Cannibalism in Size-Structured Systems

2013 ◽  
Author(s):  
André M. de Roos ◽  
Lennart Persson
Keyword(s):  
Population Dynamics ◽  
Population Level ◽  
Metabolic Rates ◽  
Intraspecific Interaction ◽  
Individual Level ◽  
Structured Systems ◽  
Level Model ◽  
Continuous Population ◽  
Resource System ◽  
Consumer Resource

The previous two chapters discussed how the size scaling of foraging and metabolic rates affected the dynamics of consumer-resource systems. Using different modeling approaches, it was shown that stage-dependent competitive ability was the main predictor of population dynamics; that is, it largely set the conditions for different types of cycles to occur. This chapter adds another intraspecific interaction on top of the consumer-resource system, namely, cannibalism. It uses a discrete-continuous population-level model based on individual-level net-production energetics to investigate the effects of cannibalism. The focus will be on the effects of cannibalism on population dynamics related to four processes that have been discussed in the literature regarding cannibalism: effects on mortality, competition, energy gain, and the size dependence of interactions.

scholarly journals The Normative Underpinnings of Population-Level Alcohol Use: An Individual-Level Simulation Model

2020 ◽  
Vol 47 (2) ◽  
pp. 224-234
Author(s):  
Charlotte Probst ◽  
Tuong Manh Vu ◽  
Joshua M. Epstein ◽  
Alexandra E. Nielsen ◽  
Charlotte Buckley ◽  
...  
Keyword(s):  
Alcohol Use ◽  
Social Norms ◽  
Drinking Behavior ◽  
Population Level ◽  
Drinking Patterns ◽  
Individual Level ◽  
Behavioral Rules ◽  
Level Model ◽  
The Individual ◽  
The Impact

Background. By defining what is “normal,” appropriate, expected, and unacceptable, social norms shape human behavior. However, the individual-level mechanisms through which social norms impact population-level trends in health-relevant behaviors are not well understood. Aims. To test the ability of social norms mechanisms to predict changes in population-level drinking patterns. Method. An individual-level model was developed to simulate dynamic normative mechanisms and behavioral rules underlying drinking behavior over time. The model encompassed descriptive and injunctive drinking norms and their impact on frequency and quantity of alcohol use. A microsynthesis initialized in 1979 was used as a demographically representative synthetic U.S. population. Three experiments were performed in order to test the modelled normative mechanisms. Results. Overall, the experiments showed limited influence of normative interventions on population-level alcohol use. An increase in the desire to drink led to the most meaningful changes in the population’s drinking behavior. The findings of the experiments underline the importance of autonomy, that is, the degree to which an individual is susceptible to normative influence. Conclusion. The model was able to predict theoretically plausible changes in drinking patterns at the population level through the impact of social mechanisms. Future applications of the model could be used to plan norms interventions pertaining to alcohol use as well as other health behaviors.

Example Four: Facultative Anadromy in Salmonid Fishes

2020 ◽  
pp. 86-92
Keyword(s):  
Life History ◽  
Life Histories ◽  
Population Level ◽  
Dynamic State ◽  
Salmonid Fishes ◽  
Individual Level ◽  
State Variable ◽  
Level Model ◽  
Fitness Benefits ◽  
The Individual

This chapter offers a fourth example model, with the objective of (1) illustrating the application of state- and prediction-based theory (SPT) to a new kind of decision—a life history decision—in a case where dynamic state variable modeling (DSVM) has been applied successfully; and (2) describing the unique ability of models utilizing SPT to address population-level questions of particular interest to conservationists and managers. In this case, SPT produced individual-level decisions similar to those of DSVM, but including them in a population-level model led to quite different conclusions than those implied by the individual-level DSVM analysis. Salmonid fishes exhibit amazing life history diversity. One fundamental distinction among salmonid life histories is whether or not individuals migrate to the ocean. In general, facultative anadromy can be seen as an adaptive behavior that trades off the fitness benefits of going to the ocean versus those of remaining resident. The anadromy versus residency decision is important to fish conservation and resource management.

scholarly journals Spatial memory shapes density dependence in population dynamics

2017 ◽  
Vol 284 (1867) ◽  
pp. 20171411 ◽  
Author(s):  
Louise Riotte-Lambert ◽  
Simon Benhamou ◽  
Christophe Bonenfant ◽  
Simon Chamaillé-Jammes
Keyword(s):  
Population Dynamics ◽  
Spatial Memory ◽  
Density Dependence ◽  
Cognitive Abilities ◽  
Population Level ◽  
Renewable Resource ◽  
Foraging Efficiency ◽  
Movement Model ◽  
Individual Level ◽  
The Impact

Most population dynamics studies assume that individuals use space uniformly, and thus mix well spatially. In numerous species, however, individuals do not move randomly, but use spatial memory to visit renewable resource patches repeatedly. To understand the extent to which memory-based foraging movement may affect density-dependent population dynamics through its impact on competition, we developed a spatially explicit, individual-based movement model where reproduction and death are functions of foraging efficiency. We compared the dynamics of populations of with- and without-memory individuals. We showed that memory-based movement leads to a higher population size at equilibrium, to a higher depletion of the environment, to a marked discrepancy between the global (i.e. measured at the population level) and local (i.e. measured at the individual level) intensities of competition, and to a nonlinear density dependence. These results call for a deeper investigation of the impact of individual movement strategies and cognitive abilities on population dynamics.

