Intrinsic Growth Rate Research Articles

Combined toxic effects of yessotoxin and polystyrene on the survival, reproduction, and population growth of rotifer Brachionus plicatilis at different temperatures.

Yessotoxin (YTX) is a disulfated toxin produced by harmful dinoflagellates and causes risks to aquatic animals. Polystyrene (PS) microplastics could absorb toxins in seawaters but pose threats to organism growth. In this study, the combined toxic effects of YTX (0, 20, 50, and 100 µg L-1) and PS (0, 5, and 10 µg mL-1) on the survival, reproduction, and population growth of marine rotifer Brachionus plicatilis at 20 °C, 25 °C, and 30 °C were evaluated. Results indicated that the survival time (S), time to first batch of eggs (Ft), total offspring per rotifer (Ot), generational time (T0), net reproduction rate (R0), intrinsic growth rate (rm), and population growth rate (r) of rotifers were inhibited by YTX and PS at 25 °C and 30 °C. Low temperature (20 °C) improved the life-table parameters T0, R0, and rm at YTX concentrations less than 100 µg L-1. Temperature, YTX, and PS had interactive effects on rotifers' S, Ft, Ot, T0, R0, rm, and r. The combined negative effects of YTX and PS on rotifers' survival, reproduction, and population growth were significantly enhanced at 30 °C. These findings emphasized the importance of environmental temperature in studying the interactive effects of microplastics and toxins on the population growth of zooplankton in eutrophic seawaters.

Cd indirectly affects the structure and function of plankton ecosystems by affecting trophic interactions at environmental concentrations

The toxic effects of potentially toxic elements have been observed at low concentrations; however, many studies have focused on single-species toxicity testing. Consequently, it is imperative to quantify toxicity at the community level at environmental concentrations. A microcosm approach was employed in conjunction with the Lotka-Volterra model to ascertain the impact of environmentally relevant concentrations of cadmium (Cd) on plankton abundance, community function, and stability. The results demonstrated that Cd led to a reduction in the abundance of Daphnia magna, yet unexpectedly resulted in an increase in the abundance of Brachionus calyciflorus and Paramecium caudatum. Additionally, Cd was observed to impede primary productivity, metabolic capacity and the stability of the planktonic community. Further model analyses revealed that the environmental concentration of Cd directly reduced intrinsic growth rates and intraspecific interactions. In particular, we found that the predation effects of Daphnia magna on Brachionus calyciflorus were significantly weakened. The findings of this study offer quantitative evidence that Cd exposure exerts an indirect influence on the structure and functioning of plankton ecosystems, mediated by alterations in trophic interactions. The findings indicate that the impact of environmental concentrations of potentially toxic elements may be underestimated in single-species experiments.

The potential for species distribution models to distinguish source populations from sinks.

While species distribution models (SDM) are frequently used to predict species occurrences to help inform conservation management, there is limited evidence evaluating whether habitat suitability can reliably predict intrinsic growth rates or distinguish source populations from sinks. Filling this knowledge gap is critical for conservation science, as applications of SDMs for management purposes ultimately depend on these typically unobserved population or metapopulation dynamics. Using linear regression, we associated previously published population level estimates of intrinsic growth and abundance derived from a Bayesian analysis of mark-recapture data for 17 bird species found in the contiguous United States with SDM habitat suitability estimates fitted here to opportunistic data for these same species. We then used the area under the ROC curve (AUC) to measure how well SDMs can distinguish populations categorized as sources and sinks. We built SDMs using two different approaches, boosted regression trees (BRT) and generalized linear models (GLM), and compared their source/sink predictive performance. Each SDM was built with presence points obtained from eBird (a web-available database) and 10 environmental variables previously selected to model intrinsic growth rates and abundance for these species. We show that SDMs built with opportunistic data are poor predictors of species demography in general; both BRT and GLM explained very little spatial variation of intrinsic growth rate and population abundance (median R2 across 17 species was close to 0.1 for both SDM methods). SDMs, however, estimated higher suitability for source populations as compared to sinks. Out of 13 species which had both source and sink populations, both BRT and GLM had AUC values greater than 0.7 for 7 species when discriminating between sources and sinks. Habitat suitability have the potential to be a useful measure to indicate a population's ability to sustain itself as a source population; however more research on a diverse set of taxa is essential to fully explore this potential. This interpretation of habitat suitability can be particularly useful for conservation practice, and identification of explicit cases of when and how SDMs fail to match population demography can be informative for advancing ecological theory.

