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opencc-zeroNov 2020View details →

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, Thasus neocalifornicus (Insecta: Hemiptera: Coreidae). </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>

opencc-zeroDec 2021View details →

Model and data for: Economical defense of resources structures territorial space use in a cooperative carnivore

Manuscript Abstract: Ecologists have long sought to understand space use and mechanisms underlying patterns observed in nature. We developed an optimality landscape and mechanistic territory model to understand mechanisms driving space use and compared model predictions to empirical reality. We demonstrate our approach using gray wolves (Canis lupus). In the model, simulated animals selected territories to economically acquire resources by selecting patches with greatest value, accounting for benefits, costs, and tradeoffs of defending and using space on the optimality landscape. Our approach successfully predicted and explained first- and second-order space use of wolves, including the population's distribution, territories of individual packs, and influences of prey density, competitor density, human-caused mortality risk, and seasonality. It accomplished this using simple behavioral rules and limited data to inform the optimality landscape. Results contribute evidence that economical territory selection is a mechanistic bridge between space use and animal distribution on the landscape. This approach and resulting gains in knowledge enable predicting effects of a wide range of environmental conditions, contributing to both basic ecological understanding of natural systems and conservation. We expect this approach will demonstrate applicability across diverse habitats and species, and that its foundation can help continue to advance understanding of spatial behavior. Model & Data Abstract: In support of the above manuscript, all model files and data to re-create the analyses for the manuscript are included on Dryad. The model can be run in NetLogo (installation file included), using the associated input files to build the Montana landscape for wolves. Expertise in NetLogo is strongly recommended for using this model. Output files are likewise included along with code to create each plot in the manuscript and SI. Software files for the model and code to create each plot in the manuscript are located at Zenodo: https://doi.org/10.5281/zenodo.5802243.

opencc-zeroDec 2017View details →

Data from: Structural and defensive roles of angiosperm leaf venation network reticulation across an Andes-Amazon elevation gradient

1.The network of minor veins of angiosperm leaves may include loops (reticulation). Variation in network architecture has been hypothesized to have hydraulic and also structural and defensive functions. 2.We measured venation network trait space in eight dimensions for 136 biomass-dominant angiosperm tree species along a 3,300 m elevation gradient in southeastern Peru. We then examined the relative importance of multiple ecological, and evolutionary predictors of reticulation. 3.Variation in minor venation network reticulation was constrained to three axes. These axes described branching vs. reconnecting veins, elongated vs. compact areoles, and high vs. low density veins. Variation in the first two axes was predicted by traits related to mechanical strength and secondary compounds, and in the third axis by site temperature. 4.Synthesis. Defensive and structural factors primarily explain variation in multiple axes of reticulation, with a smaller role for climate-linked hydraulic factors. These results suggest that venation network reticulation may be determined more by species interactions than by hydraulic functions.

publicFeb 2019View details →

Data from: Structural and defensive roles of angiosperm leaf venation network reticulation across an Andes-Amazon elevation gradient

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publicDec 2020View details →

Defensive structures influence fighting outcomes

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publicOct 2025View details →

Structural models of Cheiracanthium punctorium spider toxins with putative defensive function (CSTX-type and phospholipase A2)

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publicJan 2022View details →

Model and data for: Economical defense of resources structures territorial space use in a cooperative carnivore

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opencc-zeroJul 2020View details →

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 invest in defenses 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. Qualea multiflora (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) produced more and higher-calorie extrafloral nectar, but showed similar ant abundance, partially consistent with our prediction. </li> <li class="Normal1">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.</li> </ol>

opencc-zeroDec 2020View details →

Calcareous defense structures of prey mediate the effects of predation and biotic resistance towards the tropics

