Moving forward in circles: challenges and opportunities in modelling population cycles

Population cycling is a widespread phenomenon, observed across a multitude of taxa in both laboratory and natural conditions. Historically, the theory associated with population cycles was tightly linked to pairwise consumer–resource interactions and studied via deterministic models, but current empirical and theoretical research reveals a much richer basis for ecological cycles. Stochasticity and seasonality can modulate or create cyclic behaviour in non-intuitive ways, the high-dimensionality in ecological systems can profoundly influence cycling, and so can demographic structure and eco-evolutionary dynamics. An inclusive theory for population cycles, ranging from ecosystem-level to demographic modelling, grounded in observational or experimental data, is therefore necessary to better understand observed cyclical patterns. In turn, by gaining better insight into the drivers of population cycles, we can begin to understand the causes of cycle gain and loss, how biodiversity interacts with population cycling, and how to effectively manage wildly fluctuating populations, all of which are growing domains of ecological research

Analisis dinamik model predator-prey tipe Gause dengan wabah penyakit pada prey

This article studies the dynamics of a Gause-type predator-prey model with infectious disease in the prey. The constructed model is a deterministic model which assumes the prey is divided into two compartments i.e. susceptible prey and infected prey, and both of them are hunted by predator bilinearly. It is investigated that there exist five biological equilibrium points such as all population extinction point, infected prey and predator extinction point, infected prey extinction point, predator extinction point, and co-existence point. We find that all population extinction point always unstable while others are conditionally locally asymptotically stable. Numerical simulations, as well as the phase portraits, are given to support the analytical results

The Effects of Stocking Density and Feeding Frequency on Aggressive and Cannibalistic Behaviors in Larval Hatchery-Reared Spotted Seatrout, \u3ci\u3eCynosion nebulosus\u3c/i\u3e

The Spotted Seatrout (Cynoscion nebulosus) is a euryhaline fish that inhabits coastal regions from Massachusetts to Texas. Due to its predaceous nature and proximity to coastal shorelines it is the most important marine finfish in the Gulf of Mexico. Because of this importance, Spotted Seatrout has been identified as a possible candidate for stock enhancement. Stock enhancement is the practice of releasing hatchery-reared juveniles to increase local recruitment beyond existing levels. However, raising enough Spotted Seatrout in an intensive aquaculture system has proven difficult due to aggression and cannibalism during the larval stages. The manipulation of stocking density as well as feeding frequency might be used to reduce aggression and cannibalism. The goal of this study was to determine the effects of stocking density and feeding frequency on aggressive and cannibalistic behaviors in larval hatchery-reared Spotted Seatrout at both small-and production-scales. For the first two small-scale experiments, fish larvae were filmed and behaviors were quantified. Three different aggressive behaviors were quantified: nip (aggressor strikes prey causing prey to dart), chase (aggressor moves more than one body length toward prey), and capture (predator captures and holds prey but unable to consume). From these experiments, the author found that in all stocking densities (15, 30, and 60 fish L-1) there was a significant increase in aggression and cannibalism with time since feeding; and the author identified a density threshold of 30 fish L-1, beyond which the intensity of aggressive behaviors did not increase. These results implied that aggression in early stage hatchery-reared Spotted Seatrout might be alleviated by increasing feeding frequency, and furthermore, the Spotted Seatrout possibly could be cultured at densities higher than the current protocol allows. From the second experiment, the author concluded that the 2 h feeding frequency treatment elicited fewer aggressive and cannibalistic acts than the 1 h, 4 h, and 8 h treatments. Lower levels of aggression and cannibalism associated with the 2 h feeding frequency treatment could be attributed to a balance between the optimal amount of live feed and the gut evacuation rate of larval Spotted Seatrout. In the third large-scale production experiment, I found a significantly lower per capita mortality and correspondingly higher specific growth rate for the 30 fish L-1 treatment than for the lower density 15 fish L-1 treatment. This difference resulted in a 45% higher production yield within the high density treatment. Due to logistical constraints, only two replicates were available for the production experiment. Thus, the statistical power of this experiment was low; however, directional trends consistently suggested biological importance. Feeding every 2 h suggested an apparent decrease in per capita mortality, leading to a 15% increase in production. The observed higher specific growth in the high density treatment likely reflected a decrease in aggression. Also, size heterogeneity did not differ between density treatments, reinforcing the case that using a higher stocking density and a 2 h feeding frequency schedule should be ideal for the production of larval Spotted Seatrout. Overall, the results from the production-scale run were consistent with the results of the two earlier small-scale experiments, suggesting that a stocking density of 30 fish L-1 and a feeding frequency of 2 h should be effective for reducing aggression and cannibalism in the culture of Spotted Seatrout

Predator-prey models with cannibalism in prey

Cannibalism in the predator-prey model is the study to show the interaction between prey and predator where the presence of cannibalism exists in both species in real life. Moreover, cannibalism is ubiquitous in natural communities and also among researchers who are interested in mathematical ecology. The predator-prey model system is modelled using ordinary differential equations to describe the dynamic behaviour of the systems. This study introduces the stage-structured models where the adult and juvenile prey species are considered. The purpose of the study is to analyse the effect of the stage-structured of prey cannibalism on the stability based on the concept of Lotka-Volterra in the predator-prey model. Thus, in this study, there are two cases are considered: prey cannibalism in the predator-prey model with predation on adult prey and model with predation on juvenile prey. The objectives of this research are (i) to formulate the concept of Lotka-Volterra in a predator-prey model, (ii) to analyse prey cannibalism in predator-prey model with predation on adult prey, (iii) to analyse the predator-prey in prey cannibalism with predation on juvenile prey, and (iv) to analyse the effect of stage-structured predator-prey model with cannibalism in prey on stability. In analysing the models, the stability of the equilibrium point is obtained and described by using the properties of the eigenvalues and the Routh-Hurwitz Criteria. Last but not least, numerical examples and graph analysis are given to illustrate the stability of equilibrium points

