Adult Predators Research Articles

The impact of increasing turbidity on the predator–prey interactions of freshwater fishes

Abstract Human activities are exacerbating environmental change globally. Turbidity in freshwater systems is increasing due to extreme weather events and intensification of activities such as deforestation, urbanisation, agriculture and altering water flow with dams and other structures. Prey species may benefit from turbid habitats as turbidity creates a visual barrier to predators; such predators thus face reduced foraging success as water clarity decreases. However, the literature on the effects of water turbidity on predator–prey interactions in fish is often contrasting. Environmentally driven changes in predator and prey behaviour, foraging and survival ultimately have the potential to affect community structure and ecosystem functioning, thus understanding the impact of changes in turbidity on predator–prey interactions should be a priority. Given the contrasting results in the primary literature, the aim of this review is to provide a broad overview of the current knowledge on the impacts of increased turbidity on predator–prey interactions in freshwater fishes, summarise the published literature and identify knowledge gaps on this topic. We collated 281 studies from the peer‐reviewed literature that tested the impact of water turbidity on the foraging behaviour of predatory fish and anti‐predator behaviour of prey fish. We recorded changes in predator and prey behaviours in response to changes in turbidity levels. Furthermore, we reported whether these behavioural changes were considered to have a positive (e.g. enhanced foraging success) or negative (e.g. higher mortality) impact on the focal species, or whether the impact was unspecified (e.g. changes in anti‐predator behaviour without quantifying actual predation risk). The literature has some strong taxonomic, geographical and environmental biases, where most research focused on commercially important, temperate species. A large proportion of studies (47%) reported a negative (versus a positive or unspecified) impact of turbidity on the focal species (either predator or prey freshwater fish). Negative impacts were reported more often for predators (58%) compared to prey (19%) and while changes in behaviour were frequently reported in prey species, if these changes are adaptive or not is unclear, as actual predation risk was not assessed in the majority of relevant studies (55%). Increases in turbidity have complex effects on predator–prey interactions, with negative impacts more often reported for adult piscivore predators, while prey species may gain a relative advantage compared to visual predators. However, whether prey behavioural responses to increased turbidity are adaptive is generally unclear. We suggest that a more holistic and ecologically relevant experimental approach is needed to disentangle the underlying mechanisms and determine the adaptive nature of prey behavioural responses to increased turbidity. Our review serves as a broad and comprehensive summary of the empirical research conducted on impacts of increasing water turbidity on predator–prey interactions in freshwater fishes. It highlights knowledge gaps and provides a reference point to guide future experimentation and research synthesis in this crucial and growing area of research.

Enchanting dynamics: Juvenile and adult predators with prey model in an intuitionistic fuzzy environment

This study represents an interaction model including juvenile and adult predators along with prey, involving key characteristics like the inability of juvenile predators to reproduce, the impact of adult predators on juvenile growth rates and the transformation of some juveniles to adulthood. Furthermore, it is supposed that adult predators intake prey for sustenance, and the logistic growth of prey is assumed in the non-appearance of adult predators. Intra-species competition among adult predators, together with predation of juveniles and chasing, is conveyed. To tackle the imprecise biological parameters, most parametric values are considered as triangular intuitionistic fuzzy numbers. The model is further processed into an intuitionistic fuzzy model using the Hukuhara derivative and Yager’s ranking method is implemented to make the model crispified. Non-negativity and boundedness of the model are explored, after that, an investigation of possible equilibrium points is discussed. Local and global stability analyses close to these points are supervised. The study accentuates the significant influence of uncertain model parameters on the solution. Especially, uncertain estimates of intra-species competition among adult predators remarkably regulate the model’s stability. Extended uncertainty in intra-species competition for prey, although, is discovered to stabilize the system. In addition, increased consumption of juvenile predators by adult predators is observed to provide the system’s instability.

Density-Dependent Mortality of the Diving Beetle, Rhantus elevatus (Dytiscidae: Coleoptera) Preyed Upon Culex pipiens Larvae: Effects of Prey and Predator Densities.