Aims The importance of biotic interactions in creating and maintaining diversity is expected to increase toward low latitudes. However, the way in which predation affects diversity, can depend on how predators mediate competitive interactions and also on defensive traits of prey. Here we assessed the role of physical defences of prey to escape predation and how the importance of predation on community structure and diversity changes across latitude. Location Six sites, in three regions distributed across 45 degrees of latitude in the Atlantic Ocean: a tropical region in Angola, a subtropical region in Brazil and a temperate region in Wales-UK. Methods We manipulated predation on marine sessile communities, using exclusion cages and assessed community parameters, including their susceptibility to biological invasion during early and advanced succession. Results Predation was more intense in the tropics and in advanced communities suggesting that predation effects increase through time. In the tropical region, predators reduced the number of co-occurring species and beta diversity, limited the occurrence of exotic species and promoted a change in the identity of the dominant organisms, replacing soft-bodied organisms with calcified animals. In the subtropical region, predation promoted a similar trait-mediated change in the identity of dominant prey, although it was not strong enough to affect diversity and did not prevent bioinvasion. In the temperate region other processes than predation seem to drive the community organization and resistance to invasion. Main conclusions Our results support both Biotic Interaction and Biotic Resistance Hypotheses, showing that the importance of predation to biodiversity increases toward the tropics. In addition, where predation is intense, morphological traits of prey drive the final structure and dominance in the community. Our results suggest that physical defences are the main traits preventing predation, perhaps explaining why calcified organisms are among the most common invasive species in coastal habitats.

publicDec 2020View details →

Calcareous defense structures of prey mediate the effects of predation and biotic resistance towards the tropics

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publicAug 2020View details →

Optimal Defense Theory in an ant‐plant mutualism: extrafloral nectar as an induced defense is maximized in the most valuable plant structures

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opencc-zeroAug 2020View details →

Host plant defense produces species-specific alterations to flight muscle protein structure and flight-related fitness traits of two armyworms

Insects manifest phenotypic plasticity in their development and behavior in response to plant defenses, via molecular mechanisms that produce tissue-specific changes. Phenotypic changes might vary between species that differ in their preferred hosts and these effects could extend beyond larval stages. To test this, we manipulated the diet of southern armyworm (SAW; Spodoptera eridania) and fall armyworm (FAW; Spodoptera frugiperda) using a tomatomutant for jasmonic acid plant defense pathway (def1), and wild-type plants, and then quantified gene expression of Troponin t (Tnt) and flight muscle metabolism of the adult insects. Differences in Tnt spliceform ratios in insect flight muscles correlate with changes to flight muscle metabolism and flight muscle output. We found that SAW adults reared on induced def1 plants had a higher relative abundance (RA) of the A isoform of Troponin t (Tnt A) in their flight muscles; in contrast, FAW adults reared on induced def1 plants had a lower RA of Tnt A in their flight muscles compared with adults reared on def1 and controls. Although massadjusted flightmetabolic rate showed no independent host plant effects in either species, higher flight metabolic rates in SAW correlated with increased RA of Tnt A. Flight muscle metabolism also showed an interaction of host plants with Tnt A in both species, suggesting that host plants might be influencing flight muscle metabolic output by altering Tnt. This study illustrates how insects respond to variation in host plant chemical defense by phenotypic modifications to their flight muscle proteins, with possible implications for dispersal.

opencc-zeroDec 2011View details →

Data from: Geographic structure and adaptive population differentiation in herbivore defense genes in European aspen (Populus tremula L., Salicaceae)

When a phenotypic trait is subjected to spatially variable selection and local adaptation, the underlying genes controlling the trait are also expected to show strong patterns of genetic differentiation because alternative alleles are favoured in different geographical locations. Here, we study 71 single nucleotide polymorphisms (SNPs) from seven genes associated with inducible defence responses in a sample of Populus tremula collected from across Sweden. Four of these genes (PPO2, TI2, TI4 and TI5) show substantial population differentiation, and a principal component analyses conducted on the defence SNPs divides the Swedish population into three distinct clusters. Several defence SNPs show latitudinal clines, although these were not robust to multiple testing. However, five SNPs (located within TI4 and TI5) show strong longitudinal clines that remain significant after multiple test correction. Genetic geographical variation, supporting local adaptation, has earlier been confirmed in genes involved in the photoperiod pathway in P. tremula, but this is, to our knowledge, one of the first times that geographical variation has been found in genes involved in plant defence against antagonists.

publicFeb 2012View details →

Data from: Geographic structure and adaptive population differentiation in herbivore defense genes in European aspen (Populus tremula L., Salicaceae)

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