Host-Parasitoid Systems are Vulnerable to Extinction via P-Tipping: Forest Tent Caterpillar as an Example.

Continuous-time predator-prey models admit limit cycle solutions that are vulnerable to the phenomenon of phase-sensitive tipping (P-tipping): The predator-prey system can tip to extinction following a rapid change in a key model parameter, even if the limit cycle remains a stable attractor. In this paper, we investigate the existence of P-tipping in an analogous discrete-time system: a host-parasitoid system, using the economically damaging forest tent caterpillar as our motivating example. We take the intrinsic growth rate of the consumer as our key parameter, allowing it to vary with environmental conditions in ways consistent with the predictions of global warming. We find that the discrete-time system does admit P-tipping, and that the discrete-time P-tipping phenomenon shares characteristics with the continuous-time one: Both require an Allee effect on the resource population, occur in small subsets of the phase plane, and exhibit stochastic resonance as a function of the autocorrelation in the environmental variability. In contrast, the discrete-time P-tipping phenomenon occurs when the environmental conditions switch from low to high productivity, can occur even if the magnitude of the switch is relatively small, and can occur from multiple disjoint regions in the phase plane.

Evaluating the effects of short-term low temperature on the growth and development of Trichopria drosophilae based on the age–stage two-sex life table

BackgroundThe effects of low temperatures on parasitic wasps are crucial for maintaining farmland biodiversity and enhancing biological control, especially given the implications of global warming and frequent extreme cold events.MethodsWe studied the effects of different low temperatures (−8 ± 1 °C, −4 ± 1 °C, 0 ± 1 °C, 4 ± 1 °C, and 8 ± 1 °C) on the mating frequency and duration of male adults of Trichopria drosophilae and the number of pupae beaten by female adults, and constructed the age–stage two-sex life table of T. drosophilae.ResultsThis study found that male T. drosophilae adults exposed to low temperatures for 12 h significantly altered their mating behavior, peaking between 15:00 and 17:00. As the temperature dropped during the exposure, both the mating frequency of T. drosophilae and the duration of pupal beating were affected. The survival rate of female adults dropped from 39.55% at 8 °C to just 21.17% at −8 °C. Low-temperature treatment shortened the development period and lifespan for T. drosophilae adults. They developed 4.71 days faster and had a total lifespan that was 10.66 days shorter than those in the control group after being exposed to −8 °C. Furthermore, the average number of eggs laid by females at −8 °C was 4.46 less than that at 8 °C and 6.16 less than that in the control group, which laid an average of 21.55 eggs. The net reproductive rate (R0) of T. drosophilae decreased with lower temperatures, reaching a low of 23.64 at −8 °C. Conversely, the intrinsic growth rate (rm) actually increased as temperatures dropped, with the lowest value being 0.21 at −8 °C.ConclusionsThe findings indicate that short-term exposure to low temperatures hampers the growth and population increase of T. drosophilae, thereby reducing their effectiveness as biological control agents.Graphical