scholarly journals Components of standard metabolic rate variability in three species of gammarids

Web Ecology ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Milad Shokri ◽  
Mario Ciotti ◽  
Fabio Vignes ◽  
Vojsava Gjoni ◽  
Alberto Basset
Keyword(s):  
Body Size ◽  
Metabolic Rate ◽  
Body Condition ◽  
Population Level ◽  
Functional Trait ◽  
Standard Metabolic Rate ◽  
Individual Variability ◽  
Population Variation ◽  
Metabolic Rates ◽  
Individual Level

Abstract. Standard metabolic rate is a major functional trait with large inter-individual variability in many groups of aquatic species. Here we present results of an experimental study to address variation in standard metabolic rates, over different scales of organisation and environments, within a specific group of aquatic macro-invertebrates (i.e. gammarid amphipods) that represent the primary consumers in detritus food webs. The study was carried out using flow-through microrespirometric techniques on male specimens of three gammarid species from freshwater, transitional water and marine ecosystems. We examined individual metabolic rate variations at three scales: (1) at the individual level, during an 8 h period of daylight; (2) at the within-population level, along body-size and body-condition gradients; (3) at the interspecific level, across species occurring in the field in the three different categories of aquatic ecosystems, from freshwater to marine. We show that standard metabolic rates vary significantly at all three scales examined, with the highest variation observed at the within-population level. Variation in individual standard metabolic rates during the daylight hours was generally low (coefficient of variation, CV<10 %) and unrelated to time. The average within-population CV ranged between 30.0 % and 35.0 %, with body size representing a significant source of overall inter-individual variation in the three species and individual body condition exerting only a marginal influence. In all species, the allometric equations were not as steep as would be expected from the 3∕4 power law, with significant variation in mass-specific metabolic rates among populations. The population from the transitional water ecosystem had the highest mass-specific metabolic rates and the lowest within-population variation. In the gammarid species studied here, body-size-independent variations in standard individual metabolic rates were higher than those explained by allometric body size scaling, and the costs of adaptation to short-term periodic variations in water salinity in the studied ecosystems also seemed to represent a major source of variation.

scholarly journals Linking multi-level population dynamics: trait, role, and population

2020 ◽  
Author(s):  
Nao Takashina
Keyword(s):  
Population Dynamics ◽  
Species Interactions ◽  
Population Level ◽  
Species Traits ◽  
Trophic Niche ◽  
Niche Shift ◽  
Mathematical Framework ◽  
Ecosystem Structure ◽  
Level Model ◽  
Role Shift

Species interactions characterize population dynamics and ecosystem structure. While the population-level discussion is common in many ecological studies, trait variations within a population and ontogenetic diet/trophic niche shift are prevail across taxa. The ontogenetic development may lead to an individual’s role shift, such as inferior/superior competitor, prey, or predator. Here, we develop a novel mathematical framework to bridge multiple levels of population dynamics, such as trait, role, and population-level. We start with a nonlinear trait-level model, and derive role-level and population-level dynamics. By utilizing the connections, we demonstrate that the population-level model predicts the equilibrium status of the role-level model. In the role-level model, we discuss multiple role-shift scenarios: from (i) inferior/superior competitor to superior/inferior competitor, (ii) competitor to predator, and (iii) prey to predator. Our approach connects traits, roles, and population dynamics consistently, thus offering an opportunity to discuss the effect of species traits in the population-level dynamics.

scholarly journals LEARNING, EVOLUTION AND POPULATION DYNAMICS

2008 ◽  
Vol 11 (06) ◽  
pp. 901-926 ◽  
Author(s):  
JÜRGEN JOST ◽  
WEI LI
Keyword(s):  
Population Dynamics ◽  
Population Level ◽  
Individual Performance ◽  
The Other ◽  
Individual Level ◽  
Strategy Types ◽  
The Individual ◽  
Population Effects ◽  
Two Populations ◽  
Learning Schemes

We study a complementarity game as a systematic tool for the investigation of the interplay between individual optimization and population effects and for the comparison of different strategy and learning schemes. The game randomly pairs players from opposite populations. It is symmetric at the individual level, but has many equilibria that are more or less favorable to the members of the two populations. Which of these equilibria is then attained is decided by the dynamics at the population level. Players play repeatedly, but in each round with a new opponent. They can learn from their previous encounters and translate this into their actions in the present round on the basis of strategic schemes. The schemes can be quite simple, or very elaborate. We can then break the symmetry in the game and give the members of the two populations access to different strategy spaces. Typically, simpler strategy types have an advantage because they tend to go more quickly toward a favorable equilibrium which, once reached, the other population is forced to accept. Also, populations with bolder individuals that may not fare so well at the level of individual performance may obtain an advantage toward ones with more timid players. By checking the effects of parameters such as the generation length or the mutation rate, we are able to compare the relative contributions of individual learning and evolutionary adaptations.

