Environmental Predation Research Articles

Enhancing maximum sustainable yield in a patchy prey–predator environment

In this paper, we investigate a prey–predator community of fish coexisting in a multi-patches model, where different fishing patches are interconnected through migration terms. Only the predator is caught, while the prey grows logistically on each patch. The main objective of our research is to compare the maximum sustainable yield achieved in two contrasting scenarios: unconnected patches and connected patches with rapid stock movements. We show that the total maximum sustainable yield for the connected patches can be greater than the sum of the maximum sustainable yield on each isolated patch. The analysis of the model allows us to establish the conditions under which one of the two cases is more favorable from the viewpoint of yield. As a result, we provide a complete classification for all possible cases. This valuable information can be used to assist decision-makers in selecting the best management strategy for a particular fishery.

Research on the Impact of Lamprey's Sex Ratio on Ecosystems Based on the Lotka-Volterra Model

The aim of this study is to explore the impact of the population of the Lamprey on the ecosystem, particularly through the regulation of sex ratio, in order to provide effective strategies for environmental control. The study first improved the traditional Lotka Volterra model by introducing predator-prey relationships and environmental limiting factors. A Lotka Volterra predator environment model was established, and the stable environment of lampreys and their parasitic fish was simulated using this model. The results indicate that lower gender ratios (male population/overall population) can cause greater harm to the environment. The change in gender ratio can help control the food chain and may also exacerbate resource competition. Further integrating the relationship between gender ratio and growth rate into the Lotka Volterra predator environment model to form a gender Lotka Volterra predator environment model, the study found that a smaller gender ratio can lead to a decrease in ecological stability. When the gender ratio reaches a critical value, the ecosystem collapses. In addition, a dynamic ecosystem model was constructed for five species of organisms, including lampreys and parasites. Simulation results showed that reducing the sex ratio of lampreys can inhibit parasites and promote the prosperity of other organisms. The model has high robustness and stability. This study indicates that by regulating the sex ratio of lampreys, their impact on the ecosystem can be effectively controlled, providing a feasible environmental intervention strategy.

CHALLENGES IN EVOLUTIONARY ALGORITHM TO FIND OPTIMAL PARAMETERS OF SVM: A REVIEW

In rapidly changing classification and predation environment, optimization techniques in determining the hyper parameter of Support Vector Machine has become crucial for the accuracy of result. It’s an important tool for improving output quality of classification and prediction which includes modeling parameters relationship and resolution of optimal hyper parameter. However, determination of regularization (C) and gamma (γ), through mathematical models have undergone substantial development and expansion. In this paper, optimization techniques are categorized under several criteria. We also included the benchmarks for measuring the performance of classifier after parameter tuning, and found there is still a scope of improvement.

Behavioral response to chemical cues from injured conspecifics in the livebearing fish, Brachyrhaphis rhabdophora

AbstractPredator–prey dynamics have led to a strong selection of prey's ability to detect and respond to information about the risk environment. Further, intrinsic factors, such as sex, may cause prey to perceive and respond to information differently. Chemical alarm cues from injured conspecifics are a classic example of how prey have evolved to use publicly available information to shape their behavior and enhance fitness, yet sex‐specific alarm reactions are rarely considered. The purpose of our study was to compare how males and females respond to conspecific chemical alarm cues in the livebearing fish species, Brachyrhaphis rhabdophora. Furthermore, we tested males and females from populations with a high‐ or low‐predation environment. Brachyrhaphis rhabdophora showed strong alarm reactions, but contrary to our predictions, showed limited variation due to sex or predation environment. We found that males and females from both populations displayed lower activity levels and increased their swimming depth when exposed to an alarm cue, despite variable and consistent baseline behaviors among individuals. These data further contribute to our understanding of what factors shape the evolution of behavioral responses to chemical alarm cues in fishes.

Environmental complexity and predator density mediate a stable earwig-woolly apple aphid interaction