The assembly and dynamics of ecological communities in an ever‐changing world

AbstractAlternative perspectives on the maintenance of biodiversity and the assembly of ecological communities suggest that both processes cannot be investigated simultaneously. In this concept and synthesis, we challenge this view by presenting major theoretical advances in structural stability and permanence theory. These advances, which provide complementary views, allow studying the short‐ and long‐term dynamics of ecological communities as changes in species richness, composition, and abundance. Here, the global attractor, technically named informational structure (IS), is the central element to construct from information of species' intrinsic growth rates and their strength and sign of interactions. The global attractor has four main properties: (1) It contains all the limits of what is feasible and unfeasible of the dynamical behavior of an ecological system, therefore, (2) it provides a thorough characterization of all combinations of species' richness and composition in which species can coexist (i.e., feasible and stable equilibrium), (3) as well as all connections (paths) of assembly between coexisting communities. Importantly, (4) such topology of coexisting communities and their connections changes when environmental (abiotic and biotic) variation affects the ability of species to grow and interact with others. Overall, these four properties allow switching from a traditional evaluation of species coexistence at equilibrium to a much more realistic nonequilibrium perspective where changes in the structure of the global attractor underlie the transient ecological dynamics. Several fields in ecology can benefit from the study of an IS. For instance, it can serve to evaluate community responses after the end of a perturbation, to design restoration trajectories, to study the consequences of biological invasions on the persistence of native species within communities, or to assess ecosystem health status. We illustrate this latter possibility with empirical observations of 7 years in Mediterranean annual grasslands. We document that extremely wet or dry years generate ISs supporting few coexisting communities and few assembly paths. The remaining communities distinguish winners from losers of ongoing climate change and indicate the limits to future community assembly opportunities. A fully tractable operational framework is readily available to understand and predict the assembly and dynamics of ecological communities in an ever‐changing world.

Adaptive Strategies and Underlying Response Mechanisms of Ciliates to Salinity Change with Note on Fluctuation Properties.

The adaptability of marine organisms to changes in salinity has been a significant research area under global climate change. However, the underlying mechanisms of this adaptability remain a debated subject. We hypothesize that neglecting salinity fluctuation properties is a key contributing factor to the controversy. The ciliate Euplotes vannus was used as the model organism, with two salinity fluctuation period sets: acute (24 h) and chronic (336 h). We examined its population growth dynamics and energy metabolism parameters following exposure to salinity levels from 15‱ to 50‱. The carrying capacity (K) decreased with increasing salinity under both acute and chronic stresses. The intrinsic growth rate (r) decreased with increasing salinity under acute stress. Under chronic stress, the r initially increased with stress intensity before decreasing when salinity exceeded 40‱. Overall, glycogen and lipid content decreased with stress increasing and were significantly higher in the acute stress set compared to the chronic one. Both hypotonic and hypertonic stresses enhanced the activities of metabolic enzymes. A trade-off between survival and reproduction was observed, prioritizing survival under acute stress. Under chronic stress, the weight on reproduction increased in significance. In conclusion, the tested ciliates adopted an r-strategy in response to salinity stress. The trade-off between reproduction and survival is a significant biological response mechanism varying with salinity fluctuation properties.

Functional roles of nicotinic acetylcholine receptors in dinotefuran and flupyrimin toxicity and their sublethal effects on Sogatella furcifera (Hemiptera: Delphacidae)

Abstract Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), a serious rice pest, has developed significant resistance to a wide range of pesticides. Neonicotinoid insecticides are currently the primary choice for controlling S. furcifera, yet their impact on the species remains poorly understood. In this study, we investigated the binding sites of a conventional insecticide (dinotefuran) and a novel insecticide (flupyrimin), and evaluated their sublethal effects on S. furcifera. Our results revealed that the LC50 of dinotefuran and flupyrimin were 2.51 mg/L and 2.80 mg/L in third-instar S. furcifera, respectively. RNA interference (RNAi) knockdown of S. furcifera nicotinic acetylcholine receptor (nAChR) alpha2 subunit (Sfα2) and S. furcifera nAChR beta1 subunit (Sfβ1) significantly reduced the susceptibility to dinotefuran by 18.7% and 16.8%, respectively, but had no effect on flupyrimin. Reproduction of the F0 and F1 generations was significantly inhibited by the LC25 of both dinotefuran and flupyrimin. In the dinotefuran treatment at LC25, the intrinsic growth rate (r) and finite growth rate (λ) were reduced to 0.15 and 0.16 days, respectively; the mean generation time (T) increased to 27.77 days, and the relative fitness was only 0.76 compared to the control. Additionally, the relative fitness (Rf) of the flupyrimin-treated group was reduced to 0.93 and 0.86 times that of the control group. The population dynamics of S. furcifera are significantly affected by both dinotefuran and flupyrimin, making these insecticides valuable tools for integrated pest management and the rational use of insecticides.

