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Our objective was to assess the effects of interactions between the native Percichthys trucha and both Salmo trutta and Oncorhynchus mykiss during the juvenile period. We conducted single and multipredator (conspecific and heterospecific) functional response (FR) experiments with Meridialaris chiloeensis as native prey and estimated the functional response ratio as a predator impact metric. Our results showed that all species have type II FR, with salmonids having a greater impact on prey than native fish. In multipredator experiments, O. mykiss had a greater negative impact on P. trucha than S. trutta. The individual feeding performance of P. trucha was better under conspecific than heterospecific conditions. This study shows that the vulnerability of juvenile P. trucha to salmonid competition could be a real threat in Patagonian lotic environments. [ABSTRACT FROM AUTHOR]

ABSTRACT In India, there are 626 non‐native invasive fish species (NIFS), with 16 becoming invasive in inland waters, adversely impacting native biodiversity, and fisheries by altering the abundance of NIFS in commercial catches. Scientific findings highlight that the movement of NIFS interacts with agricultural activities and the evolving environment, facilitating their spread and establishment. The scenario of NIFS invasion disrupts biological communities, ecosystem services and fisherfolk livelihoods. Despite the implementation of existed guidelines, issues related to NIFS have persisted and escalated over time scale putting increased pressure on indigenous aquatic biological resources in inland waters. This paper suggests the need of framing a new management plans, guidelines and regulatory policies to control NIFS invasions, protecting riverine fish biodiversity and ecosystem services. Proposed management strategies include functional response (FR) and adaptive response (AR)‐based approaches, which are discussed to address NIFS management in inland waters. [ABSTRACT FROM AUTHOR]

Megalurothrips usitatus, is an important pest of cowpeas Vigna unguiculata, that causes severe damage to cowpea crops in Southeast Asia and Hainan Province in China. Neoseiulus newsami is a natural enemy of M. usitatus that was first reported from Ledong Li Autonomous County, Hainan, China. Here, we evaluated the potential of N. newsami as a biocontrol agent for use against M. usitatus. In laboratory tests, N. newsami showed a similar rate of attack on this pest as did the better-known species Neoseiulus barkeri. The functional response curve of N. newsami fed M. usitatus showed that more 1st instar prey were consumed by N. newsami at higher prey densities, indicating a Type III functional. The maximum attack coefficient (a) was 0.063 ± 0.011 and the handling time per consumed prey (Th) was 0.58 ± 0.09. The maximum attack rate (T/Th) was 41.37. Neoseiulus newsami showed higher predation and oviposition rates than did N. barkeri or Neoseiulus cucumeris. Our results suggest that N. newsami has a higher predation capacity against M. usitatus. [ABSTRACT FROM AUTHOR]

The classical Hastings–Powell model is well known to exhibit chaotic dynamics in a three-species food chain. Chaotic dynamics appear through period-doubling bifurcation of stable coexistence limit cycle around an unstable coexisting equilibrium point. A specific choice of parameter value leads to a situation, where the chaotic attractor disappears through a collision with an unstable limit cycle originated due to subcritical Hopf-bifurcation around the coexistence equilibrium. As a consequence, the top predator goes to extinction. The main objective of this work is to explore the structural sensitivity of this phenomenon by replacing the Holling-type II functional responses with Ivlev functional responses. In this work, we have shown the existence of two Hopf-bifurcation thresholds and numerically verified the existence of an unstable limit cycle. The model with Ivlev functional responses does not indicate any possibility of extinction of the top predator due to any collision of chaotic attractor with the unstable limit cycle for the chosen range of parameter values. Moreover, the model with Ivlev functional responses depicts an interesting scenario of bistable oscillatory coexistence. [ABSTRACT FROM AUTHOR]

Trophic interactions are a critical component of ecosystem stability, governing prey-predator relationships. Crayfish are involved in numerous interactions within freshwater communities and, when non-native, they can negatively impact the structure and dynamics of ecosystems. During biotic interactions or unsuccessful molts, they are able to autotomize one or more claws, which can lead to changes in ecological performance among individuals. Because crayfish claws play an important role in feeding behavior, this creates an overlooked biotic context that could influence trophic interactions and impact on prey communities. It has been shown previously that crayfish claws have a minor role in predation of slow, soft prey, but their function concerning fast hard-bodied prey remains poorly studied. Here, we investigate whether the number of claws on marbled crayfish Procambarus virginalis modulates its ecological impact (focusing on predation rate) using functional response analyses against more mobile hard-bodied prey. We showed that the number of claws in P. virginalis significantly influenced the rate of predation on the prey Gammarus fossarum, with crayfish with two claws exhibiting a higher attack rate and lower handling time than clawless individuals. In addition, we found that non-trophic interactions increased with prey density, with generally antagonistic interactions between crayfish that reduced prey risk irrespective of claw presence. The influence of biotic contexts such as claw presence, prey density and prey type, as well as consumer density, should be considered in inferences of trophic and non-trophic interactions, as well as ecological impacts of invasive species. [ABSTRACT FROM AUTHOR]

This study explores a prey-predator model with a Holling type II functional response, focusing on how predation-induced fear affects prey dynamics. Assuming a decline in prey population growth rate attributed to predator-induced fear, the model incorporates a fear response delay representing prey detection time, along with gestation delay. The system's positivity, boundedness, and permanence are proved under certain parametric conditions. The local stability is discussed at trivial, semi-trivial, and positive equilibria. The system exhibits Hopf bifurcation with respect to both delays. Hopf bifurcation analysis is done for different combinations of delays. Furthermore, the properties of periodic solutions in the delayed system are also determined. An extensive numerical simulation has been performed to validate analytical findings. The occurrence of Hopf bifurcation is shown for different combinations of delays by plotting eigenvalues. [ABSTRACT FROM AUTHOR]

When coral cover declines, numeric responses of parrotfish can facilitate top-down control of algae and help reefs recover. Yet many parrotfish are facultative corallivores and we know surprisingly little about how their numeric or functional responses to coral decline modify their interactions with coral prey to shape their impacts on surviving corals. Here, we use benthic and fish surveys conducted in the Florida Keys more than a decade apart to assess how coral communities have changed, and how these changes have impacted parrotfish and their predation rates on corals. We found that disturbances and disease have continued to drive declines in coral cover and changes in coral community composition, but that the parrotfish abundance has not changed. In turn, while parrotfish corallivory has remained relatively constant or even declined for some coral taxa, predation on preferred branching Porites species increased 10% in frequency and, when normalized to live tissue area, > 50% in intensity. These coral-mediated shifts in predation correlated with declines in conspecific cover and are indicative of depensatory predation, which can destabilize trophic interactions and drive prey to low densities or even extinction. While coral reefs cannot recover from disturbances without robust parrotfish populations, our study suggests that parrotfish corallivory has important ramifications for coral community structure and, after prolonged degradation, the ability of some diminished coral populations to recover or persist. In a world where corals bleach annually, understanding the functional responses of corallivorous parrotfish to changes in resource abundance will be increasingly important for effective ecosystem-based management. [ABSTRACT FROM AUTHOR]

