scholarly journals Density-Dependent Population Growth and Natural Selection in Food-Limited Environments: The Drosophila Model

1988 ◽  
Vol 132 (6) ◽  
pp. 786-809 ◽  
Author(s):  
Laurence D. Mueller
Keyword(s):  
Natural Selection ◽  
Population Growth ◽  
Density Dependent ◽  
Drosophila Model

NATURAL SELECTION AND DENSITY-DEPENDENT POPULATION GROWTH

Genetics ◽  
1983 ◽  
Vol 105 (4) ◽  
pp. 1029-1040
Author(s):  
R A Desharnais ◽  
R F Costantino
Keyword(s):  
Natural Selection ◽  
Mortality Rate ◽  
Population Growth ◽  
Population Size ◽  
Recruitment Rate ◽  
Equilibrium Density ◽  
Continuous Time Model ◽  
Time Model ◽  
Density Dependent ◽  
The Mean

ABSTRACT Natural selection was studied in the context of density-dependent population growth using a single locus, continuous time model for the rates of change of population size and allele frequency. The maximization principle of density-dependent selection was applied to a class of fitness expressions with explicit recruitment and mortality terms. Three general results were obtained: First, at low population densities, the genetic basis of selection is the difference between the mean recruitment rate and the mean mortality rate. Second, at densities much higher than the equilibrium population size, selection is expected to act to minimize the mean mortality rate. Third, as the population approaches its equilibrium density, selection is predicted to maximize the ratio of the mean recruitment rate to the mean mortality rate.

Density-Dependent Population Growth

2020 ◽  
pp. 29-46
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Density Dependence ◽  
Multiple Equilibria ◽  
Dynamical Behavior ◽  
Logistic Growth ◽  
Density Dependent ◽  
Per Capita ◽  
Discrete Time Models ◽  
Complex Dynamical Behavior

The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.

scholarly journals Linking individual phenotype to density-dependent population growth: the influence of body size on the population dynamics of malaria vectors

2011 ◽  
Vol 278 (1721) ◽  
pp. 3142-3151 ◽  
Author(s):  
Tanya L. Russell ◽  
Dickson W. Lwetoijera ◽  
Bart G. J. Knols ◽  
Willem Takken ◽  
Gerry F. Killeen ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Body Size ◽  
Population Growth ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Phenotypic Expression ◽  
Phenotypic Traits ◽  
Density Dependent ◽  
Individual Fitness ◽  
The Impact

Understanding the endogenous factors that drive the population dynamics of malaria mosquitoes will facilitate more accurate predictions about vector control effectiveness and our ability to destabilize the growth of either low- or high-density insect populations. We assessed whether variation in phenotypic traits predict the dynamics of Anopheles gambiae sensu lato mosquitoes, the most important vectors of human malaria. Anopheles gambiae dynamics were monitored over a six-month period of seasonal growth and decline. The population exhibited density-dependent feedback, with the carrying capacity being modified by rainfall (97% w AIC c support). The individual phenotypic expression of the maternal ( p = 0.0001) and current ( p = 0.040) body size positively influenced population growth. Our field-based evidence uniquely demonstrates that individual fitness can have population-level impacts and, furthermore, can mitigate the impact of exogenous drivers (e.g. rainfall) in species whose reproduction depends upon it. Once frontline interventions have suppressed mosquito densities, attempts to eliminate malaria with supplementary vector control tools may be attenuated by increased population growth and individual fitness.

scholarly journals Increased natural mortality at low abundance can generate an Allee effect in a marine fish

2014 ◽  
Vol 1 (2) ◽  
pp. 140075 ◽  
Author(s):  
Anna Kuparinen ◽  
Jeffrey A. Hutchings
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Gadus Morhua ◽  
Allee Effect ◽  
Population Regulation ◽  
Atlantic Cod ◽  
Adult Mortality ◽  
Natural Mortality ◽  
Density Dependent

Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite—a demographic Allee effect. Northwest Atlantic cod ( Gadus morhua ) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing.

Environmental sex determination and density-dependent population regulation in the entomogenous nematodeRomanomermis culicivorax

Parasitology ◽  
1986 ◽  
Vol 92 (2) ◽  
pp. 431-449 ◽  
Author(s):  
G. A. Tingley ◽  
R. M. Anderson
Keyword(s):  
Population Growth ◽  
Sex Determination ◽  
Population Regulation ◽  
Insect Pests ◽  
Host Population ◽  
Environmental Sex Determination ◽  
Density Dependent ◽  
Regulatory Constraints ◽  
Mermithid Nematode ◽  
Low Degrees

SUMMARYEnvironmental sex determination in the mermithid nematodeRomanomermisculicivorax is examined in the context of parasite reproductive success and population regulation. Experimental results show that the sex ratio of the nematode within its mosquito host (Culex quinquefasciatus) is dependent on parasite density. Sex ratios are biased to females at low parasite burdens and to males at high parasite burdens. Low temperature further enhances female-biased ratios. The net effect of density-dependent sex determination on parasite and host population growth is shown to be critically dependent on the frequency distribution of parasite numbers/host. Mermithid parasite distributions within natural host populations show low degrees of aggregation relative to other helminth species. The population regulation of the parasite is examined with respect to environmental sex determination and parasite-induced host mortalities by means of simple mathematical models of the dynamics of parasite transmission via its life-cycle. The significance of regulatory constraints on population growth are discussed in relation to the use of mermithids as biological control agents of insect pests or disease vectors.

Sign in / Sign up

Export Citation Format

Share Document