Diving beetles (Coleoptera: Dytiscidae) are general predators that feed primarily on mosquito larvae and can control their populations, but the evidence for such an assumption remains weak. Rhantus elevatus is an important predator of this group distributed in Egypt with both larval and adult stages preying on immature mosquito. For determine predator effectiveness, it is requisite to identify the functional response (a = rate of attack and Th = time of handling) and searching efficacy (at = area of discovery and m = mutual interference) as both correlate with biocontrol efficacy. This study assessed the density-dependent mortality of Culex pipiens larvae by eliciting functional responses of third-instar and adult predators at prey density ranging from 100 to 500 larvae per arena. By contrast, a searching efficacy for the same predator stages was examined at densities ranging from one to five predators per 500 prey. Predation rates of third-instar and adult of R. elevatus were fitted by a model of Type II response with coefficients were: third-instar (a = 0.208 h-1 and Th = 2413 h) and adult (a = 0.1191 h-1 and Th = 3723 h). The maximum number of mosquitoes which can be devoured by an individual larva and adult of R. elevatus within 24 h was 99.46 and 64.46 prey, respectively. The area of discovery for the larval stage declined more steeply than the adult stage of the predator as their density increased from one to five individuals, indicating more interference estimated for the larval stage. Considering these characteristics, larvae would seem to be the most effective stage against low mosquito populations due to low predation risk compared to that generated at high predator densities in the same arena from intra-specific interference. Eventually, we suggested a ratio of 1:100 (predator per prey) must be considered in biocontrol plans for mosquitoes.

How does Neoseiulus californicus McGregor respond to sublethal doses of entomopathogenic fungus Beauveria bassiana (Hyp.: Cordycipitaceae)?

Two-spotted spider mite, Tetranychus urticae Koch (Acari: Prostigmata), is one of the most economically important mite species, mainly controlled by chemical acaricides. Natural enemies have been assessed as reliable alternatives for management of this phytophagous mite. In the current project, demographic characteristics of Neoseiulus californicus McGregor (Acari: Phytoseiidae) to sublethal concentrations (LC10 = 6.76 × 102, LC20 = 8.74 × 103 and LC30 = 55.38 × 103 conidia ml-1) of entomopathogenic fungus, Beauveria bassiana (Bals.) Vuill. TV strain were investigated under laboratory conditions at 25 ± 2°C, 70 ± 5% RH and a photoperiod of 16:8 (L:D) h. Our results indicated that when adult predators were exposed to LC20 and LC30 of B. bassiana, the oviposition period was significantly reduced compared with other treatments. Neoseiulus californicus fecundity was significantly greater in the control (37 eggs) than in LC30 (24 eggs). Life table analysis revealed that the net reproductive rate (R0) declined as the sublethal concentrations of B. bassiana increased. The most striking result to emerge from the data is that not only intrinsic (r); but also, finite rate of increase (λ) was not significantly affected by different concentrations of B. bassiana. Our findings revealed some potential interactions of B. bassiana and N. californicus during their combinations for managing T. urticae that may be helpful for optimising control of this important pest.

Dynamical Behavior of a Juvenile Predator, Adult Predator and Prey Model Through Uncertain and Parametric Technique

In this study, an interaction model involving a juvenile predator, an adult predator, and the prey has been developed. It is considered that juvenile predators are unable to reproduce. The adult predator is considered to have an impact on the growth rate of the juvenile predators. It is also assumed that a portion of juvenile predators may become adults. Also, it is considered that adult predators consume prey for food. The logistic growth of prey has been taken into consideration in the absence of an adult predator. The intra-species competition among adult predators is discussed here. It is also assumed that adult predators could chase and eat juvenile predators. Then most of the parametric values are considered interval-valued uncertain numbers. Since it is very hard for us to solve the model when the parametric values are interval-valued. Thus, all of the interval-valued parameters have been simplified into linear parametric form. After that, the nonnegativity and boundedness of the model were discussed. Various possible equilibrium points in the model are analyzed. The model’s local stability and global stability are investigated near these points. It has been noted that the proposed model’s solution is significantly impacted by the uncertain values of the model parameters. Uncertain estimates of intra-species competition among adult predators have been found to have a considerable impact on the stability of the model. It is observed that the increased uncertainty of intra-species competition for prey may stabilize the system. It is reported that the increasing rate of conversion of prey into adult predators can destabilize the ecosystem. It is found that the increasing rate of predation on juvenile predators by adults reduces the number of juveniles that can mature into adults which may create instability in the system.