Non-native species can react to changes to their thermal environment by altering their feeding behaviour, thereby potentially causing shifts in predator–prey dynamics and competitive dominance over native species. In this study, we measured intraspecific variation in the functional response (i.e., predation rate as a function of prey density) of the rusty crayfish Faxonius rusticus (Girard, 1852) at two temperatures (18 °C and 26 °C) in the laboratory. We compared six invasive populations spanning a 2° latitudinal gradient in eastern North America to test the prediction that under warmer conditions individuals from more southerly populations exhibit a higher functional response than those from northern populations. Temperature, latitude, and the interaction between these two variables had significant effects on attack rates and handling times of individual crayfish from the tested populations. Contrary to our prediction, the attack rates of individuals from northern populations were consistently higher than those from southern populations at both temperatures. We propose that these interpopulation differences in functional response could arise, at least in part, from countergradient selection. Our results suggest that climate warming promotes spatiotemporal variation in per capita effects across latitudinally distributed populations of aquatic invasive species. [ABSTRACT FROM AUTHOR]

In 1959 Crawford S. Holling formulated a classification to model the action of the predators over their prey, doing empirical works. In this taxonomy, he introduced only three types of functional responses dependent only on the prey population, which are described by saturated functions. Later, various other types have been proposed, including the functional responses dependent on both populations. This work concerns the study of the Leslie–Gower type predator-prey model, incorporating the Rosenzweig functional response described by a power law. The elected function does not conform to the types proposed by Holling since it is unbounded, being, besides, non-differentiable for x = 0 ; nonetheless, the obtained system is Lipschitzian. Moreover, the existence of a separatrix curve Σ in the phase plane is proven, which is divided into two complementary sectors. According to the position of the initial conditions with respect to the curve, the trajectories can have different ω -limit sets, which can be the equilibrium 0 , 0 , or a positive equilibrium, or a heteroclinic curve, or a stable limit cycle. These properties show the great difference of this model with the original Leslie–Gower model, in which a unique positive equilibrium exists, which is globally asymptotically stable, when it exists. Then, the analyzed system has a richer dynamic than the original system in which a linear functional response is considered, also unbounded. Numerical simulations and bifurcation diagrams are given to endorse our analytical results. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the factors that determine the occurrence and strength of ecological interactions under specific abiotic and biotic conditions is fundamental since many aspects of ecological community stability and ecosystem functioning depend on patterns of interactions among species. Current approaches to mapping food webs are mostly based on traits, expert knowledge, experiments, and/or statistical inference. However, they do not offer clear mechanisms explaining how trophic interactions are affected by the interplay between organism characteristics and aspects of the physical environment, such as temperature, light intensity or viscosity. Hence, they cannot yet predict accurately how local food webs will respond to anthropogenic pressures, notably to climate change and species invasions. Herein, we propose a framework that synthesises recent developments in food‐web theory, integrating body size and metabolism with the physical properties of ecosystems. We advocate for combination of the movement paradigm with a modular definition of the predation sequence, because movement is central to predator–prey interactions, and a generic, modular model is needed to describe all the possible variation in predator–prey interactions. Pending sufficient empirical and theoretical knowledge, our framework will help predict the food‐web impacts of well‐studied physical factors, such as temperature and oxygen availability, as well as less commonly considered variables such as wind, turbidity or electrical conductivity. An improved predictive capability will facilitate a better understanding of ecosystem responses to a changing world. [ABSTRACT FROM AUTHOR]

Abstract Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) is an important pest in Vigna unguiculata (L.) Walp. Neoseiulus barkeri (Hughes) (Acari: Phytoseiidae) is widely used for control of pest mites and insects worldwide. We evaluated its effect on M. usitatus when predators (N. barkeri) or insecticides (Spinetoram) were applied in the fields. Neoseiulus barkeri Hughes consumed 80% of M. usitatus prey offered within 6 h, and predation showed Type III functional response with prey density. The maximum consumption of N. barkeri was 27.29 ± 1.02 individuals per d per arena (1.5 cm diameter), while the optimal prey density for the predatory mite was 10.35 ± 0.68 individuals per d per arena (1.5 cm diameter). The developmental duration of N. barkeri fed with M. usitatus was significantly shorter than those fed with the dried fruit mite, Carpoglyphus lactis (L.) (Acari: Astigmata). In field trials, the efficiency of N. barkeri against M. usitatus was not significantly different from that of applications of the insecticide spinetoram. Biodiversity of other insects in treated fields was assessed, and there were 21 insect species in garden plots treated with N. barkeri releases. The total abundance (N), Shannon’s diversity index (H), Pielou’s evenness index (J) and Simpson’s diversity index (D) of the garden plots treated with predatory mites were all significantly higher than that in the garden plots treated with spinetoram, where we found no species of predators or parasitoids and 7 herbivores. Our results show that N. barkeri is a potential means to control M. usitatus while preserving arthropod diversity at the level of treated gardens.

Background: Spatial behavior, including home-ranging behaviors, habitat selection, and movement, can be extremely informative in estimating how animals respond to landscape heterogeneity. Responses in these spatial behaviors to features such as human land modification and resources can highlight a species' spatial strategy to maximize fitness and minimize mortality. These strategies can vary on spatial, temporal, and individual scales, and the combination of behaviors on these scales can lead to very different strategies among species. Methods: Harnessing the variation present at these scales, we characterized how species may respond to stimuli in their environments ranging from broad- to fine-scale spatial responses to human modification in their environment. Using 15 bobcat-years and 31 coyote-years of GPS data from individuals inhabiting a landscape encompassing a range of human land modification, we evaluated the complexity of both species' responses to human modification on the landscape through their home range size, habitat selection, and functional response behaviors, accounting for annual, seasonal, and diel variation. Results: Bobcats and coyotes used different strategies in response to human modification in their home ranges, with bobcats broadly expanding their home range with increases in human modification and displaying temporal consistency in functional response in habitat selection across both season and time of day. Meanwhile, coyotes did not expand their home ranges with increased human modification, but instead demonstrated fine-scale responses to human modification with habitat selection strategies that sometimes varied by time of day and season, paired with functional responses in selection behaviors. Conclusions: These differences in response to habitat, resources, and human modification between the two species highlighted the variation in spatial behaviors animals can use to exist in anthropogenic environments. Categorizing animal spatial behavior based on these spatiotemporal responses and individual variation can help in predicting how a species will respond to future change based on their current spatial behavior. [ABSTRACT FROM AUTHOR]