Regulation of insect pests by predators is an integral component of biological pest control. However, predator-prey interactions often reach a stable state leading to coexistence, which can be problematic for plant protection if the persisting herbivores exceed a damage threshold. Consequently, understanding the factors mediating this stability is crucial for successful biocontrol. Here, we investigated the predator-prey interaction of an important apple pest, the woolly apple aphid (WAA) (Eriosoma lanigerum Hausm.) (Hemiptera: Aphididae), and its predator, the omnivorous common earwig (Forficula auricularia L.) (Dermaptera: Forficulidae). To this end, we introduced increasing densities of earwigs in gauze-bagged branches harbouring defined amounts of WAA and recorded predation on individual WAA colonies for almost one month. We showed that the spatial complexity of the predation environment and the earwig density determined the predation efficiency on WAAs. Earwigs could eradicate WAAs regardless of density on short apple branches without lateral twigs (first trial). However, on longer, more complex branches (second trial), stable states of WAAs and earwigs were observed. Only the highest earwig density could completely consume WAA regardless of branch complexity. We introduce a conceptual model to describe the searching capability of earwigs, which determines their efficiency in locating prey. Our model predicts that searching capability is reduced by environmental complexity; this effect is alleviated by increased earwig density, as more predators possess a higher searching capability. Conclusively, our model explains why only the highest earwig density could completely consume WAA irrespective of complexity and illustrates how predator density and environmental complexity jointly influence predation. Thus environmental characteristics not inherent to our predator-prey interaction were a decisive factor for effective predation on gauze-bagged branches. Based on these results, reducing tree complexity by pruning or augmenting earwig populations in orchards can increase biocontrol of the WAA.

Predation affects body shape in the knife livebearer Alfaro cultratus (Cyprinodontiformes: Poeciliidae).

Livebearing fishes are a common model for studying the effects of predation on prey biology. Numerous studies have found differences in life history, sexual selection, behavior, and morphology between populations of the same species that co-occur with predators and those that do not. Alfaro cultratus is a livebearing fish with populations in different predation environments, but unlike other livebearers, this species also has an extreme body shape that is laterally compressed. Given this unusual morphology, we asked if predation environment would still predict overall body shape, as has been documented in other species. We collected specimens from both predator and no predator sites in Costa Rica and used a geometric morphometrics analysis to determine if body shape is affected by predation environment, while controlling for size and river gradient. Body shape does indeed differ between predation environments; however, the observed differences contrast with the patterns found in other livebearer systems. Alfaro cultratus in predation environments had deeper and shorter bodies and deeper caudal peduncles than those found in environments without dominant fish predators.

Stability and bifurcation analysis of delayed tri‐trophic food chain model in poisoned environment with fear effect and additional food

One of the most important goals of theoretical ecologists is to find a strategy for controlling the chaos in ecological models to maintain healthy ecosystems. We investigate the influence of fear and the supply of additional food to predators in a delayed tri‐trophic food chain model, where interference among the species is determined by Holling type‐II functional response. The proposed model incorporates the fact that the growth rates of prey and middle predators are decreased due to the fear of middle and special predators, respectively. The additional food is supplied to both predators by either nature or external agencies. Furthermore, the poisoned prey in the predator's environment is taken into account. In the proposed model, we use two time delays: one for the growth term of the middle predator and another for the gestation delay of the special predator. We determine the conditions for the existence of ecologically feasible equilibrium points and their local and global stability. In addition, we establish the conditions for the existence of Hopf bifurcation around interior equilibrium to seek periodic behavior in nondelayed and delayed models. Numerical investigations are performed to justify the proposed theoretical findings through phase portraits, time series of solutions, and bifurcation diagrams. We observe that the chaotic dynamics of a tri‐trophic food chain model can be controlled by the proper choice of the fear effect and by supplying additional food parameters. As a result, our findings provide more ecological insights into the dynamics of the delayed tri‐trophic food chain model with the fear effect and additional food supply.

Growth and diet of a larval myctophid across distinct upwelling regimes in the California Current

Abstract Eastern boundary systems support major fisheries of species whose early stages depend on upwelling production. However, upwelling can be highly variable at the regional scale, leading to complex patterns of feeding, growth, and survival for taxa that are broadly distributed in space and time. The northern California Current (NCC) is characterized by latitudinal variability in the seasonality and intensity of coastal upwelling. We examined the diet and larval growth of a dominant myctophid (Stenobrachius leucopsarus) in the context of their prey and predators in distinct NCC upwelling regimes. Larvae exhibited significant differences in diet and growth, with greater seasonal than latitudinal variability. In winter, during reduced upwelling, growth was substantially slower, guts less full, and diets dominated by copepod nauplii. During summer upwelling, faster-growing larvae had guts that were more full from feeding on calanoid copepods and relying less heavily on lower trophic level prey. Yet, our findings revealed a dome-shaped relationship with the fastest growth occurring at moderate upwelling intensity. High zooplanktivorous predation pressure led to above average growth, which may indicate the selective loss of slower-growing larvae. Our results suggest that species whose spatio-temporal distributions encompass multiple regional upwelling regimes experience unique feeding and predation environments throughout their range with implications for larval survivorship.

Shifts in gut microbiome across five decades of repeated guppy translocations in Trinidadian streams.