Prey stage preference of Amblyseius paraaerialis (Acari: Phytoseiidae) on varied life stages of the spider mites Tetranychus urticae, Tetranychus macfarlanei and Oligonychus biharensis (Acari: Tetranychidae) and exploring the mass rearing possibilities of this predatory mite on alternative diets.

Spider mites Tetranychus urticae, Tetranychus macfarlanei and Oligonychus biharensis are considered to be highly polyphagous in nature and causes severe damage to a wide range of plants around the world. Amblyseius paraaerialis is an efficient phytoseiid predator of spider mites with a potential to survive on both natural and alternative diets. Evaluation of predatory potential and prey stage preference provides valuable information on the efficacy of the predatory species in controlling mite population. Feeding experiments were conducted on mulberry leaf discs under the laboratory conditions of 30 ± 2 °C and 70 ± 5% relative humidity (RH). After 24h of feeding experiment, the adult female predator exhibited a significant preference in feeding towards the eggs of T. macfarlanei (42.6%) and the larval stages of T. urticae (46%) and O. biharensis (25.3%). The mass rearing possibilities of A. paraaerialis was tested by tracking and comparing the developmental duration of individual life stages on varied food sources like, honey, castor (Ricinus communis) pollen, honey-pollen mixture and mixed life stages of T. urticae. The predator was failed to complete its development on honey and pollen when supplied separately. However it was successfully developed on honey-pollen mixture and mixed life stages of T. urticae. The developmental studies unravelled a shortest developmental duration and an extended adult longevity and lifespan of A. paraaerialis when reared on the alternative diet, thus opened up the mass rearing possibility of the predatory species under laboratory conditions.

Predator metamorphosis and its consequence for prey risk assessment.

Living with a diverse array of predators provides a significant challenge for prey to learn and retain information about each predator they encounter. Consequently, some prey respond to novel predators because they have previous experience with a perceptually similar predator species, a phenomenon known as generalization of predator recognition. However, it remains unknown whether prey can generalize learned responses across ontogenetic stages of predators. Using wood frog tadpole (Lithobates sylvaticus) prey, we conducted two experiments to explore the extent of predator generalization of different life stages of two different predators: (1) predacious diving beetles (Dytiscus sp.) and (2) tiger salamanders (Ambystoma mavortium). In both experiments, we used chemical alarm cues (i.e., injured conspecific cues) to condition tadpoles to recognize the odor of either the larval or adult stage of the predator as risky. One day later, we tested tadpoles with either the larval or adult predator odor to determine whether they generalized their learned responses to the other life stages of the predator. Tadpoles generalized between larval and adult beetle odors but failed to generalize between larval and adult salamander odors. These results suggest that the odor of some predator species changes during metamorphosis to an extent that reduces their recognisability by prey. This "predator identity reset" increases the number of threats to which prey need to attend.

When can we expect natural habitats to enhance pest control by generalist predators? Insights from a simple, simulated agricultural landscape