The recovery of many groundfish stocks in the Northwest Atlantic has been impeded by elevated mortality among older/larger individuals. The sources of groundfish mortality are generally uncertain, though predation by growing grey seal herds and unreported fishing are thought to be drivers of mortality for Atlantic cod (Gadus morhua) on the Western Scotian Shelf and Bay of Fundy (4X5Y), as well as in nearby ecosystems. We developed a statistical catch-at-age model for 4X5Y cod that accounted for grey seal predation and bycatch/discards and tested the model across a broad range of consumption and discard scenarios. We found that most cod mortality was unexplained by seal predation and fishing when cod comprised a small to moderate portion of the grey seal diet. Predation and fishing accounted for slightly more than half of recent cod mortality when cod was highly prevalent in the seal diet (45% by weight) but explained little historical mortality. Bycatch was a minor source of mortality prior to 2019 and accounted for 0.%1–8.1% of recent mortality. Increased sampling of seal diets and monitoring of emerging seal colonies is necessary for reducing uncertainties around seal predation effects in the Northwest Atlantic. [ABSTRACT FROM AUTHOR]

Trophic interaction modifications (TIM) are widespread in natural systems and occur when a third species indirectly alters the strength of a trophic interaction. Past studies have focused on documenting the existence and magnitude of TIMs; however, the underlying processes and long‐term consequences remain elusive. To address this gap, we experimentally quantified the density‐dependent effect of a third species on a predator's functional response. We conducted short‐term experiments with ciliate communities composed of a predator, prey and non‐consumable 'modifier' species. In both communities, increasing modifier density weakened the trophic interaction strength, due to a negative effect on the predator's space clearance rate. Simulated long‐term dynamics indicate quantitative differences between models that account for TIMs or include only pairwise interactions. Our study demonstrates that TIMs are important to understand and predict community dynamics and highlights the need to move beyond focal species pairs to understand the consequences of species interactions in communities. [ABSTRACT FROM AUTHOR]

The mealybug Phenacoccus solenopsis Tinsley has emerged as a widespread and detrimental pest in Moroccan crops. This study investigated the interactions between this mealybug species and its parasitoids, Leptomastix epona (Walker), Anagyrus dactylopii (Howard) and A. aligarhensis Agarwal and Alam (Hymenoptera, Encyrtidae), with a focus on field surveys and functional response dynamics. Field surveys were conducted over 3 years (2021–2023) on Portulaca oleracea (L.), Medicago sativa L. (Fabaceae), and Opuntia megacantha Salm-Dyck (Cactaceae) in Morocco. Functional response and interference experiments were conducted under laboratory conditions to understand parasitoid behaviors and their impact on mealybug populations. Percentages of infestation increased significantly from 2021 to 2023 in the field. In 2023, infestation percentages were 98.7% (P. oleracea), 56.7% (M. sativa), and 47.3% (O. megacantha). Parasitism rates by L. epona in P. solenopsis (P. oleracea) increased from 42.63% (2021) to 51.8% (2023), while they declined for A. aligarhensis from 27.73% to 20.86%, and they slightly decreased for A. dactylopii from 29.63% to 27.39%. Functional response trials indicated a type II functional response for all parasitoids, with L. epona demonstrating superior attack rates (0.92 h−1) and search efficiency (0.90). Handling time was consistent across all three parasitoids (0.04 h). For L. epona, the mutual interference constant (m) was estimated to be 2.20, while it was estimated at 2.07 for A. dactylopii, and at 1.99 for A. aligarhensis. These findings contribute to enhancing our understanding of the intricate relationships between the invasive mealybug P. solenopsis and its parasitoids, with potential implications for sustainable pest management strategies. [ABSTRACT FROM AUTHOR]

Simple Summary: The use of oophagous species from the genus Trichogramma—small wasp—in the control of pest species, both in agriculture and forestry, is the most important example of this type of control because of the area in which it is implemented. They are called parasitoids because the female seeks out the host—the pest species—from which its offspring feed and develop. Until now, this mechanism of action was thought to be due to the parasitism relationships established between the immature stages of the parasitoid and its host; however, it has been shown that the directed 'host-feeding' mechanism of the adult mothers, acting as predators, plays a very important ecological role. This proves that there are much more complex parasitoid–parasitoid relationships than predator–predator relationships. This has implications for the current state of knowledge and can be applied in biological control involving parasitoid species. Over recent decades, intraguild predation (IGP) has attracted special attention, both from the theoretical and practical standpoints. The present paper addresses the interference competition between two Trichogramma species (egg parasitoids)—on the one hand, the extrinsic interactions (i.e., the indirect competition between female T. achaeae and T. brassicae), and on the other, the intrinsic interactions between the larvae of both species. Furthermore, T. achaeae is a better competitor than T. brassicae due to a dual mechanism—the former acts as a facultative hyperparasitoid of the latter, exclusively considering parasitism relationships as well as presenting predation activity by host feeding, which gives preference to eggs previously parasitized by T. brassicae over non-parasitized eggs. Both mechanisms are dependent on the prey density, which is demonstrated by a change in the functional response (i.e., the relationship between the numbers of prey attacked at different prey densities) of T. achaeae adult female—it changes from type II (i.e., initial phase in which the number of attacked targets increases hyperbolically and then reaches an asymptote, reflecting the handling capacity of the predator), in the absence of competition (an instantaneous search rate of a′ = 9.996 ± 4.973 days−1 and a handling time of Th = 0.018 ± 0.001 days), to type I (i.e., linear increase in parasitism rate as host densities rise, until reaching a maximum parasitism rate, and an instantaneous search rate of a′ = 0.879 ± 0.072 days−1 and a handling time of Th ≈ 0) when interference competition is present. These results show that there is a greater mortality potential of this species, T. achaeae, in conditions of competition with other species, T. brassicae in this case. Based on this, their implications in relation to the biological control of pests by parasitoid species are discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: The predatory insects Macrolophus pygmaeus Ramber (Heteroptera: Miridae) and Nesidiocoris tenuis Reuter (Heteroptera: Miridae) are important biological control agents used commercially for the control of main pests in greenhouses, such as Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) and whiteflies (Homoptera: Aleyrodidae). In this study, we investigated the predation efficacy of young and old females and males of the two mirid bugs, M. pygmaeus and N. tenuis, when feeding on eggs of T. absoluta on tomato leaves. Young females of M. pygmaeus exhibited a higher predation efficiency compared to old ones, whereas males displayed a consistently low efficiency of predation irrespective of their age. Both young females and males of N. tenuis displayed a similarly high predation efficiency, although the old females exhibited a higher efficiency of predation compared to their male counterparts, but lower than the efficacy of the M. pygmaeus individuals. Our findings indicate that the two predatory species have different functional response characteristics to their prey depending mainly on their sex and age which may influence their efficacy as biological control agents. The predatory mirids Macrolophus pygmaeus Ramber (Heteroptera: Miridae) and Nesidiocoris tenuis Reuter (Heteroptera: Miridae) are used for the biological control of Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) and other pests in tomato greenhouses. The functional response of 1-day-old (young) and 10-day-old (old) adult females and males of M. pygmaeus and N. tenuis on eggs of T. absoluta was determined on tomato at two temperatures (20 °C and 25 °C) and LD 16:8. Females of M. pygmaeus exhibited higher predation efficiency than males at both tested temperatures. Young M. pygmaeus females had a higher efficiency than old ones, whereas males had a low efficiency irrespective of age. The predation efficiency of N. tenuis was high (but lower than M. pygmaeus) in both young females and males, although old females had a higher efficiency than the respective males. Our results show that the two predatory species have different functional response characteristics to their prey depending mainly on sex and age, which may affect their role as biological control agents. [ABSTRACT FROM AUTHOR]