An organism's gut microbiome can alter its fitness, yet we do not know how gut microbiomes change as their hosts evolve in the wild. We took advantage of a five-decade 'chronosequence' of translocated fish populations to examine associated changes in the gut microbiome. Populations of Trinidadian guppies have displayed parallel phenotypic convergence six times when moved from high predation (HP) to low predation (LP) environments. Across four drainages, we found microbiomes of fish translocated 5-6 years prior to sampling were already distinct from the microbiomes of their HP source populations. Changes in environmental conditions were most important in driving this shift, followed by phenotypic shifts in gut morphology. After 30-60 years in LP environments, microbiome composition was still distinct from native LP populations, but microbiome function was not. We found some evidence that nitrogen fixation enhanced gut nutrient absorption, but most functional shifts were not parallel across drainages. Stream-and drainage-specific signatures were present for both composition and function, despite our overall finding of consistent microbiome change across drainages. As we unravel the complexities of host-microbiome evolution in the wild, studies should consider environmental microbial colonization, host phenotypic plasticity in nature, and more realistic environmental conditions excluded from laboratory studies.

Inconsistent evolution and growth-survival tradeoffs in Gambusia affinis.

Growth-survival tradeoffs may be a generalizable mechanism influencing trajectories of prey evolution. Here, we investigate evolutionary contributions to growth and survival in western mosquitofish (Gambusia affinis) from 10 populations from high- and low-predation ancestral environments. We assess (i) the degree to which evolutionary components of growth and survival are consistent or inconsistent across populations within ancestral predation environments, and (ii) whether growth and survival trade off at the population level. We measure growth and survival on groups of common-reared mosquitofish in pond mesocosms. We find that evolution of growth is consistent, with fish from low-predation ancestral environments showing higher growth, while the evolution of survival is inconsistent, with significant population-level divergence unrelated to ancestral predation environment. Such inconsistency prevents a growth-survival tradeoff across populations. Thus, the generalizability of contemporary evolution probably depends on local context of evolutionary tradeoffs, and a continued focus on singular selective agents (e.g. predators) without such local context will impede insights into generalizable evolutionary patterns.

Drivers and Cascading Ecological Consequences of Gambusia affinis Trait Variation.

AbstractPhenotypic trait differences among populations can shape ecological outcomes for communities and ecosystems. However, few studies have mechanistically linked heritable and plastic components of trait variation to generalizable processes of ecology, such as trophic cascades. Here, we assess morphological and behavioral trait variation in nine populations of common garden-reared western mosquitofish (Gambusia affinis) from three distinct ancestral predator environments (three populations per environment), each reared in the presence and absence of predator cues. We then use a pond mesocosm experiment to examine the ecological consequences of mosquitofish trait variation and density variation. Our results show significant among-population trait variation, but this variation was generally unrelated to ancestral predator environment. When traits did vary congruently with respect to ancestral predator environment, this trait variation was driven by gene-by-environment interactions. Variation in several mosquitofish traits altered the cascading effects of mosquitofish on zooplankton and primary producers, but the effect of any given trait was typically weaker than that of density. We note that the relatively stronger ecological effects of density may mask the effects of traits in some systems. Our example here shows that trait variation can be highly noncongruent with respect to a perceived selective agent, phenotypic change is a product of complex interactions between genes and the environment, and numerous interacting phenotypes generate significant but potentially cryptic cascading ecological change.

Phylogenetic patterns of trait and trait plasticity evolution: Insights from tadpoles.

Environmental heterogeneity has led to the widespread evolution of phenotypic plasticity in all taxonomic groups. Although phenotypic plasticity has been examined from multiple perspectives, few studies have examined evolutionary patterns of plasticity within a phylogeny. We conducted common-garden experiments on 20 species of tadpoles, spanning three families, exposed for 4 weeks to a control, predator cues, or reduced food (i.e., increased intraspecific competition). We quantified tadpole activity, growth, and relative morphology and found widespread differences in species responses to predator cues and reduced food. We detected pervasive phylogenetic signals in traits within each environment, but the phylogenetic signal was much less common in the trait plasticities. Among different models of continuous character evolution, Brownian Motion and Ornstein Uhlenbeck models provided better fits to the data than the Early Burst model. Tadpole activity level in predator environments had much higher evolutionary rates than in the control and reduced-food environments; we did not see this pattern in the other traits. In comparing traits versus trait plasticities, activity evolved much faster than the plasticity of activity whereas morphological traits evolved much slower than morphological plasticities. Collectively, these results suggest that traits and trait plasticities can exhibit dramatically different evolutionary patterns.