Many field studies have reported that natural habitats in the agricultural landscape are associated with increased predator abundance and/or decreased crop pest load. However, recently published meta-analyses have found mixed results, with natural habitats being associated with increased pest loads as often as decreased loads. We investigate possible reasons for these conflicting results using a mechanistic model that simulates the dynamics of a generalist, omnivorous predatory bug and a plant bug pest in a landscape consisting of a 1 km2 annual field crop monoculture bisected by a 60 m wide natural habitat strip. The model simulates the movement of adult predators in the landscape via both trivial movement and long-distance dispersal, along with the movement of energy and egg reserves carried by those predators. We simulate multiple scenarios varying the presence or absence of floral resources and alternate prey in the natural habitat and crop, and the presence or absence of overwintering refuges for the predator and pest insect in the natural habitat. Food resources provided to the predator by the natural habitat did not enhance natural control in adjacent crops. When the natural habitat served as an overwintering refuge for predators, natural control of pests was enhanced if food resources were available in the crop for those predators. Availability of alternate prey was more important to the predator than floral resources. Early-season crop pest loads were always increased when pest insects overwintered in the natural habitat, however early-season availability of pest insects enhanced natural control across the whole-season. Overall, crop pest loads were highly variable across simulation scenarios, reproducing the conflicting results from field research.

Pollen provisioning attenuates pesticide side-effects on a phytoseiid predator.

Biological control with predatory mites is applied against pests in greenhouse crops. Chemical control with the use of selective, reduced-risk pesticides, is an important component of Integrated Pest Management (IPM) programs, that often needs to be combined with biological control. Here, we evaluated the effect of plant pollen when used as supplementary food on the survival, reproduction and predation of the predatory mite Amblydromalus limonicus (Acari: Phytoseiidae) after exposing young larvae and adults to flonicamid, an insecticide of moderate toxicity to phytoseiids. Pollen is an important alternative food for generalist phytoseiids ensuring survival and supporting populations build-up during periods of prey scarcity. Two regimes of cattail (Typha angustifolia L.) pollen differing in application frequency were used. In the first, the total amount of pollen was supplied once, within 30 min after insecticide application, whereas in the second regime, the same amount of pollen was supplied gradually, i.e., every 48 h. Regardless of the frequency of application, pollen provisioning results in a reduction in prey (thrips) consumption relative to the control (no pollen provisioning). Nevertheless, when adult mites were directly exposed to flonicamid residues, pollen provisioning attenuated the reduction in prey consumption as compared to the control. In addition, the gradual (every 48 h) provisioning of pollen to adult predators exposed to flonicamid residues impacted positively the intrinsic rate of population increase (rm) of A. limonicus as compared to when feeding on prey. Our results reveal an unexpected role of pollen provisioning in alleviating pesticides side-effects on phytoseiids. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Monitoring of coccinellid (Coleoptera) presence and syrphid (Diptera) species diversity and abundance in southern California citrus orchards: implications for conservation biological control of Asian citrus psyllid and other citrus pests

Abstract The abundance and diversity of three taxa of citrus pest predators, syrphids (Diptera), coccinellids (Coleoptera), and chrysopids (Neuroptera) and their association with flowering weed species in commercial citrus orchards in southern California were investigated. The occurrence and frequency of adult predators were determined with vertical yellow sticky traps and by performing 3 min visual counts on flowering weeds from May through November 2021. Syrphid abundance peaked in June and September, with the dominant species being Allograpta obliqua (Say), Toxomerus marginatus (Say), and Paragus tibialis (Fallen). Peak collections of coccinellids occurred in May, June, and September on sticky traps and during September and October in flowering weedy plants. Peak flowering of weed species occurred during May and declined sharply over summer into fall (June–November). The efficacy of yellow 355 mL glycol pan traps, yellow 1774 mL water pan traps, and yellow sticky traps orientated either horizontally or vertically with respect to capturing key natural enemies was evaluated in 2021 and 2022. Significantly more syrphids were captured on the horizontal yellow sticky traps than on the vertical yellow sticky traps or the yellow pan traps filled with glycol or water. Coccinellids were most frequently captured on vertical yellow sticky traps and yellow water pan traps. Numbers of chrysopids captured in all studies were not significant, which was most likely attributable to their nocturnal behavior. Collectively these results suggest that syrphid and coccinellid activity in southern California citrus orchards displayed two seasonal peaks, one in spring and the other in the fall. In the context of future conservation biological control, insectary plantings in spring (April–June) and fall (September–October) would be most beneficial to these predators and would coincide with population peaks of a key citrus pest, Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae).