Monkeypox virus leads to an infectious disease called Monkeypox (mpox). This disease may cause painful rashes, swollen lymph nodes, headaches and fever. Taking the vaccination for mpox can reduce these symptoms and also prevent people from becoming seriously ill. In this paper, we study the effect of vaccination on the (mpox) disease by using the functional response (Holling type II). Some analyses are made for the model and the results are confirmed by using a numerical simulation. [ABSTRACT FROM AUTHOR]

Competition for resources and space can drive forage selection of large herbivores from the bite through the landscape scale. Animal behaviour and foraging patterns are also influenced by abiotic and biotic factors.Fine‐scale mechanisms of density‐dependent foraging at the bite scale are likely consistent with density‐dependent behavioural patterns observed at broader scales, but few studies have directly tested this assertion.Here, we tested if space use intensity, a proxy of spatiotemporal density, affects foraging mechanisms at fine spatial scales similarly to density‐dependent effects observed at broader scales in caribou. We specifically assessed how behavioural choices are affected by space use intensity and environmental processes using behavioural state and forage selection data from caribou (Rangifer tarandus granti) observed from GPS video‐camera collars using a multivariate discrete‐choice modelling framework.We found that the probability of eating shrubs increased with increasing caribou space use intensity and cover of Salix spp. shrubs, whereas the probability of eating lichen decreased. Insects also affected fine‐scale foraging behaviour by reducing the overall probability of eating. Strong eastward winds mitigated negative effects of insects and resulted in higher probabilities of eating lichen. At last, caribou exhibited foraging functional responses wherein their probability of selecting each food type increased as the availability (% cover) of that food increased.Space use intensity signals of fine‐scale foraging were consistent with density‐dependent responses observed at larger scales and with recent evidence suggesting declining reproductive rates in the same caribou population. Our results highlight potential risks of overgrazing on sensitive forage species such as lichen. Remote investigation of the functional responses of foraging behaviours provides exciting future applications where spatial models can identify high‐quality habitats for conservation. [ABSTRACT FROM AUTHOR]

The control of insect pests through biological means relies on the ability of natural enemies to prey on pests. This ability, known as the functional response. It plays a crucial role in selecting the appropriate species for biological control programs. In this particular study, the researchers aimed to evaluate the functional response of the third instar grub of C. zastrowi sillemi, a species of lacewing belonging to the family Chrysopidae, towards the aphid Lipaphis erysimi, which infests Raya plants (Brassica juncea). To achieve this, five different densities of aphids were used as Predator: prey ratio (1:50, 1:100, 1:150, 1:200, and 1:250). The results of the study indicated a type II functional curve response, as determined by logistic regression analysis, of C. zastrowi sillemi towards L. erysimi. The Hollings Type II functional response implies that the rate at which the predator consumes its prey increases with increasing prey density, but eventually reaches a plateau despite further increases in prey density. The aphids' consumption, search rate (a`), and maximum predation rate (1/Th) were observed to be lower (19.68, 0.97, and 0.55) in comparison to when grubs were fed on an artificial diet, where they were higher (20.16, 0.20, and 0.59). Nonetheless, the duration required by third instar grubs to handle prey was longer (2.58) when on a natural diet but shorter (2.42) when on an artificial diet. [ABSTRACT FROM AUTHOR]

Chrysoperla zastrowi sillemi, a common predator in agricultural ecosystems, exhibits significant potential for biological pest control. Study investigated the functional response of C. zastrowi sillemi to Brevicorynae brassicae, a destructive pest of cruciferous crops through laboratory experiments and field observations. Analysed the predatory behaviour of C. zastrowi sillemi in response to varying densities of B. brassicae. The functional response curves are constructed to elucidate the relationship between predator consumption rate and prey density. Factors influencing the predatory efficiency, including prey density, predator handling time, and environmental conditions, are comprehensively evaluated. The findings provided valuable insights into the potential of predator as a biological control agent against B. brassicae infestations, facilitating the development of sustainable pest management strategies in agriculture. [ABSTRACT FROM AUTHOR]

Chrysoperla zastrowi sillemi, a common predator in agricultural ecosystems, exhibits significant potential for biological pest control. Study investigated the functional response of C. zastrowi sillemi to Brevicorynae brassicae, a destructive pest of cruciferous crops through laboratory experiments and field observations. Analysed the predatory behaviour of C. zastrowi sillemi in response to varying densities of B. brassicae. The functional response curves are constructed to elucidate the relationship between predator consumption rate and prey density. Factors influencing the predatory efficiency, including prey density, predator handling time, and environmental conditions, are comprehensively evaluated. The findings provided valuable insights into the potential of predator as a biological control agent against B. brassicae infestations, facilitating the development of sustainable pest management strategies in agriculture. [ABSTRACT FROM AUTHOR]