Dynamics of autonomous and nonautonomous Leslie–Gower model for the impacts of fear and its carry‐over effects including predator harvesting

Recently, certain biological field experiments and research findings have revealed that predators not only reduce prey populations through direct predation (lethal effect) but also indirectly affect the growth rate of prey by inducing fear; these nonlethal effects can be carried over seasons or generations. In this paper, we proposed an autonomous and a nonautonomous Leslie–Gower model incorporating some biological factors such as fear and its carry‐over effects, prey refuge, and nonlinear predator harvesting. In the autonomous model, first, we examined the well‐posedness, positivity solutions, and their boundedness. Also, it is shown that new equilibrium points emerge and disappear with the change in intrinsic growth rate of predator. Further, we compute and analyzed the local and global stability at the interior equilibrium points. Furthermore, Hopf bifurcation and direction and stability of limit cycle at interior equilibrium points are established. Moreover, the sensitivity analysis of the biological parameters is carried out numerically with two statistical methods via Latin hypercube sampling and partial rank correlation coefficients. It was found that at the small values of fear factor, carry‐over effect, and refuge behavior of prey parameters, the autonomous system exhibits oscillatory behavior, whereas for small values of prey birth rate and harvesting effort, the system remains stable. However, when intrinsic growth rate of predator increases from a low value to a higher value, the system shows transition from stability to instability and back to stability. We also explore the effects of seasonal variations in biological parameters in the nonautonomous model. Additionally, we investigate the theoretical existence of positive periodic solutions using the continuation theorem. The influences of seasonal variations in some parameters such as prey's birth rate, fear, and its carry‐over effects; refuge behavior of prey; intrinsic growth rate of predator; and harvesting effort are then numerically investigated. The results reveal the emergence of positive periodic solutions and bursting patterns in the seasonally forced model.

Local population dynamics of gray wolves Canis lupus and Eurasian lynx Lynx lynx exhibit consistency with intraspecific contest competition models

AbstractIn Europe, the gray wolf and Eurasian lynx populations are recovering after various levels of persecution. The two species differ in their social structure and spatial patterns of aggregation. Using model selection, we investigated the consistency of the available time series data on local wolf and lynx sub‐populations with a number of single‐species population growth models that pertain to two types of intraspecific competition, namely, scramble (SC) and contest competition (CC), and reflect random (R) or aggregated (A) distribution of individuals. The applied models of population growth—the Ricker (SCR), Skellam (CCR), Hassell (SCA), and Beverton–Holt (CCA) models—were all parameterized in terms of intrinsic growth rate and carrying capacity with unified definitions. The projected carrying capacity was allowed to show a temporal trend, which was justified by an observed increase in prey abundance in recent decades. For both species, the models pertaining to contest competition outperformed the scramble competition models, and the Beverton–Holt model had the greatest weight. However, for the lynx, the difference of performance between the scramble and contest competition models was considerably smaller than that for the wolves. In most of the models, when it was meaningful, an optional time lag operator was added to account for a delay in individual maturity and reproduction. However, the models with a time lag had a worse fit than the models without it. This study promotes the application of population models that reflect intraspecific competition for modeling population dynamics in a single‐ or multi‐species framework.

Sublethal and transgenerational effects of tetraniliprole on the tomato pinworm Phthorimaea (=Tuta) absoluta (Lepidoptera: Gelechiidae)

Invasive pest species of economic importance often require intensive pesticide use, leading to recurrent problems of pesticide resistance. Such is the case with the tomato pinworm, Phthorimaea (=Tuta) absoluta (Meyrick) (Lepidoptera: Gelechiidae), requiring the use of new insecticidal compounds for their management. Tetraniliprole, a novel insecticide effective against lepidopteran, coleopteran, and dipteran pests, is a potential alternative against the tomato pinworm. This study investigates the sublethal effects of tetraniliprole on the development and reproduction of the parental (F0) and progeny (F1) generations of P. absoluta while exploring the underlying mechanisms. Sublethal tetraniliprole exposure extended larval duration and reduced pupation rate, emergence rate, hatchability, and fecundity in both the F0 and F1 of P. absoluta. Additionally, the life-table parameters of the F1 generation were significantly altered, with decreases in net reproductive rate (R0) and increases in the mean generation time (T), leading to decreases in the intrinsic rate of population growth (r). The relative fitness of F1 insects exposed to tetraniloprole was reduced compared to unexposed insects (0.63 and 0.49, respectively). Furthermore, the mRNA expression levels of reproduction-related genes such as TaVg and TaVgR were down-regulated in the tetraniliprole-exposed insects. Finally, insect exposure to tetraniloprole increases the activity of the antioxidant enzymes such as glutathione S-transferase (GSTs), catalase (CAT), and superoxide dismutase (SOD). Taken together, these findings suggest that sublethal concentrations of tetraniloprole adversely affect both the development and reproduction of P. absoluta, providing a foundation for optimizing pest control strategies.