Science fiction: The biology of the alien in Alien

Parasites serve as a source of threatening outcomes for humans in many science fiction plots. Perhaps the most notable is the Xenomorph of the first Alien film (1979). Here, we use the film as the sole source of direct information to hypothesize its life cycle. We recognize a distinctive infective stage, the face-hugger. To further its development as an internal parasite in its human host, we conceive features of its physiology. It has an astonishing ability to manipulate the behaviour of its doomed host, before emerging as the famous chest-burster. It is clearly a parasitoid, requiring the death of its host. A further metamorphosis completes its development to the adult predator that roams the doomed spaceship Nostromo. The Xenomorph adult stage bears an uncanny resemblance to a parasitoid of salps, pelagic invertebrates. Conceptualizing its mythic biology offers insight into the physiology and biochemistry of real parasites.

ANALISIS KESTABILAN MODEL PREDATOR PREY DENGAN TINGKATAN USIA PADA DUA PREY DAN DUA PREDATOR DENGAN FUNGSI RESPON MONOD HALDANE DAN KANIBALISME

This paper discusses a predator-prey stage structure model for two predators and two preys with Monod Haldane and cannibalism response functions that describe the interactions between populations of young prey, adult prey, young predator, and adult predator. In this model it is assumed that only adult predators are capable of attacking to consume young predators, only adult prey are capable of reproduction, there is a Monod-Haldane effect describing the phenomenon of group defense where predation is reduced, or even prevented altogether, because the ability increases from prey for further defense or camouflage when their numbers are large enough. Dynamic analysis is carried out by determining the equilibrium point and its existence conditions and analyzing the local stability of the equilibrium point. The predator-prey model has three equilibrium points, namely the trivial equilibrium point, the prey free equilibrium point and an interior point that exists under certain conditions. The equilibrium points is locally asymptotically stable under certain conditions. The results of the numerical simulations show suitability with the results of dynamic analysis.

Evaluation of Feeding Preference and Potential of Phytoseiid Predatory Mite <i>Neoseiulus longispinosus</i> (Evans) on Different Stages of <i>Tetranychus macfarlanei</i> Baker & Pritchard

The prey stage preference and feeding potential of active stages of the predatory mite Neoseiulus longispinosus (Evans) were studied under laboratory condition 23±1° C to 28±1° C and 70-80% RH using lifestages of Tetranychus macfarlanei (Baker and Pritchard). Prey stage preference was studied by providing known number of prey stages together on a leaf bit where, larva of predator did not consume any prey stage. Protonymph and deutonymph exhibited preference towards larval and nymphal stages of the prey whereas, adult predator showed preference for larval stage followed by eggs and nymphal stages. In feeding potential study, predator was offered prey stages individually. Protonymph and deutonymph consumed 2.40 and 4.00 eggs, 3.40 and 4.70 larvae, 1.60 and 3.20 nymphs and 0.20 and 0.20 adults of the prey, respectively and the adult predator consumed a mean of 159.00 eggs, 171.60 larvae, 94.20 nymphs and 19.20 adults of prey in its lifespan.

Role reversal in a stage-structured prey-predator model with fear, delay, and carry-over effects.

The present work highlights the reverse side of the same ecological coin by considering the counter-attack of prey on immature predators. We assume that the birth rate of prey is affected by the fear of adult predators and its carry-over effects (COEs). Next, we introduce two discrete delays to show time lag due to COEs and fear-response. We observe that the existence of a positive equilibrium point and the stability of the prey-only state is independent of fear and COEs. Furthermore, the necessary condition for the co-existence of all three species is determined. Our system experiences several local and global bifurcations, like, Hopf, saddle-node, transcritical, and homoclinic bifurcation. The simultaneous variation in the attack rate of prey and predator results in the Bogdanov-Takens bifurcation. Our numerical results explain the paradox of enrichment, chaos, and bi-stability of node-focus and node-cycle types. The system, with and without delay, is analyzed theoretically and numerically. Using the normal form method and center manifold theorem, the conditions for stability and direction of Hopf-bifurcation are also derived. The cascade of predator attacks, prey counter-attacks, and predator defense exhibit intricate dynamics, which sheds light on ecological harmony.