An understanding of individual variation in animal habitat selection is important for effective conservation and management as well as predicting species responses to a rapidly changing world. Functional responses to habitat availability can explain some of this variation, but not accounting for behavioral grouping may oversimplify inference and mask the diversity of habitat use strategies present in a population. We investigated within-home range habitat selection variation at the group level in a reintroduced population of elk (Cervus canadensis) in Kentucky, USA, during 2020–2022, analyzing satellite tracking data from 103 individuals to quantify variance in responses to seven landscape variables. We used group-level selection coefficients estimated with mixed-effects resource selection functions to model population-level functional responses and classify groups into within-season behavioral clusters. We then used cross validation to assess if these methods of generalizing group-level variation improved predictions of space use. We found that elk had highly variable responses to several covariates, and that some of this variation could be attributed to functional responses to either cover type availability or configuration. When we generalized behavioral tactics via clustering, we found significant increases in group-level predictive ability over the global model and, in some cases, the functional models. This suggests that clustered behaviors are also driving individual heterogeneity in this population. Our results highlight the importance of considering individual differences when studying wildlife-habitat relationships and underscore the need for a more complete understanding of the mechanisms behind this variation to inform habitat management and conservation efforts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Tea Science is the property of Journal of Tea Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Simple Summary: Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) is one of the most potent predaceous mites in biological pest management, feeding on phytophagous mites, pollens, and plant exudates. Tetranychus urticae Koch (Acari: Tetranychidae), a global mite, infects many field crops, fruit orchards, and ornamental plants by reducing photosynthesis and feeding on plant cells. This study reveals that the functional response estimates of A. swirskii vary with temperature (14, 18, 22, 26, 30, and 34 ± 1 °C) and prey density. We found that the highest searching efficiency was at 26 °C and that the lowest was at 14 °C. The handling time for each prey item also varies with temperature and prey density. The functional response curves align with the type II functional response model, showing the inverse dependence of temperature and prey density. The predation curves for A. swirskii show a significant difference in the mean numbers of T. urticae consumed at different prey densities and temperatures. This study highlights the relationship between A. swirskii and T. urticae and the importance of temperature and prey density in natural enemies' activities. The findings can help predict A. swirskii behavior and its effectiveness in controlling T. urticae populations. Amblyseius swirskii are predaceous mites that feed on phytophagous mites, pollens, and plant exudates and are known as one of the most potent biological pest management agents. Tetranychus urticae is a global mite that is difficult to manage because of its high population growth rates, necessitating alternative management measures like biological control. Regarding the functional response, the effects of temperature and prey density are some of the essential behaviors of natural enemies. This study investigates the effect of varying temperatures and prey densities on A. swirskii, a biological control agent for T. urticae. The present results demonstrated the change in the functional response estimates when A. swirskii was reared at various temperatures and different prey densities. The results of the estimates regarding the searching efficiency (a′) showed the highest value (a′ = 0.919) at 26 °C and the lowest value (a′ = 0.751) at 14 °C. The handling time per prey item (Th) for the predatory mites changed with the temperature and prey density, showing the shortest handling time at 26 °C (Th = 0.005) and the highest value at 14 °C (Th = 0.015). The functional response curves matched the type II functional response model, demonstrating the inverse dependence of temperatures and prey density with a positive quadratic coefficient. The predation curves for A. swirskii showed a significant difference between the mean numbers of T. urticae consumed at various prey densities and temperatures, illustrating a relationship between A. swirskii and T. urticae. Therefore, the results of this research may be utilized to forecast the behavior of A. swirskii and its usefulness in controlling T. urticae populations. [ABSTRACT FROM AUTHOR]

The aim of this work is to provide a comprehensive analysis of the dynamics within an ecosystem characterized by interactions between prey and predators, through a combination of theoretical analysis and numerical simulation. The study investigates the impact of two pivotal effects: the “Hide-and-Escape” behavior exhibited by prey and the “Predation Skill Augmentation” strategy adopted by predators. Theoretical analysis identifies three equilibrium points, all of which show positive characteristics. Furthermore, local stability conditions are determined for each of these equilibrium points. The derivation of global stability conditions is also presented, and their validity and importance as local stability conditions for the coexistence point are demonstrated. In addition, Kolmogorov conditions for coexistence and extinction are verified, as well as local bifurcation analysis. For the validity of the results, a numerical simulation of the system using MATLAB is conducted.

This paper investigates the dynamics of a discrete-time predator-prey system in which the prey population is impacted by the Allee effect. Possible fixed points in the system are studied for their existence and topological categorization. Moreover, the presence and direction of period-doubling and Neimark-Sacker bifurcations at the interior fixed point are examined through the application of bifurcation theory and the centre manifold theorem. A hybrid approach is adopted to control chaotic behaviour and prevent bifurcations. Numerical examples are provided to substantiate our theoretical findings. The Allee effect has been shown to affect the dynamics of the system using numerical simulations. The moderate Allee effect stabilizes predator and prey populations, facilitating ecological cohabitation and persistence.

This work examines a discrete Leslie–Gower predator–prey system with herd behavior, focusing on the influence of the slow–fast effect on predator dynamics. We analyze the presence and stability of fixed points, investigating period-doubling and Neimark–Sacker bifurcations at the positive fixed point. A hybrid control technique is implemented to successfully handle chaotic dynamics. Numerical simulations validate the theoretical findings, supporting our analysis. The parameter 휖 in the predator–prey system has a significant impact on system dynamics due to the slow–fast effect it represents. A stable positive fixed point signifies a lasting and balanced coexistence of predator and prey populations within a certain 휖 interval. Deviation from this range results in period-doubling and Neimark–Sacker bifurcations, increasing both unpredictability and instability in the system. [ABSTRACT FROM AUTHOR]

Ladybird beetles Scymnus nubilus Mulsant, Scymnus interruptus (Goeze), and Hippodamia convergens Guérin-Méneville are key contributors to biological control of some pests including Phenacoccus solenopsis Tinsley. This study explores their feeding preferences, functional response, and interference in controlled laboratory conditions. Feeding experiments, including both no-choice and free-choice tests, were conducted at temperatures ranging from 15 to 35°C fed on different developmental stages of P. solenopsis. The study analyzed the functional response with Holling's disc equation and assessed mutual interference among predators using the Hassell and Varley model. In the no-choice feeding tests, H. convergens adults exhibited the highest consumption at 26°C, with values of 46.0 1st instar nymphs, 40.9 2nd instar nymphs, and 34.9 adult females of P. solenopsis, followed by S. interruptus. Free-choice feeding tests also showed a preference for 26°C, with H. convergens consistently consuming the most prey at all stages, followed by S. interruptus. Functional response analysis revealed a type II functional response for three predators. Hippodamia convergens exhibited a significantly higher attack rate (1.0250 h−1) and a shorter handling time (0.0449 h) compared to the other species. Interference among predators was observed, with a progressive decline in prey consumption as predator density increased. Mutual interference constants (m) were calculated as 1.70, 1.74, and 1.77 for S. nubilus, S. interruptus, and H. convergens, respectively. As predator densities increased, searching efficiency declined. This suggest that H. convergens and S. interruptus adults at 26°C with a prey density of 40 can effectively contribute to sustainable P. solenopsis management. [ABSTRACT FROM AUTHOR]