The enduring utility of customary justice in fragile and post-conflict states: why development actors need to stop searching for magic bullets and solve the political economy and human rights challenges associated with justice programming

ABSTRACT Although programming with them has lost the appeal and expectancy it enjoyed two decades ago, customary systems continue to play important roles, including in some of today’s most challenging and predatory environments. This ongoing utility raises important questions about how such systems could be better leveraged, and why programming dilemmas, including around human rights and state-non-state relations, remain unresolved. Crafting solutions to these dilemmas, it is argued, will require changes in practice, none of which will be easy or necessarily welcomed by the development community. In this process, past programming experience can offer rich lessons that should be drawn upon.

Biting kinematics do not differ between ecologically divergent populations of Trinidadian guppies

AbstractPerformance, the ability to complete an ecologically relevant task, serves as a link between underlying morphology and the maximum functional capacity and fitness of an individual. Performance can vary within species due to environmental context and the trait of interest, but this is less understood compared with variation across species. Trinidadian guppy (Poecilia reticulata) populations are separated by waterfall barriers that result in repeated selection for predator avoidance in high predation environments and resource competition in low predation environments. An array of locally adapted traits results from these shifts, however, the role of these local adaptations in prey capture performance traits remains unclear. We examined biting kinematics in replicate populations of adult female guppies collected from natural high and low predation habitats. We expected that competition in low predation populations would drive performance differences compared with fish from high predation populations. Using high‐speed videos of fish feeding on an agar substrate, we did not find support for differences in jaw or approach kinematics between populations, suggesting a lack of local adaptation in our sample. To gain further insight, we examined four representative, whole‐body morphometric traits previously shown to be divergent in guppies. Again, differences were not discovered in our sample, which may indicate limitations in the use of shape traits. We suggest that female guppies are kinematic generalists and that selection on prey capture may act on traits other than performance, such as feeding behaviors (e.g., consumption rates, kinematic integration, and prey preference).

Ecological basis and genetic architecture of crypsis polymorphism in the desert clicker grasshopper (Ligurotettix coquilletti).

Color polymorphic species can offer exceptional insight into the ecology and genetics of adaptation. Although the genetic architecture of animal coloration is diverse, many color polymorphisms are associated with large structural variants and maintained by biotic interactions. Grasshoppers are notably polymorphic in both color and karyotype, which makes them excellent models for understanding the ecological drivers and genetic underpinnings of color variation. Banded and uniform morphs of the desert clicker grasshopper (Ligurotettix coquilletti) are found across the western deserts of North America. To address the hypothesis that predation maintains local color polymorphism and shapes regional crypsis variation, we surveyed morph frequencies and tested for covariation with two predation environments. Morphs coexisted at intermediate frequencies at most sites, consistent with local balancing selection. Morph frequencies covaried with the appearance of desert substrate-an environment used only by females-suggesting that ground-foraging predators are major agents of selection on crypsis. We next addressed the hypothesized link between morph variation and genome structure. To do so, we designed an approach for detecting inversions and indels using only RADseq data. The banded morph was perfectly correlated with a large putative indel. Remarkably, indel dominance differed among populations, a rare example of dominance evolution in nature.

Conspicuous animal signals avoid the cost of predation by being intermittent or novel: confirmation in the wild using hundreds of robotic prey.

Social animals are expected to face a trade-off between producing a signal that is detectible by mates and rivals, but not obvious to predators. This trade-off is fundamental for understanding the design of many animal signals, and is often the lens through which the evolution of alternative communication strategies is viewed. We have a reasonable working knowledge of how conspecifics detect signals under different conditions, but how predators exploit conspicuous communication of prey is complex and hard to predict. We quantified predation on 1566 robotic lizard prey that performed a conspicuous visual display, possessed a conspicuous ornament or remained cryptic. Attacks by free-ranging predators were consistent across two contrasting ecosystems and showed robotic prey that performed a conspicuous display were equally likely to be attacked as those that remained cryptic. Furthermore, predators avoided attacking robotic prey with a fixed, highly visible ornament that was novel at both locations. These data show that it is prey familiarity-not conspicuousness-that determine predation risk. These findings replicated across different predator-prey communities not only reveal how conspicuous signals might evolve in high predation environments, but could help resolve the paradox of aposematism and why some exotic species avoid predation when invading new areas.