Dynamical Behavior of an Eco-epidemiological Model Incorporating Prey Refuge and Prey Harvesting

In this paper an eco-epidemiological model incorporating a prey refuge and prey harvesting with disease in the prey-population is considered. Predators are assumed to consume both the susceptible and infected prey at different rates. The positivity and boundedness of the solution of the system are discussed. The existence and stability of the biologically feasible equilibrium points are investigated. Numerical simulations are performed to support our analytical findings

The price of defence: Maternal effects in an aposematic ladybird

Offspring phenotype can be adaptively altered via maternal non-genetic inheritance. Such ‘maternal effects’ enable females to adjust their per offspring investment in response to variation in the offspring environment, and thus maximise their reproductive success. Consequently they play a pivotal role in population dynamics and the response of species to environmental change. Despite this, little is known about how maternal effects mediate reproductive investment in response to multiple or novel environmental changes, such as those driven by anthropogenic activity. I use the 2-spot ladybird intraguild predation system, where resources and predation risk are highly variable, to explore the role of maternal effects in the response of a native species to an invasive predator, as well as answering outstanding questions about how maternal effects function under complex and antagonistic sets of variables. The results indicate that it is unlikely that maternally mediated changes in egg phenotype will improve the survival of 2-spot ladybird offspring in the face of predation from larvae of the invasive harlequin ladybird. They do, however, demonstrate the importance of studying maternal effects in the context of the multiple environmental factors, which more accurately represent the complex environments in which organisms live and evolve, corroborating recent theoretical predictions. Finally I provide evidence of the multifaceted nature of parental effects in aposematic species and reveal the role that they may play in shaping the variation in defence and warning coloration observed in adult populations.NER

A Review of Chaos Control Strategies for Tri-trophic Food Chain Ecological Systems

The existence of chaos in ecological models is quite obvious due to the presence of nonlinear terms. Controlling chaotic phenomena in ecological systems remains a difficult task due to their unpredictability, and thus chaos control is one of the main objectives for constructing mathematical models in ecology today. Our aim in this paper is to review chaos control strategies for the tri-trophic food chain models by using various ecological factors. The factors include additional food, prey refuge, the Allee effect, the fear effect, and harvesting. We establish the essential conditions for the existence of ecologically feasible equilibrium points in the food chain ecological systems and their local stability. This paper provides a unified overview of recent research on the chaos control of ecological systems. The theoretical results suggest a way to control populations of species in ecological systems for fishing and pest management in farming. Numerical examples are performed to justify and compare the theoretical findings through phase portraits and bifurcation diagrams

Zombies: a simple discrete model of the apocalypse

A simple discrete-time two-dimensional dynamical system is constructed and analyzed numerically, with modelling motivations drawn from the zombie virus of popular horror fiction, and with suggestions for further exercises or extensions suitable for an introductory undergraduate course

Smart carnivores think twice: Red fox delays scavenging on conspecific carcasses to reduce parasite risk

M.M. was supported by a research contract Ramon y Cajal from the MINECO (RYC-2015-19231) . This study was partly funded by the Spanish Ministry of Economy, Industry and Competitiveness and EU ERDF funds through the project CGL2017-89905-R.The recent SARS-CoV-2 epidemic has highlighted the need to prevent emerging and re-emerging diseases, which means that we must approach the study of diseases from a One Health perspective. The study of pathogen transmission in wildlife is challenging, but it is unquestionably key to understand how epidemiological interactions occur at the wildlife-domestic-human interface. In this context, studying parasite avoidance behaviours may provide essential insights on parasite transmission, host-parasite coevolution, and energy flow through food-webs. However, the strategies of avoiding trophically transmitted parasites in mammalian carnivores have received little scientific attention. Here, we explore the behaviour of red foxes (Vulpes vulpes) and other mammalian carnivores at conspecific and heterospecific carnivore carcasses using videos recorded by camera traps. We aim to determine 1) the factors influencing the probability of foxes to practice cannibalism, and 2) whether the scavenging behaviour of foxes differ when facing conspecific vs. heterospecific carcasses. We found that red foxes were generally reluctant to consume mesocarnivore carrion, especially of conspecifics. When recorded, consumption by foxes was delayed several days (heterospecific carcasses) or weeks (conspecific carcasses) after carcass detection. Other mammalian scavengers showed a similar pattern. Also, meat-borne parasite transmission from wild carnivore carcasses to domestic dogs and cats was highly unlikely. Our findings challenge the widespread assumption that cannibalistic or intra-specific scavenging is a major transmission route for Trichinella spp. and other meat-borne parasites, especially for the red fox. Overall, our results suggest that the feeding decisions of scavengers are probably shaped by two main contrasting forces, namely the nutritional reward provided by carrion of phylogenetically similar species and the risk of acquiring meat-borne parasites shared with these species. This study illustrates how the detailed monitoring of carnivore behaviour is essential to assess the epidemiological role of these hosts in the maintenance and dispersion of parasites of public and animal health relevance.MINECO RYC-2015-19231Spanish Ministry of Economy, Industry and CompetitivenessEuropean Commission CGL2017-89905-