The functional and numerical response and the potential for mutual interference are key components in the selection of parasitoids for biological control. In this study, functional and numerical responses of Goniozus legneri to different densities of fifth instar Cydia pomonella larvae and mutual interference of this parasitoid were studied under laboratory conditions. Logistic regression was used to find the type of functional response and the result was type II. The attack rate, handling time, the parasitoid searching efficiency and the maximum host mortality rate were estimated by fitting the Holling model to the data. The numerical response of the parasitoid did not vary based on the availability of codling moth larvae. The negative value of the interference coefficient (−0.228) in the mutual interference analysis showed an inverse relationship between parasitoid density and per capita searching efficiency. This suggests that when the density of G. legneri and C. pomonella larvae is equivalent, the parasitoid proves to be more effective in pest control. The findings of this study contribute to increasing the knowledge of G. legneri and its potential as a biocontrol agent. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microplastics are widespread pollutants, but few studies have linked field prevalence in organisms to laboratory uptakes. Aquatic filter feeders may be particularly susceptible to microplastic uptake, with the potential for trophic transfer to higher levels, including humans. Here, we surveyed microplastics from a model freshwater shrimp, common caraidina (Caridina nilotica) inhabiting the Crocodile River in South Africa to better understand microplastic uptake rates per individual. We then use functional response analysis (feeding rate as a function of resource density) to quantify uptake rates by shrimps in the laboratory. We found that microplastics were widespread in C. nilotica, with no significant differences in microplastic abundances among sampled sites under varying land uses, with an average abundance of 6.2 particles per individual. The vast majority of microplastics found was fibres (86.1%). Shrimp microplastic accumulation patterns were slightly higher in the laboratory than the field, where shrimp exhibited a hyperbolic Type II functional response model under varying exposure concentrations. Maximum feeding rates of 20 particles were found over a 6 h feeding period, and uptake evidenced at even the lowest laboratory concentrations (~10 particles per mL). These results highlight that microplastic uptake is widespread in field populations and partly density dependent, with field concentrations corroborating uptake rates recorded in the laboratory. Further research is required to elucidate trophic transfer from these taxa and to understand potential physiological impacts. [ABSTRACT FROM AUTHOR]

For food chain system with three populations, direct predation is the basic interaction between species. Different species often have different predation functional responses, so a food chain system with Holling-II response for middle predator and Beddinton–DeAngelis response for top predator is proposed. Apart from direct predation, predator population can significantly impact the survival of prey population by inducing the prey's fear, but the impact often possesses a time delay. This paper is concentrated to explore how the fear and time delay affect the system stability and the species persistence. By use of Lyapunov functional method and bifurcation theory, the positiveness and boundedness of solutions, local and global behavior of species, the system stability around the equilibrium states and various kinds of bifurcation are investigated. Numerically, some simulations are carried out to validate the main findings and the critical values of the bifurcation parameters of fear and conversion rate are obtained. It is observed that fear and delay can not only stabilize, but also destabilize the system, which depends on the magnitude of the fear and delay. The system varies from unstable to stable due to the continuous increase of the prey's fear by middle predator. Small fear induced by top predator or small delay of the prey's fear can stabilize the system, while they are sufficiently large, the system stability is to be destroyed. Simultaneously, the conversion rate can also change the stability and even make the species to be extinct. Some rich dynamics like multiple stabilities and various types of bistability behaviors are also exhibited, which results in the convergence of the species from one stable equilibrium to another. [ABSTRACT FROM AUTHOR]

Many foraging models assume "perfect information" and "free movement" when describing predator foraging behavior, although this is rare in nature. Here, we quantified predation by brown bears (Ursus arctos Linnaeus, 1758) on adult sockeye salmon (Oncorhynchus nerka (Walbaum, 1792)) in a series of spatially proximate ponds that largely satisfied both assumptions. Salmon abundance varied among years, but pond area and depth were fixed, allowing us to examine interactions between prey abundance and habitat features. We applied versions of two models to 25 years of data on the number and proportion of salmon killed by bears, modifying these models to include habitat features and temporal variability. The functional response model with a year effect fit the data well, indicating bears could take almost all salmon in ponds when salmon were scarce, but bears were sated when salmon were abundant. The proportion of salmon killed by bears was similar across habitats after correcting for pond depth and area. Overall, bears foraged across all habitats but killed higher proportions of salmon in smaller and shallower habitats, consistent with ease of capture. [ABSTRACT FROM AUTHOR]

The parasitic wasps Ooencyrtus telenomicida and Trissolcus grandis are among the most common biocontrol agents of the common sunn pest (CSP), Eurygaster integriceps. The Ooencyrtus spp. act as facultative hyperparasitoids of CSP eggs, which may earlier have parasitized by Scelionidae. The preference and choice of these wasps among hosts of different quality (recently deposited eggs, 2-, and 4d-old eggs, as well as recently parasitized CSP eggs by T. grandis, 3-, 7-, and 10 d-old parasitized eggs) was studied. The results indicated that, unexpectedly, parasitism rate was the highest in 4d-old eggs, while the wasps significantly avoided 10d-old parasitized eggs. The functional response experiments were carried out with the same set of hosts. The 72h-old inexperienced fertile females were confined individually with different host densities for 6h. The response of the wasp to all kinds of the host was a type III response. No response to 7d-old parasitized eggs was evident (non-significant parameters). Depending on the treatment, the highest parasitism rate occurred at densities 5 to 9 which was between 25.7 and 46.5%. The handling time and maximum attack rate ranged between 0.61 - 1.83 h and 3.27-9.85 host eggs respectively. The maximim parasitism rates was observed in the 10d-old parasitized eggs, newly deposited eggs and 4d-old eggs. The results of the functional response and host preference experiments were not confirming, and therefore more studies are still required to reveal the impact of host quality on the parasitoid. [ABSTRACT FROM AUTHOR]

Functional responses describe foraging rates across prey densities and underlie many fundamental ecological processes. Most functional response knowledge comes from simplified lab experiments, but we do not know whether these experiments accurately represent foraging in nature. In addition, the difficulty of conducting multispecies functional response experiments means that it is unclear whether interaction strengths are weakened in the presence of multiple prey types. We developed a novel method to estimate wild predators' foraging rates from metabarcoding data and use this method to present functional responses for wild wolf spiders foraging on 27 prey families. These field functional responses were considerably reduced compared to lab functional responses. We further find that foraging is sometimes increased in the presence of other prey types, contrary to expectations. Our novel method for estimating field foraging rates will allow researchers to determine functional responses for wild predators and address long‐standing questions about foraging in nature. [ABSTRACT FROM AUTHOR]

