phenology can form an important defense strategy against pre-dispersal seed predation. The induced mismatches between herbivore and host phenology are anticipated to be adaptive when herbivory is predictable across successive flowering periods.</p>
Data from: Population variation, environmental gradients, and the evolutionary ecology of plant defense against herbivory
A central tenet of plant defense theory is that adaptation to the abiotic environment sets the template for defense strategies, imposing a tradeoff between plant growth and defense. Yet, this tradeoff, commonly found among species occupying divergent resource environments, may not occur across populations of single species. We hypothesized that more favorable climates and higher levels of herbivory would lead to increases in growth and defense across plant populations. We evaluated whether plant growth and defense traits co-varied across 18 populations of showy milkweed (Asclepias speciosa) inhabiting an east-west climate gradient, spanning 25° of longitude. A suite of traits impacting defense (e.g., latex, cardenolides), growth (e.g., size), or both (e.g., SLA, trichomes) were measured in natural populations and in a common garden, allowing us to evaluate plastic and genetically based variation in these traits. In natural populations, herbivore pressure increased towards warmer sites with longer growing seasons. Growth and defense traits showed strong clinal patterns and were positively correlated. In a common garden, clines with climatic origin were only recapitulated for defense traits. Correlations between growth and defense traits were also weaker and more negative in the common garden compared to the natural populations. Thus, our data suggest that climatically favorable sites likely facilitate the evolution of greater defense at minimal costs to growth, likely because of increased resource acquisition.
Adaptive specialization and constraint in morphological defenses of planktonic larvae
<ol> <li>Morphological defenses of plankton can include armor, spines, and coloration. Spines defend from gape-limited fish predators while pigmentation increases visibility to fishes but defends from ultraviolet radiation (UVR).</li> <li>Planktonic crab larvae (zoeae) exhibit inter- and intra-specific variability in the lengths of defensive spines, extent of pigmentation, and body size. The determinants of this variability and the relationships among these traits are largely unknown.</li> <li>Larvae may employ generalized defenses against the dual threats of UVR and predation or specialized defenses against their primary threat, with an unknown role of allometric or phylogenetic constraints. Generalization would result in longer spines compensating for the increased predation risk imposed by darker pigments, while specialization would lead to more investment in either defense from predation (long spines) or UVR (dark pigments), at the expense of the other trait.</li> <li>We examined 1) the relationship between spine lengths and pigmentation, 2) the scaling of spine lengths with body size, and 3) phylogenetic constraint in spine lengths, pigmentation, and body size, among and within 21 species of laboratory-hatched and 23 species of field-collected crab larvae from Panama and California.</li> <li>We found a negative relationship between spine length and pigmentation among species from laboratory and field. Within species, we found a marginally significant negative relationship among field-collected larvae.</li> <li>Spine lengths showed positive allometric scaling with carapace length while spine and carapace lengths, but not pigmentation, had significant phylogenetic signals.</li> <li>The negative relationship we observed between pigmentation and spine length supports our defense specialization hypothesis.</li> <li>Positive allometric scaling of spine lengths means larger larvae are better defended from predators, which may indicate that larvae face greater predation risk as they grow larger.</li> <li>Phylogenetic constraint may have arisen because related species encounter similar predation threats. Conversely, phylogenetic constraint in the evolution of spine lengths may induce convergent behaviors resulting in related species facing similar predation threats.</li> <li>Our results improve understanding of the evolution of the larval morphology of crabs, morphological defenses in the plankton, and evolutionary responses of morphology to multiple spatially-segregated selective forces.</li> </ol>
Data from: Breakdown of a defensive symbiosis, but not endogenous defenses, at elevated temperatures
Environmental factors, including temperature, can have large effects on species interactions, including mutualisms and antagonisms. Most insect species are infected with heritable bacterial symbionts with many protecting their hosts from natural enemies. However, many symbionts or their products are thermally sensitive hence their effectiveness may vary across a range of temperatures. In the pea aphid, Acyrthosiphon pisum, the bacterial symbiont Hamiltonella defensa, and its associated APSE bacteriophages confer resistance to this aphid's dominant parasitoid, Aphidius ervi. Here we investigate the effects of temperature on both endogenous and symbiont-based protection against this parasitoid. We also explored the defensive properties of the X-type symbiont, a bacterium hypothesized to shape aphid defense when co-occurring with H. defensa. We show that H. defensa protection fails at higher temperatures, although some aphid genotype and H. defensa strain combinations are more robust than others at moderately warmer temperatures. We also found that a single X-type strain neither defended against parasitism by A. ervi nor rescued lost H. defensa protection at higher temperatures. In contrast, endogenous aphid resistance was effective across temperatures, revealing that these distinct defensive modes are not equally robust to changing environments. Through a survey of field-collected pea aphids we found a negative correlation between H. defensa frequencies and average daily temperatures across North American locales, fitting expectations for reduced symbiont benefits under warm climates. Based on these findings, we propose that rising global temperatures could promote the widespread breakdown of defensive mutualisms, a prospect with implications for both human and ecosystem health.
Data from: The demographic effects of functional traits: an integral projection model approach reveals population-level consequences of reproduction-defense tradeoffs
Quantitatively linking individual variation in functional traits to demography is a necessary step to advance our understanding of trait-based ecological processes. We constructed a population model for Asclepias syriaca to identify how functional traits affect vital rates and population growth and whether tradeoffs in chemical defense and demography alter population growth. Plants with higher foliar cardenolides had lower fiber, cellulose, and lignin levels, as well as decreased sexual and clonal reproduction. Average cardenolide concentrations had the strongest effect on population growth. In both the sexual and clonal pathway, the tradeoff between reproduction and defense affected population growth. We found that both increasing the mean of the distribution of individual plant values for cardenolides and herbivory decreased population growth. However, increasing the variance in both defense and herbivory increased population growth. Functional traits can impact population growth and quantifying individual-level variation in traits should be included in assessments of population-level processes.
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