Influence of prey diet quality on predator-induced traits in wood frog tadpoles (Lithobates sylvaticus)

Abstract Diet quality and predation are two critical factors in determining the growth and development of organisms. Various anurans are susceptible to phenotypic changes influenced by these factors. Yet, few studies examined prey diet quality as potential influence over predator-induced traits. Using wood frog tadpoles (Lithobates sylvaticus) as a model species, we investigated the effects of three diet compositions (plant-based, animal-based, omnivorous) crossed with presence or absence of chemical cues from predatory dragonfly larvae (Aeshnidae). After 35 days, we recorded 11 morphological measurements, Gosner stage, and intestinal length of tadpoles to assess phenotypic changes under the six different experimental conditions. Our results showed the additive effects of both diet quality and predator chemical cue without detection of interactions between the two. Tadpoles receiving the omnivorous diet grew and developed faster with wider denticle rows than those receiving the plant or animal diets. The growth and development of tadpoles receiving only the animal diet were significantly hindered. These results emphasize the importance of diet quality in the growth and development of larval wood frogs. Chemical cues from predators significantly reduced tadpole body size but, in contrast to previous findings, did not affect tail size. Our experimental procedure of providing water containing predator and injured conspecific chemical cues on a weekly basis likely provided relatively weak predation risk perceived by tadpoles compared to previous studies using caged predators. The predator environment in our experiment, however, represents one ecologically relevant scenario in which predation risk is not urgent.

Challenges in evolutionary algorithm to find optimal parameters of SVM: A review

In rapidly changing classification and predation environment, optimization techniques in determining the hyper parameter of Support Vector Machine has become crucial for the accuracy of result. It’s an important tool for improving output quality of classification and prediction which includes modeling parameters relationship and resolution of optimal hyper parameter. However, determination of regularization (C) and gamma (γ), through mathematical models have undergone substantial development and expansion. In this paper, optimization techniques are categorized under several criteria. We also included the benchmarks for measuring the performance of classifier after parameter tuning, and found there is still a scope of improvement.

Consensus, cooperative learning, and flocking for multiagent predator avoidance.

Multiagent coordination is highly desirable with many uses in a variety of tasks. In nature, the phenomenon of coordinated flocking is highly common with applications related to defending or escaping from predators. In this article, a hybrid multiagent system that integrates consensus, cooperative learning, and flocking control to determine the direction of attacking predators and learns to flock away from them in a coordinated manner is proposed. This system is entirely distributed requiring only communication between neighboring agents. The fusion of consensus and collaborative reinforcement learning allows agents to cooperatively learn in a variety of multiagent coordination tasks, but this article focuses on flocking away from attacking predators. The results of the flocking show that the agents are able to effectively flock to a target without collision with each other or obstacles. Multiple reinforcement learning methods are evaluated for the task with cooperative learning utilizing function approximation for state-space reduction performing the best. The results of the proposed consensus algorithm show that it provides quick and accurate transmission of information between agents in the flock. Simulations are conducted to show and validate the proposed hybrid system in both one and two predator environments, resulting in an efficient cooperative learning behavior. In the future, the system of using consensus to determine the state and reinforcement learning to learn the states can be applied to additional multiagent tasks.

Evidence for the ‘behavioural character’ hypothesis: does boldness programme disparate antipredator strategies?

Risk-taking behaviours that are optimal in one context (predators absent) may be suboptimal in a different context (predators present), suggesting that individuals with ‘bold’ behaviours will experience increased predation risk. Yet, in some instances, bold individuals experience lower predation. Thus, there is not always a direct trade-off between boldness and predation risk. To better understand the relationship between boldness and predation risk, suboptimal behaviours must be viewed within the context of an organism's entire integrated antipredator strategy. Using freshwater snails exposed to a predator cue, we examined whether quickly re-emerging from the shell was a repeatable, carryover behaviour that was tied to behavioural and morphological antipredator traits. Slow-emerging snails invested in morphological shell defence and remained in the predator environment, whereas quick-emerging snails consistently avoided the predator environment and did not invest in shell defences. Therefore, slow-emerging snails used a sit-and-wait antipredator strategy by relying on their shells for protection and were less likely to avoid the predator environment; conversely, quick-emerging snails used an avoidance (or dispersal) strategy by consistently associating with the water's surface and investing less in shell defences. A path analysis of these antipredator traits indicates that the carryover effect of bold behaviour may be an important factor that mediates complementary behavioural and morphological traits that reduce predation risks. This study supports the ‘behavioural character’ hypothesis, which suggests that boldness is a latent variable upon which selection can act and thereby shape a variety of quasi-independent traits (e.g. antipredator traits). According to this perspective, selection is not acting on a single antipredator behavioural trait in isolation, but rather on an integrated antipredator strategy that is facilitated by individual differences in carryover risk-taking behaviour.