Brachycaudus helichrysi, also known as peach leaf curl aphid is a destructive pest that poses a grave threat to peach and nectarine cultivation. The existing management practices primarily rely on applying synthetic insecticides whose indiscriminate use has led to a myriad of problems. To address these issues, biological control agents like ladybirds (Oenopia sauzeti) have emerged as an environment friendly alternative strategy. Till now, there has been a dearth of precise information on the biology, fecundity as well as functional response of O. sauzeti against B. helichrysi. The present study assesses the demographic parameters and functional response of O. sauzeti preying on B. helichrysi under laboratory conditions at 25 ± 1 °C, 70 ± 5% RH and 12 L: 12 D photoperiod and aims to provide valuable insights for its potential use in pest management. The findings showed a net reproductive rate, gross reproductive rate, true generation time and intrinsic rate of increase of 59.92 females/predator, 76.95 offspring per individual, 33.36 days and 0.12, respectively. The results showed that O. sauzeti exhibited a type II functional response. The highest predation rate was observed in the adults (78.21), which was significantly different from 1st, 2nd, 3rd and 4th larval instars (19.68, 32.30, 36.49 and 51.64, respectively) of the coccinellid. This research provides essential information for using O. sauzeti as a biocontrol agent for B. helichrysi and would prove beneficial to sustainable pest management strategies in stone fruit cultivation. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, we performed DNA metabarcoding to examine prey composition and pest diversity in the diets of four insectivorous species of bats. Then, we evaluated the correlation between bat activity and insect resources and assessed dietary niche similarity and niche breadth among species and factors that influence prey consumption in bats. Additionally, we explored the functional response between these predators and their prey, understanding how bat feeding behavior adapts to the availability of different pest species. We proved that bats provide vital pest consumption services in agricultural ecosystems and their diet included arthropods from 23 orders and 200 families. Moreover, bats responded to the availability of insects. For example, a higher abundance of insects, especially Lepidoptera, and a higher insect diversity led to an increase in the duration of bat activity. In areas with more abundant insects, the number of bat passes also increased. Our results suggested that dietary niche differentiation promotes the coexistence of different bat species and increases the ability of bats to consume insect prey and agricultural pests. Our findings provide greater insights into the role of bats that prey on agricultural pests and highlight the importance of combining bat conservation with integrated pest management. Insectivorous bats are generalist predators and can flexibly respond to fluctuations in the distribution and abundance of insect prey. To better understand the effects of bats on arthropod pests, the types of pests eaten by bats and the response of bats to insect prey need to be determined. In this study, we performed DNA metabarcoding to examine prey composition and pest diversity in the diets of four insectivorous species of bats (Hipposideros armiger, Taphozous melanopogon, Aselliscus stoliczkanus, and Miniopterus fuliginosus). We evaluated the correlation between bat activity and insect resources and assessed dietary niche similarity and niche breadth among species and factors that influence prey consumption in bats. We found that the diets of these bats included arthropods from 23 orders and 200 families, dominated by Lepidoptera, Coleoptera, and Diptera. The proportion of agricultural pests in the diet of each of the four species of bats exceeded 40% and comprised 713 agricultural pests, including those that caused severe economic losses. Bats responded to the availability of insects. For example, a higher abundance of insects, especially Lepidoptera, and a higher insect diversity led to an increase in the duration of bat activity. In areas with more abundant insects, the number of bat passes also increased. The dietary composition, diversity, and niches differed among species and were particularly significant between H. armiger and T. melanopogon; the dietary niche width was the greatest in A. stoliczkanus and the narrowest in H. armiger. The diet of bats was correlated with their morphological and echolocation traits. Larger bats preyed more on insects in the order Coleoptera, whereas the proportion of bats consuming insects in the order Lepidoptera increased as the body size decreased. Bats that emitted echolocation calls with a high peak frequency and duration preyed more on insects in the order Mantodea. Our results suggest that dietary niche differentiation promotes the coexistence of different bat species and increases the ability of bats to consume insect prey and agricultural pests. Our findings provide greater insights into the role of bats that prey on agricultural pests and highlight the importance of combining bat conservation with integrated pest management. [ABSTRACT FROM AUTHOR]

Several models have been proposed as an extension to the classical Holling's disc equation to evaluate the predator and prey interactions and their applied aspect in biological control and population regulation of the target organisms. In a one prey and two predator dynamic system with mutual interference (m) as a quadratic parameter of predator density, an evaluation was made to the resultant impact on the prey. A simulation was carried out to see the extinction of prey and the stability of the system at origin, i.e., when all the three species are extinct. We assumed the data obtained for the interactions between the mosquito and the water bug predators that are common in the freshwater wetlands and involved in the population regulation. Despite the benefits to prey population due to interference competition, the expected extinction of prey is still observed. With varying magnitudes of m the declining growth curve of prey population, shifted. The equation proposed was also compared with Crowley–Martin functional response, and considerable differences were observed in selected instances when compared for the growth rate of the predators, in a species-specific manner. The stability of the system was deduced with eigenvalues of Jacobian matrix at origin to prove the extinction is stable. Our assessment supports the possible cooccurrence of the predators and mosquito prey in the wetlands with the mutual interference being one of the major factors. [ABSTRACT FROM AUTHOR]

Climate change is predicted to increase the frequency and size of wildfires. Wildfire burns can influence wildlife space use, but prior to understanding the relationship between wildlife and burns, the extent of wildfires and the regrowth of burned areas must be determined. We used remotely sensed, multispectral satellite imagery to calculate differenced normalized burn ratios (NBRs) to define areas burned by wildfire and assess temporal trends in burn frequency and extent in central British Columbia. We then used NBRs as an index of vegetation regrowth to model regrowth trajectories within burns. Next, we examined spatial responses to burns by a moose (Alces alces) population that recently declined in abundance. We utilized locations used by and available to collared moose to determine spatial responses as a function of years since wildfire and vegetation regrowth. We also assessed functional responses to burns by moose, dependent upon the proportion of burned areas available to each individual. We hypothesized that (h1) wildfire burns within our study area increased from 1985 to 2017, (h2) that moose increase their use of burns in comparison with availability as burns age as a result of vegetation regrowth, and (h3) that moose demonstrate functional responses to burns (i.e., selection of burns by individual moose declines as the amount of burned areas increases). We observed that the frequency and extent of burns are increasing within our study area. In contrast to h2, moose in summer and fall decreased the selection of burns as burns aged. We, however, observed that moose responded most positively to locations with intermediate vegetation regrowth (i.e., NBR values), which according to burn regrowth trajectories were most likely to be achieved 13 or more years post‐wildfire; given that most burns within our study area were ≤13 years of age, we predict that the use of burns will likely increase as vegetation regrows. Moose only selected for burns in fall, and we did not find support for the presence of a functional response. Our research demonstrated the utility of remotely sensed imagery and NBRs to define burn locations and to reveal current and probable future spatial responses to burns by a wildlife population of concern. [ABSTRACT FROM AUTHOR]