Role of a medicinal plant in attracting Chrysopidae predators and controlling Leucopteracoffeella

Intercropping in agricultural systems can enhance biological pest control, yet selecting the appropriate companion plants remains challenging. This study investigated the potential of Varronia curassavica Jacq. (Cordiaceae), a medicinal aromatic plant, to improve the biological control of the coffee leaf miner, Leucoptera coffeella (Lepidoptera: Lyonetiidae) by Chrysopidae predatory species. We assessed the survival of Ceraeochrysa cubana (Neuroptera: Chrysopidae) larvae and adults, and the survival and reproduction of L. coffeella adults in the presence of V. curassavica inflorescences. Additionally, we evaluated whether V. curassavica in its vegetative stage, when associated with coffee plants, would influence the oviposition of another related Chrysopidae species, Chrysoperla externa, and L. coffeella. Our findings indicated that C. cubana larvae had increased survival in the presence of V. curassavica inflorescences, whereas the survival of C. cubana and L. coffeella adults was unaffected. However, the intrinsic growth and oviposition rates of L. coffeella were reduced in the presence of V. curassavica inflorescences. Furthermore, in a greenhouse experiment, the number of eggs laid by C. externa was higher when coffee plants were intercropped with V. curassavica in the vegetative stage, while the oviposition of L. coffeella was unaffected. These results suggest that V. curassavica can enhance populations of Chrysopidae predators in coffee crops and negatively impact the fitness of L. coffeella or provide no benefit to this pest. Therefore, incorporating V. curassavica into coffee cropping systems appears promising for managing L. coffeella populations by pulling in Chrysopidae predators.

Dynamics and control of two-dimensional discrete-time biological model incorporating weak Allee's effect.

Incorporating a weak Allee effect in a two-dimensional biological model in ℜ2, the study delves into the application of bifurcation theory, including center manifold and Ljapunov-Schmidt reduction, normal form theory, and universal unfolding, to analyze nonlinear stability issues across various engineering domains. The focus lies on the qualitative dynamics of a discrete-time system describing the interaction between prey and predator. Unlike its continuous counterpart, the discrete-time model exhibits heightened chaotic behavior. By exploring a biological Mmdel with linear functional prey response, the research elucidates the local asymptotic properties of equilibria. Additionally, employing bifurcation theory and the center manifold theorem, the analysis reveals that, for all α1 (i.e., intrinsic growth rate of prey), ð1˙ (i.e., parameter that scales the terms yn), and m (i.e., Allee effect constant), the model exhibits boundary fixed points A1 and A2, along with the unique positive fixed point A∗, given that the all parameters are positive. Additionally, stability theory is employed to explore the local dynamic characteristics, along with topological classifications, for the fixed points A1, A2, and A∗, considering the impact of the weak Allee effect on prey dynamics. A flip bifurcation is identified for the boundary fixed point A2, and a Neimark-Sacker bifurcation is observed in a small parameter neighborhood around the unique positive fixed point A∗=(mð1˙-1,α1-1-α1mð1˙-1). Furthermore, it implements two chaos control strategies, namely, state feedback and a hybrid approach. The effectiveness of these methods is demonstrated through numerical simulations, providing concrete illustrations of the theoretical findings. The model incorporates essential elements of population dynamics, considering interactions such as predation, competition, and environmental factors, along with a weak Allee effect influencing the prey population.