scholarly journals Seasonal Interactions, Habitat Quality, and Population Dynamics in Migratory Birds

The Condor ◽  
2007 ◽  
Vol 109 (3) ◽  
pp. 535-547 ◽  
Author(s):  
D. Ryan Norris ◽  
Peter P. Marra
Keyword(s):  
Population Dynamics ◽  
Habitat Selection ◽  
Habitat Quality ◽  
Migratory Birds ◽  
Population Level ◽  
Seasonal Interactions ◽  
Individual Level ◽  
Habitat Occupancy ◽  
Per Capita ◽  
The Individual

AbstractAbstract. Historically, studies of habitat selection have focused on quantifying how current patterns of habitat occupancy influence condition and survival within a season. This approach, however, is overly simplistic, especially for migratory birds that spend different periods of the year in geographically distinct places. Habitat occupancy and the resulting condition of individual birds is likely to be affected by events in the previous season, and the consequences of habitat occupancy will influence individuals and populations in subsequent seasons. Thus, for migratory birds, variation in habitat quality (and quantity) needs to be understood in the context of how events interact throughout periods of the annual cycle. Seasonal interactions can occur at the individual level or population level. Individual-level interactions occur when events in one season produce nonlethal, residual effects that carry over to influence individuals the following season. Population-level interactions occur when a change in population size in one season influences per capita rates the following season. We review various methods for estimating seasonal interactions and highlight a number of examples in the literature. Using a variety of techniques, including intrinsic and extrinsic markers, the vast majority of studies to date have measured seasonal interactions at the individual level. Obtaining estimates of density and changes in per capita rates across multiple seasons to determine population-level interactions has been more challenging. Both types of seasonal interactions can influence population dynamics, but predicting their effects requires detailed knowledge of how populations are geographically connected (i.e., migratory connectivity). We recommend that researchers studying habitat occupancy and habitat selection consider how events in previous seasons influence events within a season.

scholarly journals Persistence and size of seasonal populations on a consumer–resource relationship depends on the allocation strategy toward life-history functions

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Rodrigo Gutiérrez ◽  
Fernando Córdova-Lepe ◽  
Felipe N. Moreno-Gómez ◽  
Nelson A. Velásquez
Keyword(s):  
Life History ◽  
Population Level ◽  
Impulsive System ◽  
Reproductive Season ◽  
Phenotypic Traits ◽  
Allocation Strategy ◽  
Individual Level ◽  
Incoming Energy ◽  
Consumer Resource

AbstractThe long-term ecological dynamics of a population inhabiting a seasonal environment is analyzed using a semi-discrete or impulsive system to represent the consumer–resource interaction. The resource corresponds to an incoming energy flow for consumers that is allocated to reproduction as well as to maintenance in each non-reproductive season. The energy invested in these life-history functions is used in reproductive events, determining the size of the offspring in each reproductive season. Two long-term dynamic patterns are found, resulting in either the persistence or the extinction of the population of consumers. In addition, our model indicates that only one energy allocation strategy provides an optimal combination between individual consumption and long-term population size. The current study contributes to the understanding of how the individual-level and the population-level are interrelated, exhibiting the importance of incorporating phenotypic traits in population dynamics.

scholarly journals Incorporating pushing in exclusion process models of cell migration

2014 ◽  
Author(s):  
Christian A Yates ◽  
Andrew Parker ◽  
Ruth E Baker
Keyword(s):  
Diffusion Coefficient ◽  
Exclusion Process ◽  
Population Level ◽  
Process Models ◽  
Jump Processes ◽  
Lattice Volume ◽  
Individual Level ◽  
Wide Range ◽  
Level Model ◽  
Crowded Environments

The macroscale movement behaviour of a wide range of isolated migrating cells has been well characterised experimentally. Recently, attention has turned to understanding the behaviour of cells in crowded environments. In such scenarios it is possible for cells to interact mechanistically, inducing neighbouring cells to move in order to make room for their own movements or progeny. Although the behaviour of interacting cells has been modelled extensively through volume-exclusion processes, no models, thus far, have explicitly accounted for the ability of cells to actively displace each other. In this work we consider both on and off-lattice volume-exclusion position-jump processes in which cells are explicitly allowed to induce movements in their near neighbours in order to create space for themselves (which we refer to as pushing). From these simple individual-level representations we derive continuum partial differential equations for the average occupancy of the domain. We find that, for limited amounts of pushing, the comparison between the averaged individual-level simulations and the population-level model is nearly as good as in the scenario without pushing but, that for larger and more complicated pushing events the assumptions used to derive the population-level model begin to break down. Interestingly, we find that, in the on-lattice case, the diffusion coefficient of the population-level model is increased by pushing, whereas, for the particular off-lattice model that we investigate, the diffusion coefficient is reduced. We conclude therefore, that it is important to consider carefully the appropriate individual-level model to use when representing complex cell-cell interactions such as pushing.

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