Feeding efficiency of Coccinella septempunctata Linnaeus and Propylea luteopustulata (Mulsant) against Mustard aphid Lipaphis erysimi (Kaltenbach)

Ladybird beetles are efficient natural predators of aphids, particularly the ladybird beetles are efficient natural predators of aphids, particularly the widespread mustard pest, Lipaphis erysimi. This study compared the feeding efficiency of two adult predator ladybird beetle species Coccinella septempunctata and Propylea luteopustulata against L. erysimi in an experimental set-up for forty-nine days from 29 December 2019 to 15 February 2020. Five replicates of each beetle species were supplied with 100 aphids daily and their feeding rate was counted. Negative binomial regression analysis of these predator beetles showed that C. septempunctata consumed a significantly high number of mustard aphid individuals (29.42 ± 1.33) than P. luteopustulata (23.20 ± 1.07) at room temperature and relative humidity. Temperature and relative humidity also influenced the feeding rate of these beetles. The feeding rate of P. luteopustulata against a mustard pest aphid is described for the first time. The findings of the study will be an important aspect in the biological control of pests in Nepalese agroecosystems.

Predator potential and prey stage preference of Neoseiulus longispinosus (Acari: Phytoseiidae) to life stages of Tetranychus urticae and T. macfarlanei (Acari: Tetranychidae)

Spider mites are considered as a potential threat to varying agricultural crops across the globe. Among the agriculturally important spider mite species, Tetranychus urticae Koch and Tetranychus macfarlanei Baker and Pritchard severely affect crop production and incur heavy yield loss in agriculture sector. As an ecofriendly pest management strategy, biocontrol using phytoseiid predatory mites are gaining significant attention over the past few decades. Evaluation of predatory potential and prey stage preference could provide invaluable information on the predatory efficiency of any predators. Feeding experiments were conducted using the phytoseiid predatory mite, Neoseiulus longispinosus (Evans) on mulberry leaf discs under the laboratory conditions of 30±2ºC, 70±5% Relative Humidity (RH) and a photoperiod of 11 L: 14 D h. After 24 hr of feeding experiment, the nymph and adult female predator exhibited a significant preference in feeding towards the eggs of T. urticae and T. macfarlanei. The larval stage of the predator was found to be non-feeding, thus excluded from the feeding experiment. The order of feeding preference of adult female predator towards different life stages of both the spider mite species were identified as egg>nymph>larva>adult. On the contrary, the predatory nymphal stage exhibited different trend in feeding preference towards the life stages of T. urticae and could be recorded as egg>larva>nymph>adult. For T. macfarlanei, the same could be found as egg>larva=nymph>adult. Surprisingly, irrespective of the life stage differences, N. longispinosus hardly consumed any of the T. macfarlanei adults.

Role of multiple time delays on a stage-structured predator–prey system in a toxic environment

In this paper, a stage-structured predator–prey model is considered in a toxic environment, emphasizing on the affect of the toxic substances on growth of the species in presence of time delays. The positivity and boundedness of solutions have been discussed. The analytical and numerical simulations of the proposed model show that the coexistence equilibrium point is stable for low and moderate values of the delay parameter associated with the predator’s maturity. Even though there is an interval of the maturation time in which the system exhibits oscillatory behaviour, a longer maturity duration may lead to the extinction of the predator species. The impact of toxicity on the proposed system is also investigated. The stability of the system repeatedly switches as the time delay, related to the changes of toxicity incurred in the adult predator, varies, and finally becomes unstable for a significant value of it. Besides that, the delay related to the prey’s toxicity has also led some exciting results.

Geographical variation in nest defense among cinereous tit populations in China.