Exponential growth model of weevil populations: a didactic experiment for undergraduate course of Population Ecology

Exponential model for population growth (exponential model) is a foundation to evaluate population dynamics in Population Ecology field. Here, we used a didactic experiment to teach exponential model for an undergraduate course of Population Ecology. We built nine populations of weevils with three different initial population sizes: eight, 16, and 32 individuals with three replicates each. We provided equal food resource availability, and counted their population sizes weekly for 12 weeks. We estimated the intrinsic growth rate (i.e., r parameter), by trials and errors with an exponential model build in an Excel spreadsheet. The population growth rate (i.e., dN/dt parameter) was estimated using r values. Replicates with eight and 16 individuals reached the highest values of r and dN/dt, while replicates with 32 individuals reached the lowest values. Beyond of exponential model, two density dependency issues acting in populations were observed. First, in the lowest initial population sizes we observed the effect of demographic stochasticity acting in both r and dN/dt in one of the three populations. Second, we observed the intraspecific competition reducing r values in largest initial populations. Therefore, we highlight the importance of didactic experiment into learning exponential model in Population Ecology course, both for teaching and learning practices.

Assessments of 12 Commercial Species Stocks in a Subtropical Upwelling Ecosystem Using the CMSY and BSM Methods

Twelve commercial species exploited in the eastern Guangdong and southern Fujian waters were assessed using the Catch-Maximum Sustainable Yield (CMSY) and Bayesian Schaefer Model (BSM) methods. The carrying capacity (k), intrinsic rate of population growth (r), maximum sustainable yield (MSY), and relative biomass (Bend/k and B/BMSY) were estimated. The current stock status was defined by B/BMSY and fishing mortality (F/FMSY). The results indicate that seven stocks were overfished or below safe biological limits (B/BMSY < 0.5 or F/FMSY > 1), two stocks were in a recovery phase (0.5 < B/BMSY < 1, F/FMSY < 1), and three stocks were under sustainable fishing pressure with healthy biomass, capable of producing yields close to the MSY (B/BMSY > 1, F/FMSY < 1). The stock statuses are consistent with previous studies on the utilization of pelagic fisheries in the eastern Guangdong and southern Fujian waters and with those assessments in other waters. The results of the assessments suggest that these stocks could be expected to produce higher sustainable catches if permitted to rebuild; thus, more effective and proactive management is needed in this upwelling fishing ground.

Effect of fear and non-linear predator harvesting on a predator–prey system in presence of environmental variability

In this paper, we have proposed and analyzed a predator–prey system introducing the cost of predation fear into the prey reproduction with Holling type-II functional response in the stochastic environment with the consideration of non-linear harvesting on predators. The system experiences Transcritical, Saddle–node, Hopf, and Bogdanov-Taken (BT) bifurcation with respect to the intrinsic growth rate and competition rate of the prey populations. We have discussed the existence and uniqueness of positive global solution of the stochastic model with the help of Ito’s integral formula and the long-term behavior of the solution is derived here. The existence of stationary distribution and explicit form of the density function is established here when only prey populations survive or both populations. We have shown that due to high fluctuation, the regime changes from one stable state to another state when bistability occurs in the system. The paper ends with some conclusions.

Turing–Hopf bifurcation in a diffusive predator–prey model with schooling behavior and Smith growth

This paper explores the dynamics of a diffusive predator–prey model, considering schooling behavior and Smith growth in prey. Initially, we have formulated the pertinent characteristic equations. Subsequently, We proceed to examine the existence of the Turing bifurcation and Hopf bifurcation, phenomena that describe the emergence of spatial and temporal patterns due to diffusion and oscillations, respectively, and focusing on the parameters of the intrinsic growth rate γ and the diffusion coefficient d2 of the prey. Finally, we conduct numerical simulations to validate our theoretical findings and further illustrate the dynamics of the predator–prey system, considering schooling behavior and Smith growth in prey.

Evaluation of the temperature adaptation of three rubber tree pest mites based on their two-sex life table.

