Introduction to Population Models

2021 ◽  
pp. 25-46
Author(s):  
Timothy E. Essington
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Size ◽  
Population Models ◽  
Change Model ◽  
Density Dependent ◽  
Intrinsic Factors ◽  
Model Understanding ◽  
Dynamics Of Populations ◽  
Simple Models

The chapter “Introduction to Population Models” introduces unstructured population models and shows how model decisions can change model behavior, the different ways that feedbacks can be represented, and how one evaluates the consequences of those feedbacks. The goal here is to show how modeling a single entity, population density, can be done in many different ways, depending on the purpose of the model. Understanding the dynamics of populations remains one of the fundamental goals of ecology. Not surprisingly, many models have contributed to the theory of population dynamics and regulation. The models vary considerably in terms of depth, breadth, intended uses (e.g. prediction vs. generality), and structure. This chapter will largely focus on the behavior of simple models, to see how intrinsic factors can dictate variability in population size. Density-independent and density-dependent models are covered, as well as methods used to understand model behaviors.

scholarly journals A Revisit of Infinite Population Models for Evolutionary Algorithms on Continuous Optimization Problems

2020 ◽  
Vol 28 (1) ◽  
pp. 55-85
Author(s):  
Bo Song ◽  
Victor O.K. Li
Keyword(s):  
Population Dynamics ◽  
Evolutionary Algorithms ◽  
Population Size ◽  
Optimization Problems ◽  
Continuous Optimization ◽  
Analytical Framework ◽  
Population Models ◽  
Initial Population ◽  
Infinite Population ◽  
Continuous Optimization Problems

Infinite population models are important tools for studying population dynamics of evolutionary algorithms. They describe how the distributions of populations change between consecutive generations. In general, infinite population models are derived from Markov chains by exploiting symmetries between individuals in the population and analyzing the limit as the population size goes to infinity. In this article, we study the theoretical foundations of infinite population models of evolutionary algorithms on continuous optimization problems. First, we show that the convergence proofs in a widely cited study were in fact problematic and incomplete. We further show that the modeling assumption of exchangeability of individuals cannot yield the transition equation. Then, in order to analyze infinite population models, we build an analytical framework based on convergence in distribution of random elements which take values in the metric space of infinite sequences. The framework is concise and mathematically rigorous. It also provides an infrastructure for studying the convergence of the stacking of operators and of iterating the algorithm which previous studies failed to address. Finally, we use the framework to prove the convergence of infinite population models for the mutation operator and the [Formula: see text]-ary recombination operator. We show that these operators can provide accurate predictions for real population dynamics as the population size goes to infinity, provided that the initial population is identically and independently distributed.

scholarly journals Quantifying whether different demographic models produce incongruent results on population dynamics of two long-term studied rodent species

2017 ◽  
Vol 3 (1) ◽  
pp. 18-26
Author(s):  
Giovanni Amori ◽  
Valentina De Silvestro ◽  
Paolo Ciucci ◽  
Luca Luiselli
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Size ◽  
Myodes Glareolus ◽  
Suitable Model ◽  
Demographic Model ◽  
Apodemus Flavicollis ◽  
Demographic Models ◽  
Long Term Studies

Abstract1. Population density (ind/ha) of long-term (>15 years) series of CMR populations, using distinct demographic models designed for both open and closed populations, were analysed for two sympatric species of rodents (Myodes glareolus and Apodemus flavicollis) from a mountain area in central Italy, in order to test the relative performance of various employed demographic models. In particular, the hypothesis that enumeration models systematically underestimate the population size of a given population was tested.2. Overall, we compared the performance of 7 distinct demographic models, including both closed and open models, for each study species. Although the two species revealed remarkable intrinsic differences in demography traits (for instance, a lower propensity for being recaptured in Apodemus flavicollis), the Robust Design appeared to be the best fitting model, showing that it is the most suitable model for long-term studies.3. Among the various analysed demographic models, Jolly-Seber returned the lower estimates of population density for both species. Thus, this demographic model could not be suggested for being applied for long-term studies of small mammal populations because it tends to remarkably underestimate the effective population size. Nonetheless, yearly estimates of population density by Jolly-Seber correlated positively with yearly estimates of population density by closed population models, thus showing that interannual trends in population dynamics were uncovered by both types of demographic models, although with different values in terms of true population size.