Being chemically inert and morphologically similar (<5 mm in size) to the natural prey of copepods, microplastics (MPs) affect them through entanglement, ingestion, and interference with their natural prey selection. The effects of external factors, such as MP, can be observed in the form of alterations in the functional and numerical responses of copepods. Functional response is explained as the relationship between the intake rate of a consumer and the amount of food available in a particular ecotope. Considered three types of functional response: (i) with increasing food density, when intake rate increases linearly until asymptote, called Type-I functional response; (ii) when the proportion of prey ingested by the consumer decreases monotonically with prey density, considered as a Type-II functional response; and (iii) when ingestion rate and food density show a sigmoid relationship, is considered as Type-III functional response. In the present study, we attempted to elucidate the effects of MP on the functional responses of brackish water, demersal, calanoid copepod, Pseudodiaptomus annandalei, feeding on the rotifer Brachionus rotundiformis, and the ciliate Frontonia microstoma. The ability of P. annandalei to survive environmental fluctuations and its nutritional value make it an ecologically important organism in estuarine ecosystems. The experiment for estimation of functional response included four setups with adult and copepodite stages of P. annandalei, each with six replicates at six different prey densities, in the presence and absence of MP particles. Without MPs, P. annandalei showed a typical Type-II functional response, where the proportion of prey consumed significantly declined with increasing prey density. In the MP- applied medium, the proportion of prey consumed did not exhibit a significant relationship with the initial prey density. The number of ciliates and rotifers ingested by copepodites and adults was significantly lower in MP-contaminated medium than in prey either monospecific or in combination with microalgae. Because of the comparable size of MP to the prey species and unspecialized feeding of P. annandalei in natural waters, we hypothesized reduced predation rates as a result of pseudo-satiation resulting from MP ingestion leading to malnutrition and MP storage in copepod biomass. [ABSTRACT FROM AUTHOR]

The logistic growth model is one of the most frequently used formalizations of density dependence affecting population growth, persistence and evolution. Ecological and evolutionary theory, and applications to understand population change over time often include this model. However, the assumptions and limitations of this popular model are often not well appreciated. Here, we briefly review past use of the logistic growth model and highlight limitations by deriving population growth models from underlying consumer–resource dynamics. We show that the logistic equation likely is not applicable to many biological systems. Rather, density‐regulation functions are usually non‐linear and may exhibit convex or concave curvatures depending on the biology of resources and consumers. In simple cases, the dynamics can be fully described by the Schoener model. More complex consumer dynamics show similarities to a Maynard Smith–Slatkin model. We show how population‐level parameters, such as intrinsic rates of increase and equilibrium population densities are not independent, as often assumed. Rather, they are functions of the same underlying parameters. The commonly assumed positive relationship between equilibrium population density and competitive ability is typically invalid. We propose simple relationships between intrinsic rates of increase and equilibrium population densities that capture the essence of different consumer–resource systems. Relating population level models to underlying mechanisms allows us to discuss applications to evolutionary outcomes and how these models depend on environmental conditions, like temperature via metabolic scaling. Finally, we use time‐series from microbial food chains to fit population growth models as a test case for our theoretical predictions. Our results show that density‐regulation functions need to be chosen carefully as their shapes will depend on the study system's biology. Importantly, we provide a mechanistic understanding of relationships between model parameters, which has implications for theory and for formulating biologically sound and empirically testable predictions. [ABSTRACT FROM AUTHOR]

The two-spotted spider mite (TSSM), Tetranychus urticae Koch is a polyphagous widespread herbivore pest and one of the most economically important species which feeds more than 1,100 plant species. The functional response at five different constant temperatures (15, 20, 25, 30 and 35 °C), prey switching, and mutual interference behaviors of the predatory coccinellid, Stethorus gilvifrons Mulsant on TSSM nymphs were assessed in laboratory conditions (25 ± 1 °C, 60 ± 5% RH and L:D 16:8 h) to evaluate its potential for biological control of TSSM. The predator showed a type II functional response at all tested temperatures. The shortest handling time (Th) and highest searching efficiency (α) were obtained at 30 °C and 20 °C, respectively. The highest and lowest values of the maximum attack rate (T/Th) of the predator were obtained at temperatures of 30 °C and 15 °C, respectively. The switching behavior was not observed in S. gilvifrons between different density proportions of TSSM nymph and adult. The highest value of total predation and lowest value of per capita predation rate belonged to the predator density of 16. The results revealed a strong predation capacity of S. gilvifrons on TSSM, especially in higher temperatures which makes it an efficient biocontrol agent in integrated TSSM management programs. [ABSTRACT FROM AUTHOR]

The dynamic interactions between predators and their prey have two fundamental processes: numerical and functional responses. Numerical response is defined as predator growth rate as a function of prey density or both prey and predator densities [dP/dt = f(N, P)]. Functional response is defined as the kill rate by an individual predator being a function of prey density or prey and predator densities combined. Although there are relatively many studies on the functional response in mammalian predators, the numerical response remains poorly documented. We studied the numerical response of Eurasian lynx (Lynx lynx) to various densities of its primary prey species, roe deer (Capreolus capreolus), and to itself (lynx). We exploited an unusual natural situation, spanning three decades where lynx, after a period of absence in central and southern Sweden, during which roe deer populations had grown to high densities, subsequently recolonized region after region, from north to south. We divided the study area into seven regions, with increasing productivity from north to south. We found strong effects of both roe deer density and lynx density on lynx numerical response. Thus, both resources and intraspecific competition for these resources are important to understanding the lynx population dynamic. We built a series of deterministic lynx–roe deer models, and applied them to the seven regions. We found a very good fit between these Lotka–Volterra type models and the data. The deterministic models produced almost cyclic dynamics or dampened cycles in five of the seven regions. Thus, we documented population cycles in this large predator–large herbivore system, which is rarely done. The amplitudes in the dampened cycles decreased toward the south. Thus, the dynamics between lynx and roe deer became more stable with increasing carrying capacity for roe deer, which is related to higher productivity in the environment. This increased stability could be explained by variation in predation risk, where human presence can act as prey refugia, and by a more diverse prey guild that will weaken the direct interaction between lynx and roe deer. [ABSTRACT FROM AUTHOR]

Insecticides have been known to reduce the predation efficacy of natural enemies. However, the mechanism of the sublethal effect of insecticides on the functional response of predators remains unclear. This study investigated the sublethal effects of the broad-spectrum insecticide chlorpyrifos on the predatory bug Eocanthecona furcellata (Wolff), which is a potential biological control agent against pests in integrated pest management (IPM) programs. After exposure to a sublethal concentration of chlorpyrifos, the predation capacity and the maximum predatory number of E. furcellata increased by 11.27 and 15.26%, respectively, with prey handling time decreased by 15.07%, and the searching efficiency increased by 5.88–12.61%. Additionally, the intraspecific interference effect was enhanced. Glutathione S-transferase (GST) activity was significantly decreased after 12- to 60-h treatment. At 12 h after treatment, the expression levels of GST gene (GST3), acetylcholinesterase gene (AChE), and cytochrome P450 monooxygenasegene (cyp6B1) were significantly up-regulated by 1.47-, 1.48-, and 2.05-fold, respectively, while GST gene (GST1) was significantly down-regulated by 16.67-fold. These results indicated that a sublethal chlorpyrifos concentration inhibited the GST activity and stimulated the predatory behavior of E. furcellata. The results will advance our understanding of the toxicological mechanism of predatory stink bug responses to insecticides and predict chlorpyrifos' effects on predators in an IPM program. [ABSTRACT FROM AUTHOR]