Behavioral divergence among populations is common across taxonomic groups, still we know very little about anti-predator behaviors. Animal exposure to predation risk is variable in different ecological contexts. In addition, reproduction value of animals in different geographical regions usually varies. In this study, we tested whether cinereous tits Parus cinereus in different populations exhibited nest defense behaviors similar to those of nest or adult predators and whether their nest defense behaviors showed geographical variation. By using field dummy experiments, we observed tits' nest defense behavior in nest predator common chipmunk Tamias sibiricus and red squirrel Sciurus vulgaris, adult predator Eurasian sparrowhawk Accipiter nisus and nonthreatening species Oriental turtle dove Streptopelia orientalis in the ZJ (44° N), DZ (31° N), and DLS (18° N) populations, respectively. The response scores varied significantly across the 4 dummies in ZJ-tits and DLS-tits but did not in DZ-tits. When facing the chipmunk, ZJ-tits showed the highest response score and DZ-tits showed the lowest response score. When facing the squirrel, ZJ-tits showed a higher response score than tits in the other 2 populations. However, tits among the 3 populations responded similarly to a sparrowhawk or dove with slight response behaviors. In addition, response scores to nest predators were positively correlated with brood size across the 3 populations, but no trend was found for sparrowhawks or doves. Our results indicated that the nest defense behaviors of cinereous tits have evolved in response to large-scale geographical variation in ecological contexts and reproduction value.

Diversity and Seasonality of Aquatic Beetles (Coleoptera) in Three Localities of the State of Tlaxcala, Central Mexico

Aquatic beetle diversity was compared between three study sites in the state of Tlaxcala, central Mexico: Stream 1 (San Ambrosio), stream 2 (San Tadeo), and a lake (Acuitlapilco). Sampling took place bimonthly during an annual cycle. A total of 2968 specimens were obtained, which were grouped into twenty three species, fifteen genera, and six families (Elmidae, Dryopidae, Dytiscidae, Gyrinidae, Haliplidae, and Hydrophilidae). Stream 2 showed the highest values of abundance (1570 individuals), while stream 1 had the highest richness (18 species). Abundance values showed two peaks each in rainy and dry seasons. The proportion of rare and dominant species was similar in all study sites. Based on species accumulation curves, the maximum estimated number of species has not been achieved in either of the three sites. Regarding alpha diversity (effective number of species), stream 1 presented the highest zero-order diversity estimated with 18.5 species. Regarding beta diversity, lotic systems (streams 1 and 2) presented a similarity of 75%. Finally, regarding the trophic structure of the adult aquatic beetle community, herbivores, predators, and decomposers were most representative in this study. Based on our results, Tlaxcala probably holds a significant diversity of aquatic beetles. This appears to indicate that species composition in geographic areas, regardless of their relatively small size, is worth documenting and, of course, preserving.

The impact of fear effect on the dynamics of a delayed predator–prey model with stage structure

In this paper, a stage structure predator–prey model consisting of three nonlinear ordinary differential equations is proposed and analyzed. The prey populations are divided into two parts: juvenile prey and adult prey. From extensive experimental data, it has been found that prey fear of predators can alter the physiological behavior of individual prey, and the fear effect reduces their reproductive rate and increases their mortality. In addition, we also consider the presence of constant ratio refuge in adult prey populations. Moreover, we consider the existence of intraspecific competition between adult prey species and predator species separately in our model and also introduce the gestation delay of predators to obtain a more realistic and natural eco-dynamic behaviors. We study the positivity and boundedness of the solution of the non-delayed system and analyze the existence of various equilibria and the stability of the system at these equilibria. Next by choosing the intra-specific competition coefficient of adult prey as bifurcation parameter, we demonstrate that Hopf bifurcation may occur near the positive equilibrium point. Then by taking the gestation delay as bifurcation parameter, the sufficient conditions for the existence of Hopf bifurcation of the delayed system at the positive equilibrium point are given. And the direction of Hopf bifurcation and the stability of the periodic solution are analyzed by using the center manifold theorem and normal form theory. What’s more, numerical experiments are performed to test the theoretical results obtained in this paper.