scholarly journals Population Variation Altered Aggression-associated Oxytocin and Vasopressin Expressions in Brains of Brandt’s Voles in Field Conditions

2021 ◽  
Author(s):  
Shuli Huang ◽  
Guoliang Li ◽  
Yongliang Pan ◽  
Jing Liu ◽  
Jidong Zhao ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Aggressive Behavior ◽  
Brain Regions ◽  
Population Variation ◽  
Field Conditions ◽  
Small Rodents ◽  
Density Dependent ◽  
Inner Mongolia Grassland ◽  
Dependent Change

Abstract Density-dependent change in aggressive behavior is essential for regulating the population dynamics of many small rodents, but the underlying neurological mechanisms have not been examined in field conditions. We hypothesized that aggression-associated oxytocin (OT) and vasopressin (AVP) in specific regions of the brain may be closely related to aggressive behaviors and population changes of small rodents. In this study, we analyzed the associations of OT and AVP expression as well as aggressive behavior with population density of Brandt’s voles in 24 large semi-natural enclosures (0.48 ha for each enclosure) in Inner Mongolia grassland. Then we tested the effects of population density on the OT/AVP system and aggressive behavior in experimentally manipulated populations of Brandt’s voles in the semi-natural enclosures. High density was positively and significantly associated with more aggressive behavior, and increased expression of mRNA and protein of AVP and its receptor, but decreased expression of mRNA and protein of OT and its receptor in specific brain regions of the voles. Our study suggests that OT/AVP systems are important in regulating the density-dependent population dynamics via aggressive behavior of small rodents, and they can be used as indicators of population variation or density-dependent stressors.

Population density of the eastern pygmy-possum in a heath–woodland habitat

2017 ◽  
Vol 65 (6) ◽  
pp. 391 ◽  
Author(s):  
Ross L. Goldingay ◽  
Jo Keohan
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Models ◽  
Mark Recapture ◽  
Nest Boxes ◽  
Patchy Habitats ◽  
Cercartetus Nanus ◽  
Over Time

The eastern pygmy-possum (Cercartetus nanus) has posed a challenge in attempts to describe its population density due to low rates of capture, preference for patchy habitats and periodic influxes of subadult individuals. We conducted a mark–recapture study of this species using a grid of nest boxes in a 9-ha patch of banksia heath–woodland. We captured 54 adults across the two years of our study. We estimated the density of adult pygmy-possums to be 1.5–4.2 ha–1 from different population models. This is substantially lower than previous estimates in equivalent habitat because we focussed on adults and recognised that they were not confined to the area bounded by our grid. We captured 36 subadults over the two years but they could not be reliably modelled due to extremely low recapture rates, which reflect high rates of dispersal and also mortality. For this reason, only the number of adults should be used to characterise populations of this species. Further study is required to investigate population dynamics over time and to describe the density of eastern pygmy-possums in other habitats.

Aspects of the population dynamics of the western rock lobster, Panulirus cygnus George. I. Estimation of population density

1974 ◽  
Vol 25 (2) ◽  
pp. 235 ◽  
Author(s):  
GR Morgan
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Size ◽  
Equal Probability ◽  
Rock Lobster ◽  
Single Population ◽  
Baited Traps ◽  
Unbiased Estimates ◽  
Panulirus Cygnus ◽  
Probability Of Capture

Breakdowns in the assumptions made by the Jolly (1965) method of estimating population size were detected in mark-recapture experiments with the western rock lobster. Using information gathered from sampling by both baited traps and by diving it was shown that, in particular, the assumptions of (1) a single population and (2) equal probability of capture of marked and unmarked rock lobsters, were not valid at all times in the 'population' studied, and this resulted in underestimates of population density. However, it was found possible to make suitable corrections to the raw data to arrive at apparently unbiased estimates of population density. In the cases studied, the calculated unbiased estimates of population density agreed well with unbiased estimates calculated from information gathered by marking and recapturing by different methods. Single census and the De Lury (1958) methods also grossly underestimated population density.

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