To determine the optimal temperature range for the development and reproduction of three spider mites (Eotetranychus sexmaculatus, Eotetranychus orientalis, and Oligonychus biharensis), this study investigated their developmental period, survival rate, lifespan, and reproduction under five temperatures, 21, 24, 27, 30, and 33°C, to predict and control in the field. With the gathered data, a two-sex life table was constructed for each of them. The results revealed that as the temperature increased, both O. biharensis and E. orientalis displayed a gradual reduction in their generation period. Furthermore, an inverse relationship was observed between lifespan and temperature for all three spider mite species. When examining the survival rates at varying temperatures, E. sexmaculatus exhibited the highest rate (98%) at 33°C, while E. orientalis and O. biharensis demonstrated their highest survival rates at 24°C, reaching 90% and 100% respectively. Regarding reproduction, O. biharensis displayed the highest oviposition rates at 30°C with an average of 17.45 eggs per individual. Conversely, E. sexmaculatus and E. orientalis exhibited the highest oviposition rates at 33°C, averaging at 15.22 and 21.38 eggs per individual respectively. Significantly higher intrinsic growth rates were observed for O. biharensis and E. orientalis at 33°C, with rates of 0.22 and 0.26 respectively. In contrast, E. sexmaculatus demonstrated the highest intrinsic growth rate at 27°C. The temperature of 27°C was more suitable for the growth of the E. sexmaculatus, while 33°C was the optimal temperature for the E. orientalis and O. biharensis. The current findings provide valuable guidance for the control and prevention of these three spider mites.

Exploring ocean pH dynamics via a mathematical modeling with the Caputo fractional derivative

AbstractGlobal warming is a complex problem with far-reaching global implications. One of its notable repercussions is the escalation of $$CO_2$$ C O 2 levels in the atmosphere, resulting in the phenomenon known as Ocean Acidification (OA). In this research, we have established a correlation between four key factors: marine species, human population, $$CO_2$$ C O 2 levels, and ocean pH. By formulating a Caputo fractional differential equation, we investigated the dynamics of these variables to evaluate the significance of this climatic phenomenon. The model analysis reveals that the rise in anthropogenic $$CO_2$$ C O 2 emissions causes a reduction in the ocean’s pH level and increases OA. This process, in turn, decreases the ocean’s ability to absorb $$CO_2$$ C O 2 , making it less effective in mitigating climate change. In this study, it was demonstrated that elevated levels of $$CO_2$$ C O 2 result in a reduction in pH levels, which in turn causes a decrease in the population of marine species that play a critical role in numerous economic sectors such as tourism, aquaculture, and fisheries. Moreover, we conducted a comprehensive analysis of the influence exerted by the intrinsic growth rate of the human population. We examined various theoretical aspects, including the assessment of existence and uniqueness. Numerical simulations are carried out to illustrate the effect of key parameters on the dynamics of the system using the generalized Adams–Bashforth–Moulton method.

A stochastic hormesis Ricker model and its application to multiple fields

Random noise pervades ecosystems and has the potential for having major impacts on the growth processes of pest populations. In this paper, we aim to investigate the impact of random perturbations on the hormesis Ricker model by considering control measures applied within each generation which can generate hormetic effects, where randomness is characterized by a uniform discrete distribution and white noise, respectively. The main results indicate that the addition of discrete randomness will make the model appear with blurred orbits when the intrinsic growth rate is large enough. The position of the random variable, at the end of each generation or within each generation, cause the blurred orbits to exhibit various forms. Moreover, the effects of variances and expectations of the discrete uniform random variable on the dynamics are evaluated. Further, the introduction of randomness increases the hormetic zone and the maximum response, but can increase or decrease the monotonically increasing interval under different parameter values. In contrast, the stochastic model characterized by white noise, exhibits only a small effect on the bifurcation diagrams with respect to the intrinsic growth rate and the hormesis, which may be attributed to the mean of its noise being zero. Finally, we fit the stochastic model to experimental hormetic data sets observed in multiple fields, and our results demonstrate that the stochastic hormesis Ricker model can capture the characteristics of these data accurately. These findings could provide valuable insights into the understanding of the complexities of pest population dynamics, with implications for better pest control, resource management and for other complex biological systems such as